N EUROPE U R C H UNIVERSITY OF CALIFORNIA ANDREW SMITH HALLIDIL: 18685^1901 OF SAN FRANCISCO. * oo 3^0 .+. oQo ^2 This Book may be kept Two "Weeks, <\? 4 - ^ Gj(* For each day kept over the above time, -the gfo holder will be subject to a forfeit of five cents. If a work of one volume be injured or lost, the same to be made good to the Librarian. If a volume or more of a set of books be injured or^lost, the full value of_the setjmust be paid. NOTES 07 A METALLURGICAL JOURNEY IN EUROPE. JOHN A. CHURCH, ENQIHEEE OF MINES. WITH TWENTY-TWO ILLUSTRATIONS. NEW YORK: D. VAN NOSTRAND, PUBLISHER, 23 MURRAY AND 27 WARREN STREET. 1878. TO THOMAS EGLESTON, JR., PfiOFFS^OR OP MINERALOGY AND METALLURGY IN THE 8CHOOL OF MINES, COLUMBIA COLLEGE, NEW YOKK, TI1IS VOLUME IS RESPECTFULLY INSCRIBED. 105985 IIV13EX. AGORDO copper procass 3 Size of mineral mass 3 Ore 3 Old process 4 Wet treatment 4 Cementation 5 Crystallization 5 Table of operations 6 Treatment by Fusion 7 Table of treatment by Fusion 9 Loss 11 Expense 11 Improvements 11. .18 Theory of roasting 14 Process, cost in U. 8 19 Alteuau, works at 94 Amalgamation in Austria 43 ANALYSES. Argentiferous residues, Hartz .... 98 Basic sulphate- , Agordo 16 Black copper, Hartz 96 Blue vi riol, Hartz 98 Crude copperas, Agordo 5 Gneiss at Freiberg 79 Lead at Mechernich 34 Lead from desilverization by zinc, Mechernich 34 Do., Commern 36 Do., Call 38 Lead, 1st fusion, Hartz 85 Lead pure, Hartz 93 Lead precipitation, Hartz 85 Matte at Lend 46 Matte, copper, Freiberg 72 Matte, cone., Freiberg 74 Matte, copper, Hartz 94 Ore, Hartz 83 Slag, 1st fusion, Lend 45 Slag, 3J fusion, Lend 47 SI ;g, ore fusion, Freiberg 66 Slag, matte fusion, Freiberg. 81 & 67 Antimony, removal at Call 37 Antimony, removal by poling 38 Arsenical ores, treatment of, Frei berg 77 & 58 Artificial galena from roasting 30 Augustins muffle furnace 74 Bismuth, extraction of at Freiberg.. 77 Bismuth in desilverization by zinc. . 93 Blowing copper at Altenau 96 Blue vitriol, Agordo 5 Blue vitriol, Hartz 98 Boeckstein gold ore 40 Clausthal, works at 82 Colorado ores 52 Condensation of Hg. vapors. . . 21 & 25 Copper, loss at Agordo 11 Copper ore at Agordo 3 Copper process, Freiberg 72 Cost of copper treatment, Agordo ..11 Crystallization at Agordo 5 Crystallization at Freiberg 7o Cupellation, Freiberg 70 Desilverization at Commeru 36 Desilverization in Hartz . 90 Desilverizatioti at Mechemich 33 Dezincing at C ill 37 Dezincing at Mechernich 33 FREIBERG 54 Distribution of ores 54 Yield of works 55 Products 56 Processes 56 Classification of ores 53 Preparatory series of operations. . 57 Gerstenhoefer furnace 57 Roasting 57 Pyrites- 53 Arsenical ores 77 it 58 Zinc ores 5!) Pyritiferous ores 59 Regular series of operations 61 Roasting lead ore 62 Piltz furnace 62 & 66 Piltz furnace charge 65 Charge at Halsbrucke 66 Treatment of the matte 07 3d and 4th fusions 68 Lead treatment 68 Refining 70 via INDEX. Cupellation Second appellation Copper process Roasting matte Crystallization Supplementary Series Desilverization of abstrich Fusion for hard lead Treatment of abstrich scoria Manufac ure of arsenic Extrao ion of bismuth Review oi j >rocess Furnaces inclined Gerstenhcefer process Gold in Freiberg ores Gold ore in the Tyrol 40 Gold pao, Austria 42 J ashuer furnace Hard lead prodaction, Freiberg. . . . HARTZ Mountains, Lead and Silver Worts of Works at Clausthal Composition of ore Proportion of products Charge, 1st fusion Analyses of products Shalt furnaces Kast furnace Filtz furnace Rachette furnace Dvsiheriz.xtion at Lautenthal. . . . Deziucing poor lead Deziucing rich alloy Analysis of lead. . Copper process at Altenau. .ble of copper process. . . Ta Blowing the black copper Solution of copper ia SOs Blue vitriol Herbst process for desilverization . . Idria Imbibition in Cupel furnace Improvement in roasting Addition of sulphuric acid Precipitation as sulphide Manufacture of iron Kast furnace 87 Kernel roasting Agordo Kiln roasting Altenau Laut. nthal, works at LEND, Gold and Silver Works at. . . Or s smelted at 40 - Mill process Austrian pan for gold Pxiip Ex r Action Smeltiug First fusion . . Second fusion 46 Fusion with lead 47 Cupellation 47 Tables of cost and yield 48 Cost for various ores 50 Proportionate yield Au. and Ag. . 50 Process in America 51 53 Colorado ores 52 Liquation of rich silver alloy 33 Lixiviation, Agordo 5 Matte, concentration of Cu. in 68 Matte reatmeut. Freiberg 67 Mercury lost in panproce S, Austria 44 MKCHEKNICH, Lead Works at 29 Year y product of mints 29 Roasting 29 Artificial galena 30 Fusion 31 Furnace dimensions , 32 Charge in smelting 32 Desilverization 33 Dezincing 33 Analysis of lead 34 Treatment of matte 34 Works at Comnjern 35 Desilverization, Commern ....... 35 Analys s, pure lead 30 Works at Call 36 Zinc charge 37 Removal of antimony 37 Mill process for gold, European. ... 41 Muldner Works, yield of 55 Mines of Hartz, yield, 1871 101 Ores, Classification at Freiberg 56 Pan process, Austria 41 45 Piltz furnace, Freiberg 62 Piltz furnace, Hartz 89 -101 Poling 35 Precipitation process in the Haitz. . 8k! Precipitation (Cu.), improvement in 15 Preparatory series, Freiberg 57 Products of mercury distillation. ... 26 Products of Freiberg Works 56 Proportionate yield, Au. and Ag., by fusion 50 Pulp used in p-n process, Austria. . 44 Pyritiferous ores 5759 Rachette furnace, Hartz 85 Rauris 40 Review of Freiberg process 78 Ripa 27 Roastii g, Agordo 4 14 Roas 1 ing at Freiberg 67 Roasting lead ore. Freiberg . 62 Roasting matte, Hnrtz 94 Rousting, Mechernich 3!> 35 Silver, separation at ("all 37 Skofie, cost of tre.itmcnt 15 INDEX. Blag in charge, Hartz 84 {unelting gold ores at Lend 45 Soluble sulphates in roasted ore 13 Turner, Dr. Leo 40 United States, cost of Agordo pro cess in 19 VAI.ALTA, Mercury Works at 20 Furnace 24 Condensation 2125 Dimensions 22 Condensation chambers 21 Tubes 24 Loss 26 Products 26 Expense of tret\tment 27 Compared with other works 27 Wot treatment for rich alloy 38 Zell 40 Zinc charge, M^chernich 33 Do., Comrnem 86 Do., Call 37 Do,, Lautonthal 90 9i Zinc o r e at Freiberg C9 Zinc, removal of at Co rr. morn 36 Do., in Hartz 91 Do., at Mecbcrnich. . . . 33 Do., at Call 37 FIO. FLLUSTnATIONS. PAOE. 1. Ore furnace, Agordo 8 2. Blank copper furnace, Agordo... 9 3. Mercury furnace. Valalta 23 4 5. D ors of roasting furnace ... 30 6. Smelting fort noe, Mecheruich.. 31 7. Austrian gold mill 42 8 - 9 lieverberatory furnace, Frei berg 60 10. Do. Do 61 11. Piltz furnace 6-4 1215. Cupel furnace. Freiberg .... C9 16 1H. K;ust furnace, Kurtz 86 19-20. li-iohetta furnace, Hartz-... 88 21. Do. Do 89 22. . Do. Do.. ,. 80 X* XME THE Notes which form the basis of the few papers that make up this book were taken solely for private use, and there was no intention of making them public until after the lapse of a considerable time. Their publication was then undertaken, not because they presented descriptions of novel processes, but be cause the author found that the poverty of English technical literature in this branch of industry was such as to be a serious annoyance to men engaged in the treatment of American ore. They first appeared in the columns of the Engi neering and Mining Journal, and their reception has been sufficiently favorable to warrant this republication. It is frequently said that American genius can be trusted to devise its own pro cesses and need not go abroad for instruction, but no one who is acquainted with the industry, skill and devotion of European metallurgists to thoir work can be wiling to lose the fruits of their experiment and thought. Few persons know how much labor and money are spent by them every year in the work of revising old established processes, both by laboratory examination and by experiments conducted on the largest scale. The two years that elapsed between the author s journey in Europe and the publication of these Notes was sufficient to bring about such changes and improvements in foreign practice that he could no longer rely upon the details of his work but was obliged to collate it with the latest technical publications abroad. He is therefore indebted to many writers and has endeavored to properly express this foot in foot notes to each paper. But he has not described any works that were not visited and carefully stu died by him, and trusts that the personal knowledge thus gained has enabled him to appropriate with success and incorporate with his own, the ^ork of Others. NOTES ON A METALLURGICAL JOURNEY IN EUROPE. The Copper Process atAgordo AOORDO is reached from Venice by rail to Conegliano, stage to Belluno and post-chaise to Agordo, the whole journey occupying about eighteen hours. The old process in use at this place has been fully described by KIVOT, in his work on Metallurgy ; by HA.TON, in the Annales des Mines, 1855, 5th series, vol. 8 ; by PEKCY, in his metallurgy, and many other writers. It will, therefore, receive only such attention here as is necessary to make the character of the recent changes suffi ciently clear. The ore is obtained from an irregular deposit of iron pyrites, lying in black argillaceous schist, close to the contact plane of a dolomite limestone. The dimensions allotted to this mass by Engineer FELLAH, are : Length 550 meters. Breadth 35 " Depth 200 " Contents in cubic meters 1,764,000 He reports the state of the work in 1865, as follows :] Content of mass, cubic meters 1,764,000 Already excavated " , 617,000 Worthless pyrites " 441,000 Good ore remaining " 700,003 As the weight of one cubic meter of pyrites is 4,250 k. (9,350 Ibs.) we have about 3,000,000,000 kilograms, or 3,000,000 tons. The present production is about 20,000 tons a year, at which rate the mine will hold out a hundred and fifty years. About one-third of the ore (see above statement) is worthless, containing no copper. This is sorted out, and the remainder is separated into the following varieties : Best ore. . . .with 4 per cent, copper. Good ore. . .with 24 per cent, copper. Poor ore with 0-42 per cent, copper. Small ore. ..with 12 per cent copper. 1. For information contained in these notes on Agordo, I am indebted to SIONOB N. PELLVTI, Eni<ineer in charge for the . talian Government ; and to SIONOB LUIOI HUB&BT. Director of the Smelting Works. This small ore is composed of a mixture of all the other varieties, and also of ore from a particular layer in the mine. It forms somewhat more than 15 per cent of the whole. Besides the pyrites a small amount of galena mixed with blende and contain ing a variable percentage of silver, is obtained. At the time of my visit, a gentleman had purchased a few hundred tons of this ore and was roasting it in piles, in the hope that the blende would roast to sulphate and thus be soluble, It has been ascertained that when a mixture of lead, zinc and silver sulphides are roasted together to sulphates, the silver is not soluble in the presence of so much lead. His roasting, therefore, had for its object the removal of the zinc and the concentration of the silver in the lead ; but I have never been able to ascertain what success he had, though I am under the impression that his experiment foiled. In treating this mass, remarkable for its purity, methods were adopted which made Agordo the study of scientific men. The ore was roasted in heaps contain ing 250 to 300 tons, the temperature being kept very low, and after six to nine months, when the pile was opened, a kernel of unroasted ore was found in each lump. In this kernel was concentrated most of the copper which in the begin ning had been distributed throughout the lump. A transmission of solid matter so remarkable as this, illustrating the operations by which metallic matter may be concentrated in veins by mundane fires, could not fail to attract attention, and nearly all writers on the metallurgy of copper, and processes of roasting, have discussed it. 2 These kernels were broken from the surrounding "shells," and in this way kernels of a working average of 4 8 per cent, copper were obtained from ore containing 2 per cent, and less ; while the shells would contain about 0-7 per cent The concentration of copper is so perfect that the real kernel often contains 30 per cent, but in order to make sure that none of the rich kernel shall be lost, a large quantity of shell is left around it, so that the working average is that above given. Sulphur is collected in small depressions, stamped in the top of the pile. Fine, sifted ore, from the lixiviation vats, is stamped into circular basins and a small quantity of sulphur, from one-fifth to .one-half of one per cent of the ores weight, collects in them. This is refined in the usual way. It contains arsenic and is not a very valuable product In 1865 the amount made was 50,532 k. or 60-5 tons. This is 0-3 per cent, of the ore or 6 per cent of the sulphur in the ore. The treament of the two sorts was : Lixiviation of the shells with precipita tion of the copper by iron, and fusion of the kernels. THE WET TREATMENT. Lixivialion. The ore is shovelled into vats 50 M 3-50 meters square and 1 -50 meters deep ; charge 14 tons. Fresh ore is lixiviated with liquor which hus already served for two lixiviations, and in this way it is brought up to the proper strength. The liquor remains 24 hours in contact with the ore, is then drawn off, and the ore shovelled to a fresh tank, where it is treated with water from a 2. See I lttttuur a Kojt Pr zesee. AQORDO. 5 previous third lixiviation. After 24 hours standing the pro jess is repeated, this time with fresh water. After the third contact with the ore, the liquor marks 32 BE.VUME. Liquor from the second lixiviation marks 13 11 B. The spent ore is placed on and under a new roasting heap, where the sulphurous acid fumes effect a re-roasting of it. It is then washed in 4 waters, sifted through a mesh of 1-5 centimeters = 6 inch, and the coarse ore receives a third treatment in the piles. Cementation . The liquor from the lixiviation vats is clarified by settling in tanks, and then run to the cementation vats. These are of two kinds : lead tanks 4*3 nv-ters and 1-5 meter deep, containing 21 cubic meters. They are heated by a lead stove placed in the center, and the flames of which pass downward through a large flus in the tank. Fire is kept up for 8 10 houi s, but the liquor remains 24 hours in the tank. Pig iron is placed in a bank around the sides of the tank. The temperature reaches about 60 G. Reverbarat^ry furnaces are also used for this work. They have a bottom laid in hydraulic cement, hold 17 cubic meters, and the liquor is heated by the flames passing over it. Crystallization. After the cementation is complete, the liquor runs to clarifying vats where the fine copper, and the basic salts in suspension in the liquor settle to the bottom. It then marks about 37 B. and is transferred to the crystalliza tion vats, which are wooden tanks, some being 2-20 * 3-00 M 0.50 meters, and others 8- 30 x 3-50 * 0-50 in size. Here the liquor remains as long as it is desired to continue the deposition of crystals. Agordo is cold in winter and dry in summer ; and as crystallization practically depends partly up ^n evaporation but mostly upon the depression of the temperature, the place is well fitted for the manufacture of copperas. By leaving the liquor in the vats three or four months, the greater part of the iron sulphate could be obtained. But the pro duction of Agordo is far in excess of the demand, so that there is no neeed to push the extraction so far. Practically the liquor remains 36 weeks in the vats. The crystals of sulphate collect on the bottom, on twigs suspended in the liquor, and on the sides of the tank, and these conditions afford three qualities of copperas. That collected on the bottom is the poorest, being contaminated with basic iron sulphate, which is insoluble, but is formed in such a fine condition as to separate completely from the liquor only after long standing. The copperas on the twigs has a certain amount ol bark and woody matter in it ; that on the sides is pure and of a fine color. If the tanks do not yield enough of this quality to satisfy the demand, the mother liquor, after the first crop of crystals has been obtained, is concentrated in the revarberatory furnaces. It then yields altogether first quality crystals. In the ordinary process of crystallization the strength of the liquor sinks from 37 B. to 26 B. The composition of this sulphate is as follows : Ferric sulphate 49-73 Zinc sulphate . 4-55 Hydratcd Ferric oxide 3-20 Water.. ...42-52 100 The amount of copperas which Agordo is capable of producing each year is 6 .AGORDO. immense. If we assume the percentage of ferric sulphate in the liquor to increajse 0-061 per cent, for each degree of BEAUME, we have 704 per cent, which can bo extracted from the liquor, by lowering its density from 37? to 26 B. That is, we have 774 pounds of ferric sulphate from each cubic meter of cement liquor. RIVOT says that each cubic meter will easily give 600 k. or 1320 pounds. In 1865 Agordo produced 7360 cubic meters of rich liquor and 1967 cubic meters of poor liquor. The rich alone would yield, at EIVOT S estimate, 4416 tons of copperas. But the production for the year is reported at only 754 tons. Agordo is so far from a market that its profit on this product is very small, and from its impure nature the demand is not great. , The operations connected with mining and the wet treatment, in 1865. dealt with the following quantities of material : TABLE OP OEE MINED 3 . 1. Best ore containing 7*4 per cent copper 843 tons containing 62 tons copper. 2. Good " "3-1 per cent copper 5005 " " 155 " 3. Poor " " 0-87 per cent copper 10531 " " 92 " " 4. Small j Good containing 2-48 p. c. copper 711 " " 18 " ore. (Poor 1-25 p. c. " 2261 " 28 " 19,351 355 Average percentage of copper 1 -8 TABLE OF BOASTING. The Blasting piles received bricks and fine ore for covering 4,356 tons. coarse ore 17,403 tons. Total 21,759 tons. Wood consumed, cubic meters 201 -61 " " cords 56-7 Labor Roasting 2869 days Breaking out kernels . 39121 davs 41990 days. Per ton of ore : Wood, cords 0029 Labor, days : roasting 0-132 breaking 1 -800 1 -932 Eesults: Kernels 2,324 tons containing copper 145-5 tons. Shells 17,607 " " " 209-5 tons. Rich ore 475 " " 33*7 tons. Total 20,466 tons. 388-7 tons. TABLE OF LIXTVIATION. Shells treated 17,667 tons containing copper 209-5 tons. Yield : Liquor 12,781 cubic yards containing copper. . . .116 3 tons. Loss 93-1 tons. Loss calculated on copper in shells is. . .44-5 per cent. Loss " " " " all ores is. .23-8 Labor 1471 days or 07d per ton. 8. This table is computed on 11 months and 9 days only. 4. The difference between this total and that given above is due to piles which were ot fully roasted. AOORDO. 7 TABLE OF CEMENTATIOX. Charge : Shells 17,667 tons containing copper 209-5 tons Product . . . Rich liquor 10,08G cubic yards. Poor 2,695 " Cemeatcopper, rich 188-7 tons c(mtainjng copper Loss 93-2 tons. Loss therefore 44.5 p. c. Fuel : Peat (4-9 per cent, of shells) 858 tons. Charcoal (= 0-023 per cent, of shells) 691 bush. Iron 320-4 tons. These amounts give the following as the expense per ton of shells : Charge : Shells 1 ton containing copper 23-70 pounds. Rich liquor 0-57 cubic yards. Poor " 0-16 " " Cenvnt copper. . .0.135 tons containing copper 13-16 pounds. Loss (= 44-5 per cent. ) , 10-54 Fuel : Peat 97 ponnog (= 4-9 per cent.) Charcoal 0-039 bushels. Iron: 36-23 pounds. The expense per ton of pig copper produced is as follows Charge : Shells 1519 tons containing copper 3602 pounds. Cement copper.. .. 2382 pounds " " 2000 Loss (44-5 percent) 1602 " Fuel : Peat 14,780 poun-ls. Charcoal .... 6 bushels. Iron 5,510 pounds. THE TREATMENT BY FUSION. The process consists in fusing the kernels, rich ore and cement copper with sandstone as a flux ; the rich scoria obtained in this and succeeding operations being added for the sake of their copper. The furnace employed is very peculiar, the back and front walls being strongly inclined to the horizon. The furnace is, therefore, in effect, an ordinary shaft, tilted over about 12 degrees from the perpendicular. The object of building it in this way is to make the ore pass slowly through the furnace, the inclination of the back wall increasing the friction ; and also to oblige the gases to follow the front wall and mix with the ore as little as possible in order to avoid too great reducing action. These dispositions have for their object the prevention of iron sows, and the proper preparation of the materials, during their descent, for fusion in the crucible. It is hardly worth while to discuss forms so peculiar, and so little likely at this day, to meet with copyists. But similar constructions have, in times past, been common in Europe, as in the Hartz. They have now been abandoned in most quarters, but it may be well to point out that, with ore* rich in iron, sows can be better prevented by a rapid smelting, than by any other means ; and if this rapid fusion does not permit the necessary preparation of the materials in the furnace, they can be prepared before they enter it. This preparation in the furnace consists, accord- 8 AGOKDO. ing to the Agordc view, partly in driving off the sulphur, and partly in heating the materials. But sulphur can be eliminated to but a very small extent in the shaft furnace. Raw ores, such as the greater part of those smelted at Agordo, practically are, can hardly lose more than 4 per cent, of their sulphur in passing through the furnace, a quantity which could be eliminated by roasting one- twentieth part of the ores before charging. With the Agrordo system of building is connected the very serious defect of short campaigns. Eighteen days was the average of the furnaces in 1865. By roasting (if necessary) a part of the ores and smelting 1215 tons daily instead of 9, and using a straight or a flaring urnace, the campaigns might be trebled in length, and the cost of working reduced. Figure /. Figure 1 represents a section, from front to back, of the furnace used for the fusior of ore. By reference to the tables further on it will be seen that the expense of fuel per ton of charge is, in the fusion of ore, about 25 bushels per ton, and in that of matte 37 bushels ; the former being 15 and the latter more than 22 per cent, of AGORDO. the charge. This expense would probably be considerably reduced by the adop tion of furnaces less wasteful of fuel and capable of maintaining longer cam- pudgns. Even at Lend where the campaigns, for lack of ore, are confined to a week s run, or less, the expense of fuel is i o greater. The resulting matte contains about 24 per cent of copper. It is roasted in piles six times and smelted with sandstone and rich scoria. The furnace is again inclined, but less so than before, as figure 2 shows. It is important, in this operation, to prevent the reduction of too much iron which would make a highly ferriferous black copper. The siliceous flux used at Agordo costs $1.36 a ton, and as it coutains about 10 per cent of iron the amount must be increased over that which would be necessary if the quartz were purer. It is, therefore, an object to smelt with a charge as basic as possible, a treatment which increases the danger of redui-ed iron. From this operation black copper of 95 per ceni, copper and a richer matte, containing about 60 per cent copper, are obtained. The former is fined in a common German hearth, and the latter is roasted and returned to the same operation. TAJV-ES OF THE TREATMENT BY FUSION. FUSION FOB MATTE. Charge Kernels Best 8 -67 "- :;; 2 5i Good 6-39 .1752 Poor 3 -37 287 Rich cement copper 58 -57 Poor " " 9 "89 18S 26 Grasses & Cinders 34 50 106 546 Sandstone. . 679 4182 tons. 10 AGORDO. Product : Matte containing 23 - 25 per cent, copper 1285-0 tons. Grasses * 10 " J4-9 " Cinders " 15 " " 11-3 " Labor : 16 campaigns, or 843 shifts of 8 hours each ; 4 men o each shif Fuel : Charcoal 4735 cubic me ers Charge smelted in 24 hours Lab r per ton of charge Fuel f " " Loss : The char -e con ained of copper The produc s " " 1311-2 :ons. days. 106,310 bushels. 14-8 tons. 0-8 days. 25-4 bushels. 64 s, 083 pounds. 603,742 Loss therefore " 38,346 " Or 5-9 per cent. BOASTING OP MATTE. Matte 1488 tons per ton. Charcoal 18288 bushels 12-3 bushels. Wood 251 cords 0-15 cords. Peat 55-4 tons 0-03 tons. Labor 5040 days 3 15 days. FUSION FOR BLACK COPPER. Charge : Boasted matte containing 23-2 per cent, copper 1343 tons. 60.8 " " " 175 " Grasses and cinders 25 " Scoria 380 " Sandstone. .* 477 " 2400 Products :. . .Matte containing 60-26 per cent copper. ., .191-6 tons. Black copper containing 90 " " " ....314-4 " Crasse 15 " " " 20-3 " Cinder* 10 " " ....12-8 " 539-1 Labor : 747 shifts, 4 men to each shift 2988 days. Fuel : Charcoal 88,047 bushels, Labor : per ton of charge I" 24 days. Charcoal : . .. * " " 37 bushels. Charge smelted in 24 hours . 9-5 tons. Loss : The ciiarge contained of copper 869,41 1 pounds. The products " " 837,016 Loss therefore 32,395 pounds. Or 3-7 percent FINING. Charge : Black copper 628,443 pounds. Product :.... Rosette " 492,840 Grasses and cinders 96,228 Labor : 1,296 days. Fuel : Charcoal 24,000 bushels. Copper in materials charged 597,025 pounds. obtained 589,068 Loss therefore 7,957 Or 1-33 per cent AGORDO. 11 TABLE OF LOSS. Copper In charge. C .ppor In products. LOBB. Per Cent Lixiviation ............ 4 IS, 895 pounds. 232, 600 pounds. 186, 289 44 -5 Firstfusioii ........... 641,641 " 603,742 37,899 V.l Second fusion ......... 860,400 " 837,016 32,384 3-7 Fining ............... 597,025 " 589,068 " 7,957 1 -33 2,526,961 2,262,432 264,529 f This amounts to a loss of 34-42 per cent of the copper in the ores. But this is too high, because all the products from the piles and the cementation vats were not smelted within the year. Knowing the percentage of loss on each operation we can calculate the true loss on 20,466 tons of ore containing 388-7 tons copper as follows : Lixiviation loss on ____ 418,800 Ibs. copper 44-5 per cent. = 186.366 pounds. ____ 590,834" @ 5-9" " = 34,859 Firstfusioii Second fusion loss on. 555, 975 Fining " " 535,404 = 20,571 = 7,139 the Total 777,400 Ibs. 32 -0 per cent. 248,935 It* Engineer PELLATI reports the loss for 1865 at 31 -8 per cent. From this it appears that roasting and its accompanying lixiviation are processes which cause the greatest loss, and are, therefore, the least perfect. Expense per ton. To ascertain the average cost of one ton of pyrites, we will take the following amounts; best ore 406,547k., kernels 2,081,447, shells 16,060,785 k. ; total 18,548,779 kilos or 20,399 tons. The expenses of labor and material upon each ton of this, in all the operations, is as follows : TABLE OF EXPENSE FOR 2000 POUNDS ORE, IN UNITS OF LABOR AND MATERIAL. Labor days. Wood Cords. Char- coal bushels. Peat tons. Iron pounds. Sand stone tns 1-93 003 Ijixiviation 0-07 Cementation 0-12 . .. 0-034 0-042 31-41 Fusion for matte 0-17 5-160 0-028 25 012 0.9 JO 0-002 0-15 4-310 0-023 Fining 0-06 1-18 2-75 0-015 11,584 0-044 31-41 0-051 Prices at Agordo are as follows : Mining ore 9-55 francs per ton = $1-91 per cubic meter = 8-5 cents per bushel. j " " = $2-13 per cord. " =$15-00 per ton. 1000 k. =$27-26 per ton. " day (average) = 20 cents a day. 1000k. = $1-36 a ton. Otiarooal 12-25 Wood 3-00 Peat 3-00 Iron 15U-00 Labor 1-00 Sandstone 7- 50 From the above table of loss it is apparent that the old process in use at these works was a very expensive one, considered in regard to extraction. The loss in lixiviation was enormous, and improvement in that part of the process would evidently afford the beat reward. But this truth was not immediately perceived ; 12 AGORDO. a number of minor matters first received attention, and the changes introduced were not always useful. Improvement at Agordo first took the direction of attempts to increase the amount of sulphur extracted ; and to concentrate the copper more perfectly in the kernel. Although the ore contains 50 per cent., or more, of sulphur, the piles save at most one half per cent. To increase the yield the " Styrian Kiln" was adopted. This is merely a rectangle, enclosed by walls and paved with stone. In the walls, which are very thick, there are a number of chambers, communica ting with the interior, by small passages. The ore is filled in and covered with fine ore, and fine spent ore from the lixiviation vats is stamped on the top for a cover. The ore is ignited by a canal in the bottom of the kiln, and the roasting goes on precisely as in a pile ; but the products of combustion are discharged through the side passages. As the sulphur vapors are longer in passing out, and the masonry in which they circulate is exposed to the air, they are more thoroughly cooled and condensed, Al the same time the thick walls serve to retain the heat of the mass, which reaches a temparature probably considerably higher than that of the pile. The result of these conditions is, that nearly one-half more Bulphur is condensed, and the higher heat produces better kernels. Indeed, poor ore, that gives no kernels, when roasted in piles, yields them in the kilns. The experiment was therefore a success, in having fulfilled the expectations formed of it. But this was the turning point in Agordo improvement. The high beat which made the kernels so fine, also caused the destruction of the copper sul phate, in the shells ; the sulphuric acid was driven off, and copper oxide left. This is insoluble in water, and caused a great increase of the loss in the process of lixiviation, a loss which, as we have already seen, reached 44-5 per cent of the copper treated. The sulphur at Agordo is always contaminated with arsenic, and its use is restricted. Its price is therefore low, and its production unimportant. These considerations led at once to the disuse of the Styrian kiln, ( s ) and im provement took its true direction in efforts to increase the yield of copper and lessen the expense of operations subsequent to the roasting. Great results have been attained in this work. They are 1st. The almost complete extraction of the copper by roasting and lixiviation ; 2d. Projected improvements in cementa tion, which include the disuse of all operations but Roasting, Lixiviation, Fining and Crystalization. Improvements in Roasting One of the peculiarities of the Agordo deposit is a layer of hygroscopic pyrites, which falls to pieces up<-n contact with the air. This is mnde into round, conical bricks, which are dried and then piled like the other ore. But to save the expense of ovens, which are necessary in the winter, the extraction of this ore has been confined to the summer season. It is now proposed to build crushing works, and break up all the ore, except the richest, to the size of one centimeter (O4 inch). It will then be stamped into bricks. These have the shape of a truncated cone, with a height of 10 centime ers (-1 inches), and a mean diameter of 15 centimeters (6 inches.) Three moulds are cast in one 5. One of these kilns is still in use, but only for want of room for the roasting piles. AGORDO. 13 piece, and a workman can make 600 bricks by four o clock p. M., his work being as follows : bringing and wetting his ore with mother liquor from the crystaliy-iv- tioii vats ; forming the bricks, and carrying them to the drying ground. It should be remarked in regard to the time, thut the workmen at Agordo are compelled to leave work at 4 p. M. , because of the sulphurous acid vapors from the rousting piles, near which they work, ihere is nothing in the work itself which forbidx a full day s labor, and a production of at least one-sixth more. The bricks weigh about 2 k. or 4-5 pounds each. They are air dried, and then uiled on the outwide of roasting piles in full operation, and completely dried. The weak solution of iron and zinc sulphates, which forms the spent liquor from the crystalization vatn, acts with a slight oxidizing effect upon the grains of pyrites, and binds them together like a cement ; the bricks are consequently quite hard. After drying they are piled in regular order, 70,000 or 80, 000 in a pile ; covered with small ore, and lighted as usual with logs of wood placed at the cornerw. When fully ignited a. layer of spent roasted ore from the lixiviation vats is thrown over the pile to serve as a cover. The roasting period is, as usual, 7 9 months, according to the size of the pile. This is then opened, and each brick is broken in two to ascertain whether it is fully roasted. Those which are underburueU are thrown into a pile of fresh bricks and reroasted. It is the peculiarity of thiw method that no brick is ever ouer-roasted, a fact that is full} proved by fifteen years uniform experience, A perfect roasting, for purposes of lixiviation with water, is that which leaved the greatest possible amount of sulphates. How much superior this roasting of the ore in brick form is over that in lumps, is shown by the following resulta com municated by Signer de HUBEET : Fine ore, stamped in moulds, roasts to a red-brown color and loses in lixiviation 30 @ 32 per cent Ore in lumps, well roasted, but of a darker color, loses 18 @ 25 " " The same, over-roasted, nearly black in color, loses 14 " " Thus we see that the gain by crushing and moulding the ore is twofold. Over roasting is steadily avoided, and the roasting is better than the best in any other form. This gain in soluble matter is of course principally iron sulphate, but it is a well-known fact that copper sulphate is much less easily decomposed by heat than iron sulphate, and we ought therefore to expect an increase in the proportionate extraction of copper even greater than that of the iron salt. If we take the ave rage extraction of iron sulphate, from the lump ore, to be 22 per cent., and from the brick ore 31 per cent, the latter gives about 33 per cent, greater yield of this salt than the former. We have seen that the loss of copper in roasting and lix iviation is estimated at no less than 44*5 per cent, while experiments on the new method indicate a loss of only 3 or 5 per cent, which is a gain in extraction of 75 per cent These results are astonishing, and, simple as the means taken to pro duce them are, must be underlaid by some general principles of value. Were the molecules of which each lump of ore is composed independent of each other, we should probably have an almost complete conversion of the sulphido into sulphate in roasting, as the heat produced by the combustion of one extra 14 AGORDO. atom of sulphur does not seem sufficient to destroy the sulphate salt formed by the burning of the other. When this destruction does take place, it is probably due to the fact that the particles of ore do not all reach the sulphate stage at the same moment, and those that arrive there first are subjected not only to the effects of the heat stored up in them by the combustion of their sulphur, but also to the added heat which the neighboring particles of sulphide give out in burning. Among the remedies, which have been proposed for this evil, is the admixture of inert substances to keep the particles of roasting matter apart. The improvement at Agordo may properly be placed in this class, though the substance mixed in with the ore is not a solid, but a gas ; it is air. But the air performs the func tions of an inert non-conductor, and it is to this property that it owes its value. The reason why the bricks roast better than the lumps is doubtless to be found in the difference in the physical condition of the ore, produced by crushing, or by the natural disintegration of the hygroscopic ore. The superiority of the small ore is in the severance of the mathematical contact naturally existing between ore particles, in large lumps. That it plays an important part is proved by the fact, that no kernels are ever found in the bricks formed of small ore, the concentra tion of copper in the centre being prevented by the separation of the lump into an infinite number of small grains, which have no perfect contact. In the kernel roasting, for which this place has been so famous, it has been observed that the copper in one lump has sometimes been concentrated in a neighboring lump, lower in the pile, with which it came in contact. For the transmission of copper from one lump to another by any process yet suggested, an absolutely mathema tical contact is indispeusable. Whatever the true method ot that transmission may be, it is evident that an action, so exceedingly slow and delicate as it must be, could not proceed if the least chasm or other obstruction lay in the way of the advancing copper. There must Lave been a mathematical contact between the two lumps ot ore, and it remains to explain why two neighboring grains in a brick cannot come into equally intimate union. The explanation given at Agordo for the transfer of copper from one ore mass to another, is that, in a pile made up of irregular lumps, there will be irregularity of interstices also, and some of the open spaces will be so large as to furnish air enough to cause too rapid combustion in the pieces immediately around them. The heat being thus raised, the mass of pyrites melts superficially, and flows down upon the lump below, thus establishing the close contact necessary for the transmission of the copper, in its process of concentration. In the brick made up of grains, none of which are larger than 1-16 cubic inch and most are from 1-4 to 1-10 inch iu diameter, this rapid fusion cannot proceed. Even if one particle gets into furious combustion, the air which almost surrounds it prevents the transmission of its heat and there is no general fusion of the sur face of the brick. Thus the air maintains the disaggregation of the pile. Admixture of an inert solid, like silica or shale, serves the same purpose as air. The poor ore at Agordo rarely has kernels, or only inferior ones. The interposi tion of the silica prevents the advance ol the copper ; and when kernels are formed it cannot be doubted that the gangue, always small in quantity, is absent, or nearly so, from those pieces which give the kernel. Thus we may refer the AGOBDO. 15 slow and even roasting of the bricks to the separation of the ore particles which in accomplished by crushing ; while the maintenance of this separation is due to the non-conductorair by which they are nearly surrounded, - These facts may be observed daily at Agordo. The piles made up ore brick* are much less aggregated by fusion than the others. Ordinary piles are found to consist, after burning, of a mass which has gained decided coherence by the heat it has undergone. The ore must be knocked out by strong blows of a hammer ; while the bricks, though somewhat coherent, yield much more readily. It is proposed to take advantage of these results of many years experience and erect (1) Crushing works in which whatever crusher is selected will have to exert both a crushing and a percussive action, as the Agordo ore is very hard aud tongh ; (2) Ovens for drying the ore. (The order for these had been received in 1869 ) In addition to this, there will probably be some changes in manipulation, as at the lixiviation tanks where the ore is now moved twice, instead of pumping the liquor, a much less laborious operation ; but of this kind of improvement which is merely the reforming of a bad disposition of the works, and includes no principle, I do not intend to speak. The next field in which improvement ia to enter is the precipitation of the copper by iron. Three propositions are now before the government, as follows . 1. Hot precipitation in revolving casks, 12 feet in diameter, as at Skofie in Austria. This operation is thus shortened to 12 hours, no basic salts are produced, little arsenical salt precipitated and the amount of iron used is practically a minimum ; 90 iron to 100 cement copper or 154 iron to 100 pig copper. It is difficult to institute a fair comparison between the Skofie method and that at Agordo, though the ores have about the same value, because the ore of the former is already an oxide ; but leaving out the roasting in both cases, the following comparison of loss and expense of material, in other operations, gives a good idea of the decided differences in the two systems. To produce 1000 k. (2200 pounds) rosette copper, requires at Agordo. Skofie. Copper in the ore 1412 kilos. 1202 kilos. Wood 1-90 cubic metenu Peat 19-10 " Charcoal 34-40 " " 61m. Iron 2750-00 kilos. 1540 kilos. Sandstone 4460-00 " 1540 " This comparison is the more striking when we remember the fact that only 46 per cent, of the copper which was smelted at Agordo had passed through cementation. The rest was obtained from kernels and rich ores. 2. Addition of sulphuric acid to the liquor during cementation. This is the suggestion of Signer DE HUBEBT, director of the smelting works, who has worked out the method. The greatest defect of the present system of precipitation is the production of basic salts of iron. These are the result of the long contact of the hot liquor with the pig iron in the tanks and they cause a loss of iron, a precipi tation of arsenical salts, and by adulterating the cement obtained, they prevent the immediate conversion of the cement to pig copper, and thus cause a loss of 9 per cent of the copper in the cement, by the double fusion which is necessary. 16 .AGORDO. Signer DE HUBERT finds that these inconveniences can be avoided by the addition of sulphuric acid to the cement liquor, a course which carries with it only two ob jections ; the cost of the acid and the use of more iron ; while its advantages are the production of a cement which can be smelted at one operation to fine copper ; and a larger make of copperas. The latter, it is true, arises partly from the sul phuric acid added and the extra amount of iron consumed ; but also, Irom the prevention of the basic salts. Experiments in the laboratory gave the following results : . Without sulphuric acid, the cement contained 1 3 percent, of arsenic and 30 per cent, of copper, the impurity being chiefly basic iron sulphate. With sulphuric acid the cement contained no arsenic, no basic salt, and 6773 per cent, of copper ; the impurities being carbon from the iron, iron powder, ore particles and sulphur. The latter was in so small quantity that the cement was well adapted for immediate fining. An experiment in the large way resulted as follows : Amount of cement liquor (charge for one vat) 16-75 cubic meters. Concentrated acid 1 -25 litres (4 Ibs. ) Iron consumed to 100 copper 232 -00 Cement contained copper 75-3 per cent. Arsenic none. The importance of. avoiding the formation of basic salts Is seen from the fact that of the cement obtained in 1865 : 375,800 pounds contained only 58 57 per cent, copper = 220,106 51,790 " " 9-89 " " = 5,122 Total copper ppunds 225,228 Allowing 33 per cent, for impurities by the proposed method (see experiment in the large way) the production of cement to yield this amount of copper would be 297,007 pounds. As the amount by the old method was 427,590 pounds, we may look upon the difference, or 130,533 pounds, as the amount of the basic salts. These salts have the following composition : Sulphuric acid 35 35 Ferric oxide .43-21 Iron 30-24. Alumina 15-71 Zinc oxide 5-53 96-80 In addition to this they contain a variable quantity of water. The enormous consumption of iron, two and three quarter pounds, for every pound of copper precipitated, in 1865, is, therefore, partly due to the formation of these insoluble salts ; for they are formed by the union of a certain quantity of the soluble sulphates with the iron introduced into the vat. But the amount of iron thus taken up is only a little less than 22 parts for every 100 of basic salt, 01 about 29, 000 pounds of iron thus wasted in that year. This does not by any means account for the quantity of iron nsed. But an analysis of the liquor ob tained from Agordo ore, shows that it contained an average of one-hall per cent. AGOflDO. 17 of sulphuric acid. AB there wer 345,087 cubic feet of liquor, the amount of free acid was 108,340 pounds. The statement for 1865 would therefore be as follows: Necessary -to precipitate the copper 195,610 pounds iron. Taken up by basic salts 28,601 " 44 free sulphuric acid 72,226 296,437 Amount of iron used ". 640,800 Amount not accounted for 344,363 Thus we are unable to trace more than half of the iron which is consumed. If we allow 6 per cent for carbon and other impurities in the iron, and an equal amount for the iron sand always found in the cement, we should have a further deduction of 41,324 pounds. It may be that ore roasted in the lump contains more free acid than that roasted in bricks, which was used in obtaining the liquor analysed. It is a little remarkable, however, that the formation of iron salts in a liquor which contains oue-half per cent, or more of free sulphuric acid can be prevented by the addition of so infinitesimal amount of free acid as 14 liters to 16$ cubic meters; equal to 16,750 liters of liquor. 3. A third improvement suggested is the precipitation of the copper as a sul phide from the cement liquor. To do this, bydroge*n sulphide would be made by heating the rich pyrites with sulphuric acid, or passing steam over hot pyrites, the resulting HZ S being dissolved in water contained in a large chamber. The cement liquor would drop into this liquid and the copper be resolved into sulphide which would then be smel-ed. The objections to this method are the magnitude of the chambers and generators for hydrogen sulphide which would be required to treat about 345, 00 cubic feet of cement liquor yearly ; the necessity of manipu lating the copper sulphide rapidly to prevent its taking tire, and oxidizing to copper oxide which cannot be worked in the furnace without loss, and the d fficulty of handling and compressing so large a mass of sp ngy sulphide. Assuming the yield of 1865 as a basis we have the following estimate of what would be required for this process : 231,000 Ibs. copper requires 116,600 Ibs. sulphur to make copper sulphide. 116,600 Ibs. sulphur requires 220,000 Ibs. pyrites to furnish the sulphur. 116,600 Ibs. sulphur makes 1,400,000 cubic feet of H 2 S gas. One volume water absorbs 3 volumes H2 S. Water required, 470,000 cubic feet Or 1,513 cubic feet daily for 310 days. . As the amount of cement liquor, in 1869, was only 345,087 cubic feet, the volume of hydrogen sulphide solution would be more than that of the cement liquor. The iron sulphate would no longer crystallize out. Its production would have to be given up or the liquor concentrated again by boiling, which, considering its extreme dilution, would not be profitable. Thus Agordo is con sidering one proposition to greatly increase its production of copperas and an other, which may do away with it altogether. The circumstances by which the works are surrounded are such that there is no great difference in economy betwsen these two diverse proceedings. The town in situated BO far from routes of travel, that the pron a on c pperas are nearly 18 AGOHDO. swallowed np by the freights ; so that a very slight improvement in <ho yield of copper, or in the cost of working it, might determine the sacrifice of the crystal lization part of the process. On the other hand the demand for copperas is good ; increased make will cheapen processes, and if a great improvement in yield and cost can be obtained by a method which gives more of this article, there will lx> an advantage in making it. This advantage will be increased by. the fact that Bignor BE HUBERT S method gives a fine product. 4. The manufa tare rf cast or wrought iron from the residues of the lixiviation vats, is another suggestion which was under consideration . These residues, aa now produced, would give a cast iron containing about 6 per cent, of sulphur, which, with the present process, would do no harm. By the new method of roasting, the percentage of sulphur would be very much less and would indeed be as low as that of iron made from many good brown hematite ores. As the consumption of iron is about 300 tons a year and it could be made at the works for less than $20 a ton, while it now costs $30, the saving would be considerable. With the new system of roasting there is in fact no reason why good iron, which would readily find a market, should not be made. If wrought iron is made, an open fire will be employed and the uuharnmered bloom used instead of the pig. In 1869 the recommendations of Signor PEKLATI were confined to the manu facture of bricks, and the erection of a blast furnace to make cast iron. The other proposals were under discussion. The importance of these changes can be seen at a glance, by comparing the cost of the old and new works. In doing this I will assume that the manufacture oi bricks requires the same amount of labor as breaking out the kernels. We would have on the one hand the old process comprising the 7 operations already given, on the other, the new process with 4 operations as follows : Boasting, Lixiviation, Fining and Cementation. There would be a saving upon each ton of ore of about half a day s labor, 13 bushels of charcoal and most of the sandstone. This assumes that the efforts to precipitate in such a way as to obtain finable copper are successful. The importance to this country of a cheap method for the extraction of copper can hardly be over-stated. There is a vast quantity of 2 and 3 per cent, ore in the United States, lying in deposits that are already known, and scattered through all the States. Cheap and excellent processes are already in use, though not gener ally so. There are no statistics available for making an exact comparison between the cost by them and by the Agordo method. All that can be pointed out now is the differences inherent in these systems. One works with a very great economy of iron, and the other makes sulphuric acid as a by-product. In efficiency and cheapness they nre, so far as I know, very nearly on a par. The advantage of the Italian method is the extremely low cost of the plant. When the contemplated changes have been made, this expense will be confined to the erection of a few rough roasting sheds, lixiviation vats, and a fining furnace, if the amount "f ore will warrant it. The outlay for plant which the other systems require, is offset at Agordo by the interest, on the cost of mining. This interest, for 9 mouths, at one per cent, a month would, on ore that cost $2.50 to mine, amount to 23 cents a ton, and on ore that costs $10 to mine, (as it often does in AGORDA. 1C the West) 90 cents a ton. The other expenses by the new method will be about as follows : EXPENSE PER TON. Labor Wood- Charcoal Iron Sand days. cords. bushels, pounds. pounds. Making bricks 0-7 Roasting bricks 0-3 O03 I Cementation 0-15 0-030 18 Fining 0-12 2 10 * Total 1-27 0-033 2 18 10 To this there would be a small addition for crushing which could be done by a Blake or other coarse crusher. The copperas which is a by-product of this method, would be valuable only when the mine was so situated as to enjoy cheap and abundant transportation. It should be noted that this process is applicable to other and more valuable metals than copper. The careful roasting which retains 97 per cent, of the copper in the form of soluble sulphate would be equally effective with nickel and more so with cobalt These metals or a mixture of them with copper or iron pyrites can be treated by this process and app irently with great success. In fact ores that contain too little of them to be utiiizable by ordinary methods, ought to be valuable when brought under this treatment THE MERCURY WORKS AT VALALTA. 1 A FEW miles from Agordo there is a mercury mine, and, connected with it, an establishment for treating the ore which offers some peculiarities well worth con sidering. This is the mine and works of Valalta. The mercury is obtained from cinnabar found disseminated generally in minute threads and spots through a mass of decomposed porphyry. The rock also contains iron pyrites and gypsum, the latter being usually in contact with the cinnabar when it is concentrated in Bmall veins, as sometimes occurs. Hand specimens of pure cinnabar are found, but they are rare. As at Agordo, this deposit attracts the attention of the metal lurgist chiefly on account of its poverty, and the means used to work successfully an ore of so little value Three sorts of ore 2 are obtained by hand picking as follows : Good containing 2-5 per cent, mercury Poor " 0-25 " Powder " 0-25 " In one year 4,910,000k. or 5, 400 tons of ore were mined, and the mercury ob tained was 17,000 k. or 18-7 tons which gives an average yield of 0-346 per cent The loss as ascertained at the works was 0*10 per cent calculated upon the ton ot ore, so that the value of the ore is as follows : Yield 0-346 per cent. Loss 0-10 Mercury in ore 446 " It has been found that ore containing no more than one-eighth of one per cent can be worked in this furnace. The methods by which an ore containing only 4o-100ths of one per cent, is treated with profit, are as follows : The works are so situated that the sorted ore is run in cars on a tramway 1. For the information contained in this paper I am indebted to Signor MANZONI, of Agordo, lessee of the works, and to Signor TOME, manager. 2. A fuR suite of ores and products of the distillation works can be seen at the New fork School of Mines VALALTA. 21 directly from the mine to the top of the furnace, and this work is charged to mining account At the furnace it is thrown into a wood box, which is so made that it can be lifted up, and which is placed close to a hopper which forms the mouth of the furnace. In the roof of the latter there is a small pipe, with a cover which has a water joint By looking through this pipe the workman ascertains the condition of the ore in the furnace, and by thrusting an iron rod through it he ascertains the height of the materials. The normal height of the ore ia 3 5 meters or 11 ft 8 in. When it has sunk to this level a new charge is made, pro vided the surface is red. The slide of the hopper is withdrawn and the charge alreidyin it falls upon the hot ore. The slide is then closed, the iron plate which covers the hopper, and which also has a water joint, is raised, and the new charge is dumped in by tilting the box. Charcoal, to the amount of 2 per cent, of the ore, is thrown ou top and the cover is replaced. The weight of the charge is 480 to 560 k. 1056 1232 Ibs. and a new charge is made usually every hour and a quarter. The daily work of one furnace (24 hours) is therefore 9,120 k. or 10i tons. The furnace is a shaft, and docs not differ from the ordinary HAHNEK furnace. The ore rests upon a large grate at the bottom and after each charge the work man pulls down with a hook an equal quantity of spent ore. It falls into an iron wagon, running on a tramway, which is carried under the furnace by means of an arched way. The peculiarity of this furnace is its condensation. This is by tubes and chambers similar to those employed elsewhere, but the tubes are of wood and the mercurial vapors are drawn through the condensers by suction, an arrangement very important in its results. 1. It produces perfect draft, so that there is never a return of the vnpors to the furnace and out at the furnace bottom, as sometimes happens when the draft is natural With properly proportioned chambers the condensation is therefore also perfect, and the health of the workmen does not suffer from inhaling mercury vapor. In the 12 years during which this apparatus has been in use, there has been no general sickness, though formerly the hospital, usual to these establish ments, had to be maintained and was well patronized. But there are now no cases at the works, except (I believe) one or two which are the result of pure carelessness, or else remain over from old times. Another proof of its efficacy is the revival of vegetation in the immediate neighborhood of the furnace. In former times the lessee had a yearly expense of 30,000 francs in making good the damages by the fumes which escaped from his chimney. He is now entirely freed from this tax. 2. It ensures a constant and regular now of the vapors from the furnace to the discharge pipe, and thus enables the means of condensation to be properly pro portioned to the quantity of fumes, and the rapidity of their discharge. 3. It lowers the tension of the products of combustion in the tubes and chambers a little below that of the atmosphere ; the column of gases being some what retarded at the furnace end by friction of the air against the ore. For this reason when the traps in the tubes are opened there is no discharge of vapors, but, on the contrary, an entrance of air. The workmen are therefore able to collect 22 TALALTA. tha mercury and soot from the tubes without stopping for a moment the run of the furnace. This, together with the following, permits an uninterrupted cam paign of two years. 4. By keeping the amount of air admitted within regular limits, it prevents the overheating of the furnace. If this takes place the mercury vapors leave the furnace at so high a heat that the usual means of condensation are insufficient and a loss of metal ensues. It is to the excellent condensation and the two years run of the furnace, that we must attribute the economical results which permit an ore containing only 9 pounds of mercury to the ton of 2000 pounds, to be worked. The furnace with its arrangements for charging, condensing and draft is shown in figure 3. The following are the details of construction : Furnace : Height 6 50 meters. Diameter. . -. 1-20 " Inclination of grate, about 50 Number of grate bars 5 Width " " 0-05 meters Length " 1-60 " Height of gangway under furnace 2-20 " Width 1 30 meters. Sopper : Height 1-40 Length of mouth. .-. 0-90 Width " " 0-30 Length of slide 2.25 Charging box :. . .Length 1 90 meters. Height 0-80 Width -0-80 Tubes : Number to 1 furnace 3 Length of iron tubes in masonry 1*40 meters. " wood tubes, each section 1 70 " Number of sections in each tube 8 Diameter of tubes, mean 1 00 meters. Whole length of each tube as set up .... ^ 15-40 " Thickness of wood 0-05 Inclination 5 Condensation chamters : (The dimensions given are nearly correct.) Number. Height. Width. Length. 1st 5.50 1-20 3-00 2nd 2-40 1 20 300 3d 2-65 2-80 3-40 4th 2-70 * -oO 3-40 5th 2-80 2-80 3-40 6th ... : .2-80 ? Mn 3-40 7th 2-30 1 70 3-00 Cubical contents, cubic feet 5.082 Square feet of external surface 2,000 YAIALTA. 23 24 VALALTA. Chimney : Feight from arch of 7th chamber .10-00 Length of wood pipe 10-20 Diameter " " at too . 0-30 .... at bottom 0-25 Number of upright wood partitions 2 The Furnace is built with thick walls in order to retain the heat. The outer walls are built of slate rock and the lining of large red bricks. Every two years the lining is so worn, from friction of the materials, that repairs are necessary. After the furnace is thoroughly cool, the remains of the old lining are knocked out, from above, and the new bricks are laid with a cement composed of clay, iron filings and acid water from the condensation apparatus. This water con tains about 2 per cent, of sulphuric and sulphurous acid. In the outer walla common mortar is used. While making these repairs the workmen are employed only 2 hours a day to avoid sickness from inhaling mercurial dust, as the bricks contain a good deal of the metal. The expense for repairs is, however, slight After two years, the necessary repairs cost only 150 francs for labor and 50 francs ior material ; labor being worth about 12 francs a day. With very hard bricks which could resist the friction of the ore, there is no reason why the furnace should not have a still longer campaign. The first cost of a double furnace with two shafts, 14 condensation chambers, 6 tubes, and the necessary arrangements for supplying water, is, in Valalta, 20,000 francs. As before said, the furnace with its hopper corresponds in all respects to that invented by HAHNEII. The Condensation Chambers. Tnose nearest the furnace are lined with a cement similar to that used in building the furnace. It is made of ground scoria 2 parts and lime 1 part. The scoria which is much more serviceable than sand, must contain a good deal of iron, as scorias from puddling or rehea ing furnaces, copper smelting, etc. That used at Valalta is procured in the copper works at Agordo. Those chambers which are placed beyond the tubes are lined with wood 2 inches thick. This is another peculiarity of these works. The wood not only forms a perfectly tight lining when it has been properly seasoned before use, but it affords cleaner mercury and also more of it during the campaign, from the fact that less metal and soot cling to the smooth wooden surfaces than to a cemented wall. Thus, after the first and second chambers, where the vapors are still too hot to permit the use of a wood lining, the fumes have an uninterrupted course through wood or wood-lined passages. After many experiments with cements, bricks, etc., this material has been found the best. The Tubes are also of wood, 2 inches thick. They are made in sections, slightly conical so as to fit into each other. Wooden wedges, driven firmly into the joints, make the whole tight. Iron tubes were formerly used; but they made a great deal of trouble, being rapidly eaten by the sulphurous acid vapors, emanating from the pyrites in the ore. They had to be turned every 12 or 18 months and entirely renewed in 2 or 3 years. Iron tubes for one furnace cost 8,000 Austrian florius ; wood tubes 2,050 florins. But of this sum the 3 iron rings on each section of wood tubing cost 1,200 florins, and as these remain uninjured, the cost of renew ing the wood tubing would be only 850 florins, (about $357). But the saving ia even greater than this. Though the wood tubes are kept constantly wet, their VALALTA. 25 durability is much greater than that of iron, and I believe they have been renewed only once in 12 years. A main fault of the iron tubes is that the soot obtained from them is contaminated with iron dust and iron oxides, which makeg t.ie separation of the mercury from the soot more difficult, and also introduces a cer tain amount of iron into the metaL All these advantages cheapness, durability, and serviceableuess give to wood a great superiority when it can be used. Iron tubes are still used for the sections set in the masonry of the furnace and the chambers, but all other sections are \vood. It requires a constant and pretty heavy flow of water, and the wood must be of a kind that endures a condition of moisture as long as possible without rotting. Fir and pine are used at Valalta. / Each tube section is bound with 3 iron rings, driven on to the conical tube. Two trap doors are made in each tube, one in the top and one in the side. Through these openings the workman with a long handled hoe, the blade of which is small, draws the soot and mercury on the bottom of the tube to one place and then removes it with a scoop. During this operation his face is protected by a wet sponge placed over the mouth and nostrils. This precaution should never be neglected, though when the trap is opened the appearance of the tube makes it evident that there is little danger of the escape 01 vapors. The products of com bustion are seen as a bluish gray, dense and moist cloud, moviug slowly and regularly through the tube, and there is no escape whatever through the open trap ; an accident, which if it occurred, could not escape observation, from the strongly marked color of the fumes. But as the workman has his arm at times partially immersed in this cloud, and his face is therefore brought near it, the necessity of using the sponge, as a matter of precaution, is evident. On the bottom of the tube, mercury soot, and metallic mercury lying in small pools are seen, the bright surface of the metal reflecting the light which enters through the trap, and illuminating the tube immediately around it. The course of the vapors is as follows : from the furnace to condensation chamber No. 1 which has about the same height as the furnace ; from No. 1 to No. 2 ; from No. 2 through the two lower tubts, each 15 meters long, to Nos. 3, 4, 5 and 6 in succession. These four chambers aiv so connected that all the fluid mercury collects in No. 5, whence it flows through an iron pipe to a kettle placed in a reservoir outside, fed with running water. Both metallic mercury, and mercury white collect in this kettle. Very little soot, and that very poor, collects in the chambers 1 and 2 next the furnace. Most of it falls in the two lower tubes, together with some mercury. A good deal of the latter flows into chambers 3 and 4, and runs into the kettle above mentioned. With so long a campaign it is necessary to collect as much of the metal produced as possible, while the furnace is still in operation ; and the arrangements at Valalta for doing this are very per fect. From chamber No. 6 the vapors pass through the upper tube to No. 7, thence to the 1st partition in the chimney, where they rise to the top, return downwards to the second partition, rise again through the 3d partition and finally leave the furnace by a square wood pipe which, turning downwards, rests upon the side of the chimney, and finally at the level of the tubes, or a little ab >ve, opens Into a water trompe. This has a fall of 5 or 6 meters, discharging its water upon u wooden floor placed under the tubes. This floor, which is carefully made, .so 26 VALALTA. as to be water-ana mercury -tight, slopes from the furnace to the condensation house, where the water runs off th rouuh a trough, which in. its turn empties into a cistern, in order that, by arresting the rapidity of the flow, any mercury that may have found its way to the floor may have an opportunity to settle. There are two ways in which the metal may arrive on the floor : 1st. by leaking through the joints of the tubes ; 2nd. by escaping condensation in its cour e through the various passages until it meets the stream of water. But very little does escape, however, only a few drops ever appearing on tbe floor or in the cistern. I do not know that any thing of importance has been collected from those places. The Charge consists of the ore as it comes from the mine, and ot bricks made up of fine ore. Much trouble was experienced at first, in making these bricks hard. It was found that to produce a good brick, which would not fall to pieces in the furnace, the ore must not be coarser than one centimeter (04 inch) and must be cemented with some substance, like water containing sulphurous acid, or iron sulphate, which by attacking slightly the surfaces of the clay and gyp>um in the ore, would act as a cement. The liquor in use is that which serves to con dense the last condensable matters in the fumes, and is said to contain 2 per cent, of sulphurous acid. The bricks are made in moulds 10 centimeters (4 inches) high, and with a mean diameter of 15 centimeters (6 inches)- They are dried on iron plates. About one-third of the ore. is charged in this form ; but the charge is sometimes one-half coarse ore and one-half bricks. The Loss in working is, according to the assays continually made at the works, 224 per cent. ; or 0-10 per cent, of the ore upon a content of 0446 per cent, of mercury. The Products of the distillation are : 1. Mercury. This is very pure and brings the highest price. It is all consumed in Italy and Austria. 2. Mercurial soot. This is composed of mercury in the state of powder, mixed with a little ore powder, mercury sulphide, charcoal powder, etc. It is brought to nature by rubbing it on an inclined table, when the grains of mercury powder coalesce by friction and collect in drops at the bottom of the incline. The remainder is made into-bricks and re-distilled. 3. Mercury white, which forms but a very small proportion of the product. The spent ore, as it is discharged from the furnace, is not very hot, gives out no vapors of mercury and only a slight odor of sulphur. The Labor employed consists of 2 men to each furnace ; length of shift 8 hours ; or 6 men to 24 hours. They bring the charcoal, make the small ore into bricks, charge and discharge the furnace, collect the soot, work it over to extract its mercury, and pack the mercury in sacks of kid skin which are afterwards placed in small kegs. Thus the 6 men complete the personnel of one furnace. They are paid at Valalta an average of 1 -20 francs (24 cents) a day. Two furnaces require a double number of men. The Fuel is pine and fir charcoal costing 7 francs a cubic meter ; or 5 cents, coin, a bushel, very nearly ; 600 cubic meters or 18,875 bushels are used for two furnaces yearly. 1 he Expense of Treatment was given by Signer TOME as follows : VALALTA. 27 COST OP TEEATINQ 10,000 K. ORE PRODUCING 34 6 K. MBRCTBY. Francs. Proportions. Distillation (labor) ] 5 02 25 Working soot 0-05 0-1 Royalty paid on production 2-30 4-Q Materials . : 24-78 42 Kepairs : labor and materials 1-35 2-4 Running expenses 43-50 73 5 General repairs 3-72 G.3 Administration 11-90 20.2 Cost of distillation 59-12 100*0 Cost of mining 134-73 Total cost of 34-6 k. mercury 103-85 Cost of 1000 k. ore, francs . . . 19 -39 Cost of 2000 pounds S3 -53 The cost is therefor $3-5b for one ton of ore producing 6 92 pounds of mercury, or 51 cen s a pound. The expense for abor and materials upon one ton of ore (1000 k.) is as follows ; both labor and materials being included under the head of "repairs." Labor. Charcoal. Running General Repairs. Repairs. For 1000 k 1 -G4 d. 84 Ibs. 2-7 cents. 7 5 cents. Proportionate parts. Total cost = 100. . 33-5 55-20 3-00 8-30 Mining cost per ton (2000 Ibs.) $2-45 or 69 Distilling 1-08 or 31 $3-53 100 Though comparisons are never more to be distrusted than when made upon ores of mercury, mined in distant districts and worked in furnaces more or less dissimilar, it is nevertheless instructive to set the results of the Valalta furnace against those in other works. The distinctive characteristics of the HAHNEB furnace is, that it is a shaft and that it works continuously instead of intermit tently. Other furnaces are either of the reverberatory form or, if they are built like a shaft, they are intermittent, being filled, fired and cooled down at each operation. Between the HAHNER furnace at Valalta and those at Idria in Austria and Ripa in Italy, theie are two important differences that of drawing air regu larly through the furnace, which is not done at either of the last mentioned places ; and the condensation, w r hich is by large Chambers and not by tubes, as at Valalta. The work in these furnaces shows some notable differences. At Idria 3 the ore is charged with 3 to 4 per cent, of charcoal every 1^ houit*. The ora contains , 3-11 per cent mercuiy. ihe yield is 1 90 Loss therefore 1-21 or 38-9 per cent At Ripa* 3. Berg. & Hiit. Ze/unp, 1854, p. 419. 4. Bull. d. 1. Soc. Ind. Min. II., 383. 28 VALALTA. The charge in ^4 hours is 8,800 pounds. Charcoal 352 " or 4 per cent The ore contains 1 per cent. The yield is only 25 30 per cent. The system of condensation by chambers is not so thorough as that by tubes and at Idria and Ripa the condensation is further hindered by the excessive amount of charcoal used, amounting to 50 and 100 per cent more than at Vaialta. This must add very greatly to the temperature of the gases. Whether the regular and moderate flow of air produced by the trompe would effect a re duction of the amount of fuel cannot be told without experiment. The ores are practically the same, except in regard to richness. It should be remarked that poorer ores at Idria require more charcoal. THE LEAD WORKS AT MECHERNICH. ON the left bank of the Rhine there is a sandstone layer which covers a surface several square miles in area and for a thickness of more than 100 feet, contains lead in the form of sulphide aud carbonate. The rock contains but little lead ore, from 2 to 3 per cent only, but it is so friable as to break up to sand by the mere shock of the blast, and a simple but careful concentration permits the treatment of ore so poor, even, as this. Although this ore does not resemble that which is so common in Utah and Nevada, either in mode of occurrence or in appearance, it has about the samo composition. The product consists of about 42 per cent, galena, 28 per cent lead carbonate, and 30 per cent, quartz and clay. But these proportione are not exact. The amount ol silver varies from 0*007 to OO11 per cent, or 2 to 4 ounces to the ton of washed ore. The general mode of treatment is by roast ing and subsequent fusion with puddle slag and sometimes with metallic iron. There are two works, those of the Mecher- nich Company and those of Messrs. PIRA.TH & JUNO. Three kin Is of ore are ob tained. Smelting ore, "glasur" ore used for glazing earthenware, and white- lead ore, part of which is worked up to paint by RHODIUS BROTHERS, near Linz, on the Rhine, by means of the gas which issues from natural gas wells. THE MECHERNICH COMPANY. RAMMEIASBEBG gives the following proportions as the average product of these sorts, at this establishment :* Smelting ore 20,900 tons containing 58 per cent lead. Glazingore 1,925 " " 6280 " " White lead ore 660 " " 50-52 " " BOASTING. The ore is roasted in furnaces which have a hearth 33 feet long and 12 feet 6 1. For information contained in these notes on Mechernich, I am indebted to Herr EKENHUT, chemist to the company. 2. A full ffuite of the ores and furnace products of the Mechernich Company are in th cabinet* of the New York Hchoul of Mines, 30 MECHERNICH. inches wide. The roof is made of hollow bricks to lessen the weight and the enormous thrust of an arch so very flat, a weight which soon causes the falling in of an ordinary roof. These bricks are 13i inches square, 9 inches high, and have a deep depression in their upper surface so that probably two-fifths of the material is removed. The doors are formed of a cast-iron frame set in the brick work, the iVame being 2 feet long, 1 foot high and with an opening 8 inches square. This opening is closed by a cast-iron plate. Figure 4. Figure 5. Figure 4 shows the form of the bricks and figure 5 that of the iron castings for the doors. A cast-iron box on the top of the furnace receives the ore while it is drying. About ninety centners or 9,900 pounds are charged every 12 hours, so that the furnace roasts 9 to 10 tons daily. The rapidity of the roasting depends somewhat upon the proportion of carbonate in the charge. When there is much of this, the roasting is rapid ; and the large amount passed through these furnaces is also due to this ore. At Freiberg, where the ore is altogether sulphide, the furnaces cannot work so much. The Mechernich works have 10 of these furnaces. The management of these furnaces is peculiar. The ore lies in a much thicker layer than is usually allowed, and toward the fire-place it is heaped up nearly to the roof, in the cuter sloping away to the sides, where the gases mostly pass. Next the fire-place there is a depression in the hearth, called the crucible, de signed to receive the ore which is completely melted toward the end of the opera tion. The ore forms a broad bank at the edge of this crucible, and in immediate contacv with the flames. It smelts rapidly, an! as fast as the melted ore runs down into the crucible the ore behind it is pushed forward. But it is evident that this method of treatment is not favorable to the liberation of the sulphur, a process which demands the most complete access of air, and access is prevented in these furnaces by the extreme thickness of the ore layer. Accordingly wo find that although the ore cannot contain more than 5 per cent, sulphur, as a great part of it is already oxidized and there is no pyrites present, the roasting is still far from perfect. When the ore arrives at the crucible it does so with its galena probably not more than half roasted and the melting down of the fine and intimately mixed quartz and lead oxides is then so rapid that the galena is covered with a glaze of slagged ore. It is carried down with the latter into the crucible and forms a layer under it I should judge the furnaces were producing, at the time of my visit, fully 20 per cent, of this unaltered galena. This artificial galena is very much richer in silver than the ore which has been converted into silicate ; a circumstance which is due to the stronger chemism between silver and sulphur than between silver and oxygen. An assay was made at my suggestion of the oxidized ore and the unaltered galena from a furnace, MECHERNICH. 31 which unfortunately for the trial, was running on very poor ore, containing about 25 per cent. lead. , I. The unaltered galena contained 0-055 per cent silver or 7 3 ounces per ton. II. The lead silicate " 0-008 " 2-3 To prevent the formation of this product a new furnace has been built. It has two hearths, an under and an upper, with 75 feet of hearth length. This is a success in so far as its roasting is better, its product being an almost com pletely homogeneous silicate, with but fow particles of galena distributed through it. in repeating tais experiment a furnace has been built with a total length of hearth amounting to nearly &2 feet The result has not been made public. There is, however, one difficulty connected with the reduction of the sulphur to so small an amount Under the old circumstances a certain quantity of matte, about 2 per cent of the charge, was formed and collected at the bottom of the conical pots used to receive the slag. But a less quantity than this would probably elude col lection and have to be thrown on the waste heap with the slag. A certain amount of matte is always retained by the slag, either in solution or in minute drops mechanically held. If the sulphur ccn be reduced to the amount which the slag has always retained in this manner, there would certainly be a gain ; but if the liberation of the sulphur is not carried so far, but still far enough to make the col lection of the matte impracticable, there would be a loss. In roasting by the former method it was impossible to ascertain the progress of the opera; ion, for the mass of ore in the furnace was by no means homo geneous. The amount of galena which passed un changed through the operation proved that it was very incomplete. la the new furnace, however, the amount of sulphur liberated can be ascertained ; and with ore containing 6 -5 to 7 -5 per cent, sulphur, cor responding to 48-5 and 56 per cent galena, the roasted ore has 1-5 to 1 per cent, corresponding to 11 2 and 7*5 per cent galena. The larger of these quantities, 1-5 per cent, sulphur, corresponds to an amount of matte equal to about 6 per cent of the ore ; but this would be very much les sened by the sulphur dissolved in the slag. Assum ing that only one-halt the sulphur was formerly eli minated in roasting, we find that about 3-5 per cent of sulphur in the shaft furnace gave about 2 percent, of the matte. Reduced to 1-5 per cent, the sulphur would probably all be absorbed by the slags, and the new method would therefore be advantage ous. It is hoped, however, that the ore can be Figure G. T.eart fur nace at Slecttrrnich. A Charging Poor. entirely freed from sulphur, or the latter reduced to less than one per cent at most, and in that case there would be a considerable saving by the better roasting. FUSION. The Furnaces in which the roasted ore is smelted, arc shown in figure 6. They 32 MECHERNICH. are built of ordinary red brick. They are 15 feet high, and 4 feet square, and have 4 water tuyeres, which are of the built up kind, the back piece being bolted, instead of cast, on. These tuyeres have been discarded in most works. The fur naces are closed at the top by a brick flue, the gases being led to high chimnies which complete the system. Other dimensions are as follows : Height of furnace 15 feet Section, square 4 X ^ " Height of slag hole above tap hole 14 inches " " side tuyeres above slag hole 10 " " back tuyeres above side tuyeres 6 " " " " " tap hole 30 " Length of tuyer 30 " Diameter of tuyer outside 14 " " interior 1| " Material of furnace Ked brick. f Coal ashes. Material of hearth, brasque made of -J Clay. ( Coke dust A round furnace had just been finished at the time of my visit, designed accord ing to the principles which gave such success to the Freiberg furnaces. Its dimensions were as follows : Height 15 feet Diameter at top 6 * of hearth 4 " Air is supplied at a pressure of 9 inches of -renter by two fans made after especial designs. They have the usual tapering vanes and do extremely good service. Their dimensions are . Diameter 5 feet 6 inches. Width of blades at center of fan 10 " " " " circumference 6 " Diameter of conducting pipe 10 " [Revolutions per minute, maximum 1200 " " " when regularly working 800 Only one fan is in constant use, the other being kept in reserve. In the blast house the pressure is 10i to 11 inches of water, which diminishes to 9 at the fur naces. At the time of my visit this ian supplied 5 shafts and 1 cupel furnace. The Charge. It has been found that a slag which is to be free from lead must contain at least 40 per cent, of oxide of iron, and as the Mechernich ore contains none of this metal, its only impurity being a very small amount of copper, iron has to be added to the charge in some form. For this purpose puddle slag is brought from Eschweiler near Belgium, and when t! ere is any raw ore, or much unoxiclized galena in the charge, a small quantity of cast-iron is also added. The charge is made up as follows : Boasted ore 5658 per cent, lead 100 Puddle slag 50 Limestone 48 Iron 2-5 203 Coke = 9-9 p. c. of charge or 20 p. c. of ore ... 20 MECHERNICH. 33 At the time when the charge above given was taken down, the works were compelled, for lack of sufficient number of laborers at the roasting furnaces, to add raw ore, which accounts for the iron in the charge. It will be observed that the amount of coke used is very small, a consequence of the fusibility of roasted lead ore. About 35 tons oi charge are smelted in 24 hours. Products. From this operation are obtained : Lead containing 0-0140-027 per cent silver or 4 8 ounces to the ton. Matte containing 10 per cent. lead. Slag containing -75 1 per cent lead. The slag is received in iron pots 2 feet high, 16 inches in diameter at the top and 6 inches at the lower end. In these the matte settles to the bottom, nearly every block yielding 1025 pounds. But to make this settling of the matte sure, it is indispensable that the pot be rapidly tilled. When this system of dra wing- off slag was first introduced, several trials were deemed unfavorable which failed only because the slag was allowed to drop slowly into the pot, and the lower half of the contents became solid before the upper half ran in. Perfect fluidity of the mass is necessary for the settling of the matte, and for this reason the furnace must be a closed one ; a form which has many advantages besides the collection of small quantities of matte wbich might otherwise be lost DESIXVEBIZATION OF THE LEAD. In former times three out of the five systems of desilverization by zinc were practiced at Mecheruich and in its neighborhood. The differences, ae with all these methods, were iu Uio method of dezincing the lead after the silver had been removed. Thei> three methods will be considered in describing this and the following works. At Mechernich the kettles hold 11 to 12 tons each. The zinc amounts to one and one-twelfth percent, of the lead and is added in 3 portions : (1) 0-75 per cent. ; (2) 25 per cent. , (3) 083 per cent. On 11 tons this is 1G5 55 and 184 pounds ; total 2384 pounds. The zinc alloy is ladled into moulds aud the pigs are heattd in a tube slightly inclined. By raising the temperature gradually a good deal of the lead runs out, leaving an alloy much richer in bilver. Toward the end of the operation the alloy is stirre 1 with a rod until it becomes quite " dry," and has the form of lumps or shot It is then melted and cast Its silver now amounts to 1-5 to 2-5 percent, but much richer alloy is sometimes ob tained. The lead which runs from this tube contains 0-012 0-020 per cent silver and passes again through the process of desilverizttion. Treatment of the rich alloy. These works long retained *he old method, rejected everywhere else, of fusing the rich alloy with puddle slag to reinov^ the zino. The fusion of silver at a high temperature in the presence of zincsh ulrl, accord ing to all laws of metallurgy, be an opera ion attended with considerable loss, and great care was taken to make this as smalt as possible. T.ie furnace was 10 feet high and 2i feet square, and had 3 tuyere*. It wis first started with puddle slag alone, and when this was flowing freely, the alloy was charged. To 100 of alloy 90 parts of puddle slag were added and smelted with 1718 coke. The pressure of the blaht must not be more than 6 inches of w^ter. 84 MECHERNICH. Abor.t 7,700 pounds of this mixture were smelted in 24hours, and the loes ia said to have been not mere than 1 per cent, of lead at the outside. The poor lead is de-zinced in a similar manner. It is charged with puddle slag in the proportion, of 100 lead : 4 to 6 puddle slag, and 3 to 4 coke. It is then poled and cast. It is very pure, as the ioilowing analysis by Mr. EISENHUT, chemist to the Company, shows : Silver 000025 Copper. 0-0025 Antimony 0-0050 Iron -0030 Zinc trace. Nickel 0-0021 Lead by difference 99 98715 100 THE NEW PROCESS. Within three years the method pt de-zincing by steam has been introduced at Mecheinich. \Vhen the third allo] has been taken off, steam is introduced lor two hours, the lead being kept at a red heat, and covered with a close hood. Then the hood is opened to allow the air to euter and the passage of nteana is continued one hour, to remove the antimony. The new method produces more scraps but saves in labor. Its chief advantages, however, are the more perfect removal of antimony and the complete removal ot the nickel, which by the analysis last given is seen to be present in small quantity. What alteration the change has had upon the quality of the lead is to be seen from the following arerag< of two analyses, made by Mr. EISENHUT upon lead produced by the steam process : Silver 0-00052 Copper 0-00175 Antimony 0-00405 Iron 00064 Lead by difference 99 9931)4 100 The rich lead, now freed of its zinc, is poled for one hour in a kettle, and cupelled in an English furnace, having the ordinaiy elliptical test, with axes of 3 and 4 feat. The run lasts 5 to 6 d.tys, 13,000 pounds we ght of lead is cupelled. and the button of silver weighs about 150 pounds. The tuyere ia a pipe 2 inches high and 6 inches wide, the blast parsing through a zinc pipe 3 4 inches in diameter. It is the experience of many works, that a large tuyere oi this kind mnkes poorer litharge than one with a narrower orifice. Treatment of the Matte. Matte amounting to about 2 per cent, of the ore s weight is obtained from the fusion of the ore. It is roasted and smelted with lead scraps to second quality lead. This contains more antimony than the first lead, but still considerably less than one percent, though sufficient to give it a silvery whiteness. It is partly made up into shot, an old shaft in the mine serving for a shot tower, and the shot being made on English and American account. MECHERNICH. 35 THE COMMERN WORKS. . PIRATH & JUNO have a similar establishment in Commern near Mech- ernicb, and treat ore from the same sandst >na Uyer. Their mine, howuver. produces less galena iu proportion to the lead carbouute than the other, and they consequently have le*8 unaltered galena in the ro isied ore. The record ( two of their roc sung furnaces for three weeks is interesting : Furnace No. I. Furnace No. II. Coal Ibs. Ore Ibs. Coal Ibs. Ot>< Ibs. August? 28400 180.500 32200 18(5500 " 14 30400 176,000 31800 188750 " 21 29,400 190,000 30,200 203.000 88200 546 500 94,230 578,250 Total ore roasted 1,124.750 Ibs. " coal consumed 182400 * This amounts to a consumption of 16 21 pel cent, of ecu!, and a daily product of 53,580 pounds from two iurnaoe*. Tiiere are no analyses of the roasted ore at baud but its composition is precty nearly : silion35, lead oxide 55. clay, iron, sulphur, copper and antimony, 10. Liuientoue is sometimes added iuroustiug j but only where there is too little, lead present. The lurnaces have the following dimensions : Height 14 feet Section 4y4 Tuyeres 4 " height above tap 17 inches The material is red brick and the campaign usually last 3 to 4 months. The charge is composed of Roasted ore 44,000 pounds. Unroasted ore 9,900 Limestone 18,900 " Puddle slag 27,500 Coke 11 12 per ceut 11,66012 6*0 The amount reported to be p.issed through these furnaces daily is enormous ; amounting to 132.000143,000 pound*, and if the Mechernich work , with the same ore and the same furnaces smelt only 38i t:ns in 24 hours with 10 per cent, of coke, it is hardly possible that the Com cue ru works put through 6610 71 tons with 11 to 12 per cent, of iuel. The latter qunti<its are !ul*y equal to the largest charges tue much larger furnaces of Freiberg have run through, wheu tlu- ohmrge consisted almost entirely of fusible slag. Each furnace at Commern produces 27,500 28.600 pounds of lead daily. Tue slag is reported to contain 0-30-4 percent kad. and the lead about 6 ounces to the ton. Iu the method of desilveri nation (before the introduction of the steam pro cess) there were some differences from that pursued at Mochemich. Alter rseltiug in the kettle the lead way first poled to remove all impurities. Poling consists in plunging a stick of green wood in the melted metal, which is hot enough to ciiar i: rapidly. It gives out a gre.it quantity of gas, partly composed 36 MECHERNICH. of steam from tb9 large amount of water contained in green wood and partly carburetted compounds reeultmg from the decomposition of the fibre. Tho escape of these gases throws the bath into violent ebullition and every part of the metal is brought to the surface, where the lighter alloys of iron and copper with zinc remain. As at the neighboring works 1-08 per cent, of zinc is added in three operations, but the amounts are varied, being 1st. 0*66 per cent., 2nd. 34 per cent., 3d. 0-083 per cent. The chief point of difference is in the treatment of the poor lead, in order to free it from zinc, the old method, suggested when the zinc process was first in vented, being in use. The lead is melted in a reverberatory furnace under a lnyer of coal, on which is a layer composed of salt 2 parts, sand 1 part and lime 1 part. The furnace holds 22,000 pounds lead, which it is treated for 8 to 9 Lours and the product is best selected" lead, the purity of which is sufficiently proved by the following analysis made at Clausthalin 1869 : Silver ; . 0023 Copper 0034 Antimony 0081 Iron 0-0013 Lead by difference 99-9849 100 THE WORKS AT CALL. The works at Call 3 were established tor the purpose of working over old slag, felt by the Koniaus, or some less ancient people, and this material is still treated, but the bulk of the the lead is made from purchased ores. Tha latter are obtained in Westphalia and also at Stolberg. They are mixed with brown spar, copper pyrites, and zinc blende ; the lead contains about one-half per cent of antimony. Of silver the lead contains about 0-025 per cent, or 7 -3 ounces per ton. A* at Mechernich the ore is first roasted ; the furnace being 45 feet long and 7 feet wide with double sole, which gives 90 feet of hearth length. This furnace w ll hold about 88.000 pounds of ore, which is charged every 6 hours in poi-ts of 3,300 pounds. Four ponts are drawn daily so that 13,200 pounds or 63 tons are roasted daily. Like the Mechernich furnaces there is a deep hearth next the tire place \\here the roasted ore is melted, and tBe furnace" is tapped every 12 hours. From these figures it will be seen that the ore remains from 6 to 7 days in the furnace. The blast furnaces at Call are remarkable in these days for having but one tuyere. They are 19 feet high, 4 feet from front to back aud 3 feet wide. The top is closed by a hopper built of brick and lined with cement. This hopper is large enough to contain one charge. It is closed by a slide which, being pulled out, lets down the charge. The hearth is narrowed a little to prevent the <or- niation of sows. About 16| tons of charge are smelted in 24 hours, i he blast is by fans and the pressure 8 inches of water. Another furnace is square and has 3 tuyeres. 8. PreuBB Zeitechrift, 1868, p. 288. MECHERNICH. 37 BBPABATION OF SILVKB. The lead which on an average contains 250 grammes silver in 1000 kilograms, or a little more than 7 ounces to the ton, is melted in kettles of 7 feet diameter aud 22 inches depth, holding about 25,000 pounds. The dross is taken off, the lead heated until zinc melts readily on it, when 198 pounds of zinc is added, stirred for half an hour and the whole suffered to cool until the zinc solidifies on the surface, when it is taken off. This zinc crust is at first about 3 hues thick but the removal of the surface lead is continued until the lead begins to crystal lize which, it has been found, takes place when about 2 inches of the bath havo been removed. The first charge of zinc having been taken off the kettle is filled up with liquated lead, (see below) 68-2 pounds of zinc are added, and after a repetition of the above process a third charge of 38-5 Ibs. is put in. By these three charges 304 7 pounds of zinc have been added or close on 1J per cent, aud the silver lelt in the kettle is red need to 0-00055 per cent, or 0-16 of an ounce. The source from which this liquated lead is obtained will be seen below. The lead originally contained about 0-15 per cent, of antimony and 0-2 per cent of copper. It now has nearly all the antimony concentrated in the re maining lead, but is nearly Iree from copper, which has followed the silver in uniting with the zinc. To remove the zinc a method was formerly employed which w.is the invention of Mr. HEIJBST, one of the proprietors of the works. It is to this gentleman that metallurgists owe the ro-introductiou of the zinc process after it had lain many years neglected. His improvements and perseverance established the process on a successful basis lor the first time, and the remarkable advances rnnde in thi* metho/ during the last ten years had the following process for a starting point, though it has siuce been abandoned in nearly every works. The lead containing zinc was heated to a dark red and covered with an inti mate mixture of 110 pounds salt and 320 pounds lead sulphate. Fur lead con taining 0-6 percent, of zinc, about 330 pounds of th.s mixture was charged to each kt ttle. Soda sulphate and zinc chloride were formed, but the larger part of the zinc must have been removed as zinc oxide. For 24-750 Ibs. lead at 0-6 p. c.coutaiu 1485 pounds of zinc, requiring 163 pounds of chlorine to make ZuOt. But the 110 pounds of salt charged contain only 77 pounds of chloriue, very much of which remains as sodium chloride. The salt slag" remaining cou- biited of unaltered sodium chloride, lead sulphate, mingled with zi.ic oxychlo- ride, soda sulphate and metallic let.d. After twenty-four hours the zinc was all removed. The lead now contained no impurity but antimony, and it was with a view to the removal of this troublesome in..redient that the peculiar krttles used at Call (and I believe no where else) were designed. Antimony cannot be removed by steam, but requires for its oz dation the slow action of air upon the heated lead. When steam is used for the removal of this metal, as at Mechernich and many other works, it acts merely as a mechanical stirrer of the lead, throwing it up and changing its surface constantly, so that every particle is brought in contact with the air. 38 MECHERNICH. At Call after poling the lead for half an hour it is kept a long time, u-ually 48, Bometirnes 72 houis at a red heat, and covered by a layer of lime which prevents the volatilization of the lead, but does not hinder the access of the air. Lead containing up to one per cent, of antimony can be softened in tLis way ; that at Call sometimes reaches one-half per c<mt. The complete removal of the antimony is ascertained by casting a small ladle- ful of the lead in a scorifier or assaying crucible. So long as this contracts in cooling leaving a crystalline star in the centre, antimony is indicated. But when there is merely a depression in the centre of the button, with no star, the process is known to be finished. From these operations results a metal of great purity as the following analysis shows : Silver , 00005 Copper ,. 0-OOOt Ant irnony 0008 Iron 0-0019 Bismuth 0023 Thulium 0-0003 Lead.. ..99-9938 100 EEMOVAL OF ZINC BT ACID. Tbe innnngemer.t of the zinc alloy is peculiar. The ; Hoy produced by the second and third charges of zinc is kept separate from that obtained from the first addition of zinc. The former is very much adulterated with lend. It is melted in a ket le, the alloy rising to the top, while a " liquated lead " contain ing about 3-5 ounces silver to thu ton remains under it. The temperature is raised nearly to bright red, at which the overlying layer oi alloy oxuiiz ;*. When, this oxidation is complete, the lead is drawn off by a spout, leaving the oxides vmn nearly all the silver beh nd. Tbe lead goes back to the second and third additions of zinc as before said. The oxid-s are mixed with about one-half tveir weight of chlorhydric acid, at first in the cold and afterwards the solution is completed at a low heat. When this operation is finished the liquid is evaporated until it becomes thick, a sign that all the water is removed. Then the alloy resulting from the first charge of zinc is Rddfr d. In this the lead und zinc are still in the metallic state and a reaction sets in ; the zinc is all converted into chloride and tha lead and silver mostly to metal. This process takes 24 hours. By this means a rich lead containing 1-5 to 2 per cent, of silver is obtained ^rliich is cup^li^d. The method has the advantage 01 superseding the deziucing r>f the alloy by steam, an operation not free from hazard, and one that .s always H dis urbmg element in the zinc process. The residue contains from 20 to 55 per cent, of lead chloride, the remainder hein^ zinc chloride with ]? 25 ounces to the ton. We have seen that the zino in the 2nd and 3d alloys was transformed into ziuc chloride by treatment with lead sulphate and sodium chloride at a high heat ; the result was soda sulphate MECHERNICH. 39 and zinc chloride. Precisely tho opposite reaction is now produced by mixing these residues containing lead chloride, with "suit slag " obtained in do-zincing the poor lead, and treating them with water acidified with chlorhydrio acid. This acid changes the zinc oxychloride to neutral ziuc chloride, which is soluble. Copper chloride and silver chloride are also dissolved, ihe latter in consequence of the other chlorides in solution. But the lead chloride is tr<ms- f Trued to insoluble lead sulphate by reaction with the soda sulphate. We havo then the original mixture of salt and lead sulphate restored. After settling, the liquor is ruu to a vat containing copper where the silver ie deposited, and to an other containing iron where the copper falls down. By these separations the liquor now contains nothing but zinc chloride, and iron sub-chloride. The addition of chlorine transforms the latter to per-chlorido, which is precipitated by lime. The remaining solution of zinc chloride is heated and the zinc precipitated as oxido by pure lime, super-saturation, being carefully avoided. The zinc oxide is finally distilled to metallic zinc. This process is an excellent example of a simple method of treating the rich alloy by acids, a treatment which in m my places is forbidden by the high price of chlorhydric acid. It does not appear that the acid is particularly cheap at Call, but the small percentage of silver in the lead, and the consequently small amount ot alloy to be trcaiecl, gives the acid meth >d advantages over the treat ment by fusion with slag, or by steam. The silver is obtained more quickly than would be the case if the rich alloy had to be accumulated until enough was at hand to fill a kettle, say 15,0 JO 20,000 pounds ; or to support a campaign in the furn. tce, which would require even more. Thirty centners or 6,600 poundg Buffices for the treatment with acid. It is to be remarked, too, that the shallow and extremely wide kettles, in use at this place, may not bo well adipled to the use of steam ; thougb tint question is still unanswered, as I believe steam has not been applied to kettles like them. Those recommended by COUDUIUE are very deep and of small diameter ; wliile those >n the Hirtz aro 2 leet 104 inches deep and 5 feet 6 inches in diameter, and this is about t_ie siz^ of the old Pattinsou kettles in most works, which have been used without alteration for the ziuc process. But the process described above is no longer in use at Call. Mr. HKKBST has invented another which he keeps secret, unwilling to give his disc >very gratui tous circulation and dissatisfied with the Prussian patent laws, \vhich he thinks have not yiveu him protection enough. His new method is said to be chouper than any other yet introduced* COLD AND SILVER WORKS AT LEND. THE (1) treatment of ores containing gold and silver, by fusion with lead is one of the common operations of metallurgists. A very small establishment of this kind, but in many respects characteristic of the general European practice is found at Lend, in Austria. This place lies in the Salzburg Alps, and receives its ore from the mines at Kauris and Boeckstein. The former lying 8200 feet above the sea is said to be the highest mine in Europe, some of its openings being made in glacier ice. * The ore differs in no way but extreme poverty from countless mines in the West. It consists of gneiss, quartz, chlorite and clay slate ; containing iron pyrites, copper pyrites, arsenical pyrites, galena, blende, and stilbite or sulphuret of antimony. The gold is found in two states : free gold and gold alloyed with silver. This alloy, in 1866 was composed on the average, of 15-33 gold and 84-67 silver, which gives a specific gravity of 11-28. Mercury has a specific gravity of 13-6, and as the amalgamation of gold by the Austrian method, is looked upon as a proceeding entirely mechanical, the separation being effected solely by the su perior gravity of the gold over mercury ; this alloy which is lighter than mer cury cannot be amalgamated (2). Such is the lesson of long practice, the free or fine gold beinx extracted from a part of the ore, at least, by amalgamation while the tailings are smelted to obtain the alloy. The following table will show the proportion of fine to alloyed gold and also exhibit the extreme poverty of the ore. To the Kauris and Boeckstein ores are added those from Zell in the same part of the Alps. The ore from the last named place is not now worked, the point of poverty having apparently been reached at which the auriferous rock ceases to be an ore. ] 3 Fine Gold Kauris Boeckstein n 2000 Ibs. In 2000 Ihs. "roy ounces. Troy ounces. 0-32 0-48 0-098 0-113 Zell In 2000 Ibs. Troy ounces. 0-0900-097 Auriferous Silver. L 4 0H-O 5-700 6-600 unimportant. Iron pyrites, copper py rites, grtleiia. " 8 per cent. 4 per cent. unimportant. Value of Silver and Gold i in American coin. . . . ( " $13.49 $16.92 $5.91 $8.49 $1.86 -$2.00 As in 1836 Boeckstein deliveied 63 per cent, of the ore smelted at the works and Kauris 37 per cent. ; the average value for that year was $10-28 or 0-0009 1. This paper ig mainly reprinted from one read before the Institute of Mining En gineers May 22, 1872. For the information contained in i% I am indebted to Dr. LEO TUBNEB, former director of the works, now at Brixlegg in the Tyrol. 2. See liittinger, " Auf bereilung" page 4G9 ; Ed. 1867. LEND. 41 per cent, gold and 017 silver. This does not include the value of the copper and lead which form respectively 2 per cent, and 1 per cent, of the ore. The former is extracted, the latter is not sufficient to supply the waste of the process and lead has to be bought for the works. Even in Europe these ores are con sidered extremely poor. 1 am not aware that ores from veins as poor as these have ever been utilized in this country, but if they have they owe their value to the fact that the gold is all fine and can be amalgamated. TREATMENT OF THE QBE. The ore is first sorted to six varieties for the furnace and one for amalgamation. The former are quartzose ore, rich, medium and poor, compact pyrites, galena and antimonial ores (1). The quartzose ore consists mostly of quartz with which are gneiss and chlorite it contains iron pyrites, arsenical pyrites, blende, copper pyrites, and a very littl< galena. Its value in gold and silver is 400 2240 grammes to the ton, or 12 to 7(1 oz. Of this alloy from 10 to 30 per cent, is gold. This ore gives 20-25 per cent, of raw matte. Compact pyrites is composed of iron oxide, arsenical pyrites, and copper pyrites, and these are often accompanied by magnetite, when it is usually richer. It is nearly free from gangue. Its content varies between 80 and 400 grammes of gold and silver to the ton ; or 2-512 ounces. The gold forms about 25 per cent, of the alloy Glaserz, is a name given to a mixture of quartz and gneiss with disseminated pyrargyrite ; silver and antimony sulphide ; antimony glance and galena. Its content varies very much, usually between 800 and 2000 grammes, or 2660 ounces, to the ton, of which 25 per cent, is gold. Most of this comes from Boeckstein. Glance ore, or fine leaved galena, with 4000 or 5000 grammes, or 140 160 ounces of silver, almost without gold, to the ton. The Glaserz occurs oftenest in quartz ; copper pyrites and occasionally pea cock ore, in chlorite gneiss ; blende, iron pyrites and arsenical pyrites in quartz and gneiss. The mill slimes are of three qualities, ; 1 and 2 are nearly pure pyrites, having been concentrated in milling, and giving 50 60 per cent of matte. One con tains 5001500 grammes of alloy, of which 7 14 per cent, is gold ; two contains 22 75 grammes alloy of which 2*5 4 per cent, is gold ; three is the poorest slime from the shaking table. It gives 25 30 per cent, of matte, and contains 300 1000 grammes or 1040 ounces of alloy, of which 9 18 per cent, is gold. It is used as a siliceous flux. Only the poorest ore containing merely traces of pyrites is sent to amalgamation ; which is done because it there undergoes con centration. The ore for amalgamation is stamped under stamps of 220 pounds weight (total) through sieves of 1.6 mm. (0-06 inch), the stamp chest having a sieve on each 1 A full suite of these orc-s with the furnace products at Lend can be seen at the School of Mines in New York. LEND. side to secure the most rapid discharge of the slime possible. Two methods of treatment are employed for the slimes : 1. They are first concentrated and then amalgamated ; or, 2. They are first amalgamated aad then concentrated. With Figure 7. The A\istrian Gold Mill. ore that contains much pyrites the former is best with ores very poor iu vrUes, the latter. LEND. 43 Amalgamation takes place in pans, there called "mills," an illustration of which is given in figure 7. In this figure a is the pan, I the runner, e the arms, three in number, by which the runner is fastened to the spindle, s is a brace which both stiffens the arm-s e, and also transmits the movement of the spindle to the arms. The spindle is made square at this point, and the apertare in the brace being also square, the brace, arms and runner are carried round by the revolution of the spindle. Dis charge takes place at c, a spout of sheet iron d being rivetted to the cast-iron pan. The adjusting apparatus consists of the thumb-screw m. It is to be re marked that the spindle ends at n, the end being hollowed out to receive the end of the thumb-screw. This screw works in a thread, cut to receive it, in the top of the arms e. The spindle itself rests on the beam p, and cannot move up or down. When the thumbscrew m is turned, its bearing on the top of the spindle remains constant, but the arms and consequently the runner are raised or lowered. The pan is made of cast-iron, and as it suffers little wear can be made very light. The arms, which, being three in number, form a tripod, are made of light bar iron, of about 1 k inches in width, and 4 inch in thickness. The runner is of wood, having the shape of the mill, and hollowed out on top so as to form a hopper. It is bolted to the tripod, bound with ordinary hoop iron, and a number of short pieces of sheet-iron are driven into its lower sur:ace. These wings" are from 2 5 to 3 inches long and 4 inch wide, and act like the vanes in a fan blower, or rotary pump ; that is, they force the pulp to partake of the ro tary motion and drive it out of the machine. Twenty to thirty wings are placed radially in each runner, in such a manner as to break joints, from the center to the circumfer- nee. Those which work over the slanting part of the pan are made only one-half inch wide, in order to allow the wings placed over the mercury, freedom of motion. Other methods of gearing are also employed and pans are usually wider at the bottom than the figure represents. In this pan the interior of the bottom, where the mercury is placed, is ouly 9 inches in diameter ; usual ly 15 inches in the width. As the center is taken up by the aperture through which the spindle passes, the real width of the annular space, filled with mer cury, is in this pan only 3 inches, and in the ordinary pan 63 inches. In both cases the diameter at the top is 24 inches, height 9 inches and the thickness 1-3-16 inch. When pulp is poured into the runner, it passes through the center opening or eye, down to the mercury, where the action of the wings gives it a rotary motion, and at the same time carries it toward the circumference. These wings should revolve just above the mercury, but not in contact with it. By this means, every pai tide of the pulp passes part or all the way round the pan before it is discharged, and its path over the mercury is therefore longer. It does this with the least possible turbulence, and the gold particles have opportunity to reach the mer cury, where, sinking in that fluid, they are safe from liability to be carried off on the stream. Successful work depends upon the thickness of the pulp and the speed given 44 LEND. the runner, and one of the advantages of this mill is the readiness with which its work can de altered to suit any kind or condition of ore. Condition of the Pulp. This depends upon two things, density and fineness. A concentrated ore has a much higher specific gravity than undressed ore, be cause the lighter minerals, quartz, etc., have been removed. The difference be tween its gravity and that of gold is therefore less, and we must take care, 1st to have the slirne so thin that the gold particles will have easy movement through it ; and 2nd that the motion of the runner shall be fast enough to keep the heavy material which it has to carry along, from settling on the surface of the mercury. Experience has proved that with undressed ore containing not more than 10 per cent, of heavy mineral (pyrites, etc.,) to 90 per cent, of gangue, the runner should make from 12 to 15 revolutions per minute ; from one-half to one cubic foot of pulp may be passed every minute ; and finally this pulp must be of such a thick ness that not more than 125 pounds of ore shall pass through the the mill in one hour. When the ore has been concentrated the conditions are quite different. The runner is revolved at the rate of 20 to 30 times a minute, and the pulp must be thinned so that not more than 13 to 15 pounds of ore pass through the mill hour ly. The amount of pulp however must be kept up to a half or one cubic foot a minute. If the pulp is too coarse it hangs back in the mill and chokes it, if it is too fine the gold does not settle. Good stamp work answers well. It is not well to suffer pulp to dry and then wet it to run through the mill. Experience proves that the extraction is not so good under such circumstances, probably because the particles of gold have air adhering to them which lessens their gravity. Two or three mills are usually placed one after the other. With these, of the whole amount of gold extracted from a pulp rich in galena and therefore not favorable to amalgamation. The first extracted 65 per cent. The second 25 " The third 10 With a sandv pulp which contained little heavy mineral the result was : The first extracted 74 per cent. The second 20 " The third .., 6 " One mill, or one set of 2 or 3 mills, will pass from 2,250 to 3,000 pounds of undressed pulp in 24 hours. Of dressed ore it will pass through about as much as would correspond to that quantity of unconcentrated pulp. When the ore contains 10 per cent, of heavy minerals there is no gain in previous concentration, while the extraction is better with undressed pulp. In this apparatus loss of mercury is reduced to a minimum. With two rows of pans the loss for 100,000 pounds of pulp rich in heavy mineral was 1-5 to 2 pounds "poor " " " 1 to 1-5 pounds In the first case it was therefore about one-half ounce to one ton ; in the second one-third ounces. Clayey ores and those containing antimony increase this loss. LEND. 45 The yield can be increased by concentrating the amalgamated pulp, and re- passing the tailings under the conditions necessary in working concentrated pulp. By this means from 20 to 30 per cent, of the lost mercury is recovered, while about the same amount of the ainalgamable gold is also won. The first operation extracts about 70 per cent. The power necessary to run one mill is about one twenty-fith of a horse power. A twelve pan apparatus costs in Austria about $250. Compared with the Colorado methods, these mills extract 20 per cent, more than the Colorado amalgators, though this yield necessarily depends upon the per centage of silver in the native gold. They require little watching, except when used immediately after the stamps, when the accumulation of gold might necessitate cleaning up every two or three days. Smelting. For four years the ores delivered for fusion were in the following proportions : From Kauris. From Boeckstein. Quartzose ore 6.50 24.11 Compact pyrites 0.06 0.48 Sulphuret of Antimony 1.41 0.41 Slime from Amalgamation 29. 03 38. 00 37.00 63.00 About 60 per cent, of the ore has therefore been amalgamated. As this was done because the ore was too poor to smelt we may gain an idea of the extreme pover ty of the original ore. From the table of valuos before given, it is evident that 7075 per cent, of the ore is worthless rock, and this must ba removed before adding lead, which would suffer serious loss if charged with so mujh quartz. The operations are therefore as follows : 1. Fusion for raw matte. 2. Boasting of raw matte in stalls. 3. Fusion (without lead) for a more concentrated matte. 4. Roasting of 2nd matte in stalls. 5. Fusion with lead. 6. Cupellation of rich lead. The First Faxion. Eleven years experience has proved that the most efficient slag is one approaching the composition of a bisilicate. The followiug is an analysis of an average slag from the first fusion : Silica 51.02 Alumina 2. 16 Oxide of Iron .... 19. 75 Lime 15.40 Magnesia 8.57 As. Mn. Ca Zn. S. bydif. 3.10 100,000 The furnace is not new and contains none of the late improvements ; but it does good s rvice. Its general dimensions are as follows : LEND. Height 24= feet. Diameter of hearth 3 " boshes 4 " throat 2 " Number of tuyeres 2 " Pressure of blast i in. of mercury. From 100 to 120 bushels of charcoal are required to warm the furnace, and then regular charges of 5 cubic feet, or about 3 bushels are thrown in. In blow ing in, the quantity of mixed ore and flux added to this quantity of charcoal is, at first 56 pounds, then 112 pounds, and finally when the furnace is thoroughly hot, 203 pounds, which is the constant burden of mine to three bushels of charcoal. This is usually reached in the first 24 hours. Four hours after the first charge of ore and flux the blast is turned on, at first with a pressure of i in., and then in. mercury ; or one-sixth and one-quarter pounds pressure. After eight hours the slag begins to flow. The furnace is worked with a black throat. The labor per ton of ore and flux amounts to 1.8 days. Ihe First Matte, forms 40 to 45 per cent, of the charge, the difference between this proportion and the 20 to 30 per cent, afforded by the ore being made up by roasted matte which forms a part of the charge. Its average composition is : Iron 55.1 Copper 4.3 Zinc 3. 7 Lead 2.1 Nickel, Cobalt, Arsenic and Antimony. . . . 45 Sulphur 27.9 976 It contains 30 to 40 ounces Troy of auriferous silver to 2,000 pounds ; or in American valuation $100 to $150 in coin. From the fact that the ore is un- roasted, and the metals are therefore so well "covered" by sulphur, the loss in this opoi ation amounts to only one-quarter of one per cent. About 38 bushels of charcoal are used to the ton of charge, and 9. 75 tons are smelted in z4 hours. The Second Fusion. The first matte is roasted three times in stalls containing 28 tons, the roasting not being thorough, but carried only so far as to leave about 40 per cent, of unroasted matte. It is then resmelted with quartz, and to avoid the use of too much of the latter, a basic slag is made containing about 22 per cent, silica. This requires very great care in managing the furnace, for the least irregularity will cause the formation of sov/s. To secure proper working, when ever the furnace is tapped, the hearth is exaurned by means of a bent bar. If lumps are felt the front wall is broken out, and they are removed ; if Ihe sole is slippery the presence of reduced iron is indicated. A rough, hard, even sole, is the proper one The pressure of blast is now reduced to one-sixth of an inch or one-twelth of a pound to the square inch ; the hearth is 10 to 12 inches larger in diameter than before, and the charge is increased to 222 pounds to 3 bxishels of charcoal. These changes have for their object not only the prevention of iron sows but also of speise, a compound of arsenic with all the other me als, very difficult to utilize. LEND. 41 Speise is lighter than matte, aud in the basin lies next above it. That at Lend contains a great deal of gold, and experiments made a few years ago to recover this inet.il by roasting and fusion with lead were not successful, though the speise was roasted iu 8 to 12 fires and smelted with twice its weight of lead. It was found nearly impossible to oxidize all the speise and the unroasted part retained its gold with stubbornness. The same precautions are used in blowing in as before. About 30 bushels of charcoal are used to the ton of ore and flux, and 13.5 tons are fused in 24 hours. The second matte, contains 50 to GJ ounces of auriferous silver to 2,000 pounds, worth about $200. Fusion with Lead. The second matte is roasted as before, but now 50 to 60 per cent, of raw matte is left A stronger roasting would so enrich it that two fusions with lead instead of one, would be necessary. The slag is again basic and, to keep the heat as low as possible, the pressure of blast is reduced to one and one-half hues of mercury, while the charge is increased to 277 pounds of matte and flux to 3 bushels of charcoal. In order to keep the lead in contact with the matte as long as possible, as well MS to decrease the heat, the crucible is made a foot deeper than before. The new slag has au average composition of Silica... 27.45 Oxide of Iron 56. 52 Lime 10.19 Magnesia 3.48 Alumina 1.25 The loss will not exceed 2. 5 per cent, of the lead. When the hearth is full of melted matte and lead, it is tapped, the products running into a basin where they are well stirred with poles. The matte is then partially taken off, the lead re maining until 60i> to 700 pounds has collected. For a perfect extraction of the silver, it is necessary to charge 120 to 130 pounds of lead for each pound of silver and gold, and the matte must not con tain more than 20 per cent, copper. With this proportion, 75 per cent, of the silver and gold are extracted in one operation, and the matte ought not to con tain more than 0.75 per cent, of lead. The extraction of 75 per cent, of aurifer ous silver, means that 90 per cent, of the gold and 73 per cent, of the silver has been obtxined. The absolute loss of these metals is but 0.10 of one per cent. From 14 to 16 tons are smelted in 24 hours. A certain amount of lead matte is obtained which is charged back in the same operation. Of charcoal, 28 bushels to the ton are used. If the matte is rich enough, it now undergoes a repetition of this operation, but usually it is so poor that it is treated immediately for cop per. If, however, it contains less than 35 per cent, of copper, it is roasted and charged as a flux, in the first operation for raw matte. At Lend the conditions are such that this takes place every other year, copper being made one year and matte the next. The labor amounts to 0.46 days per ton of matte and flux, and the loss of lead is about 18 pounds to the ton of matte. Oiipellation is performed in a German furnace with a moveable hood, made very low. Inasmuch as none of the side products are sold, and there is no need of having them in great purity, there is beside the fire bridge, but one opening in the hearth, through which abzug, abstrich, litharge and smoke all escape. From 48 LEND. 6,000 to 7,000 pounds of lead are first charged, and more is gradually added until about 21,000 pounds (or the entire make for the year) has been melted. The bkst is slow, and the litharge consequently flows rather cold. Kenning fallows the brightening of the silver, and metal of 985 fineness is produced. Usually the loss of lead falls between 5 and 6 per cent., while that of silver and gold seldom reaches 0. 10 per cent. About 3 tons are cupelled in 24 hours, and the labor is 0.24 days per ton. TABLES OF THE OPERATIONS. The following tables will give at a glance all the foregoing particulars. The first two operations are combined in one table, and instead of calculating the ex pense of charcoal upon the quantity of material treated in each operation, that and the amount of labor will be calculated upon the ton of ore. This is done in order to ascertain how much labor and fuel are necessary to treat a ton of ore by the Lend process. The amount of ore is taken at 109 tons since there was 21 tons of matte remaining from the previous year which was smelted with the ore. TABLE OF THE 1ST AND 2ND FUSIONS, 1866. Weight Ounces Ounces p. c. of Uiarge Tons. of Gold. of Silver. Copper. Ore 81-15 21-0094 1333-4052 Matte and Kich Scraps 89 "61 19-2918 2216-6406 . j Basic 7.41 ,-G 2 q Flux 1 Siliceous 50.88 . . . 59 29 Total 229-05 40-3012 3550-0464 Produces. First Matte 61-38 18-7193 1612-7324 5 Second Matte 30-87 20-4769 1806-7302 10 Scraps 10-25 -6824 95HJ922 Total 39.8776 3514-5548 Labor 39 twelve hour shifts ; 5 men to each shift 195 days. Charcoal for warming furnace, 291 bushels, for smelting, 6,820 7,111 Charcoal per ton of ore 65-2 bushels Labor per ton of ore 1.8 days. LEND. 49 TABLE OF THIED FUSION, 1866. Tons. Rich quartzose ore ... 1 -96 Roasted 2d Matte. . . . 30-87 (Scraps 2-09 Lead. Pounds. Copper. Per ct. 10 Gold. Troy ounces. 0-9610 20-4769 1474 Silver. Troy ounces. 59-5404 1806-7202 23-0778 Lead Matte 3-71 741 6 1 -9440 J Litharge 10-81 17,722 | Hearth 3-30 3,304 t j Slag from 1st Fusion. ..10-99 1 Quartz 2-04 66-77 Products. Lead ! -. . . . 10-51 21,030 Third Matte 15-59 Lead Matte 3-70 741 20 Scraps and Flue Dust 4-06 10 21-5442 1-9440 0-2430 175 9600 66-1500 42-4700 23-5293 21 75 9184 .1283 8320 624-5200 174-9600 46-9900 237312 2130.2920 Labor 10 twelve hour shifts ; 5 men in each 50 days. Charcoal for warming the furnace 100 bushels. " " smelting 1710 1810 Labor per ton of ore 0-46 days. Charcoal " 16-6 bushels. Lead charged " 218 pounds. TABI^E OF CUPKLLATION. Gold. Silver. Charged. Tons. Lead p. c. Troy ounces. Troy ounces. Lead 10.06 100 21-5442 1283-8320 Products. Fine Silver 1208 -58 oz. 21-5294 13869560 Litharge 10 tons 82 64-9080 Hearth 253" 50 31-9860 Loss 0-0144 Gain 0. 1800 Labor, 26 days = per ton of ore 0.24 days. Wood, 7-52 cords. " 0-69 cords. Charcoal, 40-00 bushels = per ton of ore 0-37 bushels. LEND. TABLE OF COST PEE TON OP OKE IN UNITS OF LABOR AND MATERIAL. Labor. Days. First and Second Fusion 1.8 Third Fusion 0<46 Cupellation 0-24 Charcoal. Bushels. 65-2 16-6 0-37 Wood. Cords. 0-69 Lead. Pds. 8-0 9.7 Total 2-50 82-17 0-69 17-7 To this must be added a small quantity of wood or refuse charcoal, used in roasting the matte. Some discrepancies will be noticed between the expense of charcoal as given in these tables and that allotted to each operation in the text This arises irom the fact that the latter is calculated upon the proportions of flux and ore, while the tables are calculated upon the ore alone. They are also more complete : including fuel, for blowing in, blowing out, and any extra sup plies needed in particular states of the furnace. The quantity of charcoal has been calculated on the heaped bushel of 2,748 cubic inches. The above cost is for ores of the richness before given . With richer ores there is more matte to treat and lead lost, and the cost is therefore somewhat greater per ton ; but it is proportionately less per pound of gold and silver. The following table gives the relative cost for various ores ; the cost of the poorest being taken as unity : Auriferous Silver Value in American Proportionate Cost ; lowest in 2000 Lbs. Coin. taken as Unity. 14-5. oz. $ 0-$ 61 1 14-5 29-0 $ 61 $122 29-0 58-0 $122- $244 58 -0-1 16-0 $244- $488 The Lend ore falls under the first kind ; the milling ore of Colorado is worth from $20 to $30 a ton, arid therefore is also in the lowest section ; the smelting ore," so called, would be mostly in the 2nd and 3d ranks. LOSSES. By reference to the above tables it will be found that the following is the loss and gain of the year. MO 1 31 1-73 First and Second Fusions Third Fusion G oz. 4-24 15 1 Did. p. c. jOSS. Silver. oz. rp. c. Gol< oz. 2-029 2-029 GA 1. p. c. 0.86 IN. Si oz. 0-02 0-02 iver. p. c. 0-0015 1 0.07 35-50 4563 2-8 3-6 Cupellation Total loss. . . 4-39 2-36 1-1 81-13 81-11 6-2 Dr. Turner s opinion founded upon years of experience, is that more than 90 per cent, of the silver and 96 per cent, of the gold can be counted upon in the two processes of amalgamation and fusion. Some years ago he undertook to ascer tain the loss incurred in amalgamating and found it to be 45 per cent He therefore placed no reliance upon his results, but when we consider the poverty of the milling ore, we shall see that a loss of one half the gold contained in it would affect but very little the grand result LEND. 51 The cost of all the operations in 1866, at Lend, was $883.88, and the balance sheet shows a profit of $1,355. The expense was proportioned as follows : Labor 17, materials 43, direction 40 ; total 100. At th ese works all avoidable causes of loss have been eliminated, or their opera tion recluced with the greatest care. Two analyses a year determine the propor tions of the charges and the composition of the slag. Larger works would re * quire more, but there is no reason why the largest works should not be conducted with equal care. Great care is necessary on account of the extremely small quantity of ore smelted ; only 83 tons in 1866, worth less than $2260 in gold and silver, but furnishing also a ton and a half of copper. But to treat this small quantity an engine r, and two smelters and four assistants have to be supported all the year through, though they work only 27 days of 24 hours. Of course such a state of things ca,u be maintained only by low prices, and we find the Austrian workmen paid at rates varying from 27 to 22 cents (coin) a day. Charcoal is 3 1-7 cents a bushel, and wood $1 17 a cord. In this country we should have larger supplies of ore, sufficient to carry on the largest works on a correspondingly economical scale. The nature and higher value of our ores, too, would enable us to work with less expense of labor and material to the Troy pound of gold and silver than at Lend. In considering these results for guidance in using a similar process at the "West it is evident that the American ores contain nothing to prevent the applica tion of this process. Antimony and arsenic and zinc, the bugbears of the smelter, are, with the exception perhaps of zinc, quite as prevalent at Lend as in Colorado, Our ores, too, contain more pyrites than those we have been considering and there would be no necessity for a fusion for raw matte. Whether there ought to be a fusion for concentration depends upon the richness of the ore, and its adaptability to concentration by machinery. A mixture of rich "smelting ore and concentrated tailings, such as is now worked up by the smelters, could be roasted and immediately fused with lead. One more fusion with a fresh quantity of lead and cupellation would complete the process. We should then have a pro cess divided as follows : 1. Cupellation of poor ore. 2. Boasting of concentrated and rich ore. 3. Fusion of roasted ore with lead. 4. Roasting of matte. 5. Fusion of matte with lead. 6. Cupellation, As to the cost of a process like this, we have the following details. A ton of concentrated tailings is produced in Colorado at an average cost of $6. The ex penses for the other 5 operations would be : Day s labor. Charcoal. Wood. Roasting in Piles 0-4 0-029 cords. 1st and 2nd Fusions 1-8 65-2 Roasting m atte -2 -004 Third Fusion 0-46 16-6 Cupellation 0-24 00-37 0-69 10 82-17 0-720 62 LEND. Mr. Hagne says that the millers expect to get one ton of concentrated tailing* from six tons of ore. At that basis the theoretical expense would be : Concentrating 6 tons to one $ 6 00 Smelting 1 ton, 3-10 days labor @ $3 9 30 Smelting 1 ton, 82 -17 bushels charcoal @ 25c 20 54 Smelting 72 cords wood @ $8 6 00 . Treatment of 6 tons milling ore 41 84 Mining of 6 tons milling ore @ $10 60 00 Total cost of treatment 101 84 Cost of one ton 16 94 The expense of charcoal ought to be somewhat less than this, for in conse quence of the small quantity of material treated at Lend no less than 2.5 bushels of coal to a ton of ore are expended in heating the furnace. If we add one half more for loss in blowing out we have the very large proportion of 3. 7 bushels, a quantity that would be lessened one bushel if 330 tons of ore were smelted at each campaign. With proper management this could be very much exceed d so that the expense of charcoal for blowing in and blowing out, would be too small per ton to be worth reckoning. It now remains to consider the adaptability of this process to western ores, and I will take those of Colorado as an example, for the reason that Mr. Hague s re port on mines of that Territory offers the best data for calculation. He gives commercial assays of the ore from various lodes which prove the average value of the ores to be as follows : First class ore : Gold. Silver. Consolidated Gregory 5. 6 oz. 20 oz. Illinois 4 20 Gardner 3.5 11.5 California .3. 18 Burroughs 6. 12 Average 4.42 16.3 Milling ore : Burroughs (1340 tons) 1 oz. 4.5 oz. The value of the first class ore is $91.36 for the gold and $21.03 for the silver ; total $112.13. Let us see what manipulation it requires : Boasting the ore so us to leave 33 per cent raw matte, and smelting with 180 to 195 pounds of lead to the ton of ore we ought to extract in one operation 93 per cent of the gold, or 4. 05 ounces worth $83.71 ; and 73 per cent, of the silver or 11.90 ounces worth $15.- 35 ; total yield $99. 05. (4) The expense of working would be as follows : (4) By reference to the tables of cupellation audioes it will be seen that, in 1866 more than 99 per cent, of the gold was obtained by one fusion with lead ; while of the silver 60 per cent, was obtained as metal, and 32 per cent, was retained by the third matte and went under treatment the following year, 2A per cent, was contained in the scraps and flue dust, 3.3 per cent, was retained by the litharge. The latter two should be ueglected for they are constant from year to year, and the real percentage yield was iu 1866, therefore, 63-8 per cent, fine silver, and 33- 9 per cent, silver in the matte. LEND. 53 Mining 1 ton $10 00 Koasting 0.4 days labor @ $3 $1 2J 0.029 cords wood @ $8 23 8 mos. int. 011 $10 @ 12 p. c. 80 2 23 Smelting 1 .5 days labor @ $3 4 50 8 pounds lead (& 5c 40 46 bushels charcoal @ 25c. . . 11 50 16 40 18 63 Total for mining and smelting. . . 28 63 , If our ore contains no copper the matte will not pay for further treatment and we proceed at once to cupella ion, for which we have in addition : Cupellation : 0. 24 days labor at $3 $0 75 0.37 bushels coal at 25c 09 0.69 cords wood at $8 5 52 9 Ibs of lead at 5c 45 681 Add mining and smeltiug 28 63 $35 44 Profit: $99 06 $35 44=363 62. "We have remaining a matte containing $7 48. Let us see whether this will pay to work by itself. The expense will be for Colorado rather greater than for Lend because the proportion of pyrites in the ore is greater. Assuming this excess equal to 50 per cent, and increasing each item to that extent we have : Boasting : 0.50 days labor at $3 $0 90 0.2 cords wood at $8 18 1 08 Smelting: 0.60 days labor at $3 ..... 180 27 bushels of coal at 25c 6 75 5 pounds lead at 5c 25 9 80 Total $10 88 This would leave a loss ; $7 48 $10 88=mmus $3 40. The loss by direct treatment would therefore be $3 40. This matte however could be returned to the first fusion again and again, until the copper which is present to some extent in almost all the ores were concentrated sufficiently to give the matte a value for its copper. With ores containing much copper the matte might be immediately saleable, and both silver and copper bring their value. At present however, and especially with milling ores, the process would probably consist of three stages, as follows : 1. BOASTING. 2. FUSION WITH LEAD. 3. CUPELLATION. To illustrate the working of the process with milling ore, let us take the Bur roughs ore as a specimen. It is worth one ounce gold, or $20 67, and 4 5 oz. silver, or $5 80 ; total $26 47- This is an average yield, as most of the milling ore of Colorado, so far treated, lies between $18 and $35 in value. We have foi its treatment by fusion the following expeases : FREIBERG. ALTHOUGH the processes in use at Freiberg have been described with tolerable frequency, few persons who are not instructed in schools of mines, have a just appreciation of the works there, or a correct idea of the methods in use. Those methods, in fact, change so constantly that it would require a year-book to keep pace with them. They have changed so much since 1870, that in writ ng the following description, the work ot later travellers, such as Messrs. KAST, BUAUN- INO and KUHLEMANN, all of them connected with the great works in the Hartz Mountains, and BALLING, of the Austrian service, have been freely drawn upon. After more than 500 years exploitation, the mines of Freiberg form a vast net work of galleries and drifts. Within the century ending in 1865 a total length of 25 German miles, or 115 English miles of passages was excavated, and the mines were deepened 700 900 feet. What the cubic contents amounted to is not known, but it is surmised from the number of men employed in 1765, (1255, of whom probably not more than 600 were engaged in breaking down), that about -19,200 cubic yards or 5,539 cords, of 128 cubic feet, of rock was taken out in that year. The amount excavated in 1865 was 128,206 cubic yards or 59,190 cords, which gives close on 8 cords per (Jerman Lachter (6 2-3 feet) of exeavatiou. At the same rate the excavation for 100 years past would average 36,969 cords per year. It is a matter of interest to know that in 1765 a cord of rock gave 1 ton of concen trated ore ; while in 1865 a cord of rock gave only 66-100ths of a ton. Baron VON BEUST, however, does not ascribe this falling off to a regular decrease of the ore in depth, nor to the fact that the dressing works now accept poorer ores from the miner than then, though this probably has some effect ; but rather to the very large works for drainage and improvement of communication, most of which are done in dead rock, outside of the veins, and (chiefly) to the fact, of which he is persuaded, that the Freiberg mines now and for some years back, have been worked in one of those zones of medium and poor ore which occur in all veins. According to this view these famous mines should Lave before them a renewal of their former extreme wealth when this poor zone has been worked through. More than 900 veins are known, which have been classed, according to the ores they yield, in four groups : 1. The quartz group, containing about 150 veins, from 3 inches to 6 or 7 feet wide. This would probably be called in America the silver group, for its va uaMe min eral consists mostly of various silver minerals. The gangue is quartz with some gneiss, and the ores are silver glance, ruby silver, fahlerz, miargyrite, polybasite, brittle silver ore, antimony glance and antimony sulphide. FREIBERG. OS, 2. Tlie pyritiferous group, with about 300 veins, of 2 inches to 3 feet width. The gangue is chiefly quartz, with some calc-spar, iron-spar, heavy-spar and fluor-spar. The principal ores are argentiferous galena, blende, pyrites, arsenical pyrites, with a certain proportion of the m nerals named in connection with th first group. To this group belong also the veins which yield chi fly copper ores ; as copper pyrites, peacock ore, copper glance, red oxide and carbonate of copper. 3. The noble lead group, so-called fiom its richer ores, has 340 veins, in which tlte gangue is brown spar, manganese spar i.nd quartz. The ores are galena, richer in silver than that of the preceding division, blende, pyrit s, native silver and some proper silver minerals. 4. The barytic lead group, with 130 veins, some of them very wide. The gan gue is heavy spat , with some fluor-spar and quartz, and the on s are galena, blende and pyrites, w th some carbonates and silver minerals. The ores obtained from these extensive mines may be briefly described as con taining all the lead, silver and copper minerals, that are not mere cabinet curi osities, besides most of those that are ^-uch. The total quantity delivered in 1867, was 34,163 tons (2,000 Ibs.) which contained by assay : Per Cent, In 1 Ton. 71,444-25 pounds silver and gold = 0-104 30-47 ounces. 5,130-00 tons lead = 15-01 300-20 pounds. 78-75 " copper = 0-23 4 -GO pounds. 664-25 " zinc == 1-94 38-80 pounds. 174-50 " arsenic = 0-51 11-20 pounds. There are two establishments at Freiberg, the Muldner and Hals riicke Works. Differences in the composition of the ores have given rise to slight deviations in treatment, and for the sak* of consistency this pai er will deal with the course oi operations at thn Muldner Works alone, while that in use at Halsbrucke will not be rt- ferred to, except in describing the copper treatment which is carried on only there. The Muldner Works treated in 1867, 16,702 tons of ore and furnace products, which contained by assay : Per Cent. In 1 Ton. 43,197-45 Av.pounds silver 0-129 37-02 Troy oz. 106-89 " gold 0-00032 0-093 4o4-41 " bismuth 0-0014 0-03 pounds. 608-88 nick l<fc cobalt 0-00 18 0-04 7,520,70400 " lead 22-51 450-02 137,445-90 " copper 0-41 8-20 " 7,702,54663 or 3.851 tons. By comparing this table with that above given, it will be observed that the ore treated at the Mulduer Works appears to be richer than the great average. This is because a great amount of furnace products are added to the ore, becau-e nearly all the foreign ores are taken to this establish ment, which lies immediately uu the railroad, while the other works is sev : ral miles from it. These Jo eign ores are much richer than the average Freiberg ore, as the fact that they a e able to bear a transportation of several thousand miles, and still afford a prolit, indicates. 56 FREIBERO. The total amount of these products, according to the table, is 3,851 tons, or very nearly 25 per cent Seventy-five per cent, of the ore is therefore material which must be removed. This material is of two kinds, useful, as sulphur and arsenic ; und worthless, as quartz and other gangue. The useful constituents are economised as much as possible, and this gives rise to a series of operations which are supplementary to the regular course of smelting. Thirteen different products are obtained as follows : Metals. Products. 1 Gold. 1 Sulphuric acid. 2 Silver. 2 Copper vitriol. 3 Lead. 3 Arsenic, white and yellow. 4 Zinc. 4 Orpiment, or ar.^enic sulphide. 5 Arsenic. 5 Speise, containing cobalt and nickeL 6 Bismuth. 6 Zinc paint. 7 Platinum. The process is, however, primarily one for the extraction of lead and copper, with their accompanying gold and silver, the rest being all bye products. Cer tain preliminary operations have to be undertaken in order to prepare the ores containing arsenic, sulphur and zinc, but holding no lead, for the fusion with 1-nd ores in which they part with their silver. These preliminary steps have been group* d together in the following paper in a PREPAHATORY SERIES of operations. Then follows the REGULAR SERIES, in which all the operat OLS connected with the fusion of the lead or- s and the extracti n of the silver, gold and copper, are placed. Finally, in a SUPPLEMENTARY SERIES, are given the operations in which marketable articles are prepared, not from ores, but from various products ob tained during the coui se of the previous work. Only by keeping in mind the fact, that there is one leading series of operations, which has for its object the production of lead, silver, gold and copper, and upon which a 1 the other work is dependent, can a clear idea of the varied methods in use at Freiberg, be obtained. The processes placed in these three series are as follows : Preparatory. Regular. Supplementary. Manufacture of Arsenic. Fusions for Lead. Bismuth Process. " " Sulphuric Acid. Treatment of Matte. Hard Lead Process. < " Zinc. Cupellation. Separation of Gold. 11 " Zinc Paint. Treatment of Copper. Manuf. Platinum. Treatment of Lead. Kenning Arsenic. Seven sorts of ore are recognized : 1. Pyrites; iron pyritts containing not more than 1 per cent, copper, or 15 per cent, zinc, and little arsenic. 2. Arsenic ores ; averaging 35 per cent, metallic arsenic. 3. Arsenical pyrites ; 15 per cent, arss .ic, 2628 per cent, sulphur. 4 Arsenical le id ores ; 12 per cent arsenic, 18 20 per cent. lead. 5. Blende ; with more than 30 per cent zinc. 6 Pyritiferous ores ; containing 1530 per cent. zinc. 7. Lead ores ; 1, gale7ia, with more than 30 per cent, leud, and 2, plumhifrioua ore, with 1529 per cent. lead. FREIBERG. 57 But foil :wing the system pursued in this paper, the old classification into fluxes, load ores, dry ores and copper ores, will be retained. The fluxes are in the main those which contain so much iron as to make them valuable additions to the fusion for lead. They are chiefly iron pyrites containing arsenic and zinc ; but the zinc ores also belong in this class, tha residues after the distillation of the zinc being carried to the lead process and added in the roasting furnace. The dry ores (Durrerze) , are s > called from the absence of lead. In this country they would be called distinctively silver ores, for their valuable part consists of true silver minerals. They are worked with the le id ores in the shaft furnace, and therefore come in the regular series. But if their quantity is too great to be disposed of in this way, they can be melted in a reverberatory with slag from the fusion for lead, and than belong to the preparatory series. This was formerly the basis of the Freiberg treatment. Now it is, at most, an exceptional opera tion. PREPARATORY SEKIES OF OPERATIONS. Roasting .-Chief among these operations is roasting, or the removicg of the sulphur. For this, four varieties of furnace are used : 1. kilns ; 2. Gorstenhofer furnaces ; 3. Wellner s stalls ; 4. reverberatory furnaces. The first two are con nected with the sulphuric acid chambers. Kilns are used for ore in lumps, and for matte. Those in which ore is roasted are 10 feet high, and 7X5 feet in sec tion ; those for matte are 10 feet high, and 10X5 feet in section, the long side in both cases lorming the front. They have numerous sni;ill side openings through which the workmen can observe and regulate the operation. The charge for the larger furnaces is 1,760 to 2,200 pounds, and for the smaller 650 to 1,300 pounds. A charge is drawn every twelve hours, so that one kiln roasts in twenty-four hours, of matte 3,5004,400 pounds, and of ore 1,3002 600 pounds. No fuel is used. The sulphur is reduced to 8 per cent. When it is necessary to roast the coarse ore or matte more thoroughly, Wellner s stalls are employed. These have grates upon which a fire is maintained, by which the sulphur is more tho roughly removed than can be done by any heat produced by its own combustion. But as sulphur is needed in the shaft furnace, the re-roasting of these coarse ores is rather exceptional. For fine ores, the Gerstenhofer furnace is employed for preliminary roasting. The form of this, as is well known, is that of an upright shaft containing trian gular bricks, reaching from side to side, the upper surfaces of which form shelves on which the ore periodically rests. These furnaces have not answered the ex pectations formed of them, and they are retained at Freiberg more as the best construction in some respects that has yet been devised for finely crushed ores, than as a thorough roasting apparatus. They do not reduce the sulphur beyond 12 or 13 per cent., and are used as a preparation for reverberatories. The roast- iirg is not always uniform ; but for fine ore, they are almost the only resort of the sm.-lter, who wishes to utilize his sulphur in the manufacture of sulphuric acid. Boasting only to 13 per cent., these furnaces require to be supplemented by reverberatories an int- resting variety ot which is found at Freiberg. They are all long furnaces, the ore gradually advancing from the cool to the hot end. Three kinds are in use, double hearth furnaces of 47 and of 76 leet hearth length^ 58 FREIBERG. and single hearth furnaces ; both sizes of the former have upper hearths of the width of 6 feet and low-r hearths of 5 feet 6 inches. It was found that the shorter furnaces did their work just as well as th^ longer, in less time and with less la- Lor. In building a new furnace, it was therefore made of 47 fe^ t heartU length, the upper hearth 7 feet wide and the lower 6 feet 6 inches. These double hearth furnaces, and especially the old forms, which have a Hue on top, are ex tremely hard to keep in repair ; and trial was made at the Ha sbriicke works, of a single hearth furnace, 48 feet long and 10 feet wide. This gives more hearth room than the longest of the- old furnaces, and allows doors to be made on both sides ; while the two-banked furnaces mostly have doors on one side only, a dis position which makes it very difficult -to move ore that lodges between the doors. This furnace roasts fully as well as the older forms, and also disposes of about 50 per cent, more material. The Gerstenhdfer furnaces and the kilns are connected with a system of flues, in which the arsenic, which forms a constituent of almost all the pyrites, is con densed. From the flues the sulphurous acid vapors pass to the lead chambers, where sulphuric acid is made. This condensation system is peculiar in having canals next the acid chambers, formed of sheet lead, by whuh the gas is BO much cooled as to insure tho most thorough precipitation of the arsenic. The gi?s also reaches the chambers in the best condition for condensation. The re- verbt ratory furnaces have a special system of canals, in which a dust, very rich in arsenic, collects. As the gas is not utilizable lor sulphuric acid, the canals end in a high chimney. With this description of the means for roasting, we will pass to the treatment of the various sorts of ore which are subjected to it. Pyrites : The coarse ore is roasted in kilns to about 8 per cent , and if desired, it is re-roasted in stalls. The fine ore first passes through the Gersteuhofer fur- 4 nace, in which the sulphur is reduced to 13 per cent., and is then mixed with the lead ores for roasting in a reverberatory. Arsenic ores are of three kinds. 1. True arsenic ores ; 2. Arsenical pyrites ; and 3. Arsenical lead ores. The true arsenic ores are treated both for metallic arsenic, of which they contain about 35 per cent., and for arsenic sulphide. The operation consists in a disiillation in chainotte tubes, first at a low tempera ture which drives over the arsenic sulphide, and then at a high h> at, when the metallic arsenic passes over. The first collects in the extreme end of the con densing apparatus, and the second in that part nearest the furnace. Arsenic sulphide is also obtained f rom the arsenical pyrites and from sulphu ric acid residues. The former contain about 15 per Ct nt. arsenic and 26 28 per cent, sulphur. This distillation is also performed in tubes. The residues still containing arsenic, are treated like the lead ores described in the next paragraph. Arsenical lead ores are roasted in a reverberatory furnace which has a hearth 14 feet long and 10 feet wide. In order to prevent the passage of sparks and soot into the flues where the arsenic condenses, the ordinary fir place is replaced by a simple gas generator. This is formed by merely sinking the grate about 3i feet below the firebridge, and in the shaft thus produced coke is burned. Combus tion takes place only in the lower part of the coke column, and th* upper part is not heated sufficiently to decrepitate. The cha-ge is about 2,000 pounds, which is roasted in six hours, at an expense of 275 - 330 pounds coke ; each furnace FREIBERG. 59 has a speci *1 flue 800 feet long, in which a perfectly white dust, free from soot, and suitable for the market, collects. Zinc ores consist of blende, which is roasted with great care in reverberatories, by which the amount of sulphur is reduced to one and a half per cent. The roasted ore is then distilled in Silesian muffles, and the residues from the distil lation are mixed with the roasted pyritiferous ores, and treated as described iu the next paragraph. These residues contain 9 12 per cent, zinc ; 1 2 per cent, copper ; and 0-03 0.04 per cent. (8*7 11*6 ounces) silver. Pyritiferous ores are pyrites containing blende. They have from 15 29 per cent, of zinc; 1 2per cent, copper; 0-015 0-045 per cent, silver; andmore than 20 per cent, of sulphur. Their treatment is one of the most peculiar in the whole range of metallurgy. It is impossible to utilize the zinc they contain as metal, nnd yet it must be eliminated, if the ore is to be charged in the fusion for lead, wh-re a high percentage of xinc would seriously disturb the operation. The ore is, there fore, powdered fine, and roasted first in a Gerstenhofer furnace. Residues from the zinc distillation are then added, and the whole is roasted in a reverberatory. The roasted ore is then mixed with coke slack and brown coal, and smelted at a high heat in a reverberatory furnace. The zinc oxide which has been formed in roasting, is now reduced to metal and volatilized, but immediately oxidizes again in the air, and collects in the flues in the form of a gray dust. This ope ration is conducted at a nearly white heat. About two-thirds the zinc is removed in this way, and the product called dezincing residue contains all the iron and not quite one-third the zinc of ths original charge. The regular charge con- sis t-s of 30 roasted ore ; | 1-3 brown coal ; | 1 -6 coke slack. From four to six charges are fused in twenty-four hours ; and the expense of fuel, according to the average of five days run in Septemb.r, 1809, was : For re duction 11-5 ; on the grate 30-8 ; total 42-3 per cent. Products : Residues 0-012 per cent (3 oz.) silver, 8--10 per cent, zinc. Speise, usually amounting to 4 per cent, of the ore. It contains 018 per cent. (5.2 oz. ) silver, 2 per cent, lead, and 10 per cent, copper. Lead is sometimes produced. It is very impure, forms about 0.16 per cent, of the ore, and contains 1-3 per cent. (389 oz.) silver. Flue dust, which forms about 10 per cent, of the ore, and contains 0-005 per cent. (1| oz.) silver, 10 per cent, lead, 24 per cent, zinc, and 30 per cent, sulphuric acid. The dust near the furnace contains a great deal of sulphu ric acid. It is lixiviated and the residues returned to the furnace. The re mainder is sold as paint. The furnace in which this and similar operations are performed is an adapta tion of that used in the English copper process. It is a reverberatory, in which the lining is composed of a mixture of sand, clay, and slag, sand alone, or any other material that may be desirable. A foundation of suitable size is dug out and lined with masonry. Small pillars of masonry (c c, Figures 7, 8, and 9) ara also carried ;ip nearly to the hearth level. On these strips of iron plate are laid, on which rests a number of iron plates, 6 6 forming the hearth bottom. Upon 60 FREIBERG. these is placed a layer of broken stone m, then comes a layer of quartz and cha- motte (old bricks ground up) n, and on this the hearth sole, fc, made up usually of quartz and slag, is melted. The other parts of the furnace are : d, ouier walls Figure 9. G Figure 7. Reverberator?/ Furnace at Freiberg. of hard burned brick ; e, fire-place ; /", grate ; g fire door ; h, fire bridge of re fractory brick ; j, opening in fire bridge to cool it ; /, arch made of refractory brick ; o, openings for admission of air ; p. working door ; q and r, side doors ; s, tap hole ; t, charging hole in roof ; u and v, supports for the tools ; w, the fine ; and x, the chimney, made of hard burned red brick, cemented with a mixture oi quartz and clay. The whole is strongly bound with wrought-iron bars. Fig. 7 is a vertical side section, Fig. 8 a horizontal section und Fig. 9 an end section ol the furnace. Th s operation is not one to be imitated except under peculiar circumstance?, for it is so costly and its product of so little value, that the proceeds hardly more than cover expenses. At Freiberg, it is valuable for other reasons than pecuni FEEIBERG. 61 ary profit. One of the greatest defects of the Freiberg ore was formerly its lack of iron, a want which was one of the reasons that in former times led to the adop tion of a reverberatory furnace process, after a trial of the shaft furnace had failed. Freiberg produces iron pyrites mixed with zinc, but this source of iron was use less until this method of eliminating most of the zinc, was discovered. To merely roast the ore and add it to the charge in the shaft furnace would cause the entrance of so much zinc into the slag that it would be both pasty and nearly infusible. But by distilling the zinc off, a residue rich in iron and comparatively poor in zinc, is obtained ; and this forms a very accep table addition to the lead ores. REGULAR SERIES OF OPERATIONS. From all the above operations we have the following products : 1. From Sulphur ores Roasted iron pyrites containing some lead, copper and silver. 62 FREIBEKG. 2. From Arsenic ores Roasted residues, having in the main the composition of roasted iron pyrites and still containing a certain pro portion of arsenic, together with lead, copper and silver. 3. From Zinc ores Dezincing residues, forming a Blag, which contains much iron, 810 per cent, zinc, with lead, copper and sil ver ; also a speise containing very much arsenic with iron, copper, lead, cobalt and nickel. Besides these, the following ores remain for treatment : 1. Galena ores. 2. Lead bearing ores ; (the average of the two is barely 40 per cent, lead and 0.15 percent., (43 1 oz.) silver.) 3. Copper ores. 4 Dry ores. The treatment now becomes that known as the Roasting and Reduction pro cess ; the ores being first roasted to a silicate and then reduced in the shaft fur nace. In the former operation various purchased materials containing gold aud silver, together with the residues from arsenic glass are added, and the products mentioned above serve as flux in the blast furnace. It is for this reason that the ores from which they have been obtained have received the name Fluxes. The first step is to make the " ore-mixture" for roasting. This is done by spreading out in thin layers, one upon the other, the different lots of ore, so that by cut ting the mass down vertically, the charges taken daily for the furnace will have a pretty uniform composition. This is of great importance in its effect both upon the roasting and also upon the regular working of the shaft furnace. The mix ture contained in 1867 : 60-64:5 lead ores. 18 -Hi " dry" or silver ores. 1 -703 copper ores. 11 -779 purchased products and flux. 7*759 foreign ores. 100- It contained on the average 0-2425 per cent, silver (70| oz.), 29-08 per cent lead, and 0.156 per cent, copper. Boasting : The mixed ore, which is in the state of powder, is roasted in the reverberatory furnaces before mentioned. Experiment has proved that a hearth of 47 feet length, and a grate of 25 inches width, is sufficient to insure a thorough use of fuel with the above mixture of ores. The charge is made in posts of 1,650 pounds each, which are introduced every three hours, so that a furnace roasts 13,200 pounds in twenty-four hours. The thickness of the layer of ore is six in ches. It should be remarked, however, that the new single he >rth furnace, at the Halsbriicke works roasts 21,120 pounds daily. A great difference in the amount of labor is also apparent. The 76-foot, double hearth furnaces require eight workmen to twelve hours ; the 47-foot furnaces, five men. Fuel amounts to 22 per cent, o: the ore, but the coal is of very poor quality and will avernge 20 25 per cent, of ash. Well roasted ore contains 35 per cent, sulphur, and rarely reaches 6 per cent. The ore is thoroughly iused and comes from the lur- uace as a silicate. Reduction takes place in the octagonal or "Piltz" furnace, as it is named after FREIBERG. 63 its inventor. This was as nrst made octagonal, but new ones are to be round. The earlier forms were wider at the top than at the bottom, but the new ones are to have straight sides. The new furnaces then will differ from the old 7-tuyere Stolberg furnaces only in having one tuyere more, in having tuyeres on all sides, (and theref ire, being cooled on all sides, ) and in being closed at the top ; their lower walls are only one bride thick, but this is a matter of convenience only and cannot have any material effect upon the working. Thinness of walls, in fact, has no other effect than to cool the hearth and thus prevent its rapid destruction. The furnace is built in two parts. The iipper part is built of any hard brick, is surrounded by a shell of strong sheet iron, and is carried upon eight iron col umns. It stands 4 feet above the sole of the hearth. Its shape being conical, and the base of the cone forming the top, the lining rests upon the iron shell, but the lower courses are also kept in place by a ring which is fastened to tha shell by means of an angle iron. The mode of supporting the shell upon the iron columns is somewhat peculiar. On four of the eight sides, a strip of angle iron is bolted to the shell. Tnese rest upon an I beam bent to a square with rounded corners ; and this I beam rests on the columns. The columns are not placed equi-distautly around the furnace, but are assembled in pairs on those sides where the angle iron is bolted on. At the level of the distributing air pipe brackets are placed on t ach side of the columns. Those on the outside carry the disiributiug pipe. Those next the furnace, bear against angle iron knuckles which are bolted to the shell, on those sides which do not carry the angle iron strips further up. The top of the furnace is formed by a round iron hopper or cone, the opening of which is about 20 inches less than the diameter of tne furnace. From this an iron cvlinder projects into the furnace, leaving an open annular space uf seven inches between the cylinder and the lining. The top of this cylinder is closed by a plain cylindrical sheet iron cup, resting on the inner surface of the hooper. The discharge flue is placed in the side immediately opposite the cylinder. Th<} charge is made in the hopper, around the cup, and is thrown into the fur nace by raising the cup. It falls into the cylinder, and thence passes to the body of the furnace. The gas produced by the combustion of the fuel not b> ing able to leave the furnace by the throat, collects in the annular space around the cylin der, and passes off by the flue. The flue is lined with firebrick, three inches thick. This, as will be seen, is an old form of charging apparatus, well known to iron smelters. Other methods are also in use at Freiberg, in which the gas passes off by a central pipe, running through the cup. The reason for making the change was, that the syst m of flues is not sufficiently large for the work it has to do and the furnace sometimes failed to draw. The central pipe permi s a direct dis charge into the atmosphere whenever necessary. The foundation is carried deep into the ground, and is surrounded by 2-inch plates of c. st-iron. It consists, in fact, of an 8 -sided iron box, lined with u;a- sonry. The center is filled up with sl*g, rubble, clay and bricks. Upon the masonry the hearth walls are built ; and tue hearth material, composed of clay and coke slack is laid on the bricks From this description, it will be seen, that the effective height of the furnace. 64 FKEIBERG. that is, the height through which the products of combustion act on the charge, is that from the sole to the lower edge of the cylinder, or fifteen feet four inches. Figure 1O. Shaft Furnace at Freiberg. Vertical Section. The dimensions of the furnace, reduced from French measure, are as follows : Height from sole to top 17 feet 10 inches. 1 of cylinder. . . : 2 " of slag discharge over sole 1 of tuyeres over sole 1 Diameter at tuyeres 5 " at top 6 FREIBERG. 65 Diameter of cylinder 5 feet 3 inches. of tuyeres " 2$ Number of tuyeres (water cooled) 8 Hopper ; Height 1 ft. 9 in. Diameter at top 8 9 " " at bottom 4 " 8 " Cup; Height 2 " 4 " Diameter 5 Blast pipes ; Diameter of distributing pipe (interior) 1 " of nozzle pipes Discharge flue ; Diameter (interior) 1 Reception basin ; Diameter 4 Depth 1 Slag pot ; Height 2 Diameter at top 1 Columns ; Mean Diameter. 64 Height 14 " 2 The charge for the furnace is marie up in layers like the ore-mixture, only not so carefully. Messrs. K.A.sr and BUA.UNING give the following as its composition : Boasted ore 100 Baw matte 15 Boasted pyrites from the kilns 15 Slag from the same operation 80 100 210230 But generally other products are worked into the charge such as arsenic resi dues, zinc residues, lead bearing produc s and purchased material, containing gold. Two furnaces (Stolberg) were in September, 1869, running on the follow ing mixture of ores and products. 1 II. Boas ea ore 100 100 Slag from same operati n 150 113.6 Baw matte 20 Gold scraps 1-25 Dezincing residue. 10 9 271-25 224-5 Freiberg ores contain gold, but in too small quantity to pay for extraction alone. But by increasing the proportion through the addition of gold scraps the whole is obtained. We have already seen that the material treated in 1869, con tained as much as 106 pounds of this metal. Products :L ad, containing 0-5 per cent. (146 oz.) silver. Matte, 0-2 per cent (58^ oz.) silver, 25 per cent, lead, and 6 per cent, copper. Slag, 0-005 per 0-010 per cent. (0.6 1 oz.) silver, 5 lead. Flue dust forms 1 per cent, of the ore. It contains 0.005 0*01 per cent, silver, and 3740 per cent. lead. Of coke, containing 15 20 per cent, of ash, 1011 per cent, is used. The pressure of blast is | 1 inch of mercury or | pound per square inch. One smelter, two chargers, and two to three slag-men are required to each shift. Although the amount of silica in the charge is less than is considered advan tageous in most lead works, no effort is made to increase it, but on the contrary 66 FREIBERG. basic fluxes limestone and fluor spar are added. The result is a f-lag which is but little above a proto-silicate. The regulation of the charge depends upon the amount of zinc present, io avoid the form, ition ot an infusible zinc slag, the proportion of sulphur is kept up, either by riot roasting ihe ore c inpletely or by at" 1 ding raw ores or matte. This insures the passage of part of the zinc into the matte while another part unites with the slag. The amount of zinc present also B figure 11. Horizontal Section. influences the proportion of slag repassed. At Halsbru cke, where the ores con tain less zinc, the charge of slag from the same operation, is but one-half that used at the Mulden for zinciferous ores. This slag, according to Messrs. KAST and BRAUNING, contains : Barium Oxide 3 58 Manganese oxide 2-10 Lead oxide 1-47 Copper suboxide 0. 16 Sulphur 1-85 Silica 31-15 lion oxide 41-31 Zinc oxide 7 85 Alumina 3-18 Lime 6-45 Magnesia 1-06 100 17 The slag is received in conical iron pots. A certain amount of tLe lead and matte contained in it settles to tbe bottom and the points of the cones are broken off and sent at once to the next fusion. The amount of material treated in the lead process in 1867 was 18, 359 tons, made up as follows : FRFIBEECL 67 9,071 tons lead ore. 3,330 " dry ore and copper ore. 5,303 " products containing iron (chiefly from the Preliminary Series of Operations.) 3>i4 " arsenic residues. 270 " iron ore THE TREATMENT OP THE MATTE. Tho matte is roasted in kilns or stamped and roasted first in the Gerstenhofer furnace, and when it is desired to reduce the amount of sulphur, in the reverbe- ratory furnaces also. It is then smelted with the addition of slag from the first fusion. The operation is in fact a treatment of the first slag with addition of the matte, and it exhibits in the strongest manner the peculiarities of h Freiberg methods. Though the matte is altogether basic, little acid flux is added ; and even the slight amount of silica added, is swallowed up by the limesto e and fluor spar which constantly f Tin part of the charge. Th" aim is to produce a very basic, thin slag, which on account of its fluidity will allow the ma te and lead to settle as perfectly as possible. The charge varies very much, for this fusion is the general outlet of whatever the works afford of basic products. Messrs. KAST & BBAUNING give tho follow ing as a specimen : They, it will be o! served, base the charge upon the amount of first slag it contains. This view is certainly correct, as this slag forms by far the largest part of the charge, and the operation is really a refusion of slag. Slag from firstfusion ........... . ........ 100-0 Speise ................ 1-0 Copper slag .............. .............. 4-0 Dezincing Residues . ^ . 10 Copper matte raw ...................... 23 Limestone ............ 2-0 Lead matte roasted in kilns .............. 4.3 Fluor spar ............ 2-0 Lead matte roasted in kilns and stalls ---- 8- 4 Hearth, eta ........... 7*2 Pyrites ................................ 9-0 - 141-2 Thus, matte and ore form but 26 parts to 100 slag. On September 16, 1869, the charge wa^ : First si >g ........... ........................... 100 Eoasted first matte ........................... 20 Fluor spar .................................... 10 Copper slag .................................. 5 Labor and pressure of blast are the same as before. Of fuel 13-14 per cent, is consulted, equal to 17 18 per cent, of the slag ; or 70 75 per cent, of the matte and ore. Products :-Lead=0.15-0-18 per cent. (4452 oz.) silver. 2nd matte 0-10 20 per cent, silver, 21 per cent. lead, and 15 per cent, copper. 2nd slag=0-002 per cent. ( oz.) silver, 1-52 per cent. lead. This slag is thrown away. Ther" are no full analyses of the slag, but the proportion of some of its const! tuents is as follows : Silica ............................ . ........... 29-7 Zinc oxide. . , .................................. 8-5 68 FREIBERG. Lead oxide 2-5 Silver 0025 The r xtremely basic character of this slag, and its large percentage of zinc, make the management of the furnace very difficult. When the Piltz furnace was first in-, troduced at the Muldner works, its height was made 22 feet ; but its reducing action was too great for the slag, and it had to be cut down. A new furnace which is to bn built will bo eleven feet eight inches high, the diameter of five feet cnj incho being retained. Its sides wi 1 be straight instead of it. dined. Third and Fourth Fusions : The second matte is twice roasted and resmelted with first slag, the object being to concentrate it to about 23 per cent, copper, when it is looked upon as a copper matte. These fusions form successive steps in the operation last described. The working of the fu nace is not stopped, but a second or third matte is merely substituted for the first, for a few days or un til the whole of the material at hand has been smelted. The other constituents of the charge remain the same, and the expense of labor and fuel is not to be dis tinguished from that given for the second fusion An old table, showing the gra dual change of the matte from a lead matte carrying about 57 ounces of silver to the ton, to a copper matte with one-third less silver is given below ; but it is very likely that the new method has chauged these proportions. SILVEP. LEAD. COPPEB. Decrea es. Decreases. Increases. Per c nt Oz. Per cent Per cent. in 20001bs. 1st matte 0.25 73 25 6 2nd do 0-23.... 6G 24 21... 15 3d do 0-17.... 48-96 13 32 4th do 0-15.... 43-75 13 42 In the processes just described, the ores have all bt.en treated and resolved first into t e side products obtained in the preliminary series of operations ; and into two others lead and copper matte the result of the shaft furnac treatment. In the lead is concentrated nearly all the gold and silver, and the remaining ope rations of the regular series are those belonging to the lead treatment, by which the gold and silver are separated from the former metal ; and tliose belonging to the copper process, in which copper, vitriol, and rich silver residues itre ob tained. TREATMENT OF THE LEAD. The lead obtained in the foregoing operations contains a very appreciable amount of iron, copper, arsenic, and antimony. It is nil refined by heating in a reverber.itory furn .ce, with admission ot air. The above metals are all more oxi- dizable than lead, and a product is obtained in which they are concentrated. This is used to make hard lead, while th* refiued metal goes through the Patti- son process, for the extra tion of its silver. The latter process lias been so often described, that it will not be followed here. Fourteen kettles are in use, each of 27,500 pounds capacity ; concentration proceeds on the one-third system, and poor le id is obtained with 0-0015 per cent, silver, and rich lead of 1-5 percent. 1 8 per cent. (437505 oz.) silver. The consumption of fuel in twenty-four hours is 4,220 pounds. FKEIBERG. 69 Figure 23. 70 FREIBERG. Refining : Two furnaces are in use, one shallow and one deep, the dimensions having a marked effect upon the consumption of fuel. The shallow furnace treats 10 tons in 24 hours, with 2,200 pounds coal. The deep " " 13-6 16 tons " " 1,320 1760 pounds coal In spite of this extreme difference in fuel, the saving by the deep furnace is, at Freiberg, but a few cents to a ton of lead ; the coal being very cheap. Products : Lead, containing 6 per cent. (175 oz.) silver. 1st. Abstrich, which amounts to about 19 per cent, of the charge. It contains a great deal of lead arsenate and antimonate, and a little copper and iron sulphide. 2nd. Abstrich, forming 10 per cent, of the charge, and containing but little arsenic or antimony. This is returned to the first fusion for lead. Cupellation is performed in a German hearth. It is divided into three stages, forming three separate operations. 1. The operation is stopped at the point at which the bismuth begins to oxidise. This takes place when the lead is so con centrated as to contain about 50 per cent, silver. 2. The rich lead is then re moved to a new furnace and concentrated to about 85 90 per cent, silver. All the products contain bismuth and are treated for this metal. 3. Refining takes place at the Halsbriicke works, the products being also rich in bismuth. Figure Figure IS. The operation is performed in a cupel furnace, shown in Figures 12, 13, 14, and 15. This is a round furnace, with con cave, or cup-shaped hearth, the arch of which is . formed of sheet iron lined with clay and removable. The lead is charg ed in the hearth with the cover removed, and when ready the cover is placed by means of a crane and the joint luted with clay. There are five openings to the hearth, one for the flames to enter, two for the blast, one by which the abzug is drawn out and one for the discharge of the litharge. Fi gure 12 is a view of the hearth with the cover removed, dotted lines showing the relative an gles of the blast, flame and litharge openings. Figure 13 is vertical section, also without the cover, and Fig. 14 and 15 show the skeleton of the covtr ; FREIBERG. 71 6 is the foundation wall, c the iron braces, d drying canals, e ring wall, often made of clay, packed within an outer ring of masonry, / sole, of slag from lead furnace, g brick sole laid on the slag. This is laid dry and the crevices calked with iner- gel . Upon this is stamped a mergel sole (not shown in the figure) which forms the working sole of the furnace. Mergel is an argillaceous limestone stamped fine and when of good quality, contains about 22 silica, 6 clay, 4 iron, 2 magne sia and 66 lime carbonate. When no natural rock of about this composition is at hand artificial mergel may be made by mixing intimately 1 volume cl:iy with 3 to 4 volumes powdered limestone. The powder is sifted through a mesh of 64 holes to the sqtiare inch. This is mixed with old hearth powdered, naoisteued and stamped in upon the brick sole, the layer being 2 3 inches thick. In stamping the mass may be placed iu layers, the face of each layer being criss-crossed before putting in the next, or the whole may be put in at once, lightly stamped to shape, and finished by stamping in a spiral line from the wall to the center. In the cen ter, sometimes nearer the firebridge, a shallow basin is cut out where the silver finally collects. WheD finished the sole must be so hard that pressure with the fingers makes no impression upon it. The object of the sole is to absorb the li tharge formed in the last stages of the operation It must, therefore, be porous, but not so porous as to absorb too much litharge. The bhape of the sole has some effect upon the operation. An old rule is that with a deep hearth the lead oxidizes easier, but the silver brightens less easily ; with a shallow hearth the brightening is easier, the formation of litharge slower. In the figures h and i are iron ring braces, k brick w.ill forming the sides of the hearth, m iron plate covered with mergel, forming the litharge opening n ; this usually has a hood to draw off lead fumes and protect the workmen ; o opening where the flames escape and the abzug is drawn off; this furnace has no chirn ey but is placed under a large chimney lorniing the cupelLition room ; p fire bridge r tuyeres, u and v ash pit, w grate. The cover is made of iron bars joined by concentric iron rings upon which are placed segments ot sheet iron. The sheet iron is pierced with numerous holes through which project bent pieces of hoop iron. Upon this a tough clay mixed with sand is thrown, forming the interior surface of the hood. These different parts are shown in Figure 15. Of the cupellation a good idea will be obtained from five operations, iu 1869, vhich gave ttie following results : Charge : Lead from Pattinsoning 286,165 pounds. Produces : Abzug 1,100 " Abstrich none. Red litharge 30,910 Bismuth litharge 4,290 Ordinary litharge 221,760 Lead scraps 3,410 Hearth. . .<. 25,080 The working time was 463 hours, but this evidently does not include the time employed in preparing and drying the furnace. The average amount of lead cu pelled was 552 pounds per hour ; a very high figure, and due to tbe fact that to wards 30 tons of lead are cupelled at each operation. Of fuel 4^ cords wood, 72 FREIBERG. 15,400 pounds brown coal, and 6,610 pounds bituminous coal were used ; or per ton of lead, 0-03 cords wood, 108 pounds brown coal, and 46 pounds coal (7 7 per cent.) Of the above products the red litharge is sold for paint ; the litharge containing bismuth is treated for that metal; ordinary litharge is revived to lead, lead scraps are returned to the next cupellation, and the hearth is charged in the first fusion for lead. Second Cupellation : The rich lead is not weighed but usually from 1,300 to 1,800 pounds weight, are obtained at each operation. From this second cupella tion, which is conducted like the first, the following products are obtained : First litharge, containing 4 per cent, bismuth. Second litharge containing 910 per cent, bismuth. Hearth containing 910 per cent, bismuth. The time is four to six hours, fu 1 9, 380 pounds coal. The resulting silver is refined in a cupel furnace. It contains all the gold of the ores and products, and this is separated by the usual method of dissolving the silver in hot sulphuric acid The gold remains as a residue, and th-e silver is precipitated by copper from the solution. The gold is ignited with saltpeter and melted with bisulphite of soda. The slag contains platinum, which is obtained from it in the chemical laboratory THE COPPER PROCESS . 2 Hitherto we have followed the course of the operations as they are carried out at the Muldner works ; n >w we will turn our attention to the Halsbriicke works where all the copper is extracted. The matte is subjected to one more opera tion, by which its percentage of copper is increased to 73 75 per cent. This is done by a peculiar process. The first copper matte, according to analysis ma le in the Clausthal laboratory (and the specimen may be looked upon as a iair average, though the copper sometimes rises to 43 per cent.), is made up as follows : Copper 32-9 Iron 19-5 Sliver 0-25 Sulphur 23-8 Lead 15. Arsenic, antimony, zinc, nickel, cobalt, etc., in small quantities. This is smelted in a reverberatory furnace with quartz and barium sulphate. By reduction the barinm sulphate becomes barium sulphide, which, in presence of copper oxide, gives up its sulphur to the copper, takes oxygen, and forms a silicate with the quartz. This use of barium sulphate as a re-agent is Intended to prevent the introduction of iron into the charge. Since metallic copper is not made, but copper sulphate inst ad, it is necessary to the purity of the latter that the resulting matte shall not contain more than 2 per cent, of iron. The matte is stamped and roasted in a reverberatory furnace, to 5 per cent, sulphur. This is over-roasting, for there is not enough sulphur left to make the 1 asic copper sul phide which is desired. But over-roasting is necessary in order to oxidize the 2 This account of the treatment of the copper products is taken from thn^ by Pro- fe-sor KnMemann of the Claustiaal School of Alines, in the Preusa. Zeitschrft fur b r^;, Jdutten und tialmen Weaen, 1872. FT.EIBERG. 73 iron sufficiently to insure its removal. Sulphur is then added to the charge in the form, as above stated, of barium sulphate, and by this method copper matte, of a high degree of concentration, and of a purity that is hardly attempted else where than at Freiberg, is obtained. Ill roasting, the charge is 1,1001,540 pounds of matte every three hours ; or S.bOO 11,320 pounds in twenty-four hours. The furnace is kept cooler than with or- j s or other matte, because the copper matte is very liable to soften and sinter. Of coal 30 36 pel cent is used, but it is of very poor quality, contain ing 2025 per cent of ash. The produ t contains copper oxide, basic copper sulphate, iron oxide, basic iron si Iphate, metallic silver, silver oxide, lead sulphate, zinc oxide, nickel oxide, cobalt < xide, and arsenic and antimony salts. This is fused in a reverberatory of the kind des-.-ribed when speaking of the preparatory operations. The sMes, formed of clay and quartz sand, are repaired after eveiy two or three operations, because the slag, being a siugulo sili -ate. attacks them rapid y. The charge weighs 3,630 3,960 pounds. Immediately after charging t^e turnace is fired as hotly as possible for 4= -5 hours, when tin charge is stirred, and when the matte has settled, the scoria is rake 1 off. the matte remaining behind. A second charge is immediately made, and when the scoria from that has been drawn off, a taird. Not until the matte of three charges has collected is it tapped. Five charges are made in twenty-four hours. Ihe following is the composition of a charge : Charge : -Roasted matte 100 11 w copper (;rom same opera ion).. 1427 Black coppe; (from same operation) . . 23 Barium sulphate 25-30 Raw quartzose dry ores. . . , 14-23 Sometimes fluor spar is added to make the sla^ more fusible. Products : Bla k copper, containing lead, 0-50-0-60 per cent silver, 20-25 leail, 50 60 per cent, copi er. Concentrated matte : 0-290-40 per cent i-ilver, 3 7 p r cent, lead, 7073 per cent, copper. This product Ls the one for which the operation is undertaken Copper matte : 0-300-40 per cent, silver, 9 percent, lead, 60 per cent, copper. Of these products the black copper and copper matte are returned raw to the same operation. There was an apparent loss of 0-26 per cent, silver, and 0-05 per cent, copper, and an apparent gain of 21-85 per cent lead, and 296-35 per cent. gold. This arises from the fact that both the dry ores and scoria contained lead and silver which was in too small quantity to be accounted for by the assayer, as in keep ing the books of the establishment each process is charged and credi ed with the materials it receives and delivers on the same principles which gover < the pur chase of ores. The figures of loss and profit are, therefore, rot re ], but financial. 74: FREIBERG. The resulting concentrated matte contained, by analysis : Copper 76-4: Iron 0-14 Lead 4-2 Sulphur 14-0595-08 Silver : 0-29 In this specimen the percentage of copper is somewhat above the average. An average matte contains 6974 per cent, copper, 0-2 per cent, nickel and cobalt, and 0.51 per cent arsenic and antimony. This matte is now treated with hot sulphuric acid to extract the copper. It is first stamped dry and sifted through a mesh of about 32 to the square inch in order to separate the metallic copper always existing in a matte of so high a grade. This metallic co per, if allowed to remain, would pass through the dis solving process almost undissolved, since the time of that operation is calculated for the solution of copper oxide, which is much quicker than that of the inetaL The powdered matte is then roasted d> ad in an Augustin muffle furnace that has three hearths, and is so arranged that the hot gases can be shut off wholly or partly from the middle hearth, the object being to protect the fresh charge from the action of the hot gases. If too hot, the matte might soften sufficiently to sinter. One charge only of 1,000 pounds is at one time in the furnace, which for six hours is kept quite dark, the heat being then increased for three hours to inci pient whiteuess, which is kept up for three hours more under constant stirring of the matte. The charge remains sixteen hours in the furnaces, nnd its sul phur is reduced to 1 per cent. The roasted ore should be bluish black i tom copper oxide and not reddish brown which would indicate iron oxide. Labor amounts to about six days to 2,000 | ounds, and of coal, which must be of the best quality, 110 120 per ceut. is consumed. The r asted matte is sifted to remove the lumps formed in roasting. Thee enclose raw particles which would pass unchanged through the dissolving pro cess and add to the amount of the argentiferous residues. These course particles are stamped arid re-roasted ; the fine part is ground in mills and bolted. It consist;? of oxides of copper, iron, nickel, cobalt and lead, metallic copper, silver and gold ; a small quantity of sulphates of copper and lead ; and some arsenic and antimony salts. When this is boiled with sulphuric acid the oxides are dissolved, but metallic copper, silver and gold mostly remain as a residue. If silver is dissolved it is re- precipitated by the copper present. Arsenic and antimony salts are broken up, the arsenic remaining in the liquor as free arsenious acid, and the antimony as antimomc hydrate which partly falls. The solution of the oxides takes place in thick vats of hard lead, having a capacity of 1.25 cubic meters, or about 45 cubie feet. They are 1.1 meter high and 1.22 1*30 meters in diameter Kaw chamber acid of 4950 B. is first intro duced to the height of 0. 36 meters, and super heated steam is blown in until the liquor boils. This dilutes it somewhat. The povvdered matte is gr .dually added by means of percussion troughs, during which the whole is stirred constantly. One of the drawbacks of the Freiberg method is the tendency of the matte to lump together, thus increasing the amount of residue. Boiling is continued for an hour and a half, when the vat is filled up with mother liquor irora the FREIBERG. 75 crystallization tanks, and the boiling continued. The solution then marks 32 B. It is allowed to settle for two hours, and the clear liquor is then drawn off by a syphon to the clarifying vats, and afterwards to the crystallization tanks. The entire operation lasts fivo hours, and with four dissolving vats 3,630 pounds of matte are treated in twenty-four hours. Crystallization continues for nine days. The first vitriol formed about one quarter of the wholo go< s to the market as raw vitriol. The remaining three quarters is re-dissolved, filtered through granulated copper to remove the in soluble residue, aud also precipitate any silver tuat may be in solution, and recrystallized. This operation also takes nine days. The new liquor is nearly neutral, and the crystals are very large ; they are washed to remove a brown coatiug, and dried. The yearly production is about 2,300,000 pounds, from 880,000 pounds of matte. The number of vats is eight, and of crystallization tanks 104. The mother liquor is concentrated by boiling, and a new crop of crystals taken. These contain 0.035 per cent of iron. The mother liquor is now very rich in iron, but it also contains two pounds of copper to the cubic foot. It is used as a cementing liquor in making tine pyritiferous ore into bricks. By this mea.ns the copper is returned to the process. The Residues contain the silver. Th y are washed, filtered and dried, and form about 17 per cent, of the concentrated matte. Their composition in 1869 was about 1.94 per cent, silver, 41 ptr cent, lead and 11 per cent, copper ; but the proportion of copper has since then been reduced to 5 per cent, by using stronger acid. The percentage of lead is large, because the sulphate of this metiil is entirely insoluble, and lead su phate is formed by the action of the sulphuiie acid. These residues are added to the first fusion for lead. The balance sheet, reckoned upon 100 parts by weight of concentrated matte, is as follows : Charge : Concentrated matte 100 Sheet copper 22122 Raw chamber acid reduc-d to 66 W B (by weight) 196-7 196-7 Products : Copper sulphate 251 38 Residues 16-41 Mother liquor 3 pounds copper per cubic foot . . . G8 cubic fo^t Do. do. ferruginous, for bricks, 21bs copper per cubic foot 180 Labor : Roasting, days of twenty-four hours, 16 Extraction, " 7 "55 23-55 Fuel : Roasting 116-6 Heating boiler 124-5 " liquor 100-8 Drying crystals 20-0 " residues 6-3 368-2 If to the above 251-38cwt of copper sulphate from 100 cwt. of concentrated matte we add the 8 cwt., to be extracted from the 68 cubic feet of 3-pound mother liquor, we have a total of 259-38 cwt. of copper sulphate from 71 5 cwt. 76 FREIBERG. of copper in tne matte. Tlie make is, therefore, 362 8 per cent., and 100 parts of copper require 176-1 parts of acid of 66 B, to make 362 8 parts of copper sulphate. This proportion of acid is 21-5 parts in excess of that de manded by chemical laws, an excess which is accounted for by the acid takea up by the lead oxide. It should be remembered that the coal used contains for the most part 20 30 per cent, of ash ; the remainder holding 810 per cent. All of it has about 8 per cent, of water. The loss amounted to 3-10 per cent, gold, 0-65 per cent silver, and 0-64 per cent, copper. The gain was 20-48 per cent, lead, these amounts, as before said, not representing real loss or gain, but the commercial values of the materials treated and the products obtained. SUPPLEMENTARY SERIES. Among those operations which, in the early part of this paper, were referred to as merely supplementary to the regular course of the process are the Treatment of the Hard Lead ; Manufacture of Arsenic ; Extraction of Bismuth ; Separation of Gold and Extraction of Platinum. The material treated in these operations consists of : 1. First abatrich from the refining of the lead ; 2. Crude arsenic from the arsenic ores ; 3. Litharge and hearth, containing bismuth, from the cupellation ; and 4. The alloy of gold, sil ver and platinum obtained in cupellation. Dtsiluerizaiion of the abstrich : The abstrich, which forms about 19 per cent, of the lead obtained from the blast furnaces, contains 56 per cent, antimony, 6-7 per cent, arsenic, and 0-2 per cent, copper. It is mixed with 3-4 per cent coal, and heated in a reverberatory furnace. By this method a small quantity of the abstrich is reduced to lead, which is much rcher in silver than the part of the abstrich which remains unreduced. The products are : Lead, which goes to the lead treatment. Desilvered abstrich =0001 per cent, silver, 8 per cent, antimony, 7 per cent. arsenic, and 0-17 per cent, copper ; to treatment of hard lead. Fusion for hard lead: This desilvered abstrich is charged ir a shaft furnace, the charge being as follows : Charge : 300 Desiivered abstrich. 25 SI g from fusion for lead. 5 Fluor spar. Products : Hard lead=0-01 per cent, silver, 9 14 per cent, antimony, 3 per cent, arsenic, and -4 per cent, copper. To refining. Abstrich scoria=15 per cenf. lead. Treatment of absti ich scoria : It is fused again with 25 per cent slag from the fusion for ! ad, and 5 per cent, fluor spar. The products are hard lead, which is added to that obtained in the last operation ; and 2d, abstrich scoria, which is sent to the fusion of matte. Hefming of Hard Lead : The hard lead obtained in the last two fusions is re fined in a reverbera ory. Arsenic and copper are more easily oxidized than lead FREIBEEG. 77 and antimony, and two products are c-btaim d, one rich in the former, and the other in the latter metals. These products are : 1. Refined hard lead=9 14 per cent antimony 2 per cent arsenic, 0-15 per cent, copper. To poling. 2. Scraps=12 per cent, antimony, 4 per cent, arsenic, and 9 per cent, copper. This is reduced to metal by fusion with 25 per cent lead scoria, and 5 per cent, fluor, in a shaft furnace. Poling of Hard L&id: This operation, by which th* amount of arsenic is still further reduced, consists of plunging green wood into the melted lead contained in a Pattinson kettle. The result is : 1 . Lead scraps. 2. Marketable Hard lead=9 15 per cent, antimony, 1-2 1-8 per cent arsenic, 0-15 per cent, copper. The object of these repeated operations is to separate the arsenic and obtain a lead, the hardness of which sh .11 be due u^ainly to antimony, as this is the con stituent which makes this impure lead valuable. Manufacture of Arsenic. Refining : The production of commercial arsenic from arsenical residues of the sulphuric acid process, and from flue dust, wap men tioned in treating of the preliminary operations, for the reason that these pro ducts are mixed with the ores of the metal, and the two classes of operations are inseparable. Therefore to that description remains to be added cnly the process of refining, It is only the arsenic made from ores that r quires *efining, the product obtained from the flue dust being already sufficiently pure. The former is refined by redistillation in closed kettles. These kettles must bo m^de of an iron containing as little carbon as possible, since the carbon will darken the gla c s by reducing a part of the arsenious acid to a lower degree of oxidation. The kettles serve for 150 charges, though made very thin. There are two setts, each containing 5 kettles ; the labor amounts to 1 man to each sett Yellow arse nic is made from white by adding a small quantity of sulphur. The intensity of color depends upon the proportion of sulphur, and the quantity of the Litter is usually 2 per cent Ihe Extraction of Bismuth : Only a very small part of the ore contains bismuth in sufficient quantity to warrant any payment for the metal. But minute quanti ties so small as to escape the assayer, or, at all events, too small to be worth reckoning in the price, are found in much of the ore. The bismuth is reduced like the lead, and follows that metal in all the manipulations up to cupella ion. It is, however, more difficult to oxidize than lead, but less so than silver. The first portions of lead oxidized in the cupel furnace, therefore, contain no bis muth, but when the lead is enriched to about 50 pf-r cent silver, the bismuth also begins to oxidize, and is found in the litharge and hearth. These produc s are placed in large earthen jars, of 10 cubic feet capacity, and treated with diluted hydrochloric acid, the proportions being 300 Ibs. litharge and hearth to 120 Ibs. acid. The acid remains 5- -6 hours, or until the beat arising from the chemical action subsides. The jar is then filled up with cold water and the contents well stirred, a ter which they are suffered to rest for 12 hours and the clear liquid is then drawn oft by mtans of a syphon, into a tank 78 FREIBERG. holding 50 cubic feet This tank is filled up with cold water, which throws down basic bismuth chloride hydrate. The residues are treated 9 or 10 times with quantities of acid decreasing from 20 to 5 Ibs., and the liquor is as before drawn off into the large tank. The basic bismuth chloride is fused in iron crucibles With soda carbonate, coal and quartz. In 1868 the production of bismuth was about 44,000 Ibs., worth nearly $3 25 a pound. The direct cost of manufacture was only 65 cents a pound, not counting in the extra amount of cupel hearth, which is produced by dividing the cupellation into two operations. The separation of gold and platinum was included in the treatment of the sil ver. These operations do not differ from the ordinary methods, and hardly come withiu the province of this paper, which is intended to exhibit Freiberg as a lead and copper producing establishment. In reviewing the processes in use at Freiberg, it is evident that with all their excellences, some of them have great defects. Many of the lesser operations evince an amount of skill and of scientific ingenuity which is rarely met with. But on the other hand, the most important of all the operations the fusion for lead id carried on in a way not to be commended. One of the chief purposes of a fusion of ores is, in nearly all cases, to dispose once and for all of that portion of the ore which is of no value the gangue . It is 1 of importance to get out aa much metal at one fusion as possible, but it is of at least equal importance to produce in the first operation a slag which is sufficiently poor to bo thrown away. This is rot done at Freiberg. The products from the fusion of lead ore all require re-smelting. That is inevitable with the lead and the matte, for by the nature of the case both have valuable constituents, which must be sep arated. But the slag is re-smelted only because it has about 5 per cent, of lead, and slags are not usually considered worthless until their proportion of lead has been reduced to li per cent., or less. If we assume tlese products to be in the proportion of 28 lead, 25 matte, and 47 slag, we see that fully one-third of the ore ought to leave the treatment once for all at this step ; it should be thrown away as useless slag. The fact that it is not thrown away entails considerable expense of fuel ana labor. If it were possible to reject at once 33 of the 47 per cent, of slag, the saving in fuel alone would amount to at least 3 per cent, of the original ore. The fault of the operation is the formation of a basic slag. To this is due the retention of so much lead. Basic slags are, as a rule, avoided in lead smelting, the slag from lead works in all quarters of the world having, with tolerable uni formity, pretty nearly the composition of a bisilicate. The composition of worth less lead slags may, as a rule, be put at 3540 per cent, silica, and over 40 p< r cent, iron oxide, the remainder being bases of various kinds. In many works the amount of zinc closely approaches that in the Freiberg slag. These facts in dicate that to place the lead treatment at Freiberg on a par with that of o her works, it is necessary to increase the proportion of silica in the charge without lowering that of iron oxide ; that is, the slag must be raised from a proto- silicate (nearly), as at present, to one that is nearly a bi-silicate. The problem is then, Is FREIBERG. 7VJ there any means of doing this ? Difficult as it is to prescribe means of working in an establishment so distant as the great Saxon works, and daring as is the task of criticizing the management of men so able and so experienced as those who control it, it still seems to me possible to indicate a theoretical method of reform ing this process. Whether that reformation is practicable is a question of dollars and cents, which only the most intimate acquaintance with (lie f-pecial conditions of Freiberg can determine. The Freiberg mines are situated in the midst of a great field of gneiss, of which three kinds are distinguished. The composition of these is given by SCHEEBFB as follows : L II. III. Mean. Silica 65-26 70-75 75-24 70-45 Titanic acid 0-95 050 0-20 0-55 Clay 14-82 13-70 12-86 1379 Iron oxide I 6-20 5-17 2-34 4-57 Manganese oxide f Lime 2-98 2-08 095 2-00 Magnesia 1 88 1-07 0-36 1-10 Potassa 3-93 334 4-86 404 Soda 2-43 2-42 230 2-38 Water 1-06 103 068 0-92 99-60 10006 99-80 99-80 Here, then, we have a substance capable of supplying the needed silica. But if this alone were added to the charge, the amount of iron would be decreased, and the average given by KASTand BKAUNING for the Mulduer slag (40 per cent, iron oxide) is already as low as it ought to be. Iron must be added in some form, and probably the cheapest supply could be obtained at the iron works in the neighborhood of Freiberg. Both puddU- and reheating slag, can be had and in quantity sufficient to satisfy the demands even of works that treat 25,000 30,000 tons of ore a year. This material can be had by paying the expense of removal, which, from Camsdorf, would be, delivered at Freiberg, about $1 a ton, There are other works nearer Freiberg, from which the same slag could probably be obtained at less cost. At present a large amount of slag from the same operation is smelted with the ore. It yields nothing, for it leaves the furnace with just as much lead as it had when it entered. But it makes the fusion easier, and also regulates the run by diluting any impurity in the ore as an exceptional amount of zinc oxide. It this charge of slag were entirely or partially replaced by a proper Amount of the gneiss and the iron slag, the composition of the charge could be regulated at will and without increasing the amount of material treated. Let us see what the proper proportion would be. The mean composition of the reheating and puddle slag may he taken, in the absence of analyses, at 60 iron oxide and 40 silica. Assuming that it is desired to make a lead slag containing 38 silica and 45 iron oxide, the amount of the two fluxes necessary to transform 100 parts of the present Muldner slag into a slag of the new composition is the following : 80 FREIBERG. Muldner slag. Gneiss. Iron slag. 100 parts. 20 parts. 85 parts. Total. Silica ............ 31 14 34 79 Iron oxide ....... 41 1 51 93 Other bases ...... 28 5 33 205 These melted together would give a slag containing, in round numbers, silica 38-5, iron oxide 45-3 and other bases 16-2 per cent. According to EAST and BBAUNING, 100 parts of ore and matte in the lead process yield about 25 lead and 23 matte. The slag must therefore amount to about 50 per cont. of the ore and matte in the charge. Calculating the amount of the proposed fluxes to be add >d to 100 parts of lead ore, roasted pyrites and matte, as usually charged at the Mnldner works, we have the following quantities required : New charge. Old charge. Muldner ore, etc ..................... 100 100 Gneiss .............................. 10 Reheat, and pud. slag ................ 43 Slag from same operation ............. 10 60- 75 In this estimate, which is not meant to be exact, no account has been taken of the basic fluxes limestone and fluor spar now added to the charge, and which, of course, would be useless in the new charge. The removal of these would de crease to some extent the amount of gneiss required. It is well known that the fusion of raw fluxes costs more fuel and requires a higher temperature than that of fluxes which have already been melted. Bat in the proposed charge the am unt of gneiss is too sma 1 (7 per cent, of the whole chaige, or 1 ss) to alter the present conditions of the furnace materially. It ia <juice probable, in fact, that the redur tion of the zinc oxide in the slag by one- third, and the production of a more fusible slag, would fully neutralize the dis advantage of smelting down the small quantity of raw flux required. One of the greatest difficulties met with at Freiberg is the amount of zinc present in the charge. Care hr,s to be taken to manage the previous roasting, and the composition of the shaf fuvnnce charge, so that only a part of the zinc shall pass into the slag and part into the matte. When the amount of zinc oxide is right the old slag repassed has no effect upon it, for it contains just as much of the zinc oxide as the charge has. But tbe addition of fresh material would be of grfat advantage, for it would take up its share of the zinc and thus lower the percentage in the whole amount of slag. If tbe slag from 100 ore, without gneiw* and iron slag, contains 10 per cent, of zinc oxide, that made from the same ore, with an addition of 53 parts of those fluxes, would contain only about 65 per A slag of this kind, formed according to the principles which have been proved in numberless works, and containing a not excessive amount of zinc, ought to be sufficiently poor in lead to be at once thrown away. In |froof of this, and as an indication of what resulte spring from comparatively slight changes in the com position of slags, I will cite again the analyses of tLe lead slag from the first matte fusion, as it is thrown away, at the Mulduer and Halsbrtieke works : FREIBEllG. 81 Muldner. Halsbriicko. Silica 29-7 34.1 Zinc oxirte 85 7-6 Leudoxi-ie 2-5 1-0 Silver 00025 0-0015 Lead oxide in previous ore slag. ... 5 7 1*37 The Ha T sbriicke slag, it will be observed, has about the composition of tho ideal slag proposed above. The Freiberg metallurgists may have some occult reason for smelting their ore twice over. It is not to b supposed that with such excellent materials for flux about them they have considered themselves forced to the course they have taken. But what those reasons are no traveller has yet discovered. The Frei berg works are a splendid example of the success with which the products of a large mining district may be treated in one or two works ; and the explanation of the faulty lead process has usually been sought for in the diversity and diffi culty of the ores subjected to it. That, however, as before remarked, cannot bo the case, and it is to be hoped that among the valuable treat ses on metallurgy which occasionally come from the great mining town of Saxony, there will som,e clay be one which will let the outer world into the secret of the present ^y item. At present Freiberg may fairly be said to be pursuing one path and the rest of the world another. The reasons lor a course so singular must lie either in gen eral principles or in special conditions of the place ; if the former, it might aid the cause of mining in the world to know what these principles are. The Lead and Silver Works of the Hartz Mountains. The mining region of the Hartz mountains* is second in importance to that of Saxony alone. Indeed, if the Mansfield copper mines are added to the silver, lead and copper mines of the Upper Hai tz we have a district which is in every respect extent, value of product, number of workmen and intelligent methods of work the equal of any other similar region in the world. The subject of the present paper is the smelting operations at Clausthal, Lautenthal and Alteuau. In former times the "Upper Harlz" was a name given to the works at Clausthal, Lanten- thal, Altenau and Andreasberg, each of which had a completely furnished smelting establishment where argentiferous lead ores could be resolved into merchantable lead, silver and copper. When the district passed into the hands of the Prussians in consequence of the war of 18G6, changes were made which placed the region very much higher than it had ever been in the sc le of importance. The mines * Changes have followed each other so rapidly in the Hartz that almost every year has brought out some new process or important modification of old methods. Tho above notes, therefore, though based on personal observation, have been mainly drawn from the writings of KOCH, WEDDING and BR^SUNINQ and KUHLEMANN. With the exception of Dr. WEDDING all of these gentlemen are actively engaged in the woiufl they have described. 82 CLAUSTHAL. were worked more vigorously, aad plans were laid out for increasing the amount of ore treated to 400,^00 centners or 20,000 tons (of 2,000 Ibs.) per year. The work of the several establishments was redistributed, and fundamental changes v ere made in nearly every branch of the treatment. Clausthal was made an establishment chieftly for the treatrn nt of the or?, Lautenthal for the separa tion o the silver from the rich lead, and Altenau for the copper process. Andreas- berg alone on account of the peculiarly rich arsenical ores found there, retained it-i old works, sending, however, all its copper matte to Altenau. While these changes were in contemplation the introduction, first of the Rachette, and then of the Kast iurnace, compelled some delay in order to study the performance of the new apparatus, and though years h*ve passed, the alterations are haidly yet fully carr ed out. THE WORKS AT CLAUSTHAL. First in the series comes Clausthal where the ore is run down to metallic lead and copper matte. The process in use is one which was invented at Clausthal, und wtach though often derided, has probably had move influence upon the wueltii g of galena ores throughout the world than any other. It is the method known as precipitation Galena, which is the main constituent of the J- artz ores consists of lead and sulphur. In all the works hitherto described in these notes the sulphur has be-ii removed chiefly by combining it with oxygen roasting. At Clausthal iron is used instead of oxygen. At first the metal was used direct, i>ut it was afterwards found that a silicate rich in iron oxide served not only as wel but better than the metal itself, and inasmuch as there were large stores of such silicate containing nmall amounts of copper and silver which could be had for the mere cost oi transportation, the discovery was one of great importance. Finally another modification was made which now forms the existing mode of treatment. One of the fundamental differences between the removal of sulphur by oxygen and by iron is th.tt in the former case the product is volatile and passes directly out of our hands as a gas, while in the latter it is a solid, called matte If it were possible to produce a matte containing nothing but iron and sulphur there would be a solutely no drawback to the precipitation as a process for pure lead ores, ior the matte could be thrown away and the sulphur thus removed from the process. But a matte produced by smelting lead ores always contains lead, and if silver and copper are also present these metals always pass into the matte in quantity sufneie t to make their extraction a ne essity. The mode of this ex traction is the same throughout ;he world. There is no substance available to the metallurgist which will take the sulphur from the iron in the matte as the iron has taken it from the lead in the ore, except one that is oxygen and mattes, therefore, are everywhere roasted. The oxidation of the sulphur is accompanied by oxidation of the iron, and as this is the first step toward the formation of a silicate, it is only necessary to melt the roasted matte with quartz in order to remove the oxidised iron in the form of a slag. This treatment of the matte is a Bc-rioas item of expense. The cer.niuty that the matte will contain the copper is by no menus an evil. On the contrary, were it not bo the metallurgist would bepuzzled to know how to CLAUSTHAL. 83 his copper from the lead. The whole treatment of sulphides containing] copper is based upon the chemical fact that copp<-r and sulphur will in all cases unite in the furnace, provided the amount of sulphur present is not sufficient for both the iron and the copper ; the former can be removed by the addition of quartz, a slag being the result. This action is so certain that the metallurgist, who has a copper matte which has been roasted "dead," that is, has had all the sulphur removed and the copper and iron completely transformed to oxides would have no hesitation in charging it in a furnace with an iron pyrites containing only quartz, iron and sulphur, and no copper at all. The result in all cases is that the copper unites with the sulphur and the quartz with the iron oxide. In the Hartz, the treatment of ore and nutte forms one operation. Instead of melting the ore with a si >g rich in iron, to remove the sulphur, and melting the roasted matte with another sla,^ ri<-.h in silica, to remove the iron oxide, they combine the two processes and melt the ore and the roasted matte together. As the ore contains both quartz and sulphur the oxidized iron passes partly into the slag with one and partly into a new matte with the other. The matte, therefore, makes a continuous round, being roasted and re-smelted with the ore five or six. times. It is easy to see that this is really no more nor less than a roasting process, though the roasting is transferred from the ore to a matte. There are two ad vantages to be obtained from this treatment. One is the less bulk of the matte to be roasted, amounting to not more than half, or at most, two-thirds the oro. The other is that the sulphides of iron are in all cases much easier and che per to roast than the sulphides of lead. They contain more sulphur, require less fuel, and present less liability to sintering and imperfect roasting. Other im portant advantages are, first, that the lead and silver having been mostly re moved, the loss from volatilization is much less, and, second, that the sulphur in the matte can be utilized by making sulphuric acid from it, while the ore id useless for that purpose because it contains so little sulphur. The ore treated at Clausthal had, according to KOCH (1869), the following composition : 71.676 per cent, lead sulphide or 02,07 lead. 0.945 do copper sulphide 0.75 copper. 1.880 do zinc sulphide. 0. 537 do antimony sulphide. 1.410 do iron sulphide. 0.113 do silver sulphide or 0.003 silver. 4.139 do iron carbonate. 0.150 do alumina 2.380 do lime carbonate. 1.460 do baryta sulpha .O. 0.075 do magnesia. 15.235 do silica. This is a mixture of ores obtained from a great nnmVr of mines, anfl ttie occasional preponderance of ore from some one mine will sometimes a ter the composition of the charges smelted for a few days. The usual composition of the charge, as at first established, may, however, be ascertained from the following quantities which were smelted during the months of July, 84 CLA.USTHAL. August, and September, 18G6. The quantities are hundredweights of 110 English pounds. The proportions of hearth and rich litharge are worth noticing, for the Claustbal works us^ the German cupel hearth, and these are therefore the proportions in which cupel scraps are produced in treating a 6li per cent, ore, by this method : Per ton. Ore 33,400 cwt 100 2000 Ib. Roasted matte 17,5(35 524 1050 Copper slag 22,248 663 1332 Slag from same op era tion55, 5 42 ,, 1GG 3332 ,, Cupel hearth 1,112 ,,8 6 Bich litherage 624 2 3 Scraps 262 03 lj Days labor (12 h) 1,002 3i 3-5ths day Coke 14,964 ,. ) , , r q ., ,. Charcoal.. 810 f JM lb This is therefore an expense of a three-fifths of a day s labor, and 944 pounds of coke per ton of ore. The cause of this large expense of fuel is the use of so much flux, amounting to 284 per cent, of the ore. This excessive proportion of flux is one of the peculiarities of the Hartz. Nowhere el^e is it used in such pro fusion, but innumerable attempts to reduce it there have, without exception, failed. When slag is used as a precipitating material a bulky charge is the necessary result, but even when metallic iron was the precipitating agent, 121 per cent, of i-lag was added to the ore. The causes of this peculiarity have never been published. Considerable changes have been made in the above proportions, the chief of which was to cut down the amount of slag from the same operation rep;\ssed, to 75 and 70 per cent, which reduced the flux and precipitating material to 190 per cent, of the ore. The charge at one time was made up of 100 ore, 50 roasted matte, 70 copper slag and 70 lead slag, smelted with about 43 coke. It was found, however, that with these proportions the matte became so rich in copper as to part with some of that metal to the lead. The roasted matte obtained from ore smelted with slags alone contained 3 per cent, of copper, which rose to 8 and even 9 per cent by re-fusion with ore and the lead instead of 0. 3 per cent. , as formerly, contained 0.6 to 0.7 per cent, of copper. This increased the difficulty and cost of desilverization, and the proportion of roasted matte was diminished to 28 per cent, of the ore. The exact composition of the new charge I have not been aUe to obtain, but it is probably about the following : Ore 100, roasted matte 28, slags 150-170. After the change the copper in the matte sank to 5 per cent., and in the lead to 0.4 and 0.5 per cent. The products dur ng the above-mentioned three months were From 100 Ore Lead, 21,380 cwt 65* Matte.24,253 , 72f The three methods of treatment successively used at Clanslhal, bare given the following results in regard to product : "With metalic iron. With copper slag. "With roasted matte, Lead, 54 65 65i and 05 Matte,44 55 72-} aud 66 CIAUSTHAL. 85 The simplicity of this precipitation method would recommend it in nearly all cases were it not for the large increase of cost which results from using so much flux, and the production of so much matte. The practice of adding puddle and reheating cinder to lead ores in the shaft furnace, is now so common that tho business of lead smelting has, in some regions, almost become auxilliary to tho manufacture of iron. Under these circumstances it is always a question whether the operation of roasting, costly in plant and in practice, cannot be supplanted by merely increasing the proportion of iron flux, and re-charging the matto formed. In those cases where ores, pure in Lad and rich in silver, are smelted for the silver they contain, and there is therefore no desire to keep the lead pure, it seems probable that this method would be found decidedly advantageous. The lead obtained is not pure. Analyse* of thelead and matte given by KOCH, are as follows ; although obtained by the former precipitation with copper slog, they fairly represent the same products from the present process. Lead. Matte. Antimony 0.613 0.350 Copper 0.276 4.392 Iron 0.002 55.720 Zinc 0.008 1.125 Silver 0.127 0.029 Lead 98.969 7.984 Sulphur 29.546 100 99.146 The slag is maintained with great regularity between a proto-and a bi-silicate. It is rich in iron, very poor in lead, and can be thrown away at once. OnJy a very small portion that which solidifies in the fore hearth must be re-chargyd on account of grains of lead and matte mechanically contained in it. Tho fol lowing is an analysis of this ordinary slag : Silica ,43.60 Magnesia 1.56 Iron oxide 31.68 Lead oxide 0.70 Alumina 15.50 Silver oxide 0.000087 Lime 6. 50 99.54087. The furnaces in which the fusion takes place are of two kinds, the round or Kafit furnace, and the Rachettc. The round furnaces at Clausthal form an interesting series of experiments in. the most recent progress of lead metallurgy. The principles which were introduced into the construction of lead furnaces by the English in Spain, 30 years ago or more, and have been modified by PFANDEB- HEIPKX, PILTZ, and others; have also made their way to Clausthal. Five round furnaces of various dimensions and construction are found there. One of tho peculiarities of the Clausthal system of smelting is that the ore must be in tho form of powder, and this formerly caused so much dust that from 5 to 8 per cent, was taken from the dust chambers. This gave rise to a very unusual moda of building the furnaces. A row of heavy brick piers was built, and the inter vening spaces arched over. On these arches was raised a line of dust chambers, which not being intended to condense volatilized lead, but merely to give tha CLAUSTHAL. 87 fine dust opportunity to settle, could be placed immediately over the nm ices. l>ut tLe result o this mode of construction was to place a limit to the sizo of the furnace which could be built between two of the piers, and when the nev/ doctrines in furnace building began to spread Mr. K.VST, d rector at the smelting works at Oausthal, had to experiment to ascertain what were the smallest diameters that would prevent the dust from flying out of his furnaces. At first a furnace 3 feet in diameter at the tuyeres and 4 feet at the top was built, but the amount of duct was still excessive. Then the diameter at the mouth was increase.! to 4 feet, which caused a reduction of the flae dust to 2 per cent. The slowness of the ascending current of gas in the upper part of the furnace also affects very favorably the utilization of the cok . and the amount of material run through in a day. The following table gives a comparison of the four round furnaces v.ith a Ruchette. All of the round furuaccs have the same dUmeter at the tuyeres, 3 foot, and the same height, 21 feet. The diameter of the Tlachctto at the tuyeres i i also 3 feet; Diameter at Coke per ICO ore. Flue dust. Time to sm It mouth. 11, (r>0 Ibs. ore.* No. 1 4ft. 2in. 45.39 2.8 per ccn 1 . 73.2 hours. No. 2 4ft. Sin. 41.85 2.1 " 71.8 " No. 3.... 6ft. Oin. 41.74 1.7 71.2 " No. 4 6ft 3in. 41. G2 1.1 " C J.2 " Hachette..4ft. 9in. 413 1 " 93.2 " The round furnaces, called also Kast furnaces, after the Director of the works, do not differ from the general type of modern lead furnaces, except that, being built between piers of masonry, they are not approa?hable on all sides. They are made with fore hearth, over the dam of which tho slag runs without cessation. The number of tuyeres ranges from 4 to 7. Like so many lead furnaces in Europe, these are built of ordinary red brick, only a few fire brick being placed around the tuyeres, and these are in fact often omitted. These furnaces have made an uninterrupted campaign of 2 or 3 years, a result which is due to the accuracy wi*h which the composition of the slag is calculated and maintained. The ore and flux are spread out in layers upon each other on tho floor at tho furnace mouth, and charged equally over the whole surface of the iurnace, the coke being spread out in the same way. The pressure of air is 10 to 12 lines of mercury. figures 12 to 14 givo sections of the Kast furnaces. The dimensions of one are Height 20ft Dia fcter at mouth 5ft. Do. at tuyeres 3ft Do. at sole 2ft. 4in. Number of tuyeres 4 1 re^sure of blast .11 14 lines of mercury. They are open at the month, having no hopper nor cylinder. The ore and coke are spread evsnly over the surface, the ore being thrown from wooden troughs, and tho coke from flat baskets. The charges for 24 hours are always made up in the morning, so that at night nothing but tapping the furnace and throwing the slag oil the slag-run takes place. All furnaces at Clausthal have a fore hearth, over the edge of which the slag ruos, passing down a narrow inclined 83 CLAUSTHAL. 1 KACIIETTE FUJiXACE AT CLAVSTXAZ. ISSMSWiS CLAUSTHAL. 89 bank made of brasque. It solidifies on this, and is thrown to one side by the workman who wields a two-pronged fork. The lead is not tapped f om the body of the turnace, but from the front hearth where it collects. This front hearth is formed inside of an iron box projecting from the furnace, and in the side of this box is the tap. In addition to these Kast furnaces Clausthal possesses a Piltz of the same pattern as those at Freiburg, but w th some judicious alteration in the method of suspension. It is octagonal, 24 feet high, 4ft. Sin. diameter at the tuyeres, and 6ft. Sin. at the mouth. The 8 water tuyeres are 15 iaches above the slag spouts. It was attempted to run this furnace with a closed hearth, but outside modifications do not seem to succeed in the Hartz, and it was found impossible to produce a fusible slag. The furnace was accordingly narrowed to 4ft. 2 n. at the tuyeres, and fitted with a front hearth. It is now in successful operation. The Rachette furnaces were for a long time the best that Clausthal possessed, but they seem to offer no advantages over the round furnaces, while they are not only more costly to build, but also are subject to a patent right. Their form ia Fig. 21. shown in figures 15 to 18. Figure 15 shows a vertical section of the furnace through the longer axis ; fig. 16 is a horizontal section, though the tuyeres, fig. 17, shows the tuyeres in place, and fig. 18 gives a horizontal section and end view of a tuyere. The Rachette furnace is a construction designed to obtain great capacity, with out making the diameter greater than twice the throw of the blast. To that end it is made rectangular, and long and narrow. Tuyeres are placed on each of the long sides, and throw their air through the furnace in its narrowest direction; and the form of the furnace is such that any number of tuyeres can be used by merely lengthening the furnace. Usually five on a side is the number. For- 90 IAUTENTHAL. nierly the ends had no tuyeres, but it having been observed that scaffolds and accretions collected only on the ends, these have also been furnished with Fig. 22. tuyeres, and with good effect. There is a tap at each end whieh requires a double set of men at the bottom. The main dimensions of the Altenau Eachette furnace, the first built in theHartz, are given below ; they have not been mate rially changed in any of the newer ones : Height 19 feet 6 inches. V> idth at tuyeres 2 ,, 11 ,, Width at top 4 ,, 6 Length 7 ,, 4 Distance between tuyeres 1 ,, 4 ,, It is an excellent furnace and smelts 16,500 Ib. of ore, or 44,000 Ib. of charge in 24 hours with about 5,500 Ib. coke. The increased width of the throat keeps the loss by dust down to a minimum, provided the pressure of blast does not ex ceed 10 or 12 lines of mercury. THE WORKS AT LAUTENTHAL. The lead is all desilvered at Lautenthal by the zinc and steam process, which, however, differs very greatly in its details from the system pursued at other works. The operations in the process are : 1. Fusion and treatment with zinc. 2. Treat-merit of poor lead with steam, under a hood, to remove the zinc. 3. Treatment of the poor lead with steam and admission of air, to remove the antimony. 4. Casting the purified lead. 5. Treatment of the rich crusts, or alloy, with steam, to remove the zirc. 6. Cupellatiou of the rich lead resulting from 5, with addition oi the rich ox ides to extract their silver. 7. Treatment of the poor oxides. Treatment with Zinc. The kettles used are old Pattinson kettles, of 5 feet 6i inches diameter and 2 feet 10 inches depth. Each holds 27,500 Ib. of lead, and three are worked together, forming a battery. The two .outer kettles are charged with 27i tons (of 2,000 Ib.) of lead, which is melted down in about six houi-s, when an abzug, or lead containing enough copper, iron, etc., to make its point of fusion higher than that of pure metal, is taken off and cast in moulds. Each of the end kettles, then receives 49 i Ib. zinc. The object of making this first charge so small is to concentrate the gold, of which the lead contains a very minute proportion, in a small quantity of silver. It is a peculi arity of the process that silver is not taken up except in a small quantity, uutil the gold and copper have been removed. The result of this first charge is a crust which contains all the copper and gol^, without being much riche; in silver than the original work lead. In spite of this decided concentration, the silver made from this crust contains only 0.12 to 0.20 per cent, of gold, fctill the latter met J pays for its separation. LAUTEXTHAL. 91 When t^ie zine charge has molted, the bath is stirred by two men at each kettle for twenty-five minutes, the stirrer being a broad, flat and long-handled iron disc, pierced with holes. The metal is then cooled until a cru-t of about 14 inches thickness forms on top. It is a matt r of importance to so manage the cooling that it shall take place mainly from the surface, in order to prevent the formation of a thick crust on the bottom of the kettle, for this crust would contain zinc and silver. To avoid this the fire is merely covered with ashes. Tho top crust is thrown into the middle kettle, and when this is completed a new charge of 258 Ib. zino is made to each outside vessel, and the fires are freshened. The stirring in, cooling down, and skimming are repeated, and the last cha ! ge of 77 Ib. zinc is then made, and the same operation gone through with. The time consumed in completing a change is about as follows : Drawing abzug, 30 minutes ; melting, 1 1 hours ; total, 6-7 hours. The desilverization ol 27 tons of lead requires about thirty Lours. The middle kettle is now heated, the bath stirred, cooled and skimmed, the crust being a concentration of the three crusts taken from the other two kettles. This is cast in moulds. From 20 to 40 Ib. of zinc are added to the bath, and the above operations are repeated. If necessary, a second charge of ziuc is made. According to the above the zinc charge amounts to 14 per cent of the lead. The crusts, do not contain all the zinc, but fully one-half is left in the poor lead. The removal of this zinc has been the most difficult problem in the whole process of desilverization, and though the poor lead can now be treated without difficulty, no direct and simple method of separating the zinc from the ri h crusts has yet been found, unless the costly mode of distillation is excepted. De zincing the poor lead. The three kettles now contain poor lead, which is deziuced by blowing superheated steam at 15 Ib. pressure through the bath, by means of a bent pipe, two inches in diameter, running to the bottom A sheet iron hood communicating with a large pipe is bolted down on the kettle and the joint is luted. The lead is kept at a little below cherry red, and is steamed for four hours to remove the zinc, and for tMo hours more to remove the antimony, air being admitted by opening the door of the hood. Inasmuch as the antimony is not carried over with the rich crust, the middle kettle is steamed to remove the zinc alone. In this operation the temperature is a point of great importance. Il too low, a longer time is required, and the amount of oxides formed is in- cr ased. If too high, the kettles are rapidly destroyed. At the right tempera ture 0-7 per cent, of zinc and 1 per cent, of antimony can be removed in the time given. The object of passing the steam through the bath is to oxidize the zinc, but a good deal of lead is also oxidized, and the oxide first formed is fluid, but it gradually becomes powdery nnd "dry." The oxides from the end kettles ara yellow, but those formed in the middle kettle are greenish, showing a prepon derance of zinc. Perfect dryness of the oxides is a sign that all the ziuc has been removed. Other tests are to cast a small assay in & scorifier from time to time, until no star forms in the center upon cooling. The star would indicate the presence of antimony. The kettle is also left expo-ed to the air a while, without steam, after the oxides have been removed. If a clear red litharge forms, ihe lead is pure. Another test for zinc is to take a ladle- full, Bciapa the surfa- e, 92 LAUTENTHAL. while hot, with a piece of wood, and if the silky app< arance is gone the zinc has be n remoTed. When the tests show the lead to be free from both zinc and anti mony, the lead is ladled into moulds, and forms the " Refined Hartz lead." It is so nearly pure as to contain from 99-983 to 99-987 per cent. lead. The dezinc mg of the rich crust presents more difficulties. The withdrawal of osygen from the steam by the zinc leaves a gas so high y charged with hydrogen as to be violently explosive when the hot gas conies in contact with the air. Jn dezinciiig the poor lead, the deoxydatiou of the sttam is quite imperfect, and the resulting gas never gives alarming explosions. But the rich crusts contain 5 or 6 per cent, of zinc, and severe explosions of the gas have occurred. These are, however, now complete y prevented by turning steam direct into the hood before allowing air to enter it. The products now consist of : (1) refined lead ready for market ; (2) rch lead containing about li per cent, silver which is cupelled in a German hearth. (3) Poor oxides free from antimony, and others containing antimony. The for mer are washed on a sleeping table which separates them into two qualities. Of these one consists of metallic lead and lead oxide, containing about 85 per cent, of the metal ; it is reduced to second quality metal. The remainder, containing much ziuc, is of a yellow color and is sold as paint. The oxides containin anti mony are melted with other similar products to hard lead. (4) Rich oxides. These are placed upon the bath in the cupel furnace, the heat being raised to the highest limit. The silver passes into the lead, some lead being oxidized in the exchange. A slag, consisting of zinc oxide, lead oxide and metallic lead, re mains and is drawn off. It contains about 50 ounces silver to the ton and is re duced with rich litharge to metal which passes a second time through the desil- verization process. To have a successful imbibition, or absorption of silver by the lead in the cupel hearth, it is necessary to keep the rich oxides from being too dry. With lead, such as is produced in the Hartz containing 38 ounces to the ton the oxides are in the right proportion when they form 8 to 10 per cent. oi the desilvered lead. WEDDING and BR.EUNNING give the following summary of the results obtained by this process in 1869. The German centner of 110 Ib. English weight is here given as cwL MATERIAL AND PRODUCTS. WEIGHT. PERCENTAGE. SILVER. Ib. LEAD. Ib. SILVER. LEAD. 85-389 8-662 2223 0-250 0.267 Charged : 22,053 cwt. work lend 31GS* 3243 22,U21i 18,8031 1,9071 489 ft 654 58| 102-372 Produced : 3,525$ Ib. crude silver, contain ing fine silver Refined Hartz lead Merchanlable litharge 64 cwt Total 3233$ 211,315 3921 102-36* 102-372 96-791 1-781 98 5U2 Various products not worked up : 452 cwt Total. . LAUTENTHAL. 93 It is certainly remarkable tint the intermediate products ftill in treatment, consisting of hearth, scraps, litharge, abstrich, and impure lead obtained in li quating the hard lead, should amount to only 22J tons or 1-781 per cent, of the lead treated. The second quality lead is made from the washed oxides mentioned above, the scraps formed in ladling the first quality metal from the kettle and other products free Irom silver. It is blown with steam .to remove the antimony and then casf. Its only impurity is a small proportion of copper. The hard lead is obtained by smelting the oxides containing antimony, and this also is blown with steam to remove the zinc and copper. Thus the steam process is now used for the refining of all kinds, and by its use the numerous operations which made up the old process of cupel at ion and refining by air have been entirely superseded. In ladling out the refined lead, an assay weighing about Ib. is cast for every 8 pigs c.f lead. When 5000 pigs have been cast, these assays are melted together, and some pounds are cast and sent to the laboratory for analysis. The first of the following analyses is from the lead produced at Lautenthal in 1870 up to the month of August, and represents 20,465 pigs or about 1575 tons. The other is from 1193 tons of lead T fined at Altenau, where refining was still in operation in that year. Each analysis is the mean of 4 nude upon 1400 gram in PS in one case, and 15UO grammes in the other. It is noteworthy that although refined at differ ent and widely separated establishments, and made from work lead of very dif ferent composition in regard to impurity, the refined lead shows a difference of only 4-1000 of a per cent, that from Altenau, whera the copper ores and matte are worked, showing a small excess of impurity. This similarity of composition is a proof of the method with which the operations are carried out. Leal 99-983139 99 987560 Copper 0-001413 (M;02022 An-imony 0-005698 0-003335 Bsmutk" 0-005487 0-003650 Silver 0-000460 0000721 Iron 0-002289 0-001229 Zinc 0-000834 0-000776 Niufcel 0-000680 0-000707 100- 100- In regard to the bismuth present in the above, it is worthy of remark that stenm has no effect upon this metal, which remains with the 1- ad. This circumstan-e, which has been developed only within a few years, is a matter of great impor tance to works which, like Freiberg, make considerable quantities of bismuth from intermediate products, which would be lost were it not concentrated in those products. Pattinson- s process effects this concentration, and this is another reason why that system of concentration, now so generally rejected, should be retained at Freiberg. " . The purity which now distinguishes the Harz >ead has not been obtained with out much trouble and study. Compared with the lead obtained from cupel- lation, the Pattiuson, salt-aud-poling and steam processes have yielded 8. product which has shown an advancing purity. 94: ALTENAT7. THE COPPER PROCESS AT ALTENAU. When the matte is withdrawn from the ore fusion it contains about eight per cent, copper and seven per cent. lead. It is roasted in a square kiln, twenty feet high, four feet square at the bottom, and 5X^ feet at the top. The ma te is broken into pieces, 1 or U inches square. Only the upper part of the kiln is hot, the fire not sinking below 3 feet from tho mouth, while the re maining 9 feet serve as a regenerator td heat the ascending air, a process which of course cools the matte. Two doors at the mouth are used for charging ; two others are placed two feet under them for the purpose of loosening the charge, and finally there are two more on a level with the sole, to allow for discharging. With good management of the draft the kiln burns for weeks. If too much air enters, the combustion may be sufficiently strong to sinter the charge together, or, allowed to increase still further, enough cold air to put the fire out may enter. *] he matte, \vhich contains about 22 per cent, of sulphur, is reduced to 12 per cent, by two roastings in the kiln. The kilns are connected with sulphuric acid chambers, and no difficulty has occurred in utilizing the sulphur of "the matte in this way. After the second kiln roasting, the matte is piled in a low heap and roasted with the addition of brush fuel to 6 per cent, sulphur. Jt is then sm Ited in low, square furnaces, about 9 feet in height, 1 foot 8 inches X 3 fg et 4 inches square at the bottom, and 2X3 feet 10 inches at the top. The intro duction of sloping sides has been found advantageous. Three water tuyeres are placed in the back wall, the piers between which the furnaces stand, preventing t< eir introduction at the sides. The charge consists of 100 roasted matte and about 93 slag, partly siliceous elag from the ore fusion, and partly matte slag lepassed. The products are (1) Lead containing 19 per cent, silver and more copper, iron, zinc, antimony, etc., than the metal from the ore ; (2) Copper matte, the composition of which is about : Sulphur 21-6 per cent. Iron 392 Copper 23-7 " L ad 15-0 " Silver 0-057 " (3) Sbg containing 2 per cent, lead, and 0-002 per cent, silver. When copper slag was used as a precipitating material, the mattes from this fusion contained only 11 per cent, of copper, a;>d required another roasting and fusion before entering the copper process. Now this is unnecessary. The treatment of the copper matte consists in enriching it by repeated roast ing and fusion with siliceous material, to black copper containing 95 per cent, of that metal. This is granulated, treated with hot sulphuric acid, the c pper sulphate crystallized out, and the rich residues smelted to obtain their silver and gold. The copper matte is roasted in the kilns described above. Fusions take place in what are called in Germany "spectacle" furnaces. They are 10 ft. 8 in. high, have a section of from 18 to 36 in. X 3 ft. 4 in., and owe their name to the fact that, they have two reception basins in front They have one tuyere each, use ALTEXAU. 95 250 cubic foet of air pT minute at a pressure of 7 to 9 lines of mercury, and smelt from 9,300 to 10,000 Ib. of roasted matte in 21 hours. The composition of the charge is the same as in smelting lead matte, except that instead of ore slag a siliceous slag from another operation in the copper process is charged. A very basic slag is produced which eats away the furnace wall so rapidly th\t the campaigns do not exceed 24 to 30 days. The roasting and fusion is repeated five times, and KUHLEMANN gives the following summary of the charges and products: FUSION NUMBEB 1 2 3 4 5 Charge : Kasted copper matte cwt. Siliceous slag .... " 50 ,f> 3787 988 1375 85 ( ,)0 10 8G2 27 40 20 24)0 6100 0-79 0-40 47-30 40 55 0-235 40 9 0-0725 1- 0-75 00093 24 1801 480 715 30i,0 Wio 788 210 3 Go 1400 3)J 225 6<) 95 750 10 66} 29-4 125 125 290 41-66 41-06 94 2 0-100 73 2 0-045 1-5 1-25 0-00063 125 95 35 30 25J 83i 44 6J 14J 35-20 480 05 2 0-083 73 0030 1-25 i 0-00063 Slag from same operation.. " Fuel : Coke .... " Pe<it ) for warming.. . .pieces Charcoal f furnace cu ft Matte melted in 24 hours cwt. SH 29-8 408 1050 2600 17-0 43 75 70 25 0-22 66 5 0-078 1- 1-5 0-00125 100 34-7 384 300 1160 Coke used per 100 cwt. matte 1 roJucts: Work lead=0-38p.c. silv.. Mutte K1:H 100 cwt matte give Work lead 1 Slack copper. . . Matte 30-57 28-57 935 1 0-160 70 3 0-065 1 0-75 0-00063 C n1 rroSTTTON OF THK PRODUCTS. Flack copper : Copper per ct Lt- n d Matto: Copper Lead Silver Sla" l Copper ... IjP -lil . Silver The cLarge in each lusion was therefore Roasted matte 100 Siliceous slag 75 Slag trom same operation 20 and the time required for its fusion was about 28 hours. To pass 100 cwt of tho first matte through the 5 fusions in succession requires about 51 cwt coke, 49 hours actual smelting time, and in the 5 fusions 179 cwt. matte will be treated. The data above given are, however, only a portion of the expenses. Counting them as 100 we have to add as follows : Expenses in fusion, for labor, 100 " roasting, " 45 " removing slag, 13| ** trauspor ing matte * " general expenses 97 Tlie entire cost will be about 165 p^r cent, of the cost of labor and fuel con sumed in the fu duns. for fuel, 100 " 28 06 ALTENAU. Tho das used as siliceous flux had the following composition : Silica 34-07 Lead oxide 1 -07 Alumina 4-D8 Iron oxide 48-25 Lime 3 53 Sulphur 1-25 Manganese oxide . 2 -00 Zinc oxide 2-89 98-64 The following analysis of the slag from the 5th fusion is a fair representation of the same product from all the operations : Silica 30-994 Lime 4-314 Antimony oxide O f 196 Magnesia 0-253 Iron oxide 58-605 Alumina 5-732 Copper oxide 0-933 Lead oxide 0-021 101 -048 The preceding tables show that a certain amount oi black copper is mnde in each fusion. That from the first operation is, however, small in quantity and qui^e impure, containing a good deal of lead and silver. The total amount oF black copper from all the operations is 19 per cent, of the first matte. r J he greater part of it is obtained in the 2d and 3d fusions. The black copper from all the fusions is mixed with purchased copper contain ing silver, and "blown" in a reverberatory furnace. The mixture contains from 16 to 0-20 per cent, silver and 80 to 83 per cent, copper. The furnace is a cupel hearth of the old form. That is to say, the roof is fixed and must therefore be high enough to permit the workman to enter the furnace to make the hoarth. This is formed of claj" and coke screenings, with a border of mergel, and is near ly 10 feet in diameter. In front of the furnaca is a water basin in which the cop per is granulated as it comes out. From 50 to 53 cwt. of black copper is charg ed, melted in 5 hours, a " carcase" or alloy of higher fusing point than the black copper is drawn off from the surface, and air is blown upon the bath, at first in a feeble current but at length at the rate of 250 cubic feet a minute. Lead, iron, zinc, cobalt, nickel, antimony and some copper are oxidized and, drawing silica from the hearth, form a slag which is drawn or run off from the surface. After blowing 10 or 11 hours the refined copper is tapped and granulated. It contains 91 to 97 per cent, copper and 0-20 to 0-40 per cent, silver. The analysis of a black copper made in this way in 1870 was as follows : Iron 0-070 Copper 95-00 Lead 2-71 Antimony 1-53 Nickel, cobalt, zinc . . -048 Arsenic traco Silver 0-30 99-658 In the Notes on Freiberg, the necessity of excluding iron from the matte which was to be treated with acid, and the means used to accomplish this, were spoken of. It will be observed that the same result is reached at Alteuau by re peated roastings and fusions, and finally, by an oxidizing fusion of the resulting black copper. In addition to the black copper, two products are obtained. One is the car case drawn off from the bath immediately after fusion. It contains 15 to 20 per cent, silica, 5 per cent, nickel oxide. 3 per cent, cobalt oxide, 10 to 12 per cent, copper oxide, and 35 to 40 per cent lead oxide. The amount produced is small, ALTENAU. 97 but when enough has accumulated, it will be smelted with arsenical ores and heavy spar to produce a speise rich in nickel. The other product is the very impure litharge obtained by blowing the black copper, and containing 5 U per cent lead, 16 per cent copper, and 0-016 per cent silver. It is mixed with the hearth, which is saturated with the same product, and smelted to a black copper containing a great deal of lead and some silver. This is liquated to remove tho lead, and then blown like the ordinary black copper, furnishing, however, a much greater proportion ot side products. The following are the details of the operations in 1869 : Number of charges 74 Black copper cwt 3,225| 100 Products, Granulated copper " 2,201 68i Carcase " 63 2 Litharge 976 304 Faggots * . 39,450 1220 or Bituminous coal cwt. 42 The faggots mentioned are now replaced by bituminous coal, and experience shows that 1,000 faggots are equal to about 34i cwt coaL The granulated copper is treated with dilute sulphuric acid, by which the cop per, iron, nickel, and cobalt are dissolved, leaving a residue composed of gold, silver and arsenic in the metallic state, lead sulphate and basic antimony sul phate. The vats in which the solution is accomplished, are 4 feet high and 3 feet 4 inches in diameter. They are lined with lead, and have a perforated f.xlse bottom 4 inches above the floor of the vat. Great care is taken in filling the vat, for it is important to have the mass of granules as open and porous as possible. While copper oxide dissolves readily in dilute sulphuric acid, the m.tal itself requires hot concentrated acid for its solution. At Altenau the metal is oxidized by allowing the acid in the vat to run out, the air filling the spaces between the granules, which, being hot and moist with arid, oxidize, and the oxide is taken up by the succeeding charge of acid. To ensure the com plete access of air, the layer of copper must not be more than 40 inches thick, so that the vat holds about 2,200 Ib. It is filled up as often as the surface fulls 10 inches below the normal level, which occurs two or three times a week. The vat is cleaned out once in eight or ten weeks. One vat suffices to dissolve about 93 IK of copper per day, yielding about 360 Ib. of vitriol The sulphuric acid is taken direct from the chambers, and marks 48 to 50 deg. B. It is thinned to 32 deg. B. in a tank heated by steam to 175 deg. F. Tue diluted aci l is throwu on the copper, by means of a lead pipe furnished with a rose, every half hour. The acid runs through rapidly, but has time to dissolve the oxid-.s formed, and the force of its flow is sufficient to carry along the fine in soluble residues. This is an important point, for without this removal of the residues not only will the granules be covered with an insoluble coat, but the interstices will also be filled up. A turbid liquor discharging from the spout in the bottom of the vat is therefore the sign of a good operation. This spout being left open, air draws through the mass as soon as the interstices are free from acid, the draft being aided by the heat of the copper, derived from the aciJ. 03 ALTENAU. A high temperature hastens the operation, but is liable to cause solution of the silver. The six vats at Altenau discharge into a trough 360 feet long, where the warm solution deposits first the insoluble residue it has brought along, and then, as it cools, the copper sxilphate crystallizes out The trough is 30 inches wide and 7 inches deep. The mother liquor, which is still very acid, is raised to the diluting tank by means of a Gifford s injector, made of lead. The succeeding operations are for the purification of the copper vitriol and the reduction of the residue. To accomplish the former, the raw vitriol is dis solved in hot mother liquor, the solution marking 28 deg. B. It is filtered through granulated lead, and then through granulated copper to remove by precipitation any dissolved silver, and also to retain residues that were too fine to settle in the trough. In li mouths the lead and copper have taken up 1 per cent of silver, and are removed. The copper vitriol is crystallized in vats lined with lead, and with strips of the same metal hanging in the liquor. The vats are emptied every eleven days, and the crystals dried. Their composition is : Iron 0107 per cent. Antimony 0-0123 " Arsenic 0-0064 " Zinc trace Nickel -06 Silver t; ace Tot 1 impurty 0-0300 per cent. Nine dissolving vats nnd three re-dissolving pans treat 2,500 cwt. of copper yearly, producing about 9,000 cwt of vitriol. Nine men are employed in 24 Lours, five by day and four by night The argentiferous residues are thrown into a tank, washed, dried, and made up into balls with an equal quantity of litharge. An analysis shows that they Contain : Silver 3.10 Antimony 14.33 Gold 0.004 Arsenic 3.15 Copper 7.15 Sulphuric Acid 16.67 Lead 34.46 The copper is partly sulphate and partly fine particles which are washed down by the acid. The subsequent treatment consists in smelting the mixed litharge and residue in a shaft furnace and cupelling the metal. Care is taken to treat all the products by themselves, as they are very rich in silver. The details of the foregoing operations are ,,, .. ... I. VITBIOL MANUTA.CTURE. Granulated copper treated cwt. 2305 100 Copper vitriol produced Raw vitriol. Argentiferous residues (one-half litharge) . . Sulphuric acid consumed, 50-60 deg. B . . . . Coal In twenty- four hours copper treated. 8239 357* 392 17 342 4373 8336 6-4 1891 vitriol made 2 i -88 ALTENAU. 99 IL SMELTING THE RESIDUES. Charge : Residues cwt 342 100 Litharge and hearth Iron Siliceous slag Basic slag Products :Rich work lead Rich copper matte . 674J 197J 7 2 608 1484 372 108| 481 1401 f 49 Hi , 1347 394 29!) 84| Coke . Thirty cwt residues were smelted in 24 hours. IIL CUPELLATION. Charge : Work lead cwt. 536 100 Products: Auriferous silver Ib. 424 linei Ordinary silver " 150 Abstrich cwt. 114 214 Litharge " 339 634 Hearth " 148 27| Fuel: Faggots 2862 495 It will be observed that while 100 parts pure copper should yield 393-37 parts vitriol, the product from the impure copper used was 357 29 parts of merchanta ble vitriol, and 17 parts retained by the intermediate products, a total of 374-29, or about 95 per cent. Nor does the use of sulphuric acid correspond with the theoretical requirements, being 189-65 nstead of 154-57, as required. The dif ference is due to the fact that the acid used is really below 66 deg., and that the intermediate solutions hold a considerable amount of acid, not accounted for. Labor averages 54 cents a day, and the coal, which is of good quality and bears a high charge for transportation, costs about $4.80 per ton (2240 Ib.), and cokai $6. Under these conditions, the items in the manufacture of vitriol bore the following proportions: TBEATMENT OF VITRIOL MANUFACTUBE. EESIDUE8. Sundries 8 7 Labor 20 32| Acid 52 Coal 20 Coke 34J \vood 17 General Expenses 9 100 100 The cost of treating 100 cwt. of 40 per cent copper matte was, in 1869, 301 thalers 7i sgr., or (thaler=72 cents gold) $216.90. While this is apparently high, it is to be remembered that much of it is due to the acid employed, which, however, does not go to waste, but is sold as a part of the finished product Compared with the old liquation process, the present system extracts about eight per cent, more silver, and is in every respect superior. The results of the treatment described above are very remarkable in respect to the percentage of the different metals obtained from the ore. KOCH gave the production by the " combined" process or fusion of roasted matte with the ore as, Silver, 102-5 per cent, of assayed value of ore. Lead, 100-8 " Copper, 100-3 " 100 ALTENAIT. Thus the smelting operations gave more metal than the assay calls for, a cir cumstance that is, of course, due to the fact that losses take place in making the assay which are not accounted for. WEDDING & BRJBONNING found that by the desilverization process now in use the amount of silver extracted is 2-372 per cent, more than the assay shows to be present in the lead. If, however, the sil ver absorbed by the cupel is allowed for at 3 per cent. , there would be a real loss of 0-628 per cent, of silver. Similar corrections would make still larger differences between the apparent and the real extraction of the other metals. But the Hartz process is, nevertheless, remarkable for the closeness with which it works to the assay. The exact loss is not known, but it is less than 4 per cent, of lead, and probably less than 1 per cent, silver. These results are especially significant from the fact that the Hartz works treat unroasted ore, and they sustain the view of PLATTNER, who looked upon the process of roasting as one decidedly wasteful of metal, by volatilization. Another cause of the small loss is the persistence with which intermediate products of only moderate richness are reduced to metal and again desilvered, a method which would not always pay in America. But the close extraction of metal is not the only proof of good work in the Hartz. The directors of the various smelting works there are the first to solve the problem of utilizing the sulphur in galena for the manufacture of acid. Pure galena contains only about 13 per cent, of sulphur, a quantity too small to be utilized with profit. It is only by concentrating this element in a matte that it can be made to give sufficiently concentrated fumes for oxidation in the lead chambers. But this matte usually contains so much lead that it sinters at a low heat, a difficulty that has heretofore barred the way to its use in kilns, as a source of acid. The introduction of the precipitation by slag taught the Clausthal metallurgists that it is possible to make a matte poor in lead from lead ores. It seems to be probable that precipitation is more thoroughly performed when the ore trickles through a bath of slag rich in iron than when it is brought in contact with metallic iron, even when the heat is sufficient to melt the latter. The intro duction of precipitation by slag increased the amount of matte produced, but it decreased its percentage of lead from 40 to 7 or 10 per cent., and the latter limits have been retained in the matte from the combined fusion of ore and matte. In addition to the metals they contain, the Hartz ores, which are true galenas, are now made to yield a part of their sulphur as acid. I have found it impossible to obtain any trustworthy calculations of the cost of the above treatment. The following is probably not very far from the truth, ra ther under than over. The calculation is made on one European ton, 1000 k= 2200 Ib. : Ore and lead matte fusions, 2200 Ib. ore $7. 82 Treatment of copper matte, 1 10 Ib 2. 60 Treatment of lead matte, 1227 Ib 2.76 $13.18 (coin) The products are about as follows, allowing the production of copper to form 1 per cent, of the ore: Lead 1210 Ib., or a loss of about 1 per cent. Sulphate of copper, 781 Ib. Silver 2 Ib. ; loss supposed to be about | oz. Skilled labor costs in the Hartz from 48 to 54 cents coin, and ordinary labor, ALTENAU. say from 36 to 43 cents. Coke costs $6.70 per ton; soft coal, $4.80; a "Bollock," or 60 faggots of wood (equal to 225 Ib. soft coal in use), 96 cents; and the cop per slag used as a flux in the ore fusion is brought from Oker at a cost of 96 cents a ton. THE OPERATIONS IN 1871. Doctor WEDDING contributes every year to the Preussische Zeitschrifl fiir Berg, Hiitten und Saiinen Westn, which is the official mining journal of the Prussian Government, an account of the current experiments and improvements in the smeltiug works of that Government His report of the progress made during 1871 gives so much relating to the Hartz, that I take from it the follow ing details: The mines of the Upper Hartz yielded in 1871: 154,622 tons (2204 Ib.) of ore, which by concentration was reduced to 13,546 tons of smelting ore, having a composition similar to that given above. The smelting ore, therefore, formed 8-7 per cent of the mine ore, and the latter, as it was hoisted from the mine, must have averaged about as follows: Lead, 4 per cent ; Copper, 0-065 per cent. ; Silver, 0-0085 per cent, or 3i oz. to the ton. During that year the smelting works treated 13,911 tons of home and 497 tons of foreign ore, and produced 7,930 tons lead, 47 i tons litharge, 41-58 Ib. gold, and 37,523 Ib. silver. Of this ore, 9,150 tons were smelted at Clausthal, seven furnaces being used for the first fusion. Five of them were round furnaces, of the EAST and PILTZ pattern, three having 4 tuyeres, one 5, and one 8 tuyeres. Two KACHETTE furnaces, each with 12 tuyeres, were also in operation. The charge consisted of 100 ore, " 51 roasted matte, 67 copper slag, " 43 matte slag, 47 slag from the same operation, 308 1 -2 scraps, 1 -0 flue dust, 0-5 lead scraps. 27 310-7 The fuel, including the small coke used in making the "gestttbbe," which forms the fore hearth, and also that used to warm the furnaces, amounted to 45-17 coke, 2-55 charcoal, 47-72 or 15i per cent, of the total charge, and 47| per cent, of the ore. The products were: 58-77 wo k lead, 76 -U9 matte. 124-86 If the amount of matte charged is deducted from that produced, only 25 per cent, remains, which is a very much smaller proportion than that obtained in any former modification of the Clausthal process. In working the 8-tuyered fur nace, which at first had a crucible of 4 ft 8 in. diameter, it was found impossible to blow to the center of the charge, where a pillar of unsmelted material always 102 ALTENAU. remained. By shoving the tuyeres toward the center until the diameter of th working hearth was reduced to 1 meter, or 3 ft. 4. in., this difficulty was removed, and this has, therefore, been fixed upon as the standard of a new Piltz, which will have but 4 tuyeres. The other round furnaces do very good work, running through 20 tons of charge (6-7 to is ore) in 24 hours. At Altenau, 202-6 tons of black copper were treated, producing 288,700 Ib. copper, 822 - 56 Ib. silver, and 4,275 tons of sulphuric acid. From the four establishments at Clausthal, Lautenthal, Alteuau and Andrea* berg, there were produced in 1871 the following amounts: 43-63 Ib. gold, 37,523-0 IK silver, 7,929-4 tons lead, 47-5 " litharge, 602-0 " refined copper, 6,132-0 " copper vitriol, 427 5 " sulphuric acid, 22-5 lead paint, This had a value of $1,497,965. SCIENTIFIC BOOKS PUBLISHED BY D. VAN NOSTBAND, 23 MURRAY STREET & 27 WARREN STREET, NEW YORK. Weisbacli s Mechanics. New and Revised Edition* 8vo. Cloth. $10.00. A MANUAL OF THE MECHANICS OF ENGINEERING, and of the Construction of Machines. By JULIUS WEISBACH, PH. D. Translated from the fourth augmented and improved Ger man edition, by ECKLEY B. COXE, A.M., Mining Engineer. Vol. I. Theoretical Mechanics. 1,100 pages, and 902 wood-cut illustrations. ABSTRACT OP CONTENTS. Introduction to the Calculus The General Principles of Mechanics Phoronomics, or the Purely Mathematical Theory of Motion Mechanics, or the General Physical Theory of Motion Statics of Rigid Bodies The Application of Statics to Elasticity and Strength Dynam ics of Rigid Bodies -Statics of Fluids - Dynamics of Fluids The Theory of Oscillation, etc. " The present edition is an entirely new work, greatly extended and very much improved. It forms a text-book which must find its way into the hands, not only of every student, but of every engineer who desires to refresh his mem ory or acquire clear ideas on doubtful points. Manufacturer and Builder. " We hope the day is not far distant when a thorough course of study and education as such shall be demanded of the practising engineer, and with this view we are glad to welcome this translation to our tongue and shores of one of the most able of the educators of Europe." 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PART I., on hydraulic motors, includes ninety-two experiments on an improved Fourneyron Turbine "Water-Wheel, of about two hundred horse-power, with rules and tables for the construction of similar motors; thirteen experiments on a model of a centre- vent water- wheel of the most simple design, and thirty-nine experiments on a centre-vent water- wheel of about two hundred and thirty horse-power. 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In 1855 the proprietors of the Locks and Canals on Merrimack River con sented to the publication of the first edition of this work, which contained a selection of the most important hydraulic experiments made at Lowell up to that time. In this edition the principal hydraulic experiments made there, subsequent to 1855, have be^n added, including the important series above mentioned, for determining rules for the gauging the flow of water in open canals, and the interesting series on the flow through a submerged Venturi s tube, in which a larger flow was obtained than any we find recorded. J). VAN NOSTIIAJSTD. Francis on Oast-Iron Pillars. 8vo. Cloth. $2.00. ON THE STRENGTH OF CAST-IRON PILLARS, with Tables for the use of Engineers, Architects, and Builders. By JAMES B. FBANCIS, Civil Engineer. Merrill s Iron Truss Bridges. Second Edition. 4to. Cloth. $5.00. IRON TRUSS BRIDGES FOR RAILROADS. 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A TREATISE ON THE STRENGTH OF BRIDGES AND ROOFS comprising the determination of Algebraic formulas for Strains in Horizontal, Inclined or Rafter, Triangular, Bow string, Lenticular and other Trusses, from fixed and moving loads, with practical applications and examples, for the use of Students and Engineers. By SAMUEL H. SHREYE, A.M., Civil Engineer. The rules for the determination of strains given in this work, in the shape of formulas, are deduced from a few well-known mechanical laws, and are not based upon assumed conditions; the processes are given and applications made of the results, so that it is equally valuable as a text-book for the Student and as a manual for the Practical Engineer. 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General Sections of Mississippi River at Quincy, showing location of Bridge. IV. Plans of Masonry. V. Diagram of Spans, showing the Dimensions, Arrangement of Panels, etc. VI. Two hundred and fifty feet span, and de tails. VII. Three hundred and sixty feet Pivot Draw. VIII. Details of three hundred and sixty feet Draw. IX. Ice- Breakers, Foundations of Piers and Abutments, Water Table, and Curve of Deflections. X. Founda tions of Pier 2, in Process of Con struction. XI. Foundations of Pier 3, and its Protection. XII. Founda tions of Pier 3, in Process of Construc tion, and Steam Dredge. XIII. Foun dations of Piers 5 to 18, in Process of Construction. XIV. False Works, showing Process of Handling and Set ting Stone. XV. False Works for Raising Iron Work of Superstructure. XVI. Steam Dredge used in Founda tions 9 to 18. XVII. Single Bucket Dredge used in Foundations of Bay Piers. XVIII. Saws used for Cut ting Piles under water. XIX. Sand Pump and Concrete Box. 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" The mathematical formulas are of an elementary kind, and the process admits of an easy extension so as to embrace the prominent varieties of iron truss bridges. The treatise, though of a practical scientific character, may be easily mastered by any one familiar with elementary mechanics and plane trigonometry." Holley s Railway Practice. 1 vol. folio. Cloth. $12.00. AMEEICAN AND EUEOPEAN EAILWAY PEACTICE, in the Economical Generation of Steam, including the materials and construction of Coal-burning Boilers, Combustion, the Varia ble Blast, Vaporization, Circulation, Super-heating, Supplying and Heating Feed- water, &c., and the adaptation of Wood and Coke-burning Engines to Coal-burning ; and in Permanent Way, including Eoad-bed, Sleepers, Eails, Joint Fastenings, Street Eailways, &c., &c. By ALEXANDER L. HOLLET, B. P. With 77 lithographed plates. " This is an elaborate treatise by one of our ablest civil engineers, on the con struction and use of locomotives, with a few chapters on the building of liail- roc.ds. * * * All these subjects are treated by the author, who is a first-class railroad engineer, in both an intelligent and intelligible manner. The f^cts and ideas are well arranged, and presented in a clear and simple style, accompanied by beautiful engravings, and we presume the work will be jregard- ed as indispensable by all who are interested in a knowledge of the construc tion of railroads and rolling stock, or the working of locomotives." /Scientific American. 8 SCIENTIFIC BOOKS PUBLISHED BY Henrici s Skeleton Structures. 8vo. Cloth. $3.00. SKELETON STRUCTURES, especially in their Application to the building of Steel and Iron Bridges. By OLAUS HENRICI. With folding plates and diagrams. By presenting these general examinations on Skeleton Structures, with particular application for Suspended Bridges, to Engineers, I renture to ex press the hope that they will receive these theoretical results with some confi dence, even although an opportunity is wanting to compare them with practi cal results. O. H. Useful Information for Railway Men. Pocket form. Morocco, gilt, $2.00. Compiled by W. G. HAMILTON, Engineer. Fifth edition, revised and enlarged. 570 pages. " It embodies many valuable formulae and recipes useful for railway men, and, indeed, for almost every class of persons in the world. The informa tion comprises some valuable formulae and rules for the construction of boilers and engines, masonry, properties of steel and iron, and the strength of materials generally." Railroad Gazette, Chicago. Brooklyn Water Works. 1 vol. folio. Cloth. $20.00. A DESCEIPTIVE ACCOUNT OF THE CONSTKUCTION OF THE WORKS, and also Reports on the Brooklyn, Hartford, Belleville, and Cambridge Pumping Engines. Prepared and printed by order of the Board of Water Commissioners. With 59 illustrations. CONTENTS. Supply Ponds The Conduit Bidgewood Engine House and Pump Well Ridge wood Engines Force Mains Ridge wood Reservoir Pipe Distribution Mount Prospect Reservoir Mount Prospect Engine House and Engine Drainage Grounds Sewerage Works Appendix. D. VAJST NOSTRAND. Kirkwood on Filtration. 4to. Cloth. $15.00. REPORT ON THE FILTKATION OF RIVER WATERS, for the Supply of Cities, as practised in Europe, made to the Board of Water Commissioners of the City of St. Louis. By JAMES P. KIRKWOOD. Illustrated by 30 double-plate engravings. CONTENTS. Report on Filtration London "Works, General Chelsea Water Works and Filters Lambeth Water Works and Filters Southwark and Vauxhall Water Works and Filters Grand Junction Water Works and Filters West Middlesex Water Works and Filters New River Water Works and Filters East London Water Works and Filters Leicester Water Works and Filters York Water Works and Filters Liverpool Water Works and Filters Edinburgh Water Works and Filters Dublin Water Works and Filters Perth Water Works and Filtering Gallery Berlin Water Works and Filters Hamburg Water Works and Reservoirs Altona Water Works and Filters Tours Water Works and Filtering Canal Angers Water Works and Filtering Galleries Nantes Water Works and Filters Lyons Water Works and Filtering Galleries Toulouse Water Works and Filtering Galleries Marseilles Water Works and Filters Genoa Water Works and Filtering Galleries Leghorn Water Works and Cisterns Wakefield Water Works and Filters Appendix. Tanner on Roll-Turning. 1 vol. 8vo. and 1 vol. plates. $10.00. A TREATISE ON ROLL-TURNING FOR THE MANUFAC TURE OF IRON. By PETER TUXNER. Translated and adapted. By JOHN B. PEA.BSE, of the Pennsylvania Steel Works. With numerous wood-cuts, 8v6., together with a folio atlas of 10 litho graphed plates of Rolls, Measurements, &c. " We commend this book as a clear, elaborate, and practical treatise upon the department of iron manufacturing operations to which it is devoted. The writer states in his preface, that for twenty -five years he has felt the necessity of such a work, and has evidently brought to its preparation the fruits of experience, a painstaking regard for accuracy of statement, and a desire to furnish information in a style readily understood. The book should be in the hands of every one interested, either in the general practice of mechanical engineering, or the special branch of manufacturing operations to which the work relates. American Artisan. 10 SCIENTIFIC BOOKS PUBLISHED BY G-lynn on the Power of Water. 12mo. Cloth. $1.00. A TREATISE ON THE POWER OF WATER, as applied to drive Flour Mills, and to give motion to Turbines and other Hydrostatic Engines. By JOSEPH: GLYNN, F.R. S. Third edition, revised and enlarged, with numerous illustrations. Hewson on Embankments. 8vo. Cloth. $2.00. PRINCIPLES AND PRACTICE OF EMBANKING LANDS from River Floods, as applied to the Levees of the Mississippi. By WILLIAM HEWSON, Civil Engineer. " This is a valuable treatise on the principles and practice of embanking lands from river floods, as applied to the Levees of the Mississippi, by a highly intelligent and experienced engineer. The author says it is a first attempt to reduce to order and to rule the design, execution, and measurement of the Levees of the Mississippi. It is a most useful and needed contribution to scientific literature. Philadelphia Evening Journal. Griiner on Steel. 8vo. Cloth. $3.50. THE MANUFACTURE OF STEEL. By M. L. GRTJNER, trans lated from the French. By Lenox Smith, A. M., E. M., with an appendix on the Bessemer Process in the United States, by the translator. Illustrated by lithographed drawings and wood-cuts. " The purpose of the work is to present a careful, elaborate, and at the same time practical examination into the physical properties of steel, as well as a description of the new processes and mechanical appliances for its manufac ture. The information which it contains, gathered from many trustworthy eources, will be found of much value to the American steel manufacturer, who may thus acquaint himself with the results of careful and elaborate ex periments in other countries, and better prepare himself for successful com petition in this important industry with foreign makers. The fact that this volume is from the pen of one of the ablest metallurgists of the present day, cannot fail, we think, to secure for it a favorable consideration. Iron Age. D. VAN NOSTRAND. 11 Bauerman on Iron. 12mo. Cloth. $2.00. TREATISE ON THE METALLURGY OF IRON. Contain- ing outlines of the History of Iron Manufacture, methods of Assay, and analysis of Iron Ores, processes of manufacture of Iron and Steel, etc., etc. By H. BATJERITAN. First American edition. Revised and enlarged, with an appendix on the Martin Process for making Steel, from the report of Abram S. Hewitt. Illustrated with numerous wood engravings. " This is an important addition to the stock of technical works published in this country. It embodies the latest facts, discoveries, and processes con nected with the manufacture of iron and steel, and should be in the hands of every person interested in the subject, as well as in all technical and scientific libraries." Scientific American. Link and Valve Motions, by W. S. Auchincloss. 8vo. Cloth. $3.00. APPLICATION OF THE SLIDE VALVE and Link Motion to Stationary, Portable, Locomotive and Marine Engines, with new and simple methods for proportioning the parts. By WILLIAM S. AUCHINCLOSS, Civil and Mechanical Engineer. Designed as a hand-book for Mechanical Engineers, Master Mechanics, Draughtsmen and Students of Steam Engineering. All dimen sions of the valve are found with the greatest ease by means of a Printed Scale, and proportions of the link determined without the assistance of a model. Illustrated by 37 wood-cuts and 21 lithographic plates, together with a copperplate engraving of the Travel Scale. All the matters we have mentioned are treated with a clearness and absence of unnecessary verbiage which renders the work a peculiarly valuable one. The Travel Scale only requires to be known to be appreciated. Mr. A. writes so ably on his subject, we wish he had written more. London En gineering. We have never opened a work relating to steam which seemed to us better calculated to give an intelligent mind a clear understanding of the depart ment it discusses. Scientific American. 12 SCIENTIFIC BOOKS PUBLISHED BY Slide Valve by Eccentrics, by Prof. C, W. MacCord. 4to. Illustrated. Cloth, $4.00. A PEACTICAL TEEATISE ON THE SLIDE YALYE BY ECCENTRICS, examining by methods, the action of the Eccen tric upon the Slide Yalve, and explaining the practical proces ses of laying out the movements, adapting the valve for its various duties in the steam-engine. For the use of Engineers, Draughtsmen, Machinists, and Students of valve motions in general. By C. \V. MAcCoRD, A. M., Professor of Mechanical Drawing, Stevens Institute of Technology, Hoboken, N J. Stillxnan s Steam-Engine Indicator. 12iao. Cloth. $1.00. THE STEAM-ENGINE INDICATOR, and the Improved Mano meter Steam and Vacuum Gauges ; their utility and application By PAUL STILLMAN. New edition. Bacon s Steam-Engine Indicator. 12mo. Cloth. $1.00. Mor. $1.50. A TREATISE ON THE RICHARDS STEAM-ENGINE IN DICATOR, with directions for its use. By CHARLES T. PORTER. Revised, with notes and large additions as developed by Amer ican Practice, with an Appendix containing useful formulae and rules for Engineers. By F. W. BACON, M. E., Member of the American Society of Civil Engineers. Illustrated. In this work, Mr. Porter s book has been taken as the basis, but Mr. Bacon has adapted it to American Practice, and has conferred a great boon on American Engineers. Artisan. Bartol on Marine Boilers. 8vo. Cloth. $1.50. TREATISE ON THE MARINE BOILERS OF THE UNITED STATES. By H. B. BARTOL. Illustrated. D. VAN NOSTRAND. 13 Gillmore s Limes and Cements. Fourth Edition. Jtevise l and Enlargd. 8vo. Cloth. $4.00. PKACTICAL TEEATISE ON LIMES, HYDEAULIC CE MENTS, AND MOETAES. Papers on Practical Engineering, U. S. Engineer Department, No. 9, containing Eeports of numerous experiments conducted in New York City, during the years 1858 to 1861, inclusive. By Q. A. GILLMORE, Brig-General U. S. Volunteers, and Major U. S. Corps of Engineers. With numerous illustrations. " This -work contains a record of certain experiments and researches made under the authority of the Engineer Bureau of the War Department from 1858 to 1861, upon the various hydraulic cements of the United States, and the materials for their manufacture. The experiments were carefully made, and are well reported and compiled. Journal Franklin Institute. Gillmore s Ooignet Beton. 8vo. Cloth. $2.50. COIGNET BETON AND OTHEE AETIFICIAL STONE. By Q,. A. GILLMOEE. 9 Plates, Views, etc. This work describes with considerable minuteness of detail the several kinds of artificial stone in most general use in Europe and now beginning to be introduced in the United States, discusses their properties, relative merits, and cost, and describes the materials of which they are composed The subject is one of special and growing interest, and we commend the work, embodying as it does the matured opinions of an experienced engineer and expert. Williamson s Practical Tables. 4to. Flexible Cloth. $2.50. PEACTICAL TABLES IN METEOEOLOGY AND HYPSO- METEY, in connection with the use of the Barometer. By Col. E. S. WILLIAMSOM, U. S. A. 14 SCIENTIFIC BOOKS PUBLISHED BY Williamson on the Barometer. 4to. Cloth. $15.00. ON THE USE OF THE BAKOMETEK ON SUKYEYS AND EECONNAISSANCES. Part I. Meteorology in its Connec tion with Hypsometry. Part II. Barometric Hypsometry. By E. S. WILLIAMSON, Bvt, Lieut-Col. U. S. A., Major Corps of Engineers. With Illustrative Tables and Engravings. Paper No. 15, Professional Papers, Corps of Engineers. " SAN FRANCISCO, CAI,., Feb. 27, 1867. " Gen. A. A. HUMPHREYS, Chief of Engineers, U. S. Army : " GENERAL, I have the honor to submit to you, in the following pages, the results of my investigations in meteorology and hypsometry, made with the view of ascertaining how far tho barometer can be used as a reliable instru ment for determining altitudes on extended lines of survey and reconnais sances. These investigations have occupied the leisure permitted me from my professional duties during the last ten years, and I hope the results will be deemed of sufficient value to have a place assigned them among the printed professional papers of the United States Corps of Engineers. " Very respectfully, your obedient servant, "R. S. WILLIAMSON, "Brt. Lt.-Col. U. S, A., Major Corps of U. S. Engineers." Yon Cotta s Ore Deposits. 8vo. Cloth. $4.00. TEEATISE ON OEE DEPOSITS. By BEBNHAED VON COTTA, Professor of Geology in the Hoyal School of Mines, Preidberg, Saxony. Translated from the second German edition, by FREDERICK PRIME, Jr., Mining Engineer, and revised by the author, with numerous illustrations. " Prof. Von Cotta of the Freiberg School of Mines, is the author of the best modern treatise on ore deposits, and we are heartily glad that this ad mirable work has been translated and published in this country. The trans lator, Mr. Frederick Prime, Jr., a graduate of Freiberg, has had in his work the great advantage of a revision by the author himself, who declares in a prefatory note that this may be considered as a new edition i^the third) of his own book. " It is a timely and welcome contribution to the literature of mining in this country, and we are grateful to the translator for his enterprise and good judgment in undertaking its preparation ; while we recognize with equal cor diality the liberality of the author in granting both permission and assist ance." Extract from Review in Engineering and Mining Journal. D. VAST NOSTJRANJ). 15 Plattner s Blow-Pipe Analysis. Second edition. Revised, 8vo. Cloth. $7.50. PLATTNEE S MANUAL OF QUALITATIVE AND QUAN TITATIVE ANALYSIS WITH THE BLOW-PIPE. From the last German edition Revised and enlarged. By Prof. TH. RICHTER, of the Royal Saxon Mining Academy. Translated by Prof. H. B. CORNWALL, Assistant in the Columbia School of Mines, New York ; assisted by JOHN H. CASWELL. Illustrated with eighty-seven wood-cuts and one Lithographic Plate. 560 pages. " Plattner s celebrated work has long been recognized as the only complete book on Blow-Pipe Analysis. The fourth German edition, edited by Prof. Bichter, fully sustains the reputation which the earlier editions acquired dur ing the lifetime of the author, and it ia a source of great satisfaction to us to know that Prof. Eichter has co-operated with the translator in issuing the American edition of the work, which is in fact a fifth edition of the original work, being far more complete than the last German- edition." SllUmari a Journal. There is nothing BO complete to be found in the English language. Platt ner s book is not a mere pocket edition ; it is iatended as a comprehensive guide to all that is at present known on the blow-pipe, and as such is really indis pensable to teachers and advanced pupils. " Mr. Cornwall s edition is something more than a translation, as it contains many corrections, emendations and additions not to be found in the original. It is a decided improvement on the work in its German dress." Journal of Applied Chemistry. Egleston s Mineralogy. 8ro. Illustrated with 34 Lithographic Plates. Cloth. $4.50. LECTURES ON DESCRIPTIVE MINERALOGY, Delivered at the School of Mines, Columbia College. Br PROFESSOR T. EGLESTOX. These lectures are what their title indicates, the lectures on Mineralogy delivered at the School of Mines of Columbia College. They have beea printed for the students, in order that more time might be given to the vari ous methods of examining and determining minerals. The second part has only been printed. The first part, comprising crystallography and physical mineralogy, will be printed at some future time. 16 SCIENTIFIC BOOKS PUBLISHED BY Pynchon s Chemical Physics. New Edition. Revised and Enlarged. Crown 8vo. Cloth. $3.00. INTRODUCTION TO CHEMICAL PHYSICS, Designed for the Use of Academies, Colleges, and High Schools. Illustrated with numerous engravings, and containing copious experiments with directions for preparing them. By THOMAS RUGGLES PYXCHON, M.A., Professor of Chemistry and the Natural Sciences, Trinity College, Hartford. Hitherto, no work suitable for general use, treating of all these subjects within the limits of a single volume, could be found ; consequently the atten tion they have received has not been at all proportionate to their importance. It is believed that a book containing so much valuable information within so small a compass, cannot fail to meet with a ready sale among all intelligent persons, while Professional men, Physicians, Medical Students, Photograph ers, Telegraphers, Engineers, and Artisans generally, will find it specially valuable, if not nearly indispensable, as a book of reference. " We strongly recommend this able treatise to our readers as the first work ever published on the subject free from perplexing technicalities. In style it is pure, in description graphic, and its typographical appearance is artistic. It is altogether a most excellent work." Eclectic Medical Journal. " It treats fully of Photography, Telegraphy, Steam Engines, and the various applications of Electricity. In short, it is a carefully prepared volume, abreast with the latest scientific discoveries and inventions, Hart" ford Courant. Plympton s Blow-Pipe Analysis. 12mo. Cloth. $2.00. THE BLOW-PIPE : A System of Instruction in its practical use being a graduated course of Analysis for the use of students, and all those engaged in the Examination of Metallic Combina tions. Second edition, with an appendix and a copious index. By GEORGE W. PLYMPTON, of the Polytechnic Institute, Brooklyn. " This manual probably has no superior in the English language as a text book for beginners, or as a guide to the student working without a teacher. To the latter many illustrations of the utensils and apparatus required in using the blow-pipe, as well as the fully illustrated description of the blow pipe flame, will be especially serviceable." New York TeacJier. D. VAJST NOSTEANJ}. 17 lire s Dictionary. Sixth Edition. London, 1872. 3 vols. 8vo. Cloth, $25.00. Half Russia, $37.50. DICTIONARY OF ARTS, MANUFACTURES, AND MINES. By AXDEEW UEE, M.D. Sixth edition. Edited by ROBERT HUNT, F.R.S., greatly enlarged and rewritten. Brande and Cox s Dictionary, New Edition. London, 1872. 3 rols. 8vo. Cloth, $20.00. Half Morocco, $27.50. A Dictionary of Science, Literature, and Art. Edited by W. T. BRANDE and Rev. GEO. W. Cox. New and enlarged edition. Watt s Dictionary of Chemistry. Supplementary Volume. 8vo. Cloth. $9.00. This volume brings the Record of Chemical Discovery down to the end oJ the year 1869, including also several additions to, and corrections of, former results which have appeared in 1870 and 1871. *.* Complete Sets of the Work, New and Revised edition, including 1 above supplement 6 vols. 8vo. Cloth. $62.00. Bammelsberg s Chemical Analysis. 8vo. Cloth. $2.25. GUIDE TO A COURSE OF QUANTITATIVE CHEMICAL ANALYSIS, ESPECIALLY OF MINERALS AND FUR NACE PRODUCTS. Illustrated by Examples. By C. F. RAMMELSBEKG. Translated by J. TOWLEK, M.D. This work has been translated, and is now published expressly for those students in chemistry whose time and other studies in colleges do not permit them to enter upon the more elaborate and expensive treatises of Fresenius and others. It is the condensed labor of a master in chemistry and of a prac tical analyst. 18 SCIENTIFIC BOOKS PUBLISHED BY Eliot and Storer s Qualitative Chemical Analysis. New Edition, Revised. 12mo. Illustrated. Cloth. $1.50. A COMPENDIOUS MANUAL OF QUALITATIVE CHEMI CAL ANALYSIS. By CHARLES W. ELIOT and FRANK H. STOKER. Revised with the Cooperation of the Authors, by WILLIAM HIP- LEY NICHOLS, Professor of Chemistry in the Massachusetts Insti tute of Technology. " This Manual has great merits as a practical introduction to the science and the art of which it treats. It contains enough of the theory and practice of qualitative analysis, " in the -wet way," to bring out all the reasoning in volved in the science, and to present clearly to the student the most approved methods of the art. It is specially adapted for exercises and experiments in the laboratory; and yet its classifications and manner of treatment are so systematic and logical throughout, as to adapt it in a high degree to that higher class of students generally who desire an accurate knowledge of the practical methods of arriving at scientific facts." Lutheran Observer. " We wish every academical class in the land could have the benefit of the fifty exercises of two hours each necessary to master this book. Chemistry would cease to be a mere matter of memory, and become a pleasant experi mental and intellectual recreation. We heartily commend this little volume to the notice of those teachers who believe in using the sciences as means of ital discipline." College Courant. Craig s Decimal System. Square 32mo. Limp. 50c. WEIGHTS AND MEASUEES. An Account of the Decimal System, with Tables of Conversion for Commercial and Scientific Uses. By B, F. CRAIG, M. D. " The most lucid, accurate, and useful of all the hand-books on this subject that we have yet seen. It gives forty-seven tables of comparison between the English and French denominations of length, area, capacity, weight, and the Centigrade and Fahrenheit thermometers, with clear instructions how to use them ; and to this practical portion, which helps to make the transition as easy as possible, is prefixed a scientific explanation of the errors in the metric system, and how they may be corrected in the laboratory." Nation. I). VAN NOSTRAFD. 19 Nugent on Optics. 12mo. Cloth. $2.00 TREATISE ON OPTICS ; or, Light and Sight, theoretically and practically treated ; with the application to Fine Art and Indus trial Pursuits. By E. NUGENT. With one hundred and three illustrations. " This book is of a practical rather than a theoretical kind, and is de signed to afford accurate and complete information to all interested in appli cations of the science." Round Table. Barnard s Metric System. 8vo. Brown cloth. $3.00. THE METRIC SYSTEM OF WEIGHTS AND MEASURES. An Address delivered before the Convocation of the University of the State of New York, at Albany, August, 1871. By FREDERICK A. P. BARNARD, President of Columbia College, New York City. Second edition from the Revised edition printed for the Trustees of Columbia College. Tinted paper. " It is the best summary of the arguments in favor of the metric weights and measures with which we are acquainted, not only because it contains in small space the leading facts of the case, but because it puts the advocacy of that system on the only tenable grounds, namely, the great convenience of a decimal notation of weight and measure as well as money, the value of inter national uniformity in the matter, and the fact that this metric system is adopted and in general use by the majority of civilized nations." The Notion. The Young Mechanic. Illustrated. 12mo. Cloth. $1.75. THE YOUNG MECHANIC. Containing directions for the use of all kinds of tools, and for the construction of steam engines and mechanical models, including the Art of Turning in Wood and Metal. By the author of "The Lathe and its Uses," etc From the English edition, with corrections. 20 SCIENTIFIC BOOKS PUBLISHED BY Harrison s Mechanic s Tool-Book. 12mo. Cloth. $1.50. MECHANIC S TOOL BOOK, with practical rules and suggestions, for the use of Machinists, Iron Workers, and others. By W. B. HARRISON, Associate Editor of the " American Artisan." Illustra ted with 44 engravings. " This work is specially adapted to meet the wants of Machinists and work ers in iron generally. It is made up of the work-day experience of an intelli gent and ingenious mechanic, who had the faculty of adapting tools to various purposes. The practicability of his plans and suggestions are made apparent even to the unpractised eye by a series of well-executed wood engravings." Philadelphia Inquirer. Pope s Modern Practice of the Elec tric Telegraph. Seventh edition. 8vo. Cloth $2.00. A Hand-book for Electricians and Operators. By FKANK L. POPE. Seventh edition. Revised and enlarged, and fully illustrated. Extract from Letter of Prof. Morse. " I have had time only cursorily to examine its contents, but this examina tion has resulted in great gratification, especially at the fairness and unpre judiced tone of your whole work. " Your illustrated diagrams are admirable and beautifully executed. " I think all your instructions in the use of the telegraph apparatus judi cious and correct, and I most cordially wish you success." Extract from Letter of Prof. G. W. Hough, of the Dudley Observatory. " There is no other work of this kind in the English language that con tains in so small a compass so much practical information in the application of galvanic electricity to telegraphy. It should be in the hands of every one interested in telegraphy, or the use of Batteries for other purposes." Morse s Telegraphic Apparatus. Illustrated. 8vo. Cloth. $2.00. EXAMINATION OF THE TELEGRAPHIC APPAEATUS AND THE PROCESSES IN TELEGAPHY. By SAMUEL F. B. MORSE, LL.D., United States Commissioner Paris Universal Exposition, 1867. D. VAN NOSTRAND. 21 Sabine s History of the Telegraph. 12mo. Cloth. $1.25. HISTOKY AND PROGRESS OF THE ELECTRIC TELE GRAPH, with Descriptions of some of the Apparatus. By ROBERT SA.BINE, C. E. Second edition, with additions. CONTENTS. I. Early Observations of Electrical Phenomena. II. Tele graphs by Frictional Electricity. III. Telegraphs by Voltaic Electricity. IV. Telegraphs by Electro-Magnetism and Magneto-Electricity. V. Tele graphs now in use. VI. Overhead Lines. VII. Submarine Telegraph Lines. VIII. Underground Telegraphs. IX. Atmospheric Electricity. Shaffner s Telegraph Manual. 8vo. Cloth. $6.50. A COMPLETE HISTORY AND DESCRIPTION OF THE SEMAPHORIC, ELECTRIC, AND MAGNETIC TELE GRAPHS OF EUROPE, ASIA, AFRICA, AND AMERICA, with 625 illustrations. By TAL. P. SHAFFNER, of Kentucky. New edition. Onlley s Hand-Book of Telegraphy. 8vo. Cloth. $5.00. A HAND-BOOK OF PRACTICAL TELEGRAPHY. By R. S. CULLEY, Engineer to the Electric and International Telegraph Company. Fourth edition, revised and enlarged. Foster s Submarine Blasting. 4to. Cloth. $3.50. SUBMARINE BLASTING in Boston Harbor, Massachusetts- Removal of Tower and Corwin Rocks. By JOHN G. FOSTEB, Lieutenant-Colonel of Engineers, and Brevet Major- General, U. S. Army. Illustrated with seven plates* LIST OP PLATES. 1. Sketch of the Narrows, Boston Harbor. 2. Townsend s Submarine Drilling Machine, and Working Vessel attending. 3. Submarine Drilling Machine employed. 4. Details of Drilling Machine employed. 5. Cartridges and Tamping used. 6. Fuses and Insulated Wires used. 7. Portable Friction Battery used. 22 SCIENTIFIC BOOKS PUBLISHED BY Barnes Submarine Warfare. 8vo. Cloth. $5.00. SUBMAEINE WARFARE, DEFENSIVE AND OFFENSIVE. Comprising a full and complete History of the Invention of the Torpedo, its employment in War and results of its use. De scriptions of the yarious forms of Torpedoes, Submarine Batteries and Torpedo Boats actually used in War. Methods of Ignition by Machinery, Contact Fuzes, and Electricity, and a full account of experiments made to determine the Explosive Force of Gun powder under Water. Also a discussion of the Offensive Torpedo system, its effect upon Iron-Clad Ship systems, and influence upon Future Naval Wars. By Lieut-Commander JOHN S. BABXES, U. S. N. With twenty lithographic plates and many wood-cuts. " A book important to military men, and especially so to engineers and ar tillerists. It consists of an examination of the various offensive and defensive engines that have been contrived for submarine hostilities, including- a discus sion of the torpedo system, its effects upon iron-clad ship-systems, and its probable influence upon future naval wars. Plates of a valuable character accompany the treatise, which affords a useful history of the momentous sub ject it discusses. A great deal of useful information is collected in its pages, especially concerning the inventions of SCHOLL and VEIIDU, and of JONES and HUNT S batteries, as well as of other similar machines, and the use in submarine operations of gun-cotton and nitro-glycerme." N. T. Times. Randall s Quartz Operator s Hand- Book. 12mo. Cloth. $2.00. QUARTZ OPERATOR S HAND-BOOK. By P. M. RANDALL. New edition, revised and enlarged. Fully illustrated. The object of this work has been to present a clear and comprehensive ex position of mineral veins, and the means and modes chiefly employed for the mining and working of their ores more especially those containing gold and silver. D. VAN NOSTRAND. 23 MitcheH s Manual of Assaying. 8vo. Cloth. $10.00. A MANUAL OF PRACTICAL ASSAYING. By JOHN MITCHELL. Third edition. Edited by WILLIAM CROOKES, F.R.S. In this edition are incorporated all the late important discoveries in Assay ing made in this country and abroad, and special care is devoted to the very important Volumetric and Colorimetric Assays, as well as to the Blow-Pipe Benet s Chronoscope. Second Edition. Illustrated. 4to. Cloth. $3.00. ELECTRO-BALLISTIC MACHINES, and the Schultz Chrono scope. By Lieutenant-Colonel S. V. BENET, Captain of Ordnance, U. S. Army. CONTENTS. 1. Ballistic Pendulum. 2. Gun Pendulum. 3. Use of Elec tricity. 4. Navez Machine. 5. Vignotti s Machine, with Plates. 6. Benton s Electro-Ballistic Pendulum, with Plates. 7. Leur s Tro-Pendulum Machine 8. Schultz s Chronoscope, with two Plates. Michaelis Chronograph. 4to. Illustrated. Cloth. $3.00. THE LE BOITLENGE CHRONOGRAPH. With three litho graphed folding plates of illustrations. By Brevet Captain E. MICHAELIS, First Lieutenant Ordnance Corps, U. S. Army. " The excellent monograph of Captain Michaelis enters minutely into tho details of construction and management, and gives tables of the tirr.es of flight calculated upon a given fall of the chronometer for all distances. Captain Michaelis has done good service in presenting this work to his brother officers, describing, as it does, an instrument which bids fair to be in constant use in our future ballistic experiments. Army and Navy Journal. 24 SCIENTIFIC BOOKS PUBLISHED BY Silversmith s Hand-Book. Fourth Edition. Illustrated. 12mo. Cloth. $3.00. A PEACTICAL HAND-BOOK FOE MINERS, Metallurgists, and Assayers, comprising the most recent improvements in the disintegration, amalgamation, smelting, and parting of the Precious Ores, with a Comprehensive Digest of the Mining Laws. Greatly augmented, revised, and corrected. By JULIUS SILVERSMITH. Fourth edition. Profusely illustrated. 1 vol. 12mo. Cloth. $3.00. 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TJiirteenth Edition. 8vo. Cloth. $2.00. LESSONS AND PEACTICAL NOTES ON STEAM, the Steam- Engine, Propellers, &c., &c., for Young Engineers, Students, and others. By the late W. E. KING, U. S. N. Eevised by Chief- Engineer J. W. KING, U. S. Navy. " This is one of the best, because eminently plain and practical treatises on the Steam Engine ever published. Philadelphia Press. This is the thirteenth edition of a valuable work of the late W. H. King, U. S. N. It contains lessons and practical notes on Steam and the Steam En gine, Propellers, etc. It is calculated to be of great use to young marine en gineers, students, and others. The text is illustrated and explained by nu merous diagrams and representations of machinery. Boston Daily Adver tiser. Text-book at the U. S. Naval Academy, Annapolis. 28 SCIENTIFIC BOOKS PUBLISHED B Y Burgh s Modern Marine Engineering. One thick 4to vol. Cloth. $25.00. Half morocco. $30.00. MODERN MARINE ENGINEERING, applied to Paddle and Screw Propulsion. 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General Arrangements of Engines, 11 examples General Arrangement of Boilers, 14 examples General Arrangement of Superheaters, 11 examples Details of Oscillating Paddle Engines, 34 ex amples Condensers for Screw Engines, both Injection and Surface, 20 ex amples Details of Screw Engines, 20 examples Cylinders and Details of Screw Engines, 21 examples Slide Valves and Details, 7 examples Slide Valve, Link Motion, 7 examples Expansion Valves and Gear, 10 exam ples Details in General, 30 examples Sere w Propeller and Fittings, 13 ex amples Engine and Boiler Fittings, 28 examples - In relation to the Princi ples of the Marine Engine and Boiler, 33 examples. Notices of the Press. "Every conceivable detail of the Marine Engine, under all its various forms, is profusely, and we must add, admirably illustrated by a multitude of engravings, selected from the best and most modern practice of tlie first Marine Engineers of the day. The chapter on Condensers is peculiarly valu able. 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TREATISE ON THE STEAM ENGINE in its various applica tions to Mines, Mills, Steam Navigation, Railways, and Agricul ture, with the theoretical investigations respecting the Motive Power of Heat and the proper Proportions of Steam Engines. Elaborate Tables of the right dimensions of every part, and Practical Instructions for the Manufacture and Management of every species of Engine in actual use. By JOHN BOURNE, being the ninth edition of " A Treatise on the Steam Engine," by the "Artisan Club." Illustrated by thirty-eight plates and five hundred and forty-six wood-cuts. As Mr. Bourne s work has the great merit of avoiding unsound and imma ture views, it may safely be consulted by all who are really desirous of ac quiring trustworthy information on the subject of which it treats. 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Rifling and Projec tiles ; Standard Forms and Practice Described ; Early Experiments ; The Centring System ; The Compressing System ; The Expansion System ; Armor Punching Projectiles; Shells for Molten Metal; Competitive Trial of Rifled Guns, 1802; Duty of Rifled Guns: General Uses, Accuracy, Range, Velocity, Strain, Liability of Projectile to Injury ; Firing Spherical Shot from Rifled Guns ; Material for Armor-Punching Projectiles ; Shape of Armor-Punching Projectiles ; Capacity and Destructiveness of Shells ; Elongated Shot from Smooth Bores; Conclusions; Velocity of Projectiles (Table . CHAPTER VI. Breech-Loading Advantages and Defects of the System; Rapid Firing and Cooling Guns by Machinery ; Standard Breech-Loaders Described. Part Sec ond : Experiments against Armor ; Account of Experiments from Official Records in Chronological Order. APPENDIX. Report on the Application of Gun-Cotton to Warlike Purposes British Association, 18G3; Manufacture and Experiments in England ; Guns Hooped with Initial Tension History; How Guns Burst, by Wiard, Lyman s Accelerating Gun; Endurance of Parrott and Whitworth Guns at Charleston ; Hooping old United States Cast-Iron Guns ; Endurance and Accuracy of the Armstrong 600-pounder ; Competitive Trials with 7-inch Guns. 34 SCIENTIFIC BOOKS PUBLISHED BY 1 Peirce s Analytic Mechanics. 4*. Cloth. $10.00. SYSTEM OF ANAJLYT1C MECHANICS. Physical and Celestial Mechanics. By BENJAMIN PEIRCE, Perkins Professor of Astronomy and Mathematics in Harvard University, and Consulting As tronomer of the American Ephemeris and Nautical Almanac. 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KEY TO THE SOLAR COMPASS, and Surveyor s- Companion ; comprising all the Rules necessary for use in the field; also, Description of the Linear Surveys and Public Land System of the United States, Notes on the Barometer, Suggestions for an outfit for a Survey of four months, etc., etc., etc. By W. A. BUKT, U. S. Deputy Surveyor. Second edition. ChauYenet s Lunar Distances. 8r<x. Cloth. $2,00. NEW METHOD OF CORRECTING LUNAR DISTANCES, and Improved Method of Finding the Error and Rate of a Chro nometer, by equal altitudes. By WM. CHAUVENET, LL.D., Chan cellor of Washington University of St. Louis. D. VAN NOSTRAND. 35 Jeffers Nautical Surveying. Illustrated with 9 Copperplates and 31 Wood-cut Illustrations. 8vo. Cloth. $5.00. NAUTICAL SURVEYING. By WILUAM N. JEFFEKS, Captain U. S. Navy. Many books have been written on each of the subjects treated of in the sixteen chajrters of this work; and, to obtain a complete knowledge of geodetic surveying requires a profound study of the whole range of mathe matical and physical sciences ; but a year of preparation should render any intelligent officer competent to conduct a. nautical survey. CONTENTS. Chapter I. Formulae and Constants Useful in Surveying II. Distinctive Character of Surveys. III. Hydrographic Surveying under Sail ; or, Running Survey. IV. Hydrographic Surveying of Boats ; or, Har bor Survey. V. Tides Definition of Tidal Phenomena Tidal Observations. VI. Measurement of Bases Appropriate and Direct. VII. Measurement of the Angles of Triangles Azimuths Astronomical Bearings. VIII. Correc tions to be Applied to the Observed Angles. IX. Levelling Difference of Level. X. Computation of the Sides of the Triangulation The Three-point Problem. XI. 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STUART, Author of " Naval Dry Docks of the United States," etc., etc. Embellished with nine finely executed portraits on steel of eminent engineers, and illustrated by engravings of some of the most important and original worlds constructed in America. Containing sketches of the Life and "Works of Major Andrew Ellicott, James Geddes (with Portrait , Benjamin Wright (with Portrait), Canvass White (with Portrait), David Stanhope Bates, Nathan S. Roberts, Gridley Bryant (with Portrait), General Joseph G. Swift, Jesse L. Williams (with Portrait), Colonel William McE.ee, Samuel H. Kneass, Captain John Childe with Portrait , Frederick Harbach, Major David Bates Douglas -with Por trait), Jonathan Knight, Benjamin II. Latrobe (with Portrait), Colonel Char les Ellet, Jr. v with Portrait), Samuel Forrer, William Stuart Watson, John A. Roebling. Alexander s Dictionary of Weights and Measures. 8vo. Cloth. $3.50. UNIVERSAL DICTIONARY OF WEIGHTS AND MEAS URES, Ancient and Modern, reduced to the standards of the United States of America. By J. H. ALEXANDER. New edition. 1 vol. " As a standard work of reference, this book should be in every library ; it is one which we have long wanted, and it will save much trouble and re search." Scientific American. Gouge on Ventilation. Third Edition Enlarged. 8vo. Cloth. $2.00. NEW SYSTEM OF VENTILATION, which has been thoroughly tested under the patronage of many distinguished persons. By HENRY A. GOUGE, with many illustrations. 40 SCIENTIFIC BOOKS PUBLISHED B Y Saeltzer s Acoustics. 12mo. Cloth. $2.00. TREATISE ON ACOUSTICS in Connection with Ventilation. With, a new theory based on an important discovery, of facilitat ing clear and intelligible sound in any building. By ALEXANDER SAELTZER. " A practical and very sound treatise on a subject of great importance to architects, and one to -which there has hitherto been entirly too little attention paid. The author s theory is, that, by bestowing proper care upon the point of Acoustics, the requisite ventilation will be obtained, and vice versa. Brooklyn Union. Myer s Manual of Signals. New Edition. Enlarged. 12mo. 48 Plates full Roan. $5.00. MANUAL OF SIGNALS, for the Use of Signal Officers in the Field, and for Military and Naval Students, Military Schools, etc. A new edition, enlarged and illustrated. By Brig. -Gen. ALBERT J. MYER, Chief Signal Officer of the Army, Colonel of the Signal Corps during the War of the Rebellion. Larrabee s Secret Letter and Telegraph. Code. 18mo. Cloth. $1.00. CIPHER AND SECRET LETTER AND TELEGRAPHIC CODE, with Hogg s Improvements. The most perfect secret Code ever invented or discovered. Impossible to read without the Key. Invaluable for Secret, Military, Naval, and Diplo matic Service, as well as for Brokers, Bankers, and Merchants. By C. S. LARRABEE, the original inventor of the scheme. D. VAN NOSTRAND. 41 Hunt s Designs for Central Park Gateways. 4to. Cloth. $5.00. DESIGNS FOR THE GATEWAYS OF THE SOUTHERN ENTRANCES TQ THE CENTRAL PARK. By RICHABD M. HUNT. With a description of the designs. Pickert and Metcalf s Art of Graining. 1 vol. 4to. Cloth. $10.00. THE ART OF GRAINING. How Acquired and How Produced, with description of colors and their application. By CHABLES PICKERT and ABRAHAM METCALF. Beautifully illustrated with 42 tinted plates of the various woods used in interior finishing. Tinted paper. The authors present here the result . of long experience in the practice of this decorative art, and feel confident that they hereby offer to their brother artisans a reliable guide to improvement in the practice of graining. Portrait Gallery of the War. 60 fine Portraits on Steel. Royal 8vo. Cloth. $6.00. PORTRAIT GALLERY OF THE WAR, CIVIL, MILITARY AND NAVAL. A Biographical Record. Edited by FRANK MOORE. One Law in Nature. 12mo. Cloth. $1.50. ONE LAW IN NATURE. By Capt. H. M. LAZELLE, U. S. A. A New Corpuscular Theory, comprehending Unity of Force, Identity of Matter, and its Multiple Atom Constitution, applied to the Physical Affections or Modes of Energy. 42 SCIENTIFIC BOOKS PUBLISHED BY West Point Scrap Book. 69 Engravings and Map. 8vo. Extra Cloth. $5.00. WEST POINT SCEAP BOOK. Being a Collection of LEGENDS, STORIES, SONGS, ETC., of the U. S. Military Academy. By Lieut. 0. E. WOOD, U. S. A. Beautifully printed on tinted paper. " It is the work of several different writers, whose names are withheld from the public, but whose contributions all bear a decided flavor of their origin, preserving the unity of a military education and experience. The volume abounds with personal anecdotes and humorous narratives, seasoned with copious specimens of the students songs, and presenting a vivid, and doubtless a faithful, exhibition of the peculiar lights and shades of West Point life." N. T. Tribune. History of West Point. Second Edition. With 36 Illustrations and Maps. 8vo. Extra Cloth. $3.50. HISTORY OF WEST POINT. Its Military Importance during the American He volution, and the Origin and Progress of the U. "S. Military Academy. By Bvt. -Major E. C. BOTNTON. 416 pages. Printed on tinted paper. " Aside from its value as an historical record, the volume under notice is an entertaining guide-book to the Military Academy and its surroundings. "We have full details of Cadet life from the day of entrance to that of graduation, together with descriptions of the buildings, grounds and monuments. To the multitude of those who have enjoyed at West Point the combined attrac tions, this book will give, in its descriptive and illustrated portion, especial pleasure." New York Evening Post. West Point Life, Oblong 8vo. 21 full-page Illustrations. Cloth. $2.50. WEST POINT LIFE. A Poem read before the Dialectic Society of the United States Military Academy. Illustrated with Pen and Ink Sketches. By A CADET. To which is added the song " Benny Havens, Oh ! " " Summer visitors at West Point will especially enjoy these illustrations ; and the poem itself may be regarded as a description of Cadet life, as seen from the inside, by one who appreciates it." N. Y. Journal of Commerce. Guide to West Point and the U. S. Military Academy, with Maps and Engravings. 18mo. Blue Cloth. Flexible Covers. $1.00. THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO 5O CENTS ON THE FOURTH DAY AND TO SI.OO ON THE SEVENTH DAY OVERDUE. SEP 28 1i934 OCT 2 1937 LD a 1-50 w-8, 32 YC 18958