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Natural asphaltum 
 
 AND ITS COMPOUNDS, 
 
 Their Importance, Definitions, Mineralogy, Analyses, 
 Uses, History and Statistics. 
 
 A PAPER 
 
 Prepared for the use of the Professors and Students of the Rensselaer 
 Polytechnic Institute and others at the request of 
 the Rensselaer Society of Engineers 
 
 BY 
 
 r 
 
 
 W. HOWARD, B. L„ C. E. 
 
 
 Bituminous Deposits. 
 
 jraveiueui/s cm r- -o 
 
 English, German, French, Italian, bpamsn. 
 
 Copyrighted. 
 
 PUBLISHED BY THE 
 
 Rensselaer Society of Engineers,. 
 
 TROY, N. Y. 
 
ST1TOPSIS. 
 
 I. Importance of Asphaltum . 
 
 (a) Number of mines. 
 
 (b) Branches of engineering, etc., using it. 
 
 (c) Men employed. 
 id) Capital invested. 
 
 II. Definitions.. . . ' . 
 
 (< a ) Asphaltum ; Crude, Refined and Asphaltic Cement. 
 
 (b) Asphaltic Limestone. 
 
 (c) Asphaltic Sandstone. 
 
 ( d) Asphalt Pavements ; Trinidad Asphalt class, Asphaltic 
 
 limestone class, Asphaltic sandstone class of road¬ 
 way pavements. Asphaltic mastics for walks, 
 floors, roofs, etc. Asphaltic Concretes, etc. 
 
 III. Position in Mineralogy. 
 
 (a) Group of Bitumens to which asphaltum belongs. 
 
 (b) Asphaltic compounds and occurrences by classes, 
 
 deposits and countries. 
 
 IV. Analyses and Tests. 
 
 (a) Chemical. 
 
 (, b ) Physical. 
 
 (c) Detection of coal-tar adulterations, etc. 
 
 V. Mining, Preparation and Uses. 
 
 (a) Trinidad Asphalt as a standard. 
 
 ( b ) Asphaltic limestone. 
 
 (c) Asphaltic sandstone. 
 
 VI. History. 
 
 (a) Ancient times. 
 
 (b) Modern times, 162G to 1893. 
 
 VII. Statistics. 
 
 (<?) . Mines, Europe and America. 
 
 ( b ) Pavements, Europe and America. 
 
 * Copyright, 1894, by J. \V. Howard. 
 
BARNES 
 
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 I 
 
 NATURAL ASPHALTUM 
 
 AND ITS COMPOUNDS.* 
 
 By J. W. Howard, B. L, C. E. 
 
 I. IMPORTANCE OF ASPHALTUM. 
 
 The importance of an industry can be judged by its volume, 
 value, usefulness and the kind and number of men employed. 
 Every engineer, architect and constructor needs at least a 
 general knowledge of the properties and uses of asphaltum. 
 
 This paper is intended to give simply and briefly an outline 
 of those scientific and general facts about asphaltum, which are 
 essential to technical pursuits. 
 
 The importance of the asphalt industries can be judged first, 
 from the fact that there are more than 65 known mines and 
 deposits; secondly, because it enters into constructions and 
 preparations used in all branches of engineering and archi- 
 tecture, as well as in many manufactures. 
 
 There are employed in mining, shipping, refining, preparing 
 and applying asphalt and its compounds, scores of graduates of 
 technical institutions, hundreds of business men and thousands 
 of laborers. 
 
 The volume of the industry is measured by the fact that the 
 one branch of this industry, asphalt paving, is found in more 
 than 92 American and 55 European cities. This means an in¬ 
 vestment of /it least $55,000,000 of municipal funds and a work¬ 
 ing capital, if combined, of at least $15,000,000. 
 
 The growth of asphalt industries has been very rapid during 
 the past forty years in Europe and twenty in America. 
 
 The men en g a g ed in it have been too busy to write its complete 
 
 * Copyright, 1694, by J. W. Howard. 
 
4 
 
 history or a full treatise on the subject. Fragmentary articles, 
 pamphlets, etc., in either German, French, Italian or English 
 are available; each touching upon some mine or branch of the 
 work. These are generally issued by commercial companies; 
 while acting as advertisements they contain much practical 
 information. Actual experience with asphaltum and its com¬ 
 pounds is the best teacher, especially when guided by the 
 recorded experience of others. 
 
 II. DEFINITIONS. 
 
 A series of precise definitions makes the best introduction, 
 so that it shall be clearly understood just what is meant by the 
 terms used. 
 
 (a) Definition of Asphaltum. — Asphaltum , called generally in 
 English Asphalt, is the Latin for the Greek aa^aXroq (asphaltos). 
 
 It is a natural mineral pitch and is practically unchangeable 
 at ordinary temperatures. When pure, or nearly pure, it is 
 dark brown or black. When struck with a hammer at ordinary 
 temperatures it is brittle. Its fracture is dull and conchoidal. 
 It is sectile. When rubbed or freshly broken it emits a bitumi¬ 
 nous odor. Its specific gravity in its natural state is from .9G 
 to 1.68, due to impurities and porosity. It is not soluble in 
 water. It is soluble in carbon disulphide. It begins to melt 
 at about 190° F. and Hows at about 200° F. It is partly soluble 
 in alcohol, turpentine, ether, naptha and petroleum. Its hard¬ 
 ness at 70° F. is 2-J- to 3 Dana scale. 
 
 Asphalt is often called by other names, as Trinidad asphalt, 
 Cuban asphalt, Bitumen, Jews’ Pitch, etc. 
 
 The word asphalt, with slight changes in spelling, is common 
 to all languages. 
 
 While asphaltum is a bitumen, all bitumen is not asphaltum, 
 as will be explained in Sec. III. of this paper. 
 
 In Europe certain persons, probably for brevity, have called 
 asphaltic limestone, “Asphalte” Asphalt simply saturates the 
 limestone. This compound of limestone and asphalt should 
 not be called asphalt. 
 
 In America, the public has been led into the error of suppos¬ 
 ing that the by-product of the gas works, namely, gas-tar and 
 
5 
 
 coal-tar, were asphalts. This is due to the efforts of either 
 unprincipled or ignorant persons, who have desired to sell coal- 
 tar preparations, which, while they have valuable uses, should 
 not be sold or used where asphaltum is needed. They are the 
 products of distillation. The volatile oils contained in them, 
 if exposed to the air or sun, soon disappear and black powder 
 remains. Real asphaltum retains it fixed oils and cementing 
 qualities, hence its lasting properties in its natural and artificial 
 compounds. 
 
 Refined Asphaltum is the product resulting from the refining 
 by heat, at a temperature below 400° F., of crude asphaltum. 
 The water and vegetable matter are removed. Commercially 
 refined asphalt used in engineering, architecture, etc., still con¬ 
 tains some earthy matter. It is not necessary to fully remove 
 this, because in the mixtures subsequently used it would be 
 replaced when mixed with sand, limestone dust, etc., as occasion 
 demands. 
 
 Asphaltic Cement is a combination of refined asphalt and 
 residuum oil of petroleum of a standard specific gravity at a 
 given temperature. The proportions used vary with the objects 
 for which the asphaltic cement is prepared. From 15 to 18 lbs. 
 of residuum oil is used to every 100 lbs. of refined asphalt. 
 They are mixed hot and agitated by air or mechanical means. 
 
 (h) Asphaltic Limestone .—Asphaltic limestone is a natural 
 compound of asphalt and limestone. Maltha, and other bitu¬ 
 minous substances, are sometimes present. Sulphur, sand and a 
 few other foreign substances are generally found in it. Its frac¬ 
 ture is irregular, and its color is from brown to chocolate black 
 when freshly broken. The color is darker in the specimens 
 containing the larger amounts of asphaltum. The percentage 
 of asphaltum permeating the limestone varies in different 
 deposits, and in different parts of the same mine, from less than 
 1% to above 20%. The grain of asphaltic limestone is very fine. 
 Under the microscope the smallest particle is coated with 
 asphaltum. If cut by a sharp blow of an axe it appears grayish 
 white along the cut, due to forcing out of the asphaltum and 
 leaving particles of limestone exposed. If a piece contain 
 above 10% of asphalt it can be warmed and broken in the 
 hands. A piece heated over the fire falls apart. If heated in 
 
6 
 
 a pan and held for an hour at a high temperature, the asphaltum 
 is driven off and a gray, powdered limestone remains. A bitu¬ 
 minous odor is perceptible in all samples when freshly broken 
 if they contain above 4% of asphaltum. 
 
 Asphaltic limestone is sometimes called “ rock asphalt ” and 
 “ bituminous limestone.” In France, while often referred to 
 erroneously, as “asphalte,” its real name is “ calcaire bitumi- 
 neux.” The German name is “ Asphaltkalkstein,” and for 
 brevity, “ Asphaltstein.” 
 
 (r) Asphaltic Sandstone .—Asphaltic sandstone is composed of 
 sandstone containing from less than 1% to sometimes as high 
 as 70% of asphaltum. Maltha and petroleum are often present 
 to the injury of the asphaltic sandstone for engineering uses. 
 This material is called by a few people in California by the 
 name “asphalt rock,” which is misleading. It has not yet 
 proved itself very valuable. Experiments are being constantly 
 made to establish its value and how to use it. 
 
 (d) Asphalt Pavements .—Asphalt pavements are of three 
 classes, laid upon concrete or other suitable foundation, and 
 composed of either Trinidad asphalt, sand, powdered limestone, 
 etc. ; or asphaltic limestone, or asphaltic sandstone, if laid upon 
 roadways. But if laid upon walks, floors, roofs, etc., one or 
 more of these materials are combined in various ways. I will 
 define them separately. 
 
 Trinidad asphalt pavement, the standard of this class, is laid 
 briefly as follows : The street is graded, rolled with a steam 
 roller, supplied with a cement foundation, generally five or six 
 inches thick. In case the street is covered with a Macadam 
 roadbed or old stone-block pavement, these are often used as 
 foui;dations without the hydraulic cement concrete. If Mac¬ 
 adam or old stone-blocks are used for a foundation, a thin layer, 
 about 1)4 inches thick, of asphaltic concrete, called “binder” 
 is first laid upon these old surfaces. The asphalt paving mix¬ 
 ture, called the “ wearing surface,” is laid upon the foundations, 
 prepared as described. The wearing surface is also laid on 1)4 
 inches of binder spread over 5 inches of hydraulic cement 
 concrete. 
 
 \ 
 
 This wearing surface mixture is spread with hot rakes and 
 compressed with a steam roller to the thickness desired, 1)4, 2, 
 
7 
 
 and in certain places, 2j4 inches thick, as the street and system 
 of pavement demands. The Trinidad asphalt paving mixture 
 is compounded as follows : Asphaltic cement is first prepared 
 by mixing refined asphalt and residuum oil, using from 15 to 18 
 lbs. of residuum oil, according to the climate, etc. The asphaltic 
 cement serves to cement together the sand and powdered lime¬ 
 stone entering into the wearing surface mixture, which is as 
 follows : 
 
 Asphaltic cement,.12 to 15% by weight. 
 
 Sand.. . 83 to 70%. 
 
 Powdered Limestone . . . . 5 to 15%. 
 
 The mixing is done in a special toothed mixing apparatus, 
 the teeth interlacing and revolving on two shafts in opposite 
 directions. The asphaltic cement and sand are first previously 
 heated to above 250° F., which is the temperature at which the 
 mixture should be laid upon the street. The porportions vary 
 according to the kind of sand used and the climate. The pro¬ 
 portions of oil in the asphaltic cement, as well as the propor¬ 
 tions of the materials in the paving mixture, vary with the 
 climate. More asphaltic cement is used in cold climates than in 
 warm ones. This easy adaptability to climate is one of the 
 reasons of the success of this pavement. 
 
 Asphaltic limestone pavement is a pavement laid upon a suitable 
 concrete or other foundation, and composed of powdered 
 asphaltic limestone spread upon the foundation previously pre¬ 
 pared, and compressed in position by hot iron rammers, or 
 otherwise. The process is, briefly, thus : The asphaltic lime¬ 
 stone is mined in large lumps, crushed in a suitable crusher, 
 powdered while cold in an appropriate pulverizer. The powder 
 is heated to a temperature a little above 275° F., spread 
 upon the street and compressed in position. The natural 
 asphaltic limestone, called sometimes rock-asphalt, must con¬ 
 tain about 10% of asphaltum, more or less, according to the 
 climate, for this class of paving. 
 
 Asphaltic sandstone pavement is a pavement of natural asphaltic 
 sandstone, prepared, briefly, as follows : The material is mined, 
 crushed by a crusher, if not fine enough when arriving from 
 the mine, and then disintegrated by the injection of steam into 
 the mass, or by passing the material through a revolving steam 
 
8 
 
 heated jacket, or cylinder. The material, when fine, is raked 
 upon the prepared foundation and compressed in position gen¬ 
 erally by a steam roller. Asphaltic sandstone pavements, 
 because still in an experimental stage, have not yet definite per¬ 
 centages of asphaltum decided upon as final and best. 
 
 Asphaltic mastic is of three kinds. First, that which is com¬ 
 posed of a mixture of powdered asphaltic limestone, Trinidad 
 asphalt and possibly a little residuum or other oil ; second, that 
 which is composed of sand, possibly a little limestone dust and 
 about 22 ( fc of asphaltic cement ; third, that which is composed of 
 crushed asphaltic sandstone, enriched by the addition of either 
 asphaltic cement or a little maltha. All asphalt mastics are 
 mixed or prepared hot, and generally run into molds varying 
 in shape, at the different factories. These are called asphalt 
 mastic blocks and are generally about six inches thick, and 
 either round, square or hexagonal. They are shipped to the 
 place needed and there remelted and used in making walks, 
 floors, roofs and in many other ways. 
 
 Asphaltic Concretes are composed of either crushed stone 
 cemented together with asphaltic limestone mastic ; or of 
 crushed stone cemented together with Trinidad asphalt mastic, 
 that is, a mixture of crushed stone, sand, limestone dust and 
 asphaltic cement, mixed hot and compressed in layers by hand. 
 These concrete foundations have many uses. 
 
 The details of mining, preparing and using of asphalt and 
 its compounds will be given in Section V., further on. 
 
 III. POSITION IN MINERALOGY. 
 
 % 
 
 (, a ) Group of bitumens to which asphaltum belongs. — It is best 
 to pass at once to the position of asphaltum and its compounds 
 among minerals, omitting the geology and origin of these 
 materials, which form a special field of study and investi¬ 
 gation not yet in tangible shape. 
 
 Among the hydro-carbons there is a group of minerals called 
 the Bitumens, or bituminous substances, which, arranged in 
 order of their density, are as follows: 
 
9 
 
 4 
 
 Table No. 1 
 
 BITUMENS. 
 
 1. Natural Gas, 
 
 2. Natural Naptha , 
 
 3. Petroleum , or Mineral Oil, 
 
 4. Maltha, or soft, sticky Bitumen, (at 77° F.,) 
 
 5. Asphaltum, or stiff, non-sticky Bitumen. 
 
 G. Glance Pitch , or dry, brittle Bitumen, 
 
 7. Elaterite and others. 
 
 This list suffices to establish the position of asphaltum among 
 bituminous substances. These bitumens are seldom found 
 native or pure, but are mixed two or more together; also in 
 combination with earth, clay, sand, etc. Sulphur, magnesia, 
 carbonate of lime are often present. 
 
 (I?) Asphaltic compounds and occurrence by classes , deposits and 
 countries .—The grouping of asphaltic minerals and their dis¬ 
 tribution in the world can best be shown by means of a tabular 
 arrangement. The following Table No. 2, while not fully com¬ 
 plete, is the result of fourteen years’ correspondence, reading 
 and visits to asphalt mines. This is the first time that I have 
 ventured to publish the same, and I hope it will help systematize 
 the subject of asphaltum and its compounds. The volume of 
 the industry is so great that standard definitions and systematic 
 arrangement of materials are imperative. 
 
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 Austria, Spain, etc. 
 
 Asia.Asia Minor, Palestine, Bagdad and probably in China. 
 
 Africa.Egypt and probably elsewhere in Africa. 
 
11 
 
 In order to facilitate reference, I have arranged the principal 
 deposits of asphalt and its compounds, by materials and coun¬ 
 tries or states, in the following : 
 
 Table No. 3. 
 ASPHALTUM. 
 
 Mixed With Earthy Matter. 
 
 Compounded With Lime¬ 
 stone. 
 
 Compounded With Sand¬ 
 stone. 
 
 Bagdad, 
 
 Austria, 
 
 California, 
 
 California, 
 
 California, 
 
 Colorado, 
 
 Colorado, 
 
 Dalmatia, 
 
 Cuba, 
 
 Columbia, 
 
 France, 
 
 France, 
 
 Indian Territory, 
 
 Germany, 
 
 Germany, 
 
 Mexico, 
 
 Hungary, 
 
 Indian Territory, 
 
 Montana, 
 
 Indian Territory, 
 
 Kentucky, 
 
 Palestine, 
 
 New Mexico, 
 
 New Mexico. 
 
 Peru, 
 
 Michigan, 
 
 Russia, 
 
 Texas, 
 
 Italy, 
 
 Texas, 
 
 Trinidad, 
 
 Utah, 
 
 Venezuela. 
 
 Russia, 
 
 Sicily, 
 
 Spain, 
 
 Switzerland, 
 
 Texas, 
 
 Utah, 
 
 Washington. 
 
 Utah. 
 
 Other bitumens, as maltha, etc. ; and impurities, as sulphur, 
 etc., are often present, sometimes to the commercial detriment 
 of the material. One or more mines are worked in each of the 
 above countries, except, perhaps, Columbia, Indian Territory, 
 Montana, New Mexico, Michigan, Washington and Dalmatia. 
 
 IV. ANALYSES AND TESTS. 
 
 (tf) Chemical .—Without entering into the complicated details 
 of the analysis of hydro-carbons and bituminous substances, I 
 will first call attention to the complete chemical analysis of 
 specimens of asphaltum into their elements from representative 
 deposits in the world. This is shown as follows : in 
 
12 
 
 Table No. 4. 
 
 Place . 
 
 Trinidad. 
 
 Mexico. 
 
 Peru. 
 
 Cuba. 
 
 Columbia. 
 
 Palestine. 
 
 Carbon .... 
 
 85.89 
 
 80.34 
 
 88.67 
 
 81.50 
 
 88.81 
 
 80.00 
 
 Oxygen . . •. . 
 
 .56 
 
 10.09 
 
 1.65 
 
 8.90 
 
 1.68 
 
 .40 
 
 Hydrogen . . . 
 
 11.06 
 
 9.57 
 
 9.68 
 
 9.60 
 
 9.64 
 
 9.00 
 
 Nitrogen . . . 
 
 • 
 
 • • • 
 
 • . • 
 
 • 
 
 .87 
 
 10.00 
 
 Sulphur .... 
 
 2.49 
 
 • • • 
 
 • 
 
 • • • 
 
 • 
 
 .60 
 
 Ash . 
 
 
 • 
 
 . . . 
 
 . . . 
 
 . . . 
 
 . . . 
 
 Totals. . . . 
 
 100.% 
 
 100. % 
 
 100.% 
 
 100.% 
 
 100.% 
 
 100.% 
 
 The above Table of the analysis of specimens of asphaltum 
 is that of chemically refined asphaltum. This sort of analysis, 
 while interesting has very little practical value. The commer¬ 
 cial value of an asphalt depends principally upon its physical 
 characteristics, which I will give later. Experience has shown 
 that while chemical analyses are of great value in connection 
 with asphalt industry, nevertheless they must be made upon 
 special lines of investigation. We would proceed as follows : 
 (and I take it for granted that my readers are familiar with the 
 general principles and methods of qualitative analysis, and are 
 able to appreciate, if not personally execute, quantitative 
 analysis), having one or more samples of crude asphaltum to 
 be examined, the first thing to do is to turn to the definition of 
 asphaltum, Section II., heading ( a ), and compare the sample or 
 samples with the characteristics set forth in the definition. See 
 if it remains brittle and retains its form at ordinary tempera¬ 
 tures of the air. Is it dark brown to black ? Is it brittle when 
 struck ? Conchoidal ? Sectile ? Break it and see if it has a 
 bituminous odor ? Specific gravity about 1.00 to 1.08 ? Is it not 
 soluble in water ? Do not be deceived by the clay or other 
 matter being soluble in water. It should begin to melt at 
 190' F., and flow at a little above 200° F. See if the hardness 
 at 70° F. lies between 2^4 and 3 Dana scale. 
 
 Dessicate a piece in vacuo , keeping the temperature below 
 212° F. Dissolve out the asphaltum from the crude material 
 with carbon disulphide. Try the solubility of pieces in alcohol 
 of standard specific gravity, in turpentine, ether, petroleum, 
 naptha. By taking a little time, with the assistance of the sand 
 bath, the distillation tests can be made at given temperatures 
 
13 
 
 and for given periods of time. It is well to get the ash of each 
 crude sample by combustion. The penetration tests can be 
 made upon different samples of refined asphalt at constant tem¬ 
 peratures a little above the temperatures used in making pene¬ 
 tration tests upon samples of asphaltic cement. 
 
 The expert chemist will think of additional tests. What I 
 have given above is in the way of suggestions to facilitate the 
 comparison in a laboratory of different asphalts. 
 
 While the above chemical experiments and investigations are 
 of great value in indicating the advisibility of trying an asphalt 
 from a new source of supply in pavements or other branches of 
 engineering, nevertheless the only safe test is to finally try the 
 asphalt in actual practice, keeping carefully tabulated records 
 of what is done, and finally of the results of the asphalt pave¬ 
 ments, mastics, concretes, or other construction into which the 
 new asphalt was introduced. 
 
 I will omit the experiments upon asphalts with the spectro¬ 
 scope, in which I am taking great interest. Possibly, in the 
 future, I may try to tabulate the results in this interesting field 
 of asphalt investigation, as yet so little developed. 
 
 (h) Physical .—As each student of science knows, the physical 
 and chemical characteristics of a material are so interlaced that 
 it is difficult to treat of them separately. Hence some of the 
 physical characteristics and tests are contained under heading 
 (a) above, because chemistry is necessary to, at least, in part, 
 establish the physical properties. 
 
 The physical characteristics of the three principal asphaltic 
 substances, asphaltum, asphaltic limestone and asphaltic sand¬ 
 stone are best given separately. 
 
 Trinidad asphalt supplies more than 00 r /o of the asphaltum 
 used in the world. It should therefore be described in detail, 
 being, as it is, a standard asphalt and a type of all. Trinidad, 
 an island at the mouth of the Orinoco, north coast of South 
 America, is the property of Great Britain. Upon this island is 
 found the “Trinidad Asphalt Lake,” often referred to as the 
 “Pitch Lake.” It is a large, Hat crater or deposit of asphaltum, 
 mixed with much earthy and a little vegetable matter and 
 water. This deposit is the property of the British Government. 
 It is about a mile from the Southwest corner of the island, and 
 covers almost 11G acres. The surface is hard, very slightly 
 undulating, intersected by shallow cracks, covered at spots with 
 
14 
 
 low temporary vegetation and pools of water. The asphalt is 
 softer as we approach the centre, where it is very soft. 
 
 Leaving the description of gathering this material in carts 
 driven upon the deposit, hauling it to the shore, loading it in 
 vessels, refining it in America or Europe, until we reach Section 
 V., where details of mining, etc., will be given, we will pass at 
 once to the description of Trinidad asphalt. 
 
 Crude Trinidad Asphalt is dark brown and very brittle at ordi¬ 
 nary temperatures. It is easily detached from the surface of the 
 “Asphalt Lake ’’ with a pick. Its irregular fracture shows parti¬ 
 cles of clay and vegetable matter in it. When warmed in the 
 hand it can be slightly bent. When broken it emits a bitumi¬ 
 nous odor. It is very porous. The chemical and physical tests 
 indicated above and by the definition of asphaltum are easily 
 made. ^ 
 
 The average analyses of crude Trinidad asphalt are as follows: 
 
 Table No. 5. 
 
 First, by weighing, then driving off the water: 
 
 Authority, Richardson. 
 
 Water. 27.85 
 
 Asphalt, earthy and vegetable matter. 72.15 
 
 100 . % 
 
 Second, analyzing the dry, crude asphalt: 
 
 Asphalt. 52.87 
 
 Earthy and vegetable matter. 47.13 
 
 100 .% 
 
 Third, combining results gives average analysis of crude 
 
 Trinidad asphalt. 
 
 Asphalt. 38.14 
 
 Earthy and vegetable matter. 34.01 
 
 Water. 27.85 
 
 100 .% 
 
 Finally the complete analyses of the materials contained in 
 crude Trinidad asphalt are as follows: 
 
 Authority, 
 
 Asphalt. 
 
 Earthy matter . . 
 Vegetable matter 
 Water. 
 
 Bowen. Richardson. 
 39.83 38.14 
 
 33.99 20.38 
 
 9.31 7.03 
 
 10.87 27.85 
 
 100 .% 100 .% 
 
15 
 
 These are mechanical mixtures. The variation in water is 
 very great. A lump of crude asphalt in a room loses its water 
 in a few weeks. Powdered crude asphalt loses its water by 
 evaporation in a few days. Samples of asphalt from the 
 centre of the “Lake” vary slightly from those near the shore. 
 But for commercial uses the asphalt from within the 
 Asphalt Lake is more constant, reliable and better than that 
 which, for a short time, came from places outside of the “Lake,” 
 and was known as “ overflow or land pitch.” This material 
 contained many variable impurities, and lacked cementing 
 qualities. It is no longer imported into the United States. 
 
 Asphaltic limestone has many physical characteristics, due to 
 the various compositions of this material in the same and 
 different mines throughout the world. 
 
 The definition of asphaltic limestone, already given under 
 Section II., heading ip), indicates many of the characteristics of 
 this material. The analyses of representative asphaltic lime¬ 
 stones from four mines is shown in the following : 
 
 Table No. 6. 
 
 Composition. 
 
 Val de Travers, 
 Switzerland. 
 
 Seyssel, 
 
 France. 
 
 Ragusa, 
 
 Sicily. 
 
 Limmer, 
 
 Germany. 
 
 Asphaltum. 
 
 10.15 
 
 8.15 
 
 8.92 
 
 14.30 
 
 Calcium Carbonate . . . 
 
 88.40 
 
 91.30 
 
 88.21 
 
 67.00 
 
 Clay and Iron Oxide. . . 
 
 .25 
 
 .15 
 
 .91 
 
 ) 
 
 Sand. 
 
 • • • 
 
 ... 
 
 .60 
 
 y 17.52 
 
 Magnesium Carbonate . . 
 
 .30 
 
 .10 
 
 .96 
 
 ) 
 
 Insoluble. 
 
 .45 
 
 .10 
 
 • • • 
 
 
 Loss. 
 
 .45 
 
 .20 
 
 .40 
 
 1.18 
 
 Total. 
 
 100.% 
 
 100.% 
 
 100.% 
 
 100.% 
 
 These analyses are made by the usual solutions in re-agents 
 of qualitative and quantitative analyses. There are many other 
 mines and deposits, varying greatly in the proportions of 
 asphaltum, calcium carbonate and sand present. Traces of 
 many other substances are often found. A little water is gener¬ 
 ally present; sulphur sometimes appears. It is difficult to dis¬ 
 tinguish the petroleum and maltha if these happen to be present. 
 This is done, generally, by dissolving out the bituminous sub¬ 
 stances in the bituminous limestone by means of carbon disul- 
 
10 
 
 * 
 
 phide, then separating by evaporation at a very low tempera¬ 
 ture just above the temperature of the air, the carbon disulphide 
 from the bituminous substances. The separation finally, of the 
 bituminous substances present into petroleum, maltha and asplial- 
 tum can practically only be indicated by a series of distillations 
 at given temperatures, increasing the temperatures according to 
 the amounts at which the substances desired are known to be 
 distilled. This analysis of one bitumen from another, that is 
 asphaltum from petroleum, is exceedingly difficult and can 
 only be undertaken by special chemists in well-equipped 
 laboratories. 
 
 A piece of asphaltic limestone lying exposed and undis¬ 
 turbed for several months, appears upon its surface of a grayish 
 white color. When prospecting for this material this should be 
 borne in mind, for the undisturbed outcroppings of a ledge or 
 deposit of asphaltic limestone is always gray or white. I 
 attribute this to the chemical and physical action of the car¬ 
 bonic acid gas, moisture and air of the atmosphere assisted by 
 the sun. These agencies disintegrate the surface of the lime¬ 
 stone, leaving it covered with a light gray film. 
 
 Asphaltic sandstone is found in nature sometimes dense and 
 sometimes soft. The grain varies in some mines from very 
 fine to others where it is very course. Small particles of clay 
 and other substances are often present. Little shells, of several 
 kinds, are frequently found. Its color is almost invariably 
 black. A piece heated upon a stove quickly falls to pieces if 
 above G% of asphaltum is present. Asphaltic sandstone very 
 often contains petroleum and maltha in large quantities. In 
 America, where crude asphaltum is cheap, it does not pay to 
 extract the asphaltum from the asphaltic sandstone, as is done 
 at a few places in Europe. 
 
 (c) Detection of coal-tar , distillates and other imitations and adulter¬ 
 ations. —Just after the success of asphalt pavements in Europe 
 and the consequent reports sent to this country, a desire arose 
 to have smooth and noiseless pavements in American cities. 
 At that time the public did not know what asphalt was, and 
 because of the expense of transporting asphaltic limestone from 
 Europe to America, many artificial compounds and imitations 
 were proposed. Before long that which was previously known 
 as gas-tar or coal-tar began to be sold under the name “asphal- 
 
17 
 
 turn.” Tar was mixed with sand and gravel, first for walks and 
 then for roadways. These mixtures were called “asphalt 
 walks” and “asphalt pavements.” This went so far that at the 
 time of the Tweed ring in New York City, many streets were 
 spread over with coal-tar imitations of asphalt pavements, 
 which were soon called “ tar poultice pavements ” and rapidly 
 disintegrated. The use of coal-tar preparations for pavements 
 of streets has almost ceased. It is still too extensively used for 
 roofs in this country, whereas, in Europe it is not used at all, 
 except, perhaps, in cases of small temporary sheds where a 
 temporary substance, like coal-tar, is admissible. 
 
 The real names of these coal-tar products, manufactured by 
 re-distilling the by-products from the gas-works, are “coal-tar 
 distillates,” and they are numbered distillate No. 1, 2, 3, etc., 
 according to their comparative density. A name sometimes 
 given them, probably to hide their origin, is “bituminous 
 cement.” 
 
 These artificial coal or gas-tar products have legitimate uses; 
 but they cannot take the place of natural mineral asphaltum. 
 Coal-tar must not be used as an adulteration of asphalt or its 
 compounds. 
 
 Asphalt and coal-tar differ in origin, composition, odor and 
 fracture. A general similarity in appearance deceives a few, 
 especially when some asphalt is mixed with the tar. 
 
 “ Paving-pitch ” is another name given to coal-tar, especially 
 when it is used for pouring between granite paving blocks, and 
 otherwise in pavements. Coal-tar, a product of distillation of 
 the gas-works, when exposed to water, air or the sun soon loses 
 by evaporation its volatile oils and becomes a dry powder. 
 
 Genuine natural asphaltum retains its oils, hence its lasting 
 qualities in pavements, concretes, etc. 
 
 A practical method to tell asphalt from coal-tar is as follows : 
 Apply to any gas-works or coal-tar roofer and get a piece of 
 coal-tar. Then apply to some dealer in natural asphaltum for 
 a sample of refined Trinidad or other asphaltum. Having two 
 samples, one of coal-tar and one of asphalt, place them side by 
 side. The coal-tar emits a sharp, acrid odor, easily perceived. 
 The asphalt must be rubbed hard to emit a strong odor. The 
 asphalt odor will be quickly learned. It is entirely different 
 from the coal-tar odor. The asphalt odor is known as a 
 
18 
 
 “bituminous odor.” It is rather agreeable, perhaps a little sour 
 smelling. Crude and refined asphalt, when quite cold, emits a 
 weak, clay-like odor. Next taste one sample, then the other. 
 Then attempt to chew a little of the refined asphalt. It will 
 crumble. If it be an “asphalt paving cement,” made from 
 genuine asphalt and residuum oil of petroleum, a fairly agree¬ 
 able chewing gum is the result. Any attempt to chew coal-tar 
 will result in disaster to the teeth, for it is very sticky and hard 
 to remove from the teeth. 
 
 Next-turn to the definition of asphaltum Section II., and to 
 the analyses and tests of asphaltum Section IV., and apply the 
 tests there suggested. The differences between gas-tar and 
 asphalt will be at once apparent. 
 
 Expert analysis of mixtures to detect any coal-tar present, 
 if present in small quantities, is exceedingly difficult, but when 
 large amounts of tar are present in the mixture, they are quickly 
 discovered by the sharp odor and otherwise. Much pavement 
 was laid in one or two cities under the name “ vulcanite,” which 
 was a mixture of about 25% of asphalt and 75% of coal-tar, 
 mixed with sand, powdered limestone, etc. This material is no 
 longer laid where engineers have full control as to what shall 
 enter into the pavements, unless they are influenced by other 
 reasons than technical ones 
 
 Asphaltic cement is generally composed of refined asphaltum 
 and residuum oil of petroleum, but at some places a mixture of 
 asphaltum and maltha is being tried, with the promise of possi¬ 
 ble success. The questions of sufficient and constant supply of 
 a standard grade of maltha enter into the problem. 
 
 This mixture of asphalt and maltha should not be regarded 
 as an adulteration, simply an experiment. 
 
 Mixtures of asphalt and crude petroleum or asphalt and cer¬ 
 tain shale oils are not suitable for engineering purposes and 
 must be avoided. 
 
 V. MINING, PREPARATION AND USES. 
 
 It is best to treat of the mining, preparation and uses of the 
 three substances separately, because they are mined, prepared 
 and used in different ways. 
 
 («) Trinidad asphalt as a standard , comes from the Island of 
 
19 
 
 Trinidad, and from the Trinidad Asphalt Lake upon that 
 Island, as described in Section IV. under heading (b). 
 
 The carts and horses used to haul the crude asphalt from the 
 deposit to the shore, drive upon the “ Pitch Lake.” The mater¬ 
 ial, which has already been described as dark brown, brittle and 
 similar to dense, dry peat, is picked loose, thrown into the 
 carts, hauled to the ocean beach, loaded upon scows and lighters 
 and thence into the steamers and sailing vessels which bring it 
 to America or take it to Europe. 
 
 The excavations made on the surface of the deposit soon 
 disappear by being filled up with new material from the sides 
 and bottom. 
 
 Upon arrival at a refinery in the United States or Europe it 
 is either unloaded and stored up for future use, or conveyed 
 directly into large refining tanks, called “asphalt stills,” which 
 are, in brief, cylindrical retorts set in brick work and heated by 
 indirect fire. 
 
 The crude asphalt is heated somewhat above boiling water 
 and not above 400° F., for several days. By a few improvements 
 this refining has been reduced to half the time it used to take. 
 This process drives off the water, certain light volatile oils and 
 gases. The vegetable matter floats and is disposed of. A part 
 of the earthy matter settles to the bottom. The product is 
 refined Trinidad asphalt and is drawn off into light barrels with 
 one end out. This refined asphalt is sent by rail or boat from 
 the several refineries to the many cities using it. 
 
 A full description of refined asphalt has been given in Sec¬ 
 tion II., heading («), under its definition. 
 
 The uses of refined asphalt are many and varied. In engi¬ 
 neering constructions, generally speaking, it forms the basis of 
 asphaltic cement, although sometimes used otherwise. This 
 asphaltic cement is valuable where a cementing material 
 is needed which is not affected by water, jarring, slight 
 movements and weather temperatures, when used in con¬ 
 nection with other materials, in pavements, bituminous foun¬ 
 dations for steam hammers, dynamos or other rapidly 
 revolving machinery. For the same reason it is valuable for 
 roofing, especially where the roof is needed for a promenade or 
 other foot traffic, for upper floors of buildings needing durable 
 and water-proof floors, as in stables with the horses upon the 
 
20 
 
 upper floors, granaries, etc., in connection with water-proof 
 tunnels under rivers, as at Chicago, in powder magazines and 
 other military constructions where earth-works cover the 
 masonry, in reservoir linings, in natatorium linings. One of 
 the most valuable applications of asphaltum, and more valuable 
 than realized at first thought, is in connection with “damp 
 courses” in buildings. A damp course, I may explain, is a 
 course of asphaltic cement, either alone or in connection with 
 fine hot sand or gravel, laid over the eittire upper surface of a 
 foundation on a line just above the earth. The first layer of 
 bricks, preferably heated, is laid upon this damp course, which 
 thus intervenes between the foundation and the upper construc¬ 
 tion of a building, preventing moisture from below ascending 
 the walls, as takes place in almost all buildings when there is 
 no damp course to prevent it. If, in addition to this, the outer 
 surface of the foundation is coated with asphaltic cement and 
 the cellar floor covered with, first, a little hydraulic cement 
 concrete and then a layer of asphaltic mastic, a thoroughly dry 
 building results. 
 
 Asphalt, as well as maltha and gilsonite, are valuable as a 
 basis for coatings for iron pipes. They are not slowly soluble 
 in water, as is the case with coal-tar products. All specifica¬ 
 tions for the dipping of iron pipes and many other kinds of 
 iron should demand that this be done in hot natural asphaltum, 
 or its equivalent, made from gilsonite, asphalt, maltha or some 
 mixture of these to suit the case. 
 
 Electric, mining, mechanical and naval engineering consume 
 large quantities of asphalt. 
 
 With a knowledge of the properties of asphaltum and its 
 compounds, the working engineer will be enabled to produce 
 results which otherwise would perplex him beyond measure. 
 
 Trinidad asphalt pavements absorb more than 90% of the 
 asphalt imported from Trinidad. This pavement is laid, briefly, 
 as follows: The street is graded, rolled with a steam roller, 
 supplied with a suitable foundation and then covered with a 
 layer of a mixture of sand and powdered limestone, held 
 together by asphaltic cement. A full description of Trinidad 
 asphalt pavement has already been given under Section II., 
 heading (d). 
 
 The volume and importance of this class of pavement can be 
 
21 
 
 judged from the fact that it is found in 72 American cities, 
 covering an area of almost 14,000,000 sq. yds., on January 1st, 
 1894, equivalent to more than 911 miles of roadway, laid in six¬ 
 teen years by thirty contractors or companies. 
 
 (6) Asphaltic limestone is mined either by open quarrying or 
 by tunneling. In warm weather open quarrying is difficult 
 because of the tenacity of the material. Tunneling is carried 
 on sometimes by drills and wedges alone, but generally with 
 powder. Gas is not to be feared in most asphaltic limestone 
 mines. Water, however, often appears and must be constantly 
 pumped out. It is mined in large lumps, crushed generally in 
 a rotary, toothed crusher into pieces three inches and less in 
 size. These pieces are passed through a pulverizer, generally 
 the centrifugal type, sometimes in cylinders revolving and 
 containing loose cast steel balls. The resulting powder is 
 about as fine as mustard seed. It is stored up, preferably under 
 cover, for future use, unless needed at once. 
 
 One of the chief uses of this powder is for laying compressed 
 asphaltic limesto?ie pavement , known generally as “ rock asphalt 
 pavement,” and like other pavements into which asphaltum 
 enters, it is called, simply, “asphalt pavement.” While techni¬ 
 cally incorrect, practically it is proper to call a pavement con¬ 
 taining asphaltum, an asphalt pavement, because though asphalt 
 forms but from 10% to 15% of the mixture, it is the character¬ 
 istic which determines the name of the pavement. 
 
 The process of laying asphaltic limestone pavements is, 
 briefly, as follows: The powdered material is heated to about 
 275° F., either upon flat hearths or in revolving heaters. It is 
 hauled to the streets in ordinary wagons, raked to such a depth 
 over its concrete foundation that, when compressed by heated 
 rammers or otherwise, it will have the required thickness, gener¬ 
 ally two or two and one-half inches. This form of asphalt 
 pavement for streets is not popular in the United States, and 
 appears at but few places in cities near the Atlantic Coast. 
 
 Asphaltic limestone street pavements, like all limestone, 
 become polished and prove somewhat slippery under heavy fog 
 or a light rain. They are also slippery in clear, cold, dry 
 weather when clean. The class of asphalt pavement known as 
 “Trinidad asphalt pavement,” and others made on this system, 
 are not slippery at any time, except when covered Avith a sheet 
 
of ice. This is due to the fact that Trinidad asphalt pavement 
 is composed of about 80% of sand, making it gritty and not 
 susceptible of becoming polished. Paris, London and Berlin 
 keep large supplies of sand at several points near the streets 
 paved with asphaltic limestone, for use during times of fog, 
 slight rain, snow and ice. This is not necessary and is not 
 done upon streets paved with Trinidad asphalt pavements, nor 
 with pavements composed of asphaltic sandstone in California. 
 
 Asphaltic mastic , called often simply asphalt mastic, is made as 
 follows: The powdered asphaltic limestone is heated in revolv¬ 
 ing retorts, refined Trinidad asphalt is added until the mass 
 contains about 20% of bituminous substances, including the 
 original asphaltum, etc., in the asphaltic limestone. The 
 melted mass is constantly stirred until run off into moulds. The 
 mastic blocks or cakes thus formed are shipped all over the 
 world. 
 
 The preparation of the mixture for sidewalks, floors, roofs 
 and other applications of asphaltic mastic is as follows : Put a 
 little refined Trinidad asphalt in a large kettle, about 7 lbs., 
 when melted add 100 lbs. of mastic, stir while heating. When 
 soft add sand or fine gravel little by little up to GO lbs., as the 
 nature of the work demands. Where necessary, several hundred 
 pounds, even thousands of pounds can be mixed at one time. 
 The amounts given indicate the proportions. The mixture, 
 when ready, is taken from the melting kettles, spread upon the 
 surface to be covered by means of thick wooden spatulas or 
 trowels and rubbed down with pressure, by hand. The surface 
 is finally covered with fine white sand, which is also rubbed 
 over the finished walk, lloor, etc. 
 
 Asphalt mastic, when warm, is like a soft mortar, and can be 
 used in many ways to great advantage. When cold it is slightly 
 pliable and thoroughly water-proof. It can be thickened by the 
 addition of fine sand or powdered limestone for uses in places 
 subject to the direct heat of the sun, etc. 
 
 This form of asphalt mastic is used upon the roofs of all 
 modern public buildings of Europe, and in many of America, 
 where the roofs are flat or almost flat. It is the official sidewalk 
 of the streets of Paris, where almost 1200 miles exist. One 
 reason for this is because most of the pipes being under the 
 
23 
 
 sidewalk the asphalt walk is easily removed and quickly 
 replaced. It is without joints and easy to walk upon. 
 
 Asphaltic mastic made from asphaltic limestone, asphalt, etc., 
 as well as that made from fine sand, powdered limestone and 
 Trinidad asphalt, is used in almost every branch of engineering 
 and architecture. 
 
 (c) Asphaltic sandstone , the third class of natural compounds 
 of asphaltum and other minerals, has as yet but little value. It 
 is quarried generally by blasting. It is seldom, if ever, mined 
 in tunnels. The definition of this material found in Section II., 
 heading ( c ), shows that it is very variable. The additional 
 characteristics of this material already described in Section IV. 
 at the latter part of heading (h), indicate the possible uses, not 
 yet fully determined, to which asphaltic sandstone may be 
 applied. 
 
 Asphaltic sandstone pavements are laid as indicated in Section 
 II., heading (d), under the definition of this class of pavement. 
 
 VI. HISTORY OF ASPHALTUM AND COMPOUNDS. 
 
 (a) Ancient times .—The briefest reference to ancient times will 
 suffice. Asphaltum is mentioned by the Arabic writers under 
 the name“ chemar,” by the Greeks a<upa)-oc, (asphaltos), by the 
 Latin writers as asphaltum, and sometimes by its generic name, 
 bitumen. 
 
 It was used in Egypt in connection with embalming the dead, 
 as found in mummies. They got their supply, in part, from Is, 
 modern Hit, near Babylon and near modern Bagdad, which 
 mines are still worked. Refined asphaltum 60 minas in weight 
 was a part of the annual tribute sent during the years just 
 previous and subsequent to 525 B. C. from Babylon to Egypt. 
 
 The Bible, in Genesis, relates in connection with the Tower 
 of Babel (near Babylon), as follows: “Asphaltus fuit eis vice 
 coementi ” (asphalt was used by them for cement). Concerning 
 Noah’s Ark we read: “Bituminabis earn bitumine,” which reads 
 in the English Bible: “ Pitch it with pitch.” 
 
 There are many places where the substance is mentioned in 
 the Greek and Latin Bibles under the names indicated. The 
 
24 
 
 use of asphalt was clearly known in ancient times, as indicated 
 by the writings of Pliny, Virgil, Curtius, Ovid and others. 
 Herodotus described the use of asphalt in the construction of 
 the walls of Babylon. Diodorus gives details of the use of 
 asphalt for cement, especially as poured upon reeds, laid cross¬ 
 wise the entire thickness of these walls, thus binding them 
 transversely. When we remember that three chariots could 
 drive abreast upon the walls of Babylon, we realize the immense 
 amount of asphaltum consumed in connection with their con¬ 
 struction. 
 
 The Dead Sea was called in ancient times “Lacus Asphaltites.” 
 
 (£) Modern times, 1626 to 1893 .—The use of asphaltum became 
 practically a lost art during the Middle Ages. The first men¬ 
 tion of the subject, as far as I have discovered, was in 1626 in a 
 German pamphlet upon “ Hartz-Erde,” (Pitch-earth). Dr. 
 Amiest referred in 1692 to the deposits in Val de Travers, Switz¬ 
 erland. These deposits were subsequently fully described and 
 uses suggested and tried by Dr. Erynis, from 1711 to the time 
 of his death, 1736. He also discovered the asphaltic limestone 
 of Lobsann, Germany. In 1802 the deposits of Seyssel, France, 
 were discovered. The asphaltic limestone from Seyssel, was 
 very successful for many years. 
 
 I 11 1832 Count de Sassenay united the asphalt interests of 
 France and Switzerland. Paris adopted asphalt sidewalks in 
 1838. The engineer Merian developed compressed asphaltic 
 limestone pavements in 1849. Soon afterward the eminent 
 French engineer M. Leon Malo began his long and successful 
 career in connection with asphaltic materials. Paris received 
 its first successful asphalt street pavement in 1854 ; London, 
 1869; Buda-Pesth, 1871; Dresden, 1872; Hamburg, 1872; Berlin, 
 1873; Brussels, Geneva, Leipzig, Frankfort and others soon 
 afterward. 
 
 The American cities were at first deceived, having expressed 
 a desire for smooth, quiet pavements, and having heard of the 
 asphalt pavements of Europe. The spurious article which 
 encumbered our streets previous to 1873, was nothing more or 
 less than coal-tar, sand and gravel. 
 
 Because of the difficulty of transporting the asphaltic lime¬ 
 stone from Europe to America, inventors were encouraged to 
 seek some durable substitute. Successful experiments made 
 
25 
 
 between 1871 and 1873 in Newark, N. J., and New York City 
 with an artificial mixture of Trinidad asphalt, residuum oil, 
 limestone dust and sand, gave rise to the class of pavements 
 now so successful, and called Trinidad asphalt pavements. In 
 187G this pavement appeared in Washington as a pronounced 
 success. In 1878 it became the standard pavement of Washing¬ 
 ton. It has been rapidly adopted by more than 71 American 
 cities. It is being laid at the rate of about 140 miles annually. 
 
 Asphalt pavements in some form are found in 92 American 
 cities. Leaving the statistics to the following Section VII., I 
 will state that it is necessary to carefully select the materials 
 and constantly supervise all asphalt constructions. It is neces¬ 
 sary to examine very carefully the size and quality of the sand 
 
 * 
 
 and limestone powder, as well as the asphalt and residuum oil 
 to be used in pavements. 
 
 New and experimental asphalt pavements should not be tried 
 at public expense. 
 
 VII. STATISTICS. 
 
 (a) Mines , Europe and America .—Inasmuch as detailed statis¬ 
 tics are very uninteresting, I will give only summations and 
 
 results. 
 
 $ 
 
 A reference to Tables Nos. 2 and 3 under Section III., will 
 show the location of the asphalt deposits of the world. 
 
 Inasmuch as no asphaltum is exported from the United States 
 to Europe, it is best to confine our attention to that which is 
 imported into this country or mined here. From 1867 to 1893 
 inclusive, there were unloaded at United States refineries 
 488,086 tons (2240 lbs. each) of Trinidad asphalt. During the 
 past few years it has been arriving at the rate of about 70,000 
 tons of “ Lake Asphalt” per year. This asphalt is from within 
 the celebrated Asphalt Lake. From 1888 to 1892 some inferior 
 “land” or “overflow” asphalt from outside of the Lake was 
 imported. The variable impurities and lack of cementing 
 qualities of this land asphalt injures it for engineering work 
 and it is no longer imported. 
 
 The importations of asphaltic limestone, principally in the 
 form of asphaltic mastic blocks or cakes, is very variable, rang- 
 
26 
 
 ing from 900 tons to 20,000 tons per year. This comes princi¬ 
 pally from Sicily, France, Germany and Switzerland. 
 
 The output of the mines of asphaltic materials of the United 
 States is very difficult to ascertain, because dissimilar materials 
 have been grouped in the straggling reports heretofore 
 obtainable, and because several mines are closed and others 
 opened each year. As a whole, the asphalt mining industry of 
 the United States is not a success. The demand for the class 
 and quality of materials produced in our mines is far less than 
 the available supply. Trinidad asphalt coming from a deposit 
 large enough to warrant ample supplies of any amount and of 
 constant quality, is used almost to the exclusion of all other 
 asphalts. However, after careful experiment in due time our 
 asphalt mines may become more valuable. 
 
 The total production per year of asphaltum, asphaltic sand¬ 
 stone, etc., from the U. S. mines has been within the last six 
 years at the rate of about 42,000 tons. A reference to Sec¬ 
 tion III., Tables Nos. 2 and 3, will indicate the location of the 
 American as well as foreign deposits. 
 
 ( b ) Pavements of Europe and America .—I will dismiss this por¬ 
 tion of the subject by briefly giving the latest statistics, January 
 1st, 1894. The asphalt pavements of all kinds in the United 
 States and Canada on this date are as follows: 
 
 Table No. 7. 
 
 Kind of Pavement. 
 
 Sq. Yds. ' 
 
 Miles. 
 
 Trinidad asphalt*. 
 
 13,900,000 
 
 911. 
 
 Asphaltic limestone. 
 
 151,000 
 
 10. 
 
 Asphaltic sandstone and other asphaltic materials, 
 
 experimental and otherwise. 
 
 019,000 
 
 41. 
 
 Totals. 
 
 14,670,000 
 
 962. 
 
 N. B.—The above is street roadway pavements and does not 
 include sidewalks. 
 
 * Subject to slight corrections from final 1893 reports. 
 
The total asphalt pavements of European cities at the same 
 date were as follows: 
 
 Table No. 8. 
 
 ClTV. 
 
 Sq. Yds. 
 
 Miles. 
 
 Berlin. 
 
 1,280,796 
 
 83. 
 
 Paris. 
 
 401,617 
 
 26. 
 
 London... . 
 
 370,000 
 
 24. 
 
 Other Cities. 
 
 271,000 
 
 18. 
 
 Totals. 
 
 2,323,413 
 
 151. 
 
 ' N. B.—In the preceding tables, the roadway is reduced to a 
 common width of 26 feet for comparisons. The roadways 
 themselves vary above and below this width. 
 
 The asphalt pavements of America have been laid within 
 twenty years and those of Europe within the past forty years. 
 
 The civilization of cities can be gauged by the condition of 
 their streets. The suppression of noise and dirt, made possible 
 by asphalt pavements, in a great measure determines the char¬ 
 acter and progress of a city. 
 

FROM 
 
 OJVIL ENGINEER* 
 HO. 1 BROADWAY. 
 Ȥ* YORK CITY* 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 *>