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By Joseph D. Davis, GEORGE S. POPE

This bulletin is the fourth of a series a showing the results of the purchase of coal by the Government under specifications. The work of inspecting and analyzing coal delivered on Government contracts was transferred to the Bureau of Mines by an act of Congress effective July 1, 1910. It had been carried on for several years before that date by the technologic branch of the United States Geological Survey. The purchase of coal on the dealer's statement as to quality or on the reputation of the mine or district producing the coal is gradually being discontinued. At present most coal-purchasing contracts make definite provision regarding the desired heating value of a coal and the composition as shown by analysis. The heating value is usually expressed in British thermal units" and the composition specified is that shown by proximate" analysis. The price to be paid for delivered coal is made to depend on whether the analyses and heating-value tests of samples representing the delivery show the quality to be above or below the quality set forth in the contract. Large coal consumers are beginning to appreciate more and more the importance of the cost of power as a factor in the cost of producing a finished article. The endeavor to increase the efficiency and the economical operation of a power plant calls for an intimate knowledge of the quality of the coal being used. The purchase of coal under specifications insures the purchaser getting what he pays for and the coal being of the quality guaranteed. In addition, the analyses and tests of the delivered coal furnish data whereby the power-plant results can be comprehensively studied and a continuous check maintained on the conditions of operation.

Jan 1, 1912

By George A. Burrell, Frank M. Seibert

The Bureau of Mines, as part of its designated duty of investigating the causes of mine accidents, is conducting at its experiment station in Pittsburgh, Pa., a study of mine gases. Some of the work already done in connection with this study is outlined below. A large number of mine-gas samples have been collected under normal conditions in returns and in splits, and at other points in the ventilating current, also at the face, in the goave or gob, in unventilated places, and wherever the air was still. Samples have also been obtained under abnormal conditions, as after explosions and while mine fires were in progress, or from sealed areas behind stoppings and darns where the air had been stagnant for some time. Chemical changes in the composition of mine atmospheres during mine fires have been studied," and conditions peculiar to certain mines have been investigated. The question of the effect of a change in atmospheric pressure on the escape of gas (methane) in coal mines has been studied. Explosives have been fired in both coal and metal mines, and samples of resulting gases have been collected to ascertain the degree to which these gases vitiate the air. A series of samples in mines where gasoline locomotives were being used have been examined in order to ascertain the degree to which the exhaust gases from such locomotives foul the mine air. Experiments have also been performed in regard to the relative effect of carbon monoxide b upon men and small animals. A preliminary report relating to the inflammable gases in mine air has been published. Full reports of the results of the investigations outlined above will be published as soon as all the necessary data have been gathered. The first part of this report deals with the methods used by the bureau in the collection and examination of the various mine gases; the latter part discusses the bureau's methods of sampling and examining natural gas.

Jan 1, 1913

By R. M. Strong, Lauson Stone

Under the terms of the act establishing the Bureau of Mines, this bureau was authorized to carryon the work of testing and analyzing fuels which had been conducted by the technologic branch of the United States Geological Survey. That work included in its scope an investigation of the availability and uses ofliquid as well as solid fuels, for the original outline of the fuel-testing investigations contemplated, as soon as the funds would be available, a study of the liquid-fuel resources of the country and the making of related researches to determine how these resources could be utilized with greatest efficiency. Owing to the fact that many difficulties were being encountered in the adaptation of the heavier fuel oils for convenient use in internalcombustion engines, it was deemed best to begin the investigation of liquid fuels with tests of gasoline, a fuel in more or less general use. When this investigation began, the extensive introduction, especially by foreign powers, of liquid fuels for small naval craft had awakened much interest. However, the quality of gasoline was reported to vary materially in different countries and the quantity available was said to be rapidly decreasing, with the probability of a prohibitive increase in price. At the same time the claim was made that denatured alcohol, of fairly uniform quality, could be procured in all parts of the world, that unlimited quantities could be readily produced at a low cost, and that this fuel could be used much more efficiently than gasoline in internal-combustion engines. Such statements naturally led to a widespread belief that the time was near at hand when denatured alcohol would entirely displace gasoline as engine fuel. Therefore, the first investigations of the liquid mineral fuels logically embraced a careful series of comparative tests of gasoline and denatured alcohol in engines. A series of over 2,000 such tests was conducted at the Government fuel-testing plants at St. Louis, Mo., and Norfolk, Va., details of which are given in the following pages. The report is published by the Bureau of Mines because of the transfer of the fuel-testing investigations to this bureau.

Jan 1, 1912

By Albert H. Fay, Herbert M. Wilson

The national mine-safety demonstration at Pittsburgh, Pa., was projected and undertaken in the hope that it would aid the increase of safety in the mining industry. That the national mine-safety demonstration was warranted and has served a useful purpose was evidenced by the attendance, not only at the public demonstration in Forbes Field, but also at the more special exhibit of the work of the Bureau of Mines at the arsenal grounds and at the experimsntal. mine. Nearly 2,000 persons witnessed the demonstrations and exhibits of the Bureau of Mines at the arsenal grounds on the morning of October 30, 1911. The spectators were all mine operators, miners, or persons interested in mining, and represented operations in all parts of the United States. Nearly 1,200 of these persons visited the bureau's experimental mine at Bruceton to witness ~th~explosion of coal dust. Had the weather, which was exceptionally inclement, been more favorable, there would doubtless have been a much larger attendance. At the public demonstration in Forbes Field, which· was witnessed by President Taft, from 12,000 to 15,000 persons, chiefly mining men, were present and attested their interest and enthusiasm in the minesafety exhibits by remaining throughout the proceedings, regardless of the rain which fell all the morning .. Sincethis demonstration, the organization of first-aid corps and of rescue corps has been undertaken at mines where there had previously been no such organizations. The bureau has received letters of commendation attesting the value of the demonstration in drawing· attention to the dangers and to possible means of greater safety in mining. Many of these letters have urged that the results of the demonstration be published for the guidance and instruction of those who were present. In response to these reauests the following account of the mine- BlIIeLY demonstration lias been prepared. IIi its preparation various division and section chiefs of the Bureau of Mines have cooperated. The authors acknowledge the assistance they have received from those section chiefs and other members of the bureau who contributed detailed descriptions of apparatus exhibited at the demonstration or of investigations represented.

Jan 1, 1912

By N. H. Darton

In mining coal in the anthracite region of Pennsylvania the general custom has been to leave a large percentage of the coal in place as pillars to support the roof. Evidently any practice that involves partial waste of an important mineral resource is bound to be discarded. It is well recognized that one method of obviating probable waste is to fill the workings with cheap or worthless materials, a process extensively employed in the anthracite and some European mines. At present many of the collieries in the anthracite region of Pennsylvania are utilizing refuse from the old culm banks, which formerly were prominent features in the landscape, and are flushing the fine waste underground so that pillars may be reduced in size or removed. As a result the banks are now disappearing and soon will be gone. The fine culm from the breakers and rock from the mines will continue to be available, but the volume of these materials is insufficient to replace any considerable proportion of the coal removed. The next stage of progress suggested is the use of sand. Fortunately there are available large deposits of this material, much of which can be handled by dredges and pumps. This report is issued by the Bureau of Mines in the interest of safer and more efficient mining methods. I ts purpose is to describe the sand deposits in the northern anthracite coal field in Luzerne and Lackawanna Counties, Pa, Much of the information available is presented in the map, Plate I. Field studies, mostly preliminary, were made in the summer of 1911 to determine the distribution, amount, and character of the larger deposits. It was not thought desirable to make a detailed examination of the region because when the coal companies decide to utilize the sand their engineers will make precise surveys and drill test holes. In preparing the map the various coal companies were consulted; they contributed a large number of facts, especially as to the deposits in the buried valley of the Susquehanna between Pittston and Nan- ticoke, where nearly 1,000 test holes have been bored. The results of these borings were placed at the author's disposal, and have been utilized in drawing the boundaries given in the wide valley area and its extensions up Lackawanna River and NewportCreek. Wyoming Valley contains deposits of sand that are 100 feet thick over a wide area, 200 feet thick in places, and over 300 feet thick in the deep old channel south of Plymouth.

Jan 1, 1913

By Samuel B. Flagg

The Bureau of Mines is endeavoring to ascertain how mineral fuels in which the Government has a direct interest, by ownership or use, can be utilized with highest efficiency. For this reason the bureau has been, and is, carrying on investigations to ascertain the condi- tions of furnace construction and management that are necessary to insure the smokeless combustion of the different coals that are found in public lands or are purchased for Government ships and power plants. Another reason for the bureau undertaking these investigations is the need of better furnace management and a more careful selec- tion of fuel at many Government plants. There are Federal build- ings in hundreds of cities. The coals available at many of these cities differ greatly in quality, and the furnaces in some of the Fed- eral buildings were not designed for efficient utilization of the cheap- est available coal. Hence, some of the boiler plants smoke badly unless fed with low-volatile coal and have caused repeated com- plaints not only from neighboring property owners who have suffered damage, but from persons endeavoring to create a civic pride in clear air. In the course of its fuel investigations the bureau has noted the conditions governing fuel consumption in different cities and has studied the attempts made by these cities to abate smoke through the passage of ordinances imposing penalties on smoky stacks. Some results of that study are presented in this report. The most im- portant conclusion reached is that smoke abatement by ordinance can not hope to succeed unless supported by public sentiment and that a smoke ordinance should look to future prevention rather than to immediate prohibition. In other words, strict control of furnace construction offers much greater hope for smoke abatement than desultory imposition of severe penalties on the escape of "dense" or "black" smoke.

Jan 1, 1912

By L. C. IlsLey, H. H. Clark

As part of its investigations of the causes of mine accidents and of the safest and most efficient methods of handling electricity underground, the Bureau of Mines undertook a study of the ignition of mine gases by the filaments of electric incandescent lamps. This bulletin describes the investigation in detail and gives a complete record of the results obtained.

Jan 1, 1913

By A. W. BELDEN

Among the investigations that the Bureau of Mines is conducting witha view to increasing efficiency in the utilization of fuels belonging to or for the use of the Government is an investigation of the processesthat take place in a foundry cupola during a melt. Some observations on the results of cupola tests of cokes at the Government fuel-testing plant in St. Louis, Mo., the coke being fromcoal from many coal fields of the United States, have been stated in a previous bulletin.s Especial attention was given to the meltinglosses that resulted from the use of different grades of coke, light and porous or heavy and dense. These losses amounted in one instance to 52.5 per cent of the iron charged and showed, in convincing manner, the need of exact information in regard to conditions in the fuelbed of the cupola.b Melting losses of iron have been fully appreciated but little under-- stood. The fact that these losses were possible with either light or heavy coke led to the belief that by using small charges 80 placed that. melting would take place in that zone of the cupola where the highest heat and the smallest percentage of oxygen prevailed and by confiningall melting to this zone these losses would be eliminated and the economical use of practically any coke produced for metallurgical purposes would become possible. This widening of the field from whichcoke might be drawn for foundry purposes would serve to place the foundryman in an independent position as regards his source of supply, and would tend to conserve the better grades of coking coals, which are being rapidly exhausted, by making the poorer grades available for mixing with them. In order to investigate conditions within a cupola, the Bureau of Mines as a first step decided to install a commercial cupola, to sample the gases during their travel from the tuy~res upward, and to determine the temperature of the fuel bed.

Jan 1, 1913

By R. H. Fernald

In investigating general problems that relate to the fuel resources of this country, and in testing fuels belonging to or for the use of the Government, the Bureau of Mines has given considerable attention to the efficiency and economic value of producer-gas power plants. Government inquiries during the past eight years not only have shown a very low fuel consumption per horsepower-hour for these plants but have demonstrated conclusively the possibility of utilizing commer- cially low grades of bituminous coal, lignite, and peat in plants prop- erly designed for the use of these fuels. The anthracite plant has been recognized as a commercial possibility for several years, although the cost of the fuel used has in general restricted these plants to com- paratively small units. The commercial development of the producer-gas power plant in the United States has been largely within the past six or eight years. In 1909 the United States Geological Survey published in a bulletin entitled "Recent Development of the Producer-Gas Power Plant in the United States" a list of producer-gas power-plant installations. The data presented in that bulletin showed a strong development in this field and led to much conjecture as to the future of this type of power. Owing to the extensive introduction of the steam turbine, however, many persons predicted the almost immediate doom of the producer-gas plant. In addition to the inroads made by this formida- ble rival, the interest of the gas-engine enthusiasts became centered to such an extent in the oil engine that the gas producer was relegated to second place by many and absolutely abandoned by some. During the past three years the belief of many who were formerly firm be- lievers in the gas producer has been that this type of power has reached its height of development in this country and that from a commercial standpoint it can no longer be regarded as a complete success. This feeling of commercial decadence has become so general

Jan 1, 1913

By W. L. EGY, GEORGES. RICE, L. M. JONES, J. K. CLEMENT

This report has been prepared, not only for the purpose of recording the results of the first series of coal-dust tests conducted in the experimental mine of the Bureau of Mines, but also to place before the mining public a description of the mine and an account of the objects sought in its establishment. Soon after the organization of the technologic branch of the United States Geological Survey, J. A. Holmes, then chief of the branch, concluded that for the solution of various problems relating to the causes and prevention of mine explosions it would be best to carry on large-scale tests in a mine rather than in a surface gallery. The idea of utilizing the underground passage of a mine for making explosion experiments did not at' first meet with general approval among investigators in this country or abroad. Many thought a mine passage was not a proper place in which scientific tests could be conducted, as great difficulty in controlling conditions was expected. However, after all arguments for and against such an investigation had been carefully considered, plans for opening an experimental mine were definitely adopted by the Bureau of Mines in 1910, and an allotment of funds was made to carry out the project. The first endeavor was to find an existing mine suitable for the purpose, but the mines offered by owners were either worked out, were wet, had poor roofs, or presented complications of various kinds, so that it was finally decided to open a mine if a site could be obtained having natural conditions that would fill the various requirements. A most desirable location was found on property of the Pittsburgh Coal Co., near Bruceton, Pa. The president of this company, Mr. W. K. Field, the general manager, Mr. G. W. Schluederberg, and the chief engineer, Mr. E. J. Taylor, rendered every possible service in

Jan 1, 1913

By John A. Davis, David W. Brunton

During the past few years great progress has been made in the United States toward safer, more efficient, and more economical tunneling methods. This advance is partly due, no doubt, to the recent increase in the number of tunnels and adits driven for devel- oping and draining mines and transporting ore. The Bureau of Mines during 1911 and 1912 made a special examination of this phase of mining operations, in connection with an investigation of mining methods and means for preventing accidents. The details especially studied were the provisions for the safety of employees, the kinds of equipment, the methods of driving, and the costs of con- struction. The results and conclusions obtained from that investi- gation are discussed and summarized in this bulletin. Up-to-date information concerning tunneling methods is difficult to obtain. There are few books on the subject; and much of the material they contain, although interesting and of value historically, is now obsolete. The engineering periodicals, it is true, endeavor to keep abreast of the times, and several in nearly every issue present some article bearing upon tunnel work. But the very multiplicity of these articles prevents one from reading them all, and the foreman or superintendent in charge of a tunnel, or the mining engineer designing one, and especially the business man financing the project, has no time for a lengthy search after scattered articles in order to determine the present status of tunnel work. Then, too, knowledge of new methods travels slowly. Valuable inventions and improve- ments in tunneling as well as in all the other industries frequently remain in the notebook of the investigator, or as theses are buried in university libraries, or are published only in journals of small scien- tific societies. New tunneling methods and equipment that are prov- ing safe, efficient, and economical may be totally unknown outside the district in which they originate. This paper, based on a special examination both in the field and in engineering literature, is in- tended to supply data concerning modern and recent tunneling practice in the United States, and to make suggestions that, it is hoped, will result in a saving to the mining industry of energy, capital, and life.

Jan 1, 1916

By Clarence Hall, Spencer P. Howell

Among the more important factors involved in the use of high explosives in blasting operations is the means employed to bring about the detonation of the charge. When flame is applied to high explosives many of them may burn if not confined; but all of them when burning under certain conditions of confinement may detonate. Detonation may also be effected by mechanical means, such as frictional impact caused by a blow or by rubbing between surfaces. By this means, however, the full effect of the explosive charge may not be developed, so that a partial detonation, often accompanied by the burning of the explosive, results. When nitroglycerin was first used it was fired by the application of flame, but considerable difficulty was experienced in exploding it with certainty and in obtaining uniform resl'llts. In 1864 Allred Noble, a Swedish engineer, discovered that nitroglycerin could be surely and completely detonated by exploding in contact with it a small quantity of an initiatory explosive. Mercury fulminate was the substance then found capable of producing the best results There are many other fulminates and other substances that will produce complete detonation of commercial" high" explosives, but detonators or electric detonators containing mercury fulminate as the characteristic ingredient are still almost exclusively used in this country. The term" detonator" is used in the publications of the Bureau of Mines to designate what the miner calls a "blasting cap "-a copper capsule containing a small quantity of some detonating compound that is ignited by a fuse. The term" electric detonator" is applied to a blasting cap that is similar except for being ignited by means of a small wire which is heated to incandescence or fused by the passage of an electric current. One of the conditions prescribed by the Bureau of Mines for a permissible explosive a is that it shall be :fired by a detonator, or preferably an electric detonator, having a charge equivalent to that of the standard detonator used at the Pittsburgh testing station. A further requirement is that this charge shall consist by weight of 90 parts of mercury fulminate and 10 parts of potassium chlorate (or their equivalents). At the request of a manufacturer of permissible explosives, an investigation was undertaken by the bureau to determine the relative strength of detonators and electric detonators having different compositions. The tests of electric detonators herein reported were conducted by H. F. Braddock, junior chemist; J. W. Koster, J. E. Tiffany, junior mining engineers; and A. S. Crossfield, junior explosives chemist, at the Pittsburgh testing station of the bureau. Similar tests of detonators were not conducted because it was believed that the results would not show sufficient variation to warrant such tests. It is hoped that the conclusions drawn from the tests made will be of service to those using explosives by enabling them to select the grade of detonator or electric detonator that will insure the most effective results. The conclusions are given in this bulletin, which is published by the Bureau of Mines as one of a series of publications dealing with the testing of explosives and the precautions that should be taken to increase safety and efficiency in the use of explosives in mining operations. The results of tho experiments described in this bulletin show that the average percentage of failures of explosives to detonate was increased more than 20 per cent when the lower grades of electric detonators were used instead of No. 6 electric detonators, and was increased more than 50 per cent when these lower grades were used instead of No. 8 electric detonators. It is noteworthy, however, that when sensitive explosives, such as 40 per cent strength ammonia dynamite (p. 33), were tested under conditions ideal for detonation, the same energy was developed irrespective of the electric detonator used. When tests were made with a less sensitive explosive, such as a 40 per cent strength ammonia dynamite containing nitrosubstitution compounds (p. 32), the energy developed increased with the grade of the electric detonator used. For example, the average efficiency of four different explosives was increased 10.4 per cent when a No.6 electric detonator was used instead of a No.4 electric detonator, and 14.9 per cent when aN 0.8 electric detonator was used (see tabulation onp.45). The results of the tests emphasize the importance of using explosives in a fresh condition, but as fresh explosives can not always be had in mining work, strong detonators should be used in order to offset any deterioration of explosives from age.

Jan 1, 1913

By A. H. WHITE, PERRY BARKER

In a consideration of the various means whereby more economical and more efficient use may be made of the fuels in the United States, the possibility of obtaining for the production of illuminating gas other and cheaper fuels than the Pennsylvania coals demands attention. For the Government, as well as for private corporations and the householder, there can be no more economical and efficient way of using some coals than through the medium of illuminating gas. In the stove, gas reduces the labor cost of heat production and lessens the drudgery of the kitchen; burned in the Welsbach mantle, it is an excellent and cheap illuminant. In addition, the coke that remains after the gas has been recovered furnishes a smokeless fuel that has about the same heating value as anthracite. Hence any investigations that will indicate how local coals through proper treatment may be substituted for the higher priced and rapidly vanishing Pennsylvania gas coals will bring about lower prices for both gas and coke and will also aid to conserve for use in metallurgical processes the coking coals of Pennsylvania and of ot,her States. The annual drain on the gas-coal resources of this country and the importance of the gas and coke industries are indicated by the fact that 8,390,129 tons of coal were carbonized in retorts in the United States in 1909. The resulting salable products from by-product ovens were 15,791,220,000 cubic feet of coal gas, 6,254,644 tons of coke, and 60,126,000 gallons of tar. The total value of all by-products was about $28,508,637.

Jan 1, 1911

By Frederick W. Horton

The lack of comparable and accurate statistics of coal-mine accidents in the United States as a whole led the Bureau of Mines in 1911 to undertake the collection of such data. The importance of such statistics as a basis for remedial legislation can not be overestimated, moreover they serve to indicate the results of the efforts made by the Federal Government, State mining departments, and mine operators throughout the country to lessen the hazard of coal mining. The mining departments of the leading foreign coal-producing countries have long taken cognizance of the importance of such statistics. In Great Britain, official statistics of coal-mine accidents have been collected and published since 1851, in France since 1853, in Austria since 1875, in Germany since 1852, and in Belgium since 1831. The United States not only leads these countries in the production of coal but the output of its coal mines is greater than those of Great Britain, France, Belgium, Austria, India, Japan, and New South Wales combined. Accordingly, it is proper that there should be some official record of the accidents in this, the greatest mining industry not only in the United States but in the world. It is especially appropriate that this work should have been undertaken by the Bureau of Mines, as, through its investigations of mine accidents in the field, it is constantly in close touch with coalmining conditions throughout the country. Its engineers are not only able to obtain first-hand information as to a great many accidents, but, through their special training and experience, are able to appreciate the significance of the figures reported by the coal-mine operators, thus aiding an intelligent and uniform classification 01 the accidents for the country as a whole. Further, the State mining dnpartments and State mine inspectors of every State in the country having a system of coal-mine inspection are cooperating with the bureau by sending it monthly reports of accidents in the coal mines of their respective States. The receipt of such reports places the bureau in a most advantageous position to publish promptly statistics of these accidents. Although a few years ago accurate statistics of c~al-mine accidents in the United States as a whole were entirely lacking this bureau was able to pubjiish the 1912 statistics within three n:onths after the close of the year and long before corresponding statistics had been issued by the mining departments of the leading foreign coal-producing countries. The cooperative agreement with the State coal-mine inspectors has not only made possible the prompt publication of the statistics, but it has also enabled the bureau to classify the fatalities by months and according to cause, showing the months in which the greatest and the least number of men were killed and from what causessomething that has never before been accomplished for this country.

Jan 1, 1913

By L. H. ADAMS, C. N. HASKINS, J. K. CLEMENT

In the course of its investigations of the fuel resources in the United States and of the methods by which these resources could be utilized with greatest efficiency, the United States Geological Survey tested a great variety of coals and lignites as gas-producer fuel. Early in these testa it was found that many factors controlling the formation of gas in the generating chamber of the producer and, consequently, having a direct bearing on the management of producer-gas plants, were not as well understood as they should be. The Geological Survey therefore took up a detailed investigation of the chemical and physical processes that take place in the producer, keeping in view not only the possibility of increasing the efficiency of the producer as a source of energy, and the ensuing benefits to the public of cheaper power and greater utilization of low-grade fuels, but also the application of the results to the problems of boiler-furnace operations. - The Bureau of Mines, to which the testing and analyzing of fuels as carried on by the United States Geological Survey has been transferred, is continuing producer-gas investigations at the testing station at Pittsburg, Pa. Results of the gas-producer tests a made at the coal-testing plant erected at St. Louis, Mo., and of a study of some of the problems° that came up in the tests have been published by the Geological Survey. Results of the tests made at Norfolk, Va., and Pittsburg, Pa., and of further studies of particular problems, will be published by the Bureau of Mines. In the gas producer solid fuel is transformed into more readily combustible gaseous fuel. The transformation is relatively slow and consists of several processes: 1. The distillation of the volatile hydrocarbons from the freshly fired fuel at relatively low temperatures. 2. The combustion of the fuel by its combining with the oxygen of the air forming carbon dioxide (COO. 3. The formation of carbon monoxide (CO) and hydrogen (11 3), the essential constituents of producer gas, in accordance with the equations:

Jan 1, 1911

By N. H. Darton

This report presents the results of an investigation begun by the Government in the summer of 1907, the investigation being started under the immediate supervision of Dr. J. A. Holmes and continued under him as director after it was transferred to the Bureau of Mines in 1910, the field studies being completed in the spring of 1912. The purpose of the investigation was to obtain information on the origin of the inflammable gases in coal and the conditions under which they occur. It was especially intended to ascertain whether there was any relation between the occurrence of gas and the structural or other geologic features of the coal beds. To this end many months were spent in mines and much time was devoted to the examination of mine maps, bore-hole records, and other data made available by the kindness of various coal companies. Two fields of work were selected-one in the northern anthracite basin of Pennsylvania, where the beds are considerably flexed, and the other in the southern part of the bituminous coal field of Illinois, where the beds lie nearly horizontal. In order to take advantage of results of previous investigations of the same general subject, an extended examination was made of reports of various investigators in Europe and America. A digest of the information obtained from these publications is included in the first part of this report, which constitutes an introduction to the discussion of the conditions governing the occurrence of inflammable gas in coal beds.

Jan 1, 1915

By O. P. Hood, R. H. Kudlich

When a gasoline locomotive is used in a mine there is danger of the noxious gases of the exhaust vitiating the air, but if enough air is circulating in those parts of the mine in which the locomotive is used, these gases are so diluted that they are rendered harmless, and the health of the workmen is not affected. In some mines the use of gasoline locomotives is impracticable, though in the majority of mines where they have been tried they have proved to be safe and economical. To determine the limitations that should surround the use of these machines in mines so that they shall not be detrimental to health and so that their economic advantage may be retained, it is necessary to ascertain the volume and the character of the exhaust gases and the amount of these gases that may be safely allowed in the mine air, and also to determine safe conditions of operation. The problem is primarily one of ventilation and like all ventilation problems must be intelligently computed to meet the conditions of each mine. The investigation described in this bulletin was undertaken 'by the Bureau of Mines in an endeavor to obtain exact information on some of the basal questions involved in the use of gasoline locomotives in mines, this investigation being one of many that the bureau has been conducting in its efforts to increase safety and efficiency in mining.

Jan 1, 1915

By Van H. Manning

Chemical and physical tests of coals for the use of the Government have been made by the United States Bureau of Mines. These tests form part of a general study of the coals in the United States with respect to the manner in which each coal can be utilized most efficiently. As a result of this study, much information of value to all industries using coal has been compiled. Special investigations by the Bureau of Mines of the fuels used by the Government have, until recently, been for the most part limited to coal. In the course of these investigations the bureau has de- veloped new methods for use in the purchase of coal by the Gov- ernment. The application of these methods permits an intelligent selection of the coal adapted to the requirements of particular heat- ing or power plants, and has already resulted in the saving of large sums of money. In addition, these investigations have led to the compiling of a series of carefully made analyses of samples of coal collected in a predetermined manner in the mines of all the impor- tant coal fields in the United States, and these analyses are being published to enable Government purchasing agents and all users of coal to select the coal best suited to their needs. The purpose of this paper is to describe briefly the general char- acter and commercial quality of some of the coals mined in the United States that reach tidewater shipping ports, and to show in a general way the important characteristics of those coals that by reason of transportation facilities and the situation of the coal fields are most available for export. Coals of excellent physical character and of high heating value are available for export. For this reason and because of the modern facilities at the collieries for properly grading large shipments, American producers can supply coals suitable for any kind of service. The transportation system from the mines to tidewater and the coal- handling equipment for loading boats at the various ports are highly developed, so that producers are able to give excellent service to foreign buyers. Enormous quantities of these coals have been used by railroads, manufacturing, illuminating-gas, and coke plants, and seagoing vessels, and for household purposes. Much of the coal available for export is superior to the coals that have been supplied to foreign users from other sources.

Jan 1, 1916

By JOSEPH F. CULLEN, Dorsey A. Lyon

In connection with its investigation looking to the prevention of waste and the increase of safety and efficiency in the mineral indus- tries the Bureau of Mines has undertaken a study of the possible uses of the electric furnace in metallurgy. This bulletin presents a com- pilation of such data as seem to be useful for the information of persons who may be interested in the matter. In the application of electricity to metallurgy three kinds of processes are involved, namely, mechanical, thermal, and electrolytic. Under the mechanical application of electricity come those proc- esses of dressing and concentrating ores that are known as either electrostatic or electromagnetic processes. In electrothermic processes the current is used as a source of heat. The fundamental differences between the various types of electric furnace that are at present in commercial use relate to the manner in which the electric current is applied, as may be noted by reference to that part of this report in which the subject is discussed. In electrolytic processes the electric current is used for depositing metals from solutions. The process may be conducted in one of the following ways: (1) The material to be treated may be put into solu- tion and then electrolyzed, the material thus treated forming the electrolyte; (2) the material to be treated may form the anode or be placed in contact with the anode; or (3) the material to be treated may form the cathode or be placed in contact with the cathode. This report treats of electrothermic processes, with the possible exception of those for the reduction of aluminum from its ores. Moreover, of the processes used in the so-called electrochemical in- dustries only those for the reduction of an ore to metal, or to a com- pound of the metal that is of value in itself, or is an aid in metallurgical work, are here discussed.

Jan 1, 1914

By L. C. IlsLey, E. J. Gleim

Electrical apparatus because of its flexibility and its adaptability to all classes of service has become essential to the mining industry. Hence the problem of providing electrical equipment that is safe for use in explosive mixtures of methane and air is of prime importance in coal mining. Ilwestigatorsand experiment stations early recognized this fact and much work has been done in the investigation and the development of electrical apparatus for use in atmospheres containing fire damp. The term "fire damp" as applied throughout this bulletin means an explosive mixture of methane and air. Direct-current motors and alternating-current motors of the slipring type when running usually give off electric arcs or flashes that will ignite fire damp. Other 'motors that ha,'e no moving electric contacts may become dangerous through accident, deterioration, or neglect. Auxiliary apparatus such as fuses, switches, rheostats, and controllers may arc, flash, or become heated to snch a degree that fire damp can be ignited. Such equipment is still more dangerous when worn or out of repair. In the United States the development of apparatus for use in gaseous mines has been associated largely with coal-cutting equipment run by electricity. This is undoubtedly due to the use of such equipment at the face of the mine workings, where the chance of igniting fire damp is necessarily greatest. One American manufacturer built a coal-cutting equipment of the totally inclosed type for use in firo damp atmospheres in 1903. Another built similar equipment with special protective devices in 1906, for export. During the years 1910 and 1911, the Bureau of Mines at its Pittsburgh experiment station conducted a preliminary investigation of the safety of such protection as was then in use or under consideration. Five motors were submitted for this investigation, each having somewhat different methods of protection. The results of this investigation were published in Bulletin No. 4G.a

Jan 1, 1920