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By M. R. Pickus

THE study of the plastic deformation and recrystallization of metals has been the subject of many investigations. In regard to the simple deformational processes, such as tension and compression, the early knowledge gained from studies of polycrystalline material has been supplemented by many significant researches on the behavior of single crystals. Unfortunately, this has not been true for more complicated deformational processes. As far back as 1927, G. I. Taylor1 wrote: It is impossible in the present state of knowledge to do more than give a possible reason why (face-centered cubic) crystals set themselves with a (110) direction in the plane of rolling, and at right angles to the direction of rolling. The explanation of why the orientation of the crystal axes round the transverse direction is what it is, must be left till the distortion of metals, and particularly single crystals of metals in the process of rolling, has been studied in greater detail. That this gap in the systematic study of deformation and recrystalliza-tion has not yet been filled was indicated by C. H. Samans,2 who wrote in 1934 that "only four investigations upon cold-rolled single crystals of any of the face-centered cubic metals have been reported in the literature." Of these four studies, only those of S. Tanaka3 and T. Sakao,4 both of whom worked with aluminum crystals, had quantitative significance. The other two, carried out by F. Wever5 and W. G. Burgers,6 were of a. qualitative nature. It is our hope that the present investigation may contribute some-thing to the knowledge necessary for a rationalization of the origin of rolling textures in terms of the known behavior of single crystals, and may add pertinent information concerning the recrystallization characteristics of deformed single crystals.

Jan 1, 1938

By Charles Seastone

Location THE hydro-electric plant of the Peninsular Power Co., is located at what is commonly known as Lower Twin Falls on the Menominee River. This location is about 33 miles north of the city of Iron Mountain, Mich. The principal points of delivery of electric energy from this plant are in the mining regions adjacent to Florence, Wis., and Iron River, Mich., and in the cities of Iron River and Iron Mountain. The hydro-electric plant at Twin Falls and the substation of the Iron Mountain Electric Light & Power Co. are connected by a 6,600-volt transmission line carried on steel towers and steel poles, the latter being used within the city limits. The plant at Twin Falls and the substation at Iron River, about 36 miles distant, are connected by a 66,000-volt, duplicate, three-phase transmission line, supported on steel towers. At Iron River, are located a 1,500-kw. auxiliary steam plant, and the substation, from which the current is distributed to the mines in this vicinity. A description of the auxiliary plant, main and customers' substations, and of the main and secondary transmission lines, follows later in this paper.

Jan 2, 1915

By R. W. Raymond

Most of US, in this hurrying age, take little pains to preserve such records of our doings as will make the work of' our biographers easy. Now and then there is an exception, and Dr. Trippel was one. Methodical in all his habits, he kept diaries and journals comprising his own personal experiences, the details and results of his numerous scientific investigations, and his impressions concerning men and events; and also copies of all his technical essays, published by various societies or periodicals. It is a striking instance of " the irony of fate," that these carefully-preserved materials, which would now have a real historical, as well as biographical value, were totally destroyed by an accidental fire a few years ago. In addition to my own recollections of an acquaintance covering more than thirty years, I am indebted, for the fads upon which this sketch is based, chiefly to Mr. Engene J. Trippel, a son of the deceased, and now Register of the United States Land Office at Tucson, Arizona. Mr. Trippel, however, frankly confesses that his own knowledge of his father's work is, in the absence of written records, imperfect.

Jan 1, 1898

By E. J. Valyi

The purpose of the continuous casting processes is twofold: As the name implies, they aim at performing a heretofore intermittent operation continuously; in this respect, they tend to satisfy the appetite of the beast that modern extrusion plants and rolling mills have grown to be. The effort invested in the development of these methods bore rich dividends in economy and in the improvement of technical characteristics. The other purpose of many continuous casting methods is to reduce the number o-f operations mushrooming between the liquid alloy and the finished mill product, essentially by substituting adequate chill in comparatively small cross sections for one or more "breakdown" steps. It is this second tendency of continuous casting that justifies description of the Soro process within the frame of our symposium: although not continuous, the Soro method constitutes a means of converting molten metal into a nearly finished mill product. The Process The name, Soro, is a composition of initials and abbreviations, with no particular technical significance. The process originates in Switzerland; it was adopted by numerous European plants between 1937 and 1940 and is now being installed in this country. It is applicable to ferrous and nonferrous alloys of an exceptionally wide range of composition. It is capable of producing rod from 1/2 in. to approxi- mately 4 in. in diameter, or other simple solid shapes of corresponding cross-sectional area. , Fig. I shows schematically the succession of operations involved. A ring is cast in a two-part centrifugal-casting metal mold. The cross section of the ring may be round, hexagonal, rectangular or some other solid shape, with the exception of any contour that is undercut with reference to the mold parting line. As cast, the ring has a riser along its inner periphery, which is removed in the next operation, so as to leave the ring with a dean cross section. Following the removal of the riser, the ring is severed at one point and one end is bent outward, leaving a slight clearance between the two ends. The next step is straightening of the ring in a special device, forming a bar with a slight bend; this is followed by any one of the conventional finishing operations that are necessary to obtain forging rod, screw-machine stock or strip. The outstanding features of this procedure are: I. The cross section cast is the same or within a few per cent of the cross section of the finished product (except for fabricating into strip and wire). 2. All operations following casting of the ring are performed cold. Equipment The equipment required is simple and inexpensive. The casting machine is a conventional horizontal-shaft mold assembly, similar to those found in centrifugal-casting foundries. Fig. 2 shows a battery of three machines- with their protecting hoods .swung open. One of these machines,

Jan 1, 1945

By R. G. Baughman

With the constantly increasing sales competition, coal to be sold today must meet the test of quality in every respect. The producers must be able to make all marketable sizes that will meet such general requirements as follows: 1. Ash content must be consistently low, depending upon the use to be made of the coal. 2. Sulfur content must be controlled accurately according to requirements. 3. All sizes must be positively free from visible impurities. 4. Free moisture of washed sizes must be reduced to a minimum. 5. The freezing of wet coal in cars must be prevented. 6. The percentage of fines in small mixed sizes must be controlled to give the uniform and proper combustion when used on various types of automatic stokers. 7. The undersize particles or degradation caused by handling must be kept to an absolute minimum in all sizes loaded. Many difficulties may be met in bringing any particular coal to meet these quality requirements, because the extent to which the quality of a coal may be controlled is determined largely by its physical characteristics. Preparation of an Impure Coal Bed The application of modern and scientific methods in the controlled preparation of bituminous coal from a bed in the mid-western field will illustrate the results that can be accomplished by adequate preparation: The bed referred to contains coal inherently excellent as to low ash and other desirable characteristics; in fact, the coal itself is one of the best in the field. It is, however, divided into four layers by dirt bands of soft shale 1 to 2 in. thick. It also contains much sulfur in the form of sulfur lenses and laminated sheets. Horsebacks or rolls varying from 6 in. to 12 ft. in width are encountered in the mining of the bed and heretofore have rendered it practically unworkable. The mines operating in this

Jan 1, 1931

By Carl Henrich

The Ducktown copper-mines are located in the southeast corner of Tennessee. The name Ducktown was originally given to a district occupying the southeast corner of Polk county, which in turn occupies the southeast corner of the State. Fig. 1 is a map of the vicinity of Ducktown, taken from the topographical surveys of the United States Geological Survey. The Ducktown district is bounded on the east by Cherokee county, North Carolina (the boundary-line between the two States running here a little east of north along the western slope of Pack mountain), and on the west by the eastern foot-hills of Little Frog mountain. On the north, Stansbury mountain, really a chain of low mountains or hills, forms the dividing-line between Ducktown and Turtletown districts. On the south, the Ducktown district extends beyond the Ocoee river to the Georgia State line.. This line, in going west, gradually recedes southwards from that river into the foot-hills of Big Frog mountain, the highest mountain of the neighborhood, which rises about 4300 feet above sea-level, while the surface of the Ocoee river, where it leaves the Ducktown district, is less than 1500 feet above sea-level. It will be seen from this description, and from a study of the map, that the Ducktown district occupies the northern part of a kind of basin, bounded on the east by Pack mountain and on the west by Little and Big Frog mountains. Between these mountains the Ocoee river, draining the basin, cuts its way to the Hiwassee and the Tennessee rivers in a narrow gorge, through the crystalline slates and schists, which from their excellent exposure in this Ocoee gorge have received the local

Jan 1, 1896

By E. C. Houston

The presence in the Tennessee Valley of extensive deposits of olivine, a silicate of magnesium and iron that contains approximately 28 per cent magnesium, has been recognized since 1896 when Lewis8 published a survey of basic magnesium rocks of western North Carolina. A recent field survey by T.V.A.7 showed that more than two hundred million tons of high-grade olivine occurs above local drainage levels in western North Carolina and northern Georgia. Except for sporadic attempts to work the olivine for its nickel and chromium contents,10 the ore received little attention industrially until 1926 when Goldschmidt3 suggested its use in the manufacture of refractories. Only one instance is recorded of an attempt to utilize the ore commercially for its magnesium content;" in this case a process was used in which olivine was treated with sulphuric acid, the resultant mixture was leached with water, and the leach solution was purified and evaporated to form epsom salts, which was the end product. As a part of its program of contributing to the development of the natural resources of the region, the Tennessee Valley Authority became interested in the olivine deposits as a source of metallic magnesium because of their high magnesium content and proximity to hydroelectric power. Studies were undertaken to determine the feasibility of producing magnesium chloride by extraction of olivine. The experimental work was carried out successively at the T.V.A. Minerals Testing Laboratory, Norris, Tenn., at the Georgia State Engineering Station,* Atlanta, Ga., and at the T.V.A. laboratory at Wilson Dam, Ala. The present paper describes a process. developed through the pilot-plant stage, whereby magnesium chloride suitable for reduction to metallic magnesium can be prepared from olivine by extraction with hydrochloric acid and subsequent purification. Research on the magnesium-from-olivine process, originally intended for peacetime use, was given impetus by the shortage of magnesium that existed at the beginning of the current world war. By the time the process was sufficiently developed to justify a proposal for its inclusion in the war program, the shortage had been met by expansion and development of other processes. However, it is believed that the magnesium-from-olivine process may have advantages that will warrant consideration of its use after the war, when the economics of the various processes rather than production on a wartime scale will be the criterion for commercial production of magnesium. Description OF Process Metallic magnesium is produced electro-lytically by the Dow and the Elektron

Jan 1, 1949

By John R. Hutchins

1ms is a report of nickel (wire) oxidation studies designed to test the validity of Valensi's1 equation developed for the kinetics of a reaction controlled by diffusion in a continuously growing product layer on cylindrical surfaces. The equation is:

Jan 1, 1968

By E. C. Houston

The presence in the Tennessee Valley of extensive deposits of olivine, a silicate of magnesium and iron that contains approximatcly 28 per cent magnesium, has been recognized since 1896 when Lewis8 published a survey of basic magnesium rocks of western North Carolina. A recent field survey by T.V.A.7 showed that more than two hundred million tons of high-grade olivine occurs above local drainage levels in western North Carolina and northern Georgia. Except for sporadic attempts to work the olivine for its nickel and chromium contents,10 the ore received little attention industrially until 1926 when Goldschmidt3 suggested its use in the manufacture of refractories. Only one instance is recorded of an attempt to utilize the ore commercially for its magnesium content;11 in this case a process was used in which olivine was treated with sulphuric acid, the resultant mixture was leached with water, and the leach solution was purified and evaporated to form epsom salts, which was the end product. As a part of its program of contributing to the development of the natural resources of the region, the Tennessee Valley Authority became interested in the olivine deposits as a source of metallic magnesium because of their high magnesium content and proximity to hydroelectric power. Studies were undertaken to determine the feasibility of producing magnesium chloride by extraction of olivine. The experimental work was carried out successively at the T.V.A. Minerals Testing Laboratory, Norris, Tenn., at the Georgia State Engineering Station,* Atlanta, Ga., and at the T.V.A. laboratory at Wilson Dam, Ala. The present paper describes a process, developed through the pilot-plant stage, whereby magnesium chloride suitable for reduction to metallic magnesium can be prepared from olivine by extraction with hydrochloric acid and subsequent purification. Research on the magnesium-from-olivine process, originally intended for peacetime use, was given impetus by the shortage of magnesium that existed at the beginning of the current world war. By the time the process was sufficiently developed to justify a proposal for its inclusion in the war program, the shortage had been met by expansion and development of other processes. However, it is believed that the magnesium-from-olivine process may have advantages that will warrant consideration of its use after the war, when the. economics of the various processes rather than production on a wartime scale will be the criterion for commercial production of magnesium. Description of Process Metallic magnesium is produced electro-lytically by the Dow and the Elektron

Jan 1, 1948

By E. C. Houston

The presence in the Tennessee Valley of extensive deposits of olivine, a silicate of magnesium and iron that contains approximatcly 28 per cent magnesium, has been recognized since 1896 when Lewis8 published a survey of basic magnesium rocks of western North Carolina. A recent field survey by T.V.A.7 showed that more than two hundred million tons of high-grade olivine occurs above local drainage levels in western North Carolina and northern Georgia. Except for sporadic attempts to work the olivine for its nickel and chromium contents,10 the ore received little attention industrially until 1926 when Goldschmidt3 suggested its use in the manufacture of refractories. Only one instance is recorded of an attempt to utilize the ore commercially for its magnesium content;11 in this case a process was used in which olivine was treated with sulphuric acid, the resultant mixture was leached with water, and the leach solution was purified and evaporated to form epsom salts, which was the end product. As a part of its program of contributing to the development of the natural resources of the region, the Tennessee Valley Authority became interested in the olivine deposits as a source of metallic magnesium because of their high magnesium content and proximity to hydroelectric power. Studies were undertaken to determine the feasibility of producing magnesium chloride by extraction of olivine. The experimental work was carried out successively at the T.V.A. Minerals Testing Laboratory, Norris, Tenn., at the Georgia State Engineering Station,* Atlanta, Ga., and at the T.V.A. laboratory at Wilson Dam, Ala. The present paper describes a process, developed through the pilot-plant stage, whereby magnesium chloride suitable for reduction to metallic magnesium can be prepared from olivine by extraction with hydrochloric acid and subsequent purification. Research on the magnesium-from-olivine process, originally intended for peacetime use, was given impetus by the shortage of magnesium that existed at the beginning of the current world war. By the time the process was sufficiently developed to justify a proposal for its inclusion in the war program, the shortage had been met by expansion and development of other processes. However, it is believed that the magnesium-from-olivine process may have advantages that will warrant consideration of its use after the war, when the. economics of the various processes rather than production on a wartime scale will be the criterion for commercial production of magnesium. Description of Process Metallic magnesium is produced electro-lytically by the Dow and the Elektron

Jan 1, 1948

By E. C. Houston

THE presence in the Tennessee Valley of extensive deposits of olivine, a silicate of magnesium and iron that contains approximately 28 per cent magnesium, has been recognized since 1896 when Lewis8 published a survey of basic magnesium rocks of western North Carolina. A recent field survey by T.V.A 7 showed that more than two hundred million tons of high-grade olivine occurs above local drainage levels in western North Carolina and northern Georgia. Except for sporadic attempts to work the olivine for its nickel and chromium contents,10 the ore received little attention industrially until 1926 when Goldschmidt3 suggested its use in the manufacture of refractories. Only one instance is recorded of an attempt to utilize the ore commercially for its magnesium content;" in this case a process was used in which olivine was treated with sulphuric acid, the resultant mixture was leached with water, and the leach solution was purified and evaporated to form epsom salts, which was the end product. As a part of its program of contributing to the development of the natural resources of the region, the Tennessee Valley Authority became interested in the olivine deposits as a source of metallic magnesium because of their high magnesium content and proximity to hydroelectric power. Studies were undertaken to determine the feasibility of producing magnesium chloride by extraction of olivine. The experimental work was carried out successively at the T.V.A. Minerals Testing Laboratory, Norris, Tenn., at the Georgia State Engineering Station,* Atlanta, Ga., and at the T.V.A. laboratory at Wilson Dam, Ala. The present paper describes a process, developed through the pilot-plant stage, whereby magnesium chloride suitable for reduction to metallic magnesium can be prepared from olivine by extraction with hydrochloric acid and subsequent purification. Research on the magnesium-from-olivine process, originally intended for peacetime use, was given impetus by the shortage of magnesium that existed at the beginning of the current world war. By the time the process was sufficiently developed to justify a proposal for its inclusion in the war program, the shortage had been met by expansion and development of other processes. However, it is believed that the magnesium-from-olivine process may have advantages that will warrant consideration of its use after the war, when the economics of the various processes rather than production on a wartime scale will be the criterion for commercial production of magnesium. DESCRIPTION OF PROCESS Metallic magnesium is produced electrolytically by the Dow and the Elektron

Jan 1, 1945

The primary purpose of the Institute is to advance the technologic and engineer-. in- arts embraced by it through inter¬change of knowledge. This can best be clone by the presentation and discussion of technical papers by its members. Short " practical papers are especially welcome. An author should always satisfy himself that his material is of a quality that Will be a credit to him and to the Institute. The preparation of a good paper fre¬quently leads to a reorientation of the author's thoughts, and publication con¬tributes much to the professional standing of the author. Members are urged to submit papers presenting the results of their work. Attention to the following sugges¬tions will greatly further the prompt and efficient handling of manuscripts. 1. SUBJECTS: The subject must be within the field of the Institute.

Jan 1, 1943

Utah greets the members of the American Institute of Mining and Metallurgical Engineers on this occasion with the assurance that their presence is gratefully appreciated. The fact that this is the second time the Institute has so honored Utah is viewed by us as an approval of a past achievement and an incentive to a greater one. Our sincere hope is that our guests this year will have experiences so pleasant and profitable that they will be disposed to come yet again-and again. As use is the measure of value, we appraise our hospitality by the extent to which our friends accept it. World changes incomprehensible at that time have taken place since the Institute met here in 1914. The mining industry of Utah undertook to bear its full share of the responsibilities that came with those changes and, we believe, carries its additional burdens with all the resolution and optimism characteristic of American citizenship and especially characteristic of mining men and mining operations.

Jan 1, 1925

By Sherwin Kelly

RED LAKE has suffered from its over-zealous friends, who had something to gain by their zealousness and were, for the time being, friends indeed. Now, what was once hailed as a new El Dorado is anathema to many. Neither extreme view was justi-fied, and in time a new gold district may be expected to develop slowly, but surely. The marvel is that little streaks of valuable metal are ever uncovered by the few men who roam that tre-mendous, almost unexplored area that is the "North Country." The area to be explored is so immense, and the men who can do it so few, that once they leave the "steel," take their canoes and packs, and disappear into the bush, they may travel the innumerable watercourses that are the highways of the wilderness for days or weeks, and never see one of their own kind. Patricia, for example, is one of the mining districts of Northern Ontario, lying at the western side of the

Jan 8, 1927

By D. J. Reed

Concord coal mine near Bessemer, Ala., built, owned, and operated by Tennessee Coal & Iron Div., U. S. Steel Corp., produces only a metallurgical grade for use as coke in blast furnaces of the division at the Fairfield and Ensley works. Capacity of the operation is approximately 800 tph, half of which is delivered to the coke and coal chemical plant at Fairfield after beneficiation to metallurgical grade coal. The remaining portion of the mine run is rock and refuse removed during preparation. Concord mine coal is hoisted to the surface coal preparation plant by an underground slope conveyor. The slope conveyor is 2449 ft long and has a lift of 729 ft. At time of installation the Concord mine slope conveyor was the largest single conveyor unit ever made with respect to belt horsepower and total lift. After several years it became necessary to determine the cause of slope conveyor cover wear.

Nov 1, 1956

By Charles Barrett

METALLURGISTS are making use of the stereographic projection to a steadily increasing extent. In the last five years no less than 20 papers in American metallurgical journals alone have employed the stereographic projection; recent books on physical metallurgy, plastic deformation, X-rays and their applications, and crystal structure use it. Mineralogists have used the stereographic projection for many years in the description of symmetry classes and crystal planes, for it presents an accurate, easily understood plot of any angular relations in crystals with all unessential features eliminated (such as the accidentally deter-mined size and shape of crystal faces). In metallography and physical metallurgy the projection is much used for the analysis of markings appearing on polished grains: slip lines, twins, cracks, structures formed by precipitation, magnetic-powder patterns, etch pits, etc. Data from certain types of X-ray photograms are most conveniently analyzed by its use, particularly those for determining the orientation of single crystals or the preferred orientation of grains in an aggregate. Calculations of how to tilt or cut a crystal parallel to a certain crystallographic plane or to reflect X-rays from a certain plane are rapidly carried out. It has been adopted almost universally to the exclusion of other methods by those studying the deformation of metallic crystals, save where the accu-racy required is greater than a few tenths of a degree. Any directional property in a crystal or polycrystalline material can be shown on a stereo-graphic projection; for example, the modulus of elasticity, yield point, etc. It has been repeatedly called to our attention that there is need of all elementary explanation of the principles and methods of stereographic projection, covering all the, common applications in the field of metal-lography and physical metallurgy. The following contribution is an attempt to fill this need. The description of each method is supplemented with references to publications in which the method has been used. For convenience to the reader, these illustrative references are chiefly in American journals, particularly the publications of the American Institute of Mining and

Jan 1, 1937

By Charles S. Barrett

Metallurgists are making use of the stereographic projection to a steadily increasing extent. In the last five years no less than 20 papers in American metallurgical journals alone have employed the stereographic projection; recent books on physical metallurgy, plastic deformation, X-rays and their applications, and crystal structure use it. Mineralogists have used the stereographic projection for many years in the description of symmetry classes and crystal planes, for it presents an accurate, easily understood plot of any angular relations in crystals with all unessential features eliminated (such as the accidentally determined size and shape of crystal faces). In metallography and physical metallurgy the projection is much used for the analysis of markings appearing on polished grains: slip lines, twins, cracks, structures formed by precipitation, magnetic-powder patterns, etch pits, etc. Data from certain types of X-ray photograms are most conveniently analyzed by its use, particularly those for determining the orientation of single crystals or the preferred orientation of grains in an aggregate. Calculations of how to tilt or cut a crystal parallel to a certain crystallographic plane or to reflect X-rays from a certain plane are rapidly carried out. It has been adopted almost universally to the exclusion of other methods by those studying the deformation of metallic crystals, save where the accuracy required is greater than a few tenths of a degree. Any directional property in a crystal or polycrystalline material can be shown on a stereographic projection; for example, the modulus of elasticity, yield point, etc. It has been repeatedly called to our attention that there is need of an elementary explanation of the principles and methods of stereographic projection, covering all the common applications in the field of metallography and physical metallurgy. The following contribution is an attempt to fill this need. The description of each method is supplemented with references to publications in which the method has been used. For convenience to the reader, these illustrative references are chiefly in American journals, particularly the publications of the American Institute of Mining and

Jan 1, 1937

By W. H. Adams

Inasmuch as] the mining of phosphate rock and its transportation has so general a bearing on the great industries of this continent, entering as well into the problem of our trade with foreign countries, it may be useful to place on record the following list of localities from which certain products of a like nature are received by us in a business way, or in which we are interested more or less either by ownership or by competition. As a ready means of comparison, the percentages of the mine products and the deteriorating constituents are given : Coprolite (Cambridge).—This material is obtained from the Upper Greensand formation in Cambridgeshire. The phosphate runs from 50 to 60 per cent., and averages 64 per cent. It contains much carbonate of calcium, but little iron, in the ferric condition. The superphosphates manufactured from the material are permanent and little liable to a revert." They contain from 28 to 35 per cent. of soluble phosphate. Coprolite (Buckingham).—From the same formation as the Cambridge variety, and very similar in composition.. It averages 60 per cent. phosphate. Coprolite (Suffolk).—These coprolites are not so valuable for the manufacture of superphosphate as the two previous varieties, as the iron they contain is in the ferric state, and liable to "revert" the soluble phosphate. The phosphate varies from 48 to 60 per cent., but averages 54 per cent. They are of Tertiary formation. Coprolite (Potton or Bedford).—The average amount of phosphate in these coprolites is about 50 per cent. In some cases they may, however, run up to 60 per cent., and in others may not exceed 45 per cent. They belong to the Lower Greensand formation. The ferric iron frequently is as high as 4 per cent., and the alumina as much. Russian phosphate comes from the chalk, and occurs in carious rounded masses. It contains from 28 to 35 per cent. of phosphate, but may run up to 69 or 70 per cent. Curacoa phosphate is also of very high class quality, giving 80

Jan 1, 1890

By Douglas Bunting

THE first presentation of this paper was before the Pennsylvania Anthracite Section of the Institute in May, 1914, after which a committee was selected to verify and add to the data contained in the original paper. The author is indebted to G. W. Engel, H. W. Montz, R. V. Norris, and H. H. Otto, of this committee, for additional information. I also wish to acknowledge the courtesies extended me by a number of the mining companies for information relative to accidents, systems of proving, and mining practice. The paper should bring forth additional criticism and recommendations, which will be of value in establishing future practice relative to this subject. Throughout the northern anthracite field of Pennsylvania glacial and alluvial deposits of sand, gravel, and clay exist in varying quantities. The extent and character of these deposits are described by N. H. Darton in Bulletin 45 of the U. S. Bureau of Mines, entitled, Sand Available for Filling Mine Workings in the Northern Anthracite Basin. It is estimated that the northern field contains 10,000,000,000 tons of these deposits, or a sufficient quantity to cover the 176 square miles of coal area to a depth of about 25 ft. These deposits of sand, etc., overlying the coal measures attain a maximum depth of more than 300 ft., and are usually saturated to such an extent as to render them semi-fluid. It is .this condition of fluidity that limits the mining of coal seams cropping in or in close proximity to these deposits, and it is in the interest of safer and more efficient mining methods under these conditions that the study of this -subject is here presented. The dangers incident to mining under deep deposits of sand have long been realized by operators in the northern anthracite field, and much has been done to prove the contour of the rock and vein croppings underlying these water-bearing deposits of sand and gravel.

Jan 1, 1915

By Portland P. Fox, Berlin C. Moneymaker

THE development, within recent years, of core drills capable of drilling holes up to 72 in., or even more, in diameter, has made possible an entirely new and valuable method of geologic exploration. Although little used until recently as an exploratory tool except in the United States, by the Tennessee Valley Authority and the Corps of Engineers of the U. S. Army, for the exploration of damsites, the large-diameter core drill may be used to good advantage in other types of geologic exploration. Its principal utility is that of supplementing, rather than replacing, other means of exploration. Although core is frequently recovered intact, the greatest advantage of large-diameter drilling is that the holes produced are large enough to be entered by the geologist and engineer, and thus afford an excellent means of examining undisturbed rock. The walls of the holes are smoothly cut, and in some rocks nearly or quite polished, so that the most minute details of structure and stratigraphy are clearly disclosed. Such features as faults, joints, bedding planes, weathered "seams," and beds or layers of soft materials, which are not always amenable to disclosure by cores recovered from small-diameter holes, are conspicuously displayed in the walls of large holes. Frequent reference to the drilling of large-diameter holes is made in engineering literature, but comparatively little emphasis has been placed on their value in geologic investigation. It is, therefore, intended that the present paper acquaint the geologist, as well as the engineer, with the large-diameter core drill and the technique involved in its use, and also with its advantages, disadvantages and limitations as an implement of geologic exploration. THE EQUIPMENT The equipment generally employed in the drilling of large-diameter holes consists of a trunnion-type drill head mounted on a sliding base, which allows it to slide clear of the hole and thus permit the introduction

Jan 1, 1938