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By Gerhard Derge

A series of studies of the corrosion of tin is under way in the Metals Research Laboratory at the Carnegie Institute of Technology. The complete program includes examination of the corrosion properties of high-purity tin and the changes produced in these properties by the addition of varying amounts of alloying elements. Other studies of this subject have been made recently under the sponsorship of the International Tin Research and Development Council, but these researches have been confined largely to the weakly acid environments commonly encountered in the canning industry.' There is little information available regarding the corrosion of tin under alkaline conditions, but such data would be of value, for a large amount of the metal is used under such conditions. The potential measurements to be described were made because they seemed to offer the most rapid method for obtaining a general view of the conditions to be encountered in such service. These experiments will also serve to establish a technique that will be of value in further studies. It must be emphasized that the results reported are those of controlled laboratory experiments and that the conclusions drawn cannot yet be applied to service conditions; rather, they point to the directions in which more exhaustive experimental work may be done to best advantage. Experimental Procedure The first work was devoted entirely to the problem of obtaining reproducible results from a series of potential measurements. Only the methods finally adopted as standard will be described here, except when the variations from these have furnished results of interest. The cell used is shown schematically in Fig. 1. The electrolyte is contained in the vessel A (an inverted bell jar), whose ground top is fitted to the transite-board lid B. The controlled atmosphere can be admitted

Jan 1, 1938

By Gerhard Derge

A series of studies of the corrosion of tin is under way in the Metals Research Laboratory at the Carnegie Institute of Technology. The complete program includes examination of the corrosion properties of high-purity tin and the changes produced in these properties by the addition of varying amounts of alloying elements. Other studies of this subject have been made recently under the sponsorship of the International Tin Research and Development Council, but these researches have been confined largely to the weakly acid environments commonly encountered in the canning industry.' There is little information available regarding the corrosion of tin under alkaline conditions, but such data would be of value, for a large amount of the metal is used under such conditions. The potential measurements to be described were made because they seemed to offer the most rapid method for obtaining a general view of the conditions to be encountered in such service. These experiments will also serve to establish a technique that will be of value in further studies. It must be emphasized that the results reported are those of controlled laboratory experiments and that the conclusions drawn cannot yet be applied to service conditions; rather, they point to the directions in which more exhaustive experimental work may be done to best advantage. Experimental Procedure The first work was devoted entirely to the problem of obtaining reproducible results from a series of potential measurements. Only the methods finally adopted as standard will be described here, except when the variations from these have furnished results of interest. The cell used is shown schematically in Fig. 1. The electrolyte is contained in the vessel A (an inverted bell jar), whose ground top is fitted to the transite-board lid B. The controlled atmosphere can be admitted

Jan 1, 1938

By Kim Beattie

IN spite of the fact that in 1944 Canada experienced a decline in production of all her leading base metals-nickel, zinc, lead, and copper; despite uncured headaches in the coal-mining industry; and cheerfully ignoring a still further drop in gold, the most valuable product of her mines, which had the lowest output of any year since 1931, the Canadian miner retains the traditional optimism of miners everywhere as he looks forward to the postwar period. Some factors should keep the Canadian mining industry from being too optimistic of the coming era of peace, but the fraternity generally holds that its confident attitude towards the future is based on sound reasons. The decline in production in the Canadian mining industry last year can be almost wholly attributed to the serious shortage of labor and the difficulty in obtaining transport and supplies in remote areas. Some falling off occurred in the demand for certain strategic metals, but the diversion of gold miners, especially, without replacements being obtainable, to direct war work or allied pursuits, was certainly the principal cause of the reduced output in 1944. But that is a situation which will right itself at the close of the conflict.

Jan 1, 1945

By E. Gaujot

IN connection with the question of coal waste and economy in mining, we would call the attention of those interested to an apparatus invented by M. Dernencourt, Superintendent of the Anzin Division of the Anzin Coal Company, North of France. This apparatus is known in France and Belgium under the name of prop screw-jack (vis botte), and has been used with good results in the above-named countries for some years past. M. Ponson gives, in his " Trait6 de I'exploitation des Mines," a description of it (page 533), but as the description given is old, the work not widely known in this country, and as some valuable improvements have been made since, I thought it might be useful to give a description of it, having seen it in 'operation in 1867, while in Europe to attend the great Exposition, and on a scientific tour to the mining districts of France, Germany, Belgium, and Italy. The prop screw-jack is composed of the following pieces : I. The body or column B, Fig. 4 [Plate (I)], of oak or yellow pine, sawed square, the bark taken off, and any length, proportionate to the vein. The smallest are 10 inches diameter at the base, and 9 inches at the top, the height being from 12 to 15 inches less than the size of the vein. In the axis of this column, and at the top end, is a cylindrical opening or hole, C, 22 inches diameter, 10 inches deep, for the screw, S. II. Two wrought-iron rings, R R, to strengthen the two extremities of the column ; the rings must be put on hot. III. A cast,-iron washer, E, with hole in centre a little larger than the screw, to be put on the top of the column, and on which the nut is to rest; the top side of this washer must be faced on the lathe, also the bottom of the nut, to prevent friction. IV. The screw, S, having a total length of 12 inches and a diameter of 24 inches (for very high veins this diameter may be increased to 3 inches), and has on its top a wrought-iron plate, T,

By V. T. BERNER

THIS apparatus was designed primarily to meet the demand for a quick, efficient stopping to seal off the burning area temporarily during a mine fire, but it can be used in any circumstance where an immediate brattice is required for ventilation control. In using the old style brattice, mine-rescue workers have found it difficult, in smoke-laden drifts and stopes, to erect an effective stopping with wooden frame and canvas. Stulls must first be cut to the proper length, the canvas tacked in place, and the numerous irregularities of the walls and back must be caulked. This operation requires the employment of axes, saws, and hammers, which cannot easily and safely be handled in dense smoke. The fire fighters have often been forced to abandon their brattice, unfinished, because of the rapid approach of the fire, or because of the exhausted sup- ply of oxygen in their breathing apparatus. It is neces-

Jan 1, 1930

By AIME AIME

HIS many admirers regard the "official"' candidate for president of the Institute in 1934 as far above the average in ability and capacity; but perhaps his outstanding characteristic is dependability. Some men of great brilliance succeed indifferently because they cannot be relied upon. When Howard Nichols Eavenson undertakes to do something he either does it, or he proves to his own satisfaction that the particular object is not attainable. And the latter outcome is exceptional because his judgment is so good that he generally foresees the impossibility and selects in advance a practical alternative. Though a tireless worker he is pretty sure that his energy is not spent futilely.

Jan 1, 1933

By R. W. Raymond

ALL history testifies that the mineral resources of a region have furnished both the impulse for its first development by man, and the foundation for its subsequent occupation by civilized and prosperous communities. In the pre-historic ages, the hunters, fishers, shepherds and gardeners of the world may have wandered or tarried without regard to the attractions of the mineral deposits which they could not utilize, and therefore did not value. But with the rise of civilization, as expressed in manufactures and commerce, the national value of such deposits began to be realized. Barbarous and remote tribes, possessing the sources of such supplies, won recognition in trade long before they could attain it through any other means. Thus, the North American Indians of Lake Superior exchanged their native copper for the mica of North Carolina; the ships of Tyre sailed all the way to Spain for lead and to Britain for tin; and the fleets of Solomon brought gold from Tarshish. In more modern times it has been chiefly the precious metals that have stimulated exploration and conquest. The inherent qualities and the traditional value of gold and silver sufficiently explain this historic fact, the continued existence and potency of which is evidenced, even in our own times, by the occasional rush of eager adventurers to new districts where gold and silver have been discovered. The history of North and South America has been peculiarly influenced by this factor. It was the prospect of obtaining gold and silver that led the Spanish adventurers to the shores of America, and the conquests of Mexico by Cortez and of Peru by Pizarro were inspired by the stories of the wealth of the Aztecs and the

Mar 1, 1909

By M. G. Corson

THE iron-silicon alloy series has always been one of the most puzzling among the binary alloys. Examining the well known mechanical properties of the iron-rich alloys only we meet the following situation: The ultimate strength and yield point of alloys worked and annealed under the usual conditions represent nearly a straight line function of the silicon content up to 4.5 per cent. silicon (Fig. 1). Starting at the ultimate strength of 35,000 lb. and at a yield point of 16,000 lb. for pure electrolytic iron, one reaches a maximum strength of 93,000 lb. and a maximum yield point of 74,000 lb. at 4.5 per cent. silicon. This corresponds to an increase in ultimate strength by 13,000 lb. per each per cent. of silicon added and nearly the same rate applies to the yield point. The data mentioned are taken from the investigation by T. D. Yensen,1 and while they do not exactly corroborate the results obtained by earlier investigators, they seem to be the most correct. Plastic properties of the alloys are controlled by a much more complicated relationship. Up to 2.5 per cent. Si, the elongation stays close to 50 per cent. (in 2 in.) and the area reduction amounts to 85 per cent;, a situation that forms the usual feature of all alloys representing strictly solid solutions. The plasticity of the latter is always nearly equal to that of their base metal. Beyond 2.5 per cent. silicon, the situation becomes much more complicated. Yensen observed an enormous drop in elongation and area reduction at about 2.65 per cent. silicon, where the first hardly reaches 10 per cent. and the second is still lower; he found, however, a considerable recovery in plasticity at about 2.8 per cent. Si and up to 4.5 per cent. Si it is represented by 20 per cent. for the elongation and 30 per cent. for area reduction.

Jan 1, 1928

With a total value to date of well over $200,000.000.00 for its ore production, the Tintic mining district, which is about 100 miles southwest of Salt Lake City, ranks as one of the three main ore producing areas of Utah. In it are located the biggest silver mines of the country, silver having been the chief metal produced in the camp since its start. Tintic's silver production to date has a total value of over $1 00,000,000, approximately half of the value of the camp's ore production, the balance being roughly divided among lead, gold and copper. Discovery of the camp was made in the late sixties. Lack of transportation and ore reduction facilities delayed extensive development of the area for nearly a decade. In recent years Tintic's ore production has ranged from 350,000 to 400,000 tons annually. In 1924 the camp produced one-eighth of the silver produced in the nation with an output of 7,729,700 ounces. Its lead production was 77,765,000 pounds and its gold production 26,285 ounces.

Jan 1, 1925

By J. D. Lubahn

Prior tests by Dorn, where the strain rate in a tensile test was suddenly changed, have shown a small, but definite rate-history effect to exist. If this effect is neglected in the calculation of creep behavior from tensile results, an error should occur. This paper shows that this error is smaller than experimental scattering, and may be neglected. DORN1 has found a small but definite rate-history effect in the aluminum alloy 250 at liquid-nitrogen temperature using tensile tests with an abrupt rate change. Such an effect is to be expected from pre-viously known2-6 temperature-history effects, together with general experience that effects produced by changing the strain rate a large amount are simi-

Jan 1, 1959

By Gordon E. Frantti

Under the auspices of the Geophysical Committee of Michigan College of Mining and Technology, an investigation was made in Michigan's Upper Peninsula to obtain geophysical data related to the regional subsurface geology in the area covered by Paleozoic sediments. The area surveyed includes that portion of the Upper Peninsula which lies between R18W to R26W and T41N and T49N, covering approximately 1300 square miles. On the index map, Fig. 1, it is represented by the cross-hatched zone west of Munising. Four of the five sites of detailed investigation are indicated by the letters A, B, C, and D. A detailed gravity and magnetic survey had previously been conducted by J. G. Wilson near Perkins, 8 miles north of Rapid River, on a local anomalous area. Results of his work, which showed a large positive magnetic anomaly associated with a gravity anomaly, aroused interest in the possible economic significance of the formations underlying the Paleozoic sediments in this part of the Upper Peninsula.

Jan 1, 1956

By L. S. Allen, R. L. Caldwell, W. R. Mills

Borehole models used in the study of nuclear well logging are reviewed and the merit of heterogeneous us homogeneous formation simulation is discussed. .A heterogeneous model for simulating sandstone formations of variable porosity is described. Simulation adequacy was checked by steady-state and pulsed-neutron measurements. INTRODUCTION In the course of developing new methods of nuclear well logging, the problem of testing new logging instruments under controlled conditions always arises. This testing is usually done in wells of known lithology, porosity and fluid saturation, or in laboratory test facilities which simulate the borehole environment. Although the former approach is possibly more satisfying, it is frequently difficult or inconvenient to find wells with enough variation in the cited parameters for a truly comprehensive study, On the other hand. laboratow- test facilities can simulate a wide variety of formation and borehole conditions if care is exercised to maintain adequate simulation under all conditions. Workers concerned with the development of nuclear well logging methods have reported several types of research facilities in the past. Tittle, et a1 used cubical tanks filled with Ottawa silica sand to study the steady-state behavior of thermal and epithemal neutrons in simulated sandstone logging environments.1 In addition to the effects of fresh vs salt water, a wide variety of casing sizes and compositions were investigated. Tittman also used a large tank of Ottawa sand to measure the slowing down length of sio2;2 for making the same measurement in CaCO3, however, an assembly of solid Vermont marble blocks was used. More recently a very useful and carefully planned test pit for nuclear logs was constructed under the auspices of the API.3 This facility consists of three massive limestone sections, each 6-ft thick and more than 5 ft in diameter. The blocks are buried, one on top of the other, in a concrete- lined pit having a total depth of 24 ft. Each section is made of a different limestone to achieve porosity variation, the selection being Carthage (2 per cent), Indiana (19 per cent) and Austin (26 per cent). The blocks are traversed by a 7 7/8-in. diameter borehole and are saturated with fresh water. Great care was taken to insure total saturation of the stone. Homogeneous mixtures and materials have not been used exclusively for simulating earth formations. Tittle, et a1 4 showed that a heterogeneous lattice of water and graphite could be used to simulate Liquid furfural with very little effecton measured thermal and epi thermal neutron distributions. Subsequently, a lattice-type model for simulating limestone earth formations was designed and built by Berry This limestone model was constructed of 7/8- x 11/4- x 36411. marble rods glued together with a plastic resin to form a 36-x 42- x 42in. cube. The cube was honeycombed vertically with 7/8- x 7/8- x 3641-1. holes for porosity and had a 111/2-in. diameter hole in the center to serve as the borehole. Lower porosities were simulated by placing marble rods in the square holes. The finished cube was used with the borehole vertical and set in a tank to hold liquid for filling the holes in the rock matrix. A second type of heterogeneous borehole model has been proposed by Kukharenko, et a1.6= In this concept the model is composed entirely of solid material. The hydrogen equivalent of formation fluids is simulated by making the model of alternating layers of dense rock and celluloid. Additional hydrogen is included by drilling vertical holes in the rock sections and filling them with solid forms of hydrogeneous material. The volume of the holes is equal to the volume of the celluloid layers, so an axial and radial dispersion of the hydrogeneous material is thus obtained. One such model was composed of alternate 50 mm-thick sand layers and 2 mm-thick celluloid sheets. Approximately 200 appropriately spaced plastic tubes were used in each sand section. The plastic tubes were filled with paraffin for additional hydrogen concentration. This arrangement yielded a model with a water-equivalent hydrogen concentration of 10 per cent. Experimental data taken in this model and in a model consisting of the same material but homogeneously dispersed showed that the heterogeneous system adequately

Jan 1, 1966

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members) Member, Graduate Colorado School of Mines. Four years' experience in West and Northwest. Two years with American Smelting and Refining Co. Wishes to join field party on geological work, mining or areal, where opportunity will be given to be of direct assistance to chief of party in solution of field problems. Age, 26. Unmarried. At liberty June 1. No. 342. Member, technical graduate, aged 30, with' 7 years' experience in concentrating and mining, desires a position of authority with reliable company. At present employed. No. 343. Member. Ambitious, energetic, tactful engineer, college graduate, married, aged 30, desires location with a large coal mining organization. Seven years with present employers -n middle west; has had broad experience in the past eight years on examination, development and construction; successful record in handling men. Position must carry responsible work and a future. Will go anywhere for proper opportunity. Exceptional references as to reliability, character and capacity for work. No. 344.

Jan 3, 1917

E. E. Russell Tratman, New York City (communication to the Secretary): Mr. Glenn's paper brings up again the question of the part played by coal-dust in colliery-explosions. In the discussion of Sir Frederick Abel's paper on " Accidents in Mines," read before the Institution of Civil Engineers,? much was said about the dangerous properties of coal-dust, and several instances were given of the successful use of a spray of water, water and compressed air, or exhaust-steam from an engine, to keep the mine SUEciently damp to prevent the formation of dust clouds. Methods of preventing shots from blowing out; of using water cartridges to prevent flame ; and of using lime cartridges, wedges and other means of breaking down the coal were also discussed. Mr. Emerson Bainbridge referred to the explosive termed " roburite " (ammonium nitrate and

Jan 1, 1895

CONTENTS PAGE Simons, Theodore.-Basic Principles of Gravity Concentration-A Mathematical Study : :.. 1 Taggart, Arthur F. and Gaudin, A. M.-Surface Tension and Adsorption Phenomena in Flotation 11 Hersam, Ernest A.-Factors Controlling the Capacity of Rock Crushers 12 Shaw, S. F.-The Ore Deposits of Sierra Mojada, Coahuila, Mexico 12 Wilson, Philip D.-The British Columbia Batholith and Related Ore Deposits 26 Greensfelder, N. S.-Shot-firing by Electricity 27 Mitke, Chas. A.-Metal Mine Ventilation in the Southwest 28 Foley, F. B. and Howell, S. P.-Neumann Bands as Evidence of Action of Explosives upon Metals 30 Schwartz, H. A., Payne, H. R., Gorton, A. F., and Austin, M. M.-Conditions of Stable Equilibrium in Iron-carbon Alloys 30

Jan 12, 1922

By R. W. Heckel

The conzpaction of metal powders is analyzed through density-pressure curves as a three-stage process — die filling, individual particle motion, gross compact deformatim. The densification occurring during each of these stages is evaluated quantitatively. The amount of densification in the first and second stages is primarily a function of particle geometry. The densification taking place in the third stage is dependent mainly upon the material. AT the present time the densification of powders during compaction is usually described by terms such as "compactibility," "compressibility," and "compression ratio." Schwarzkopfl has proposedthat compactibility be defined as the minimum pressure needed to produce a given green strength, while compressibility be used to indicate the extent towhichthe density of a powder is increased by a given pressure. Compression ratio is generally defined as the ratio of the compact density obtained at a given pressure to the apparent density of the loose powder. 13alshina found that the pressure imposed on a compact affects the relative volume of the compact according to the following relation: hP= - LV + C [ll where: P is the applied pressure, V is the relative volume of the compact, Ratio of the specific volume of the compact to that of the material without porosity. Lisa constant described as the modulus of pressing and is determined by the slope of a plot of h P vs V, and C is a constant which is determined by the intercept of a plot of InP vs V. Several drawbacks of the Balshin analysis may be noted from Fig. 1, which is a plot of pressure (loga-

Jan 1, 1962

By William P. Shinn

IT seems proper to present in the Transactions of the Institute, from time to time, formal record of the advances made in the arts and sciences to which our organization is devoted-milestones in the highway of progress-from which our successors may measure what they in their turn have gained. The admirable address of the Hon. Abram S. Hewitt, then president elect of the Institute, on "A Century of Mining and Metallurgy in the United States," read at the opening of the meeting held in this hall in June, 1876, forms a point of departure, and the conclusion of the eighth decade of the nineteenth century and the end of the first five years of our country's second century seem to offer a fitting time for again making up our record. The period since 1875 has been marked by a degree of activity in mining and metallurgical industry never before equalled in our history, while the progress made in the science and art has been, if possible, still more noticeable. Whether we consider the mining of iron, ore, and coal, or of the precious metals,-the advances made in smelting the former and in reducing the latter, the extraordinary increase in the production of Bessemer steel, or the science of Thomas and. Gilchrist, which makes the hitherto rejected phosphorus the corner-stone of success,-the past five years are alike memorable for the progress they have shown and to some of the most marked features of this progress I will now oriefly call your attention. It may be of interest in this connection to note the following figures, showing the growth of the population of the United-States during the last three decades :

Jan 1, 1881

A tentative plan for the Colorado Meeting has been formulated as follows: One day will be spent at Denver, one day at Colorado Springs, one day at Cripple Creek, a trip by automobile to the top of Pike's Peak, one day at Pueblo, one day at Leadville. All the principal mines and mills of the districts mentioned will be visited, including the gold mines in Cripple Creek, the lead, zinc, and steel works. of Pueblo, the production of ferro-molybdenum by electric furnace at Leadville, etc. Special arrangements are being made for the social entertainment of ladies at all points; one evening at Colorado Springs will be devoted to a reception and dance, and the usual dinner will he given on another evening. The following papers have already been accepted for the Colorado Meeting, and some have already been published: Fireproofing Mine Shafts by the Anaconda Copper Mining Co. By E. M. Norris. (March Bulletin.) Air Blasts in the Kolar Gold Field, India. By E. S. Moore. (March Bulletin.) The Use of Coal in Pulverized Form. By H. R. Collins. (April Bulletin.) Coal Mining in Washington. By F. A. Hill. (April Bulletin.) Carbocoal. By C. T. Malcolmson. (May Bulletin.) Gaging and Storage of Oil in the Mid-continent Field. By O. U. Bradley. (March Bulletin.) An Interpretation of the So-called Paraffin Dirt of the Gulf Coast Oil Fields. By A. D. Brokaw. (April Bulletin.) The Theory of Volcanic Origin of Salt Domes. By. E. DeGolyer. (May Bulletin.)

Jan 5, 1918

By L. K. Jetter, J. C. Ogle, C. L. McHargue

The preferred orientation developed in extruded aluminum rods has been studied as a function of extrusion temperature, extrusion speed, and position in the rod. Duplex <111> - <001> textures were developed for slow extrusion speeds at temperatures of 75° to 850° F and for fast extrusion speeds at temperatures of 75° to 450°F. The <001> texture component was shown to be primarily due to re crystallization occurring during fabrication. At fast speeds and billet temperatures of 650° to 850°F, complete recrystallization occurred and <115>or<118> textures were found. The nature of the structure has proved to be an important variable in the production and use of extruded products. Data on the flow of aluminum and aluminum alloys summarized by Smith,&apos; Hardy,&apos; and Locke3 show that the extruded product may possess a deformed, a partially recrystallized, or a completely recrystallized structure, and there may be important variations in the structure from surface to center and from front end to back end of an extrusion. This inhomogeneity in grain structure and preferred orientation affects both the mechanical properties of the extruded section and its response to subsequent heat treatment. Among the fabrication variables causing these differences are temperature, extrusion ratio, and extrusion speed. Preferred orientation which develops during the extrusion of rods is of the fiber-type and, in general, has been assumed to be similar to that developed in rods or wires fabricated by drawing through dies, rolling, or swaging.4 Because of the nature of the flow of metal being extruded, this assumption may be valid for material near the center of the rod but probably is not valid for the outer layers. In most face-centered-cubic metals a duplex fiber texture has commonly been reported in which the grains have either <Ill> or <001> directions parallel to the longitudinal axis. Sachs and fichiebold5 reported cold-drawn aluminum (99.6 pct pure) to have a single <Ill> fiber texture, and this observation was confirmed by Schmid and Wassermann.6 Hibbard, on the other hand, observed a minor <001> and a major <111> texture in 99.994 pct A1 cold drawn to 98 pct reduction in diam.7 He concluded that the <001> component resulted from a small amount of room-temperature recrystallization. Dayal8 concluded that the <001> component was an intermediate component which disappeared at high reductions in 99.5 pct pure Al. Kostron and schippers9 found duplex <111> — <001> textures in extruded 99.5 pct Al, as did Gow and cahnl0 and GOW11 for extruded rods of commercial and superpure aluminum. Similar duplex fiber textures have been reported for aluminum alloys by Kostron,= Unckel,13 and Van Horn.14 The present paper is concerned with the variation in texture with fabricating conditions and with the nature of the texture components in extruded aluminum rod (99.99 pct pure). EXPERIMENTAL PROCEDURE Ingots were chill-cast in cast-iron molds and machined to 3-in. diam by 6-in. long extrusion billets. These billets were upset to 3.125 in. diam and extruded through a flat-face 0.690-in. diam die. Quenching of the rods was accomplished by a water spray at the die face. The combinations of fabricat-

Jan 1, 1960

By John W. Buch

NeaRly 25 years ago operating officials in the northern anthracite field were confronted with the problem of profitably mining virgin beds of thin coal (those 48 in. and under) or destroying them by mining underlying thick beds. To solve this problem costly hand-mining methods were replaced by cheaper mechanical methods, which eliminated the need for the lifting of bottom or the brushing of top in excessive quantities, which was essential if proper height for hand loading1 was to be provided. During this period long-face mining was an outstanding development. In its favor in comparison with any other method were the ease with which undercutting machines could be used, a differential in powder cost of about fifteen cents per ton in favor of this method over mining from a solid chamber or pillar face, and a greater production per day from a single working place, resulting in lower capital expenditures for a given total production, closer supervision and lower transportation cost. The long faces were drilled by jackhammer and undercut by machines. The coal from the cut was loaded into mine cars placed on the gangway road by means of a double-drum mechanical scraper engine and a mechanical V-type scoop. A tugger hoist was used to spot empty cars at the loading point from a supply placed at the operation by an electric mine locomotive. During loading the roof was supported by vertical wooden props paralleling the face. After the loading was completed the scraper engine and the ropes that had been used to propel the scoop in the loading of coal transferred the props to and along the face. A row of unfilled cogs was then built parallel to the new face and about 6 ft. from it. These cogs were usually made 6 by 3 ft., the longer dimension paralleling the face; they were placed on an average at 12-ft. centers. These wooden cogs were left in place and were buried later by falling roof. Attempts to remove them were never successful. When a new long face was started, the cog spacing would be increased to about 20-ft. centers. As successive cuts were made, weight would begin on the cogs, and they

Jan 1, 1940