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FOR four years your Committee has been engaged in the study of problems connected with the educational preparation of professional geophysicists. The present report represents the conclusions drawn from the investigations and deliberations undertaken since it was first organized. These studies have shown that the evolution of geophysics has proceeded along lines that differed from those marking the advance of classical geology. The latter science developed as a descriptive one, dealing with directly observable terrestrial phenomena, and the elementary, rational explanations that could be offered therefor. The fact that these phenomena were also chemical and physical in nature was seldom given more than passing acknowledgment. During the last half century, however, a new approach to problems of terrestrial phenomena has become of greater significance. This new attack has come through the sciences of physics and chemistry, as the people trained therein have investigated the facts of the earth as problems in their respective sciences. This development has been chiefly at the hands of European investigators, and European universities have long recognized it by establishing departments or institutions of geophysics. In the universities of North America, their arbitrary departmentalization into fields of physics, chemistry, astronomy, geology, etc., has prevented the academic recognition of such domains of science as geophysics and geochemistry. In consequence, the development of these subjects in the United States has been largely at the hands of nonacademic institutions, while the universities themselves are evidently in a state of confusion as to how the subject should be handled. In some places an attempt to teach geophysics is made in the physics department, in others in the geology department, in some in the engineering school, and occasionally as a cooperative effort; a Department of Geophysics is seldom found in North America. In some instances, proper academic planning has been precluded by interdepartmental jealousies, or by lack of appreciation of the significance of the subject. For the background upon which these conclusions are based, the reader is referred to reports previously issued or sponsored by your Committee. These reports are available from Institute Headquarters. The "First Report of the A.I.M.E. Mineral Industry Education Division's Committee of Geophysics Education, 1939," summarizes the replies received to question-

Jan 1, 1942

By Ming-Kao Yen, W. R. Hibbard

Various rationalizations of preferred orientations in cold worked polycrystalline metals have been based on the operation of at least two three2 five, an indefinite number, and all,6 slip systems of the type occurring in single crystals. Pickus and Mathewson3 suggested that the cold rolling texture in face-centered cubic metals could be rationalized on the basis of two or more operating slip directions symmetrically disposed about the direction of flow in such a manner that the resolved shear stress factor is equal for all operating slip systems and lattice rotations cancel each other. The importance of the direction of flow, the necessity for the operation of slip systems capable of producing the required changes in external dimensions, the maintenance of a common surface between adjacent grains and a symmetrical arrangement of the operating slip systems in order to produce an end orientation which is stable under additional deformation lead to the following rationalization of textures based on the type of slip systems operative in single crystals. The rationalization is intended to explain why certain orientations are suitable for deformational flow without a change in orientation and thus are stable end orientations or ideal texture orientations. It does not attempt to explain how the grains of a randomly oriented polycrystalline aggregate will reach this orientation. The rationalization is based on the following four postulates: 1. The ideal textures for polycrystalline aggregates are the result of reorientations of individual crystals toward the same stable end orientation at which no further reorientation will occur even during additional deformation. Since, in simple slip, the relative orientations of the stress axis and the active slip system determine the change in orientation during slip, it is considered that the orientation of the stress axis with respect to the ideal texture determines what slip systems must be active to retain the stable end orientation. Therefore the stable end orientation should be a symmetrical one around the stress axis with respect to the active slip systems such that lattice rotations resulting from slip will cancel each other and prevent a resultant change in orientation. (Rotational symmetry only—not translation, inversion, nor others—is considered here.) Thus a metal under a pure stress should develop a texture consisting of one or more of the crystallographically symmetrical directions, <100>, <110> or <111> for cubic metals or <0001>, <1010> or <1120> for hexagonal close-packed metals, parallel to the stress axis. 2. Since the active slip direction is the direction of glide during simple slip and thus the direction of maximum shear movement, in the ideal texture the active slip

Jan 1, 1949

By Arthur Winslow

Location.—The Liberty Bell gold-mine is in the San Juan region, in the southwestern corner of Colorado. It is situated about 2 miles from the town of Telluride, near the summit of the Uncompahgre range, at the head of Cornett basin, at an altitude of 11,000 feet, and in a district of excellent record in the past and of great promise for the future. In the immediate vicinity are such well-known and important mines as the Smuggler Union, with a total production of over $12,000,000; the Virginius and Revenue Tunnel group, with a production of probably $5,000,000; the Tom-Boy, with a production of probably at least $3,000,000; the Japan, the Cimarron, and a number of others. History.—The first prospecting in this district is reported to

Jan 1, 1900

By Anson Hayes

THE quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The varia-tion in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the British Iron and Steel Institute.1 From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots.

Jan 1, 1938

By W. Spencer Hutchinson

The experiments described in this paper were undertaken primarily for the purpose of measuring the quality of work done in screening and sorting in American concentrating-mills for Prof. Richards&apos; work on Ore-Dressiag. For this purpose a series of samples of screened and sorted products was obtained from four different mills, and a plan was devised for sizing these products, and for tabular and graphic representation of the results. The results, together with discussions as to their significance, so far as they serve to interpret the quality of mill-work, have already been published in the above-mentioned work, and it is not the purpose of this paper to duplicate the work, except so far as is necessary to explain and illustrate methods and appliances. The sizing of coarse products was clone by sifting on screens of sheet-metal with round punched holes. These holes ranged in size from 64 mm. to 0.5 mm. in diameter. Below the smaller limit, punched metal, suitable for this work, was not obtainable, and the sizing was carried on by sifting on woven wire-sieves. The finest woven wire-cloth obtainable gave a hole 0.073 mm. square, and the finest silk bolting-cloth pave a pentagonal hole with an average diameter of 0.069 mm. Even these very fine screens served no useful purpose in sifting certain of the very fine classifier-products, of which all, or nearly all, passed through the finest screen. A new adaptation of a method of settling and decantation with water in beakers was therefore worked out, and by this means the sizing mas carried down to grains of a diameter as small as 0.012 mm. Description of Apparatus and Manipu1ntion.—Sieves of sheet-metal with round punched holes were used as far as practicable, chiefly because, as already explained, the primary object of the experiments was to test mill-work, and the mills had all used

Jan 1, 1905

By C. F. Cigliana

TO accommodate a large tonnage at high speed from a single level at San Manuel, a very flexible haulage system was designed to give maximum access to stoping areas, minimize delays, and pro- vide for safety. With these requirements as a guide, the haulage was laid out as a simple double loop with one-way traffic of continuous pull. These loops consist of two parallel drifts 100 ft apart, center to center. Haulage drifts are numbered from north to south, the northernmost being the No. 1 drift. This holds true on both the North and South haulage loops. Haulage drifts are connected at 1000-ft intervals with crossovers so that it is possible to bypass any given section that may be inaccessible. Two of these turnouts are double diamonds, one located on the approach to the rotary dumps at the hoisting shafts and the other on the departure from the dumps. The turnout on the approach or North haulage is 835 ft in front of the rotary dump, and the one on the departure, or South haulage, is 1058 ft from the dump. This type of turnout allows trains coming down either haulage drift No. 1 or No. 2 to be routed into either shaft and expedites movement by avoiding delays due to congestion in the dumping area. The double diamond on the return haulage loop facilitates returning empty ore trains to the panels.

Jan 5, 1958

By R. J. Borg, C. E. Birchenall

Vapor pressures of eight compositions of Mg-Cd have been determined by the Knudsen effusion technique. Measurements are made at several temperatures for each alloy and the results interpolated to a common temperature for the calculation of the activities. It is not possible to obtain values for the partial molar enthalpies because of the narrow temperature range spanned by the measurements. The results show less precision than those obtained for pure Cd which are also reborted. These alloys are extremely susceptible to corrosion which provides a possible explanation for the lack of precision. Nevertheless, the values of the activity are in good agreement with the results of electromotive force measurements previously reported for the Mg-Cd system. MAGNESIUM and cadmium are mutually soluble in all proportions in the solid state and form a single phase which has the hexagonal close-packed structure. X-ray investigations of this system1,2 have revealed a rapid variation in the relative dimensions of the unit cell occurring at approximately 50 at. pct. The rate of change of the c/a ratio with composition increases markedly for alloys containing more than 50 at. pct Cd. The purpose of this investigation was to determine the activity of Cd in the neighborhood of 50 at. pct and to discover whether or not the thermo-dynamic properties undergo a similar rapid change. The activities are calculated from vapor pressure data obtained by the Knudsen effusion method. Unfortunately the precision of the data from which the thermodynamic values are calculated is insufficient to establish unequivocally a departure from the normal trend. The results are reported primarily because they substantiate the only previously reported activity measurements3 and because they include values for pure Cd which in contrast to those of the alloys show excellent precision. The Cd-Mg system is known to contain several ordered phases. However, this investigation was made at temperatures considerably above the transition temperatures, and the alloys may be regarded as nearly random solid solutions. EXPERIMENTAL Apparatus—The effusion cells are machined from solid tantalum rod. The lids consist of threaded, flanged rings of tantalum onto which are welded shallow cups of 4 mil molybdenum foil. The orifice, which is located at its center, is made by grinding off a small dimple produced with a sharpened punch. Such an orifice has been mounted in plastic, sectioned, and the thickness of the orifice edge measured in a microscope. The maximum thickness is 0.00016 in., and the Clausing factor is consequently equated to unity. The area of the orifice is determined by tracing its projection on the screen of the metallograph at a known magnification and measuring the area of the tracing with a planimeter. Excellent temperature control is achieved with a 4 by 18-in. alundum core, gradient-wound, furnace

Jan 1, 1960

By C. W. Washburne

Recently, Messrs, Mills and Wells1 published a thorough chemical study of the waters associated with oil in parts of the Pennsylvania, Ohio, and West Virginia region. Many of their conclusions are of general application and the writer wishes to discuss some of these. Messrs. Mills and Wells show that the composition of the deep brines oi the Appalachian fields is such as would be produced by the evaporation of sea water and the precipitation of sodium chloride, combined with reactions with hydrocarbons and other substances. The brines are altered, also, by considerable mixing with meteoric water. They give good reasons for believing that the concentration of the brines was produced by evaporation in the rock pores induced by migrating gas, much of which probably escaped to the surface of the ground. This hypothesis was considered by the writer in a former paperJ2 in which main stress was laid on a second hypothesis, that the excess of chlorine in the deep brines may have been due to the entrance of solutions rich in magnesium and calcium chloride which ascended from a deep, possibly intratellurie, source. Messrs. Mills and Wells present good arguments for the first hypothesis. Underground evaporation by ascending gases probably will be accepted as the best available explanation of the concentration and composition of deep well waters. They have not considered the possibility that salt waters in deep sands may be concentrated by the diffusion of water vapor through gas into shale. The writer has given reasons3 for believing that capillary forces concentrate gas and oil in the larger openings of rock, such as the pores of sandstones embedded in shale. The gas underground must be nearly saturated with water vapor at all times, because it always is in contact with the interstitial water of enclosing shales and of the sandstone. Experimental studies of soil moisture have shown that approxi-

Jan 1, 1921

By G. Derge, M. Bourgon, G. M. Pound

A STUDY of electrical conductance in molten Cu-Fe sulfide mattes&apos; has shown that pure molten Cu,S behaves like a semi-conductor in that it is an electronic conductor and its specific conductance, of the order of 100 ohm-&apos; cm-&apos;, increases with increase in temperature. On the other hand, pure molten FeS, another electronic conductor, behaves like a metallic conductor in that its specific conductance, about 1500 ohm-&apos; cm-&apos;, decreases with increase in temperature. Molten solutions of Cu,S and FeS follow a roughly additive rule of mixtures with respect to both specific conductance and temperature coefficient. The behavior of molten Cu,S may be understood, by analogy to the situation in solids, in terms of semiconductor theory.&apos; It is thought that, although the melt consists of cuprous and sulfide ions, the bond between these atoms has a certain degree of cova-lency. According to the simplest concept the electrons in the partially covalent bonds are thermally promoted to a conduction band. In another concept, small amounts of impurities (undetermined) provide donor or acceptor levels in the forbidden zone between the valence and conduction bands and thus facilitate semi-conduction in the usual way. However, the metallic behavior of molten FeS is difficult to explain, because one might expect from similar reasoning that it too should act like a semi-conductor. It was suggested that the apparent metallic behavior of molten FeS might be explained by a large negative temperature coefficient of density. Thus if molar conductance instead of specific conductance were plotted versus temperature, the slope might prove to be positive, indicating semi-conduction instead of apparent metallic conduction. Accordingly, density measurements were made in order to answer this question in regard to molten FeS and also to provide data for conversion of specific conductance to molar conductance for molten Cu,S and a molten 50-50 wt pct Cu-Fe sulfide matte. Experimental Diagrams of the apparatus are given in Figs. 1 and 2. A 3 x 8-cm dense alundum crucible containing the prefused specimen is positioned in the uniform temperature zone of an induction furnace tube and melted under a helium atmosphere. Then the cell assembly, consisting of two 3-mm spectro-graphite rods, one of which is in a 1-cm ID open

Jan 1, 1959

By Carl R. Davis, J. L. Willey, S. E. T. Ewing

The first tube-mill on the Rand was put into operation in May. 1904, at the Glen Deep Mine. From that time onwards, tube-mills were added to various plants, although little was known regarding the capacity of a given tube-mill when working on banket ore. Within a few years, however, the so-called standard size (length of shell, 22 ft. 0 in.; diameter, 5 ft. 6 in.) was generally used until the last year or two. Practically the only exceptions were about 30 tube-mills having a length of 16 ft. and a diameter of 6 ft., and a few open-end mills of the roller-supported type. Most of the information obtained during the last 15 years has been obtained with mills of the standard dimensions. The adoption of the tube-mill as an accessory to the stamp mill was rapid; and where 3 tube-mills were working on the Rand at the end of 1904, 244 were in use seven years later.&apos; By 1910, good practice provided 1 tube-mill for 20 stamps of 2000-lb. falling weight. The horsepower of the motors driving the tube-mills had increased from 80 to 100 and then to 125 at this date. Broadly speaking, current practice at that date aimed at a ha1 product of which 60 per cent. was suitable for sand treatment and 40 per cent. for slime. The sand grading was +60 mesh, 6 per cent.; +90 mesh, 25 per cent.; — 90 mesh, 69 per cent.; and the slime grading +200 mesh, 2 per cent.; —200 mesh, 98 per cent. It was recognized comparatively early that the tonnage of — 90-mesh product produced by a tube-mill per 24 hr. was a convenient measure of

Jan 1, 1925

By T J. Orr

The changing demographics of the mining industry make successful passing of knowledge and skills to the next generation critical. Training methods and technologies are being developed to meet this need. Twenty years ago classroom training was largely a one-way transfer of knowledge through instructor lectures. In contrast, instructors today can use virtual reality technologies to guide trainees as they fully participate in learning experiences. Trainees can interact with the virtual work environment, co-workers, and equipment without being exposed to workplace hazards. The speed of advancement in mine safety, health, and production training shows no sign of slowing in the next 20 years. Researchers at the National Institute for Occupational Safety and Health have studied and participated in the evolution of miner training. A look at training materials they have created in the past and those they are currently developing reveals changes in methods and technologies over time and also key characteristics which have remained constant. Possibilities for the future can be discussed in the framework of an implementation of virtual reality in new miner training sessions. The example computer-based training package teaches new miners to read mine maps and provides opportunity to practice navigation skills in a virtual mine. With this æserious gameÆ, trainees experience the look and feel of moving through an underground coal mine while in the safety of their classroom. During field-testing in 2007, trainees and instructors responded very favourably to this new way of learning. The software was usable by mine trainers with even limited computer expertise and could be installed on the affordable computers they were using for their more traditional slide presentations. The Underground Coal Mine Map Reading TrainingÆs foundation on past successful development strategies and its acceptance by todayÆs instructors and trainees provide valuable lessons for developing training materials, strategies, and technologies for miningÆs future.

Jan 1, 2008

By Albert Sauveur

AT the New York meeting of the Institute, February, 1914, Professor Hopkinson and Sir Robert Hadfield presented an important paper entitled Research with Regard to the Non-Magnetic and Magnetic Conditions of Manganese Steel.1 Any contribution on manganese steel by its discoverer necessarily carries with it much weight and is entitled to serious and close consideration. The momentous discovery of that alloy by Sir Robert Hadfield some 30 years ago was the signal for great activity in the field of alloy steels; and the remarkable results obtained in the last two decades probably constitute the most important modern advance in the metallurgy of steel. The authors of the paper referred to above are unable to reconcile with the allotropic theory the interesting results obtained by them in heat treating manganese steel. When they speak of the allotropic theory, however, I understand that they have more especially in mind the existence of beta iron. It is not my understanding that they question the occurrence of iron in the two allotropic varieties known as gamma and alpha. If I am wrong, I trust they will correct me. A careful consideration of the experimental results reported and discussed by the authors leads me to believe that on the contrary they can be very satisfactorily explained in terms of allotropy and that, in the light of our present knowledge, they cannot be accounted for in any other way. The physical properties of non-magnetic manganese steel described by the authors are those pertaining to iron-carbon alloys in which iron is present in the gamma condition, or, in other words, to austenite. The metal is then characterized by great tenacity and ductility and low elastic limit, while its hardness, mineralogically speaking, is not excessive, but of a special kind termed "tough hardness" by the authors. Even when subjected to the restraining influence of a large amount of manganese and of considerable carbon, however, relatively rapid cooling

Jan 9, 1914

By George J. Young

DURing the spring of 1910 1 visited a number of open-pit brown-coal mines and underground workings in the vicinity of Halle, Halberstadt, Leipsic, Cologne and Bonn. The notes which I took and the observations which I made at the time have been condensed and make up the principal part of this paper. Certain supplementary information has been taken from several sources which are given in the paper. The mining of brown coal is one of the important industries of Germany. The coal varies in color from dark brown to almost black and is soft like loam. Pieces of wood and strips of bark and even parts of tree trunks are frequently encountered in the excavation although the coal for the most part consists of a pulverulent, more or less matted mass of small particles of vegetal matter. It is a product between peat and lignitic coal. An analysis, taken from Coal Resources of the World shows the approximate composition of the material: Moisture, 53.73 per cent.; ash, 4.98; fixed carbon, 18.08; volatile carbon, 23.31 per cent. Thc principal characteristic is the amount of moisture. This seldom runs less than 48 per cent. The ash is usually low and ranges from 5 to 10 per cent. The sulphur content is usually less than 0.5 per cent. The heating effect of the fuel ranges from 2,000 to 2,500 calories. The commercial deposits are confined to the Tertiary period although

Jan 1, 1916

By C. E. Lawall, C. T. Holland

When this study was started very little information was available regarding the physical characteristics of West Virginia coals. This was particularly true of friability and of crushing strengths of the coals. Some work had been done on specific gravity studies but the available information applied to only a few coals. In practically all coal-classification systems thus far proposed, the predominating factors of classifications are largely based on the chemical characteristics of the coal. Recently some investigators have pointed out that a classification based on chemical and physical properties of coal might serve to place coals in their proper group better than classification systems based on chemical properties alone. One of the aims of this study was to obtain some data on the physical properties of coal which might help to classify West Virginia coals. The Samples Fig. I shows where the coal samples were obtained and the approximate division line of the high and low-volatile coal fields of the state. The relative geological horizons of the coal beds tested are shown in Fig. 2. In securing samples of coal for friability and specific gravity tests, it was the aim always to obtain a representative sample of lump coal produced at a particular mine. The samples were obtained from the loading boom, the railroad car, or the mine cars. Wherever it was possible to secure samples from a loading boom they were taken from it by taking shovelfuls of coal from the loading boom every minute until about 200 lb. of coal was obtained. If there were no loading booms used at the mines sampled, the coal sample was taken from a loaded railroad car by systematically taking shovelfuls of coal at definite intervals over the whole top of the car until about 200 Ib. of coal was obtained.

Jan 1, 1932

By H. A. Kuhn

THE Pittsburg coal field in western Pennsylvania, is conceded to be the most important in the world. To measure its importance it is necessary to understand the extent of its service in the various industries of the country. Probably 90 per cent. of the pig iron manufactured in the United States up to the present time has been made by using coke manufactured from the Pittsburg coal seam in western Pennsylvania. This coal field is the foundation on which the city of Pittsburg rests and is the reason for the great growth of the iron industry in the Pittsburg district. Iron ore is brought to this district, not because Pittsburgh is a. natural location, over other locations, for the iron and steel industry-as its position places the manufacturer at the mercy of the railroads-but the ore is brought 1,100 miles to meet the fuel. It can be said that the illuminating-gas industry in the United States has used this coal exclusively to the same extent that the pig-iron maker has used it. It may be also said that 20 to 25 per cent. of the fuel used on railroads in the United States conies from this coal field. The Pittsburg coal field is unquestionably the center of the industrial population of the United States, for in addition to the industries of the district and those closely adjoining, it has tributary to it all the cities and industries along the Great Lakes and practically all of Canada with the exception of the extreme western and eastern ends. It supplies the industries and population west of Duluth and Superior many hundreds of miles. This coal is floated down the Ohio and Mississippi rivers, supplying the towns en route, and is delivered in New Orleans, a distance of 2,200 miles, for approximately SO to 90 c. per ton transportation cost. It is delivered on the docks of Superior and Duluth at a cost of transportation 50 c. a ton less than the cost of transporting the same coal from Pittsburg to a local consumer in Philadelphia. With other Appalachian coals it has large markets east and along the seaboard, especially for byproduct-coke making and the illuminating-gas industry. It is considered the premier railroad fuel of the world on account of the fact that this coal in a given-sized locomotive will probably haul more cars than any other coal in the

Jan 10, 1914

Virtually all mineable Appalachian coal seams exist in a multi-seam environment. This makes it inevitable that most seams will eventually experience interaction induced ground control and mining problems. Indeed, it has been estimated that every working face will experience interaction effects from previous or current workings at least once during its lifetime (1), and that these problems are considerably exaggerated when seams are in close proximity -- a distance of less than 110 feet. The continued increase in multi-seam problems has resulted in considerable research activities over many years (2,3,4,1). Theoretical analysis, numerical and physical model studies, statistical and empirical analysis of numerous interaction related field data have been applied to multi-seam mining situations and have identified many useful trends and design criteria (4,5,6,7). To fully utilize research results and transfer multi-seam mining technology to field engineers, a design model -- USEAM was constructed (8). This model, designed for close seam under-mining situations, was computerized to facilitate utilization. In the current research, a new computer program "MSEAM" was developed to produce a model for both under- and overmining close seam situations. It is hoped that both of these software packages will aid field engineers in using important interactive design criteria to gain a better understanding of interaction mechanisms. Through advance planning with these programs, detrimental interaction may be avoided and minimized, and occasionally a design can be selected which will allow interaction effects to be utilized to the benefit of mining operations.

Jan 1, 1987

By R. L. Robinson, P. DeFrank, R. F. Hatfield

Production equal to or greater than open-hole completions is possible through perforated completions if the flow paths throughout the perforations are free of obstructions.&apos; Previous investigations have indicated that, in some cases, maximum productivity is not obtained due to plugging of the perforations with debris from the wellbore fluid and/or debris from the perforating process. Control of wellbore fluid and proper well completion techniques are very important in the elimination of perforation plugging.&apos; Selection of properly designed perforating equipment also is quite important for maximum well productivity. Studies made with the use of the perforation flow laboratory, in which perforating tests are run under simulated well conditions, have shown that perforation plugging occasionally occurs. Plugs in perforations result from various causes. One of the contributors to plugging that can be controlled by the perforating device is the slug or carrot resulting from jet perforating. This condition has undergone extensive study, and previous developments have resulted in a decrease in carrot size—but not in complete elimination. It was felt that, if a method of completely eliminating the carrot could be found (with charge performance equal or better than previously obtained), a significant contribution would have been made. Such a charge has been developed and is reviewed in this paper. THEORETICAL CONSIDERATIONS OF CARROT ELIMINATION There are several popular theories of how a shaped charge jet is formed."," One of these is the hydrodynamic theory, wherein the liner is treated as a fluid under the impact of the explosive forces. Another is the spalling theory, where the interaction of shock waves in the liner causes small particles to be torn from the inner surface of the liner and projected at high velocity toward a common focal line to form the jet. It is not unreasonable to assume that both of these theories may be partially correct. For purposes of our discussion, it is simpler to use the second theory. Generally speaking, when a plate of metal is attacked by an explosive shock pulse, the pulse is transmitted through the metal at high velocity, as shown in Fig. 1(A). Pressures at the shock front may be 6 X 10&apos; psi or higher. This shock wave (a compression wave) upon striking a free surface, Fig. 1(B), is partially reflected back as a tension wave. The interaction of the tension wave with the decaying compression wave causes a stress concentration in the metal; when this stress becomes great enough, a failure occurs and a small particle flies off and is projected away from the metal surface, as shown in Fig. 1(C). A new free surface is then presented to the shocks; the process repeats itself until there is no longer enough energy to cause failure, leaving a portion of the metal relativcly untouched. See Fig. 1(D). To apply this theory to a perforating shaped charge, consider the flat plate to be folded into a somewhat conical shape, with a column of explosive placed in intimate contact with the cone (Fig. 2). An explosive initiator detonates the charge, creating a shock wave

By R. S. Archer

In the microscopic examination of aircraft-engine parts made of heat-treated alloy steels, the writer has been forcibly impressed by the failure of the usual etching processes to disclose any but gross defects in heat treatment. It seemed particularly desirable to bring out the grain size of the steel, which is indicated in the ordinary etching processes chiefly by the change in orientation of structure from grain to grain. After various attempts, a fairly successful method has been found, which is here presented in the hope that it may be of use to those who have occasion to examine these steels in the hcat-treated condition. The specimens worked with have been mostly chrome-nickel steels heat treated (that is, hardened and tempered) to a Brinell hardness of around 300. A few experiments with other specimens will be referred to later. Briefly, the method employed consists in etching the steel about 10 min. in a fresh solution of picric acid in ethyl alcohol, and then rubbing off the smudge of carbonaceous matter on moist broadcloth. Different samples of almost identical analysis, heat treatment, and physical properties (including resistance to impact) respond quite differently to this treatment. In some, the grain boundaries are developed quite readily, while in others, especially in those whose grain is unusually fine or in which the final hardening heat has not quite obliterated the previous crystallization, the results are more obscure. The exact time of etching to secure the best results also differs for various samples, and the greatest success is usually attained by a process of "tinkering." Such a process is illustrated in a series of micrographs, the first six of which were taken at a magnification of 300 diameters. The properties of the steel are as follows: Carbon, per cent............... 0.42 Brinell hardness.............. 293 Nickel, per cent................ 1.35 Yield point, pounds per square Chromium, per cent............. 0.90 inch........................ 131,000 Copper, per cent................ 0.025 Maximum strength, pounds per Manganese, per cent............ 0.74 square inch................. 144,500 Phosphorus, per cent............ 0.024 Elongation in 1 in., per cent... 28 Sulfur, per cent................ 0.036 Lod impact, foot-pounds...... 51 Reduction of area, per cent...... 57.3

Jan 1, 1920

By S. W. Zanolli

The history of labor relations in the coal industry of the United States is a study of its collective bargaining. This study of collective bargaining is largely the history of the United Mine Workers of America and its contractual relations with the various coal mining employers who have produced this country&apos;s coal over the years under a free enterprise system. There have been other unions in the picture from time to time and some coal miners have mined coal without representation by any union. Even today some 25% of the nation&apos;s coal is produced outside of the collective bargaining relationship with the UMWA. However, more than 100,000 coal mine wage employees - well over 75% of the total in the industry - are covered by labor agreements negotiated for them by the UMWA. Practically all of these work in bituminous mines.

Jan 12, 1972

By William E. Ford, Edward Salisbury Dana

I. Oxides of Silicon. 11. Oxides of the Semi-Metals : Tellurium, Arsenic, Antimony, Bismuth ; also Molybdenum, Tungsten. III. Oxides of the Metals. The Fifth Class, that of the OXIDES, is subdivided into three sections, according to the positive element present. The oxides of the non-metal silicon are placed by themselves, but it will be noted that the compounds of the related element titanium are included with those of the metals proper. This last is made necessary by the fact that in one of its forms TiOz is isomorphous with MnOp and PbOz. A series of oxygen compounds which are properly to be viewed as salts, e.g., the species of the Spinel Group and a few others, are for convenience also included in this class.

Jan 1, 1922