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By John Chipman, Eric R. Jette, O. B. Ellis

In the study of the chemical reactions orcurring in the open-hearth furnace, it is frequently assumed that a condition of equilibrium between slag and metal is attained. In order to test this assumption it is necessary to have dependable operating data as well as an exact knowledge of the equilibrium state. Considerable progress has already been made in the study of slag-metal equilibria, notably in the earlier work of Hertyl and of Oberhoffer and Schenck2 and in the more recent researches of Krings and Schack-mann3 and of Koerber and Oelsen.4 None of these investigators, however, have employed basic slags comparable to those encountered in basic open-hearth practice, so that up to the present time our only information regarding the equilibria of these slags is based upon observations drawn from steelmaking practice in which there is little assurance that actual equilibrium was attained. The original plan of this investigation was to secure simultaneous slag and metal samples at intervals during the making of an open-hearth heat, recording the heat history in detail and obtaining complete allalyses of slag and metal, then to bring these slag samples into equilibrium with liquid iron in the laboratory induction furnace and thus to determine directly whether or not the observed relationships in the open hearth represent conditions approaching equilibrium. This plan was only partly successful. While slags were obtained from the open hearth under satisfactorily recorded conditions and these were re-melted in the laboratory under equilibrium conditions, changes in slag composition, which accompanied the remelting operation, were so great that the final slag from the induction furnace bore little resemblance to its open-hearth parent and the direct comparison was therefore abnndoned. The results, however, lie within a range of slag composition that is of interest in the making of low-carbon steel. As far as we are aware, they represent the first published laboratory study of equilibria involving slags that contain all the con stituents of basic open-hearth slag. Experimental Heats The first set of measurements on slag-metal equilibrium was made in the Research Laboratories of the American Rolling Mill Co, at Middletown, Ohio. This will be known as series A. The second set was made in the Metallurgical Rescarch Laboratories at Massachusetts Institute of Techology, and will be referred to as series B. Series A.—The induction furnace used has been described. Approximately I kg. of a special ingot iron containing less than

Jan 1, 1941

By Thomas Leonard Watson

Sulphide ore-bodies of more or less lenticular shape occurring in metamorphic crystalline schists, gneisses, and slates, and conforming closely in strike and usually in dip to the inclosing rock, have been recognized and described along the Atlantic seaboard from Quebec to Alabama. The ore-bodies do not entirely conform, in all cases, to the structure of the inclosing schists, but they sometimes cut across the foliation in dip, though conforming more closely with the direction of strike. In composition the principal sulphide mineral is usually py-rite or pyrrhotite, or both, accompanied by copper, frequently gold, and almost always some sphalerite and galenite. Other metallic ores are, so far as these sulphide bodies have been investigated, less common; silver is not uncommon, and in some of the pyrrhotite masses nickel is present in quantity sufficient to be commercially valuable. Cobalt frequently accompanies the nickel, usually in smaller amount, and the two vary much in relative proportion. Quartz and calcite are probably the most common of the non-metallic minerals. A number of silicate minerals are frequent representatives in one place or another ; garnet, am phi-bole, biotite, pyroxene, zoisite and others. The sulphide bodies of Virginia, comprising both pyrite and pyrrhotite, are among the most extensive along the Atlantic seaboard. Among the pyrite bodies may be mentioned the well-known and extensively worked mines of Louisa and Prince William counties, located on the main pyrite belt (A, Fig. 1) of the middle and northern, eastern Piedmont region in Virginia, and among the pyrrhotite bodics is the famous " Great Gossan Lead" (13, Fig. 1) of the Floyd-Carroll-Grayson coun-

Jan 1, 1908

By R. I. Jaffee, H. R. Ogden, D. J. Maykuth, W. L. Finlay

Titanium with up to 7.5 pct Al forms single-phase a alloys that are work hardening, not heat treatable, and ductile as welded. The high aluminum Y phase alloys are not usefully ductile, despite their low hardness, but they have excellent oxidation resistance and hot hardness. LITTLE has been published on the effect of aluminum on the mechanical properties of titanium, despite the fact that two of the first four commercial alloys released by titanium alloy producers contained aluminum as an important alloying ingredient. These were both a-ß type alloys, one containing 4 pct A1 and 4 pct Mn and the other containing 3 pct A1 and 5 pct Cr. However, neither of these alloys reflects the true alloying nature of aluminum, since each contains important amounts of the ß-stabilizing addition, manganese or chromium. In a previous publication on the constitution of Ti-A1 alloys,' the authors showed that aluminum had a high solubility in a titanium and was strongly a stabilizing in nature. About 25 wt pct A1 is soluble in a titanium at room temperature. With as little as 5 pct added aluminum, the a transus temperature is increased from 882" to 970°C, and the correspond- ing ß transus to 995°C. The first intermediate phase in the Ti-A1 system is the ordered face-centered tetragonal TiAl phase, which extends from 34 to 46 wt pct Al. The present paper presents hardness data over the entire titanium-rich region of the system, through the TiAl phase, and mechanical property data on the alloy range capable of being fabricated. Methods of Investigation The materials used and general preparation of alloys, as well as experimental techniques used in the investigation of Ti-A1 alloys, have been adequately described.' Briefly, the preparation consisted of arc-melting the desired amount of high purity aluminum (99.99 pct purity) and iodide titanium (maximum hardness 100 Vickers, as deposited) together on a water-cooled copper hearth under a partial pressure of argon. The resulting button ingot was of such form that it could be fabricated without further treatment. All work was done using ingots weighing 10 to 15 g, which were hot-rolled to strip form whenever possible. Tensile samples were 3.25 in. long, 0.5 in. wide, and 0.040 in. thick, with a reduced section 1.25 in. long by 0.250 in. wide. The gage length used was 1 in. Electrical strain gages mounted on the

Jan 1, 1954

By L. L. Swift

AT the present time there are four base metals being used for automo-tive bearing alloys. Of course there are numerous variations in the amounts of alloying elements added to each base metal and nearly all of these alloys have the conventional, if not classical duplex structure; that is, they are composed of a hard constituent embedded in a soft matrix. The well-known theory is that the former will wear well, while the latter will be plastic enough to allow the bearing to be broken in and conform to the contours of the shaft. The requirements of the modern bearing have been most aptly described by W. M. Corse: In order to meet the engineering demands of today a good bearing metal must be able to carry the weight of the shaft and stand up under steady or suddenly applied loads, or even blows in some types of service. A certain amount of plasticity is desired to compensate for minute irregularities in the shaft or bearing surface, and to permit yielding, thereby avoiding dangerous stresses in bearing and shaft and pre-venting overheating and rapid wear of parts. Less plasticity is required in a bearing metal if the surfaces of bearings and journals are machined accurately, aligned, and kept in alignment. It is desirable, of course, that a bearing metal have a low coeffi-cient of friction. Under most operating conditions the friction depends on the unit pressure of the bearing, the speed, the temperature, and the properties of the lubricant. A good bearing metal must have a low rate of wear to reduce the necessity for frequent replacements, and adjustment of the bearings. It must wear more rapidly, however, than the journal or shaft running on it, because replacement of the journal or shaft is more difficult and costly than replacement of the bearing.1 The hardness of the bearing alloy is a property closely related to several of the foregoing. With a duplex microstructure, the measure-ment of hardness with any of the usual commercial devices means little. The Bierbaum method of measuring the hardness of the individual constituents was developed to fill this need.

Jan 1, 1938

By J. L. Dumanoir, Maurice Martin

The induction-electrical log is a combination of a SP curve, a short normal curve, and an induction log; all three logs being recorded simultaneously in a single run. The spacing of the short normal is 16 in. The induction log is designated as 5FF40, which means that the sonde involves five coils and a focusing system, and that the distance between the main coils is 40 in. Examples of induction-electrical logs are shown in Figs. 13 and 15. The right-hand track contains the induction conductivity curve. The scale of this curve is linear with the units of conductivity, i.e., mhos/m or millimhos/m (mmhos/m), increasing from right to left. The same curve can be read in the reverse direction as a resistivity log, with a hyperbolic scale. In the middle track, the solid curve represents the short normal. (An amplified short normal is also shown in Fig. 15). The dotted curve is the resistivity curve of the induction log, i.e., the reciprocal of the conductivity curve, recorded with the same linear scale as the short normal. The SP is in the left-hand track. In this combination, the SP curve and the 16-in. normal are the essential correlation curves, as in the conventional electrical log. The induction log provides a more accurate and detailed record of formation boundaries than the conventional log, especially in hard rock territories. Furthermore, the induction-electrical log makes possible the determination of fluid content, particularly in thin beds—at least qualitatively and very often quantitatively. In such thin beds, because of the adverse effect of the adjacent formations, the responses of the conventional devices are generally doubtful and/or incom-plete. Another advantage of the new combination is that the induction log is little affected by the presence of thin hard streaks interbedded within the permeable sections, whereas such occurrences are the cause of serious distortions of the long normal and lateral curves. The evaluation of saturation from any resistivity log implies the knowledge of the true resistivity R, of the bed and of the resistivity R.. of the flushed zone, or at least of the ratio Rxo/Rc. With the induction-electrical log run in fresh mud, the 16-in. nor-mal has a smaller radius of investigation than the induction log, so that the former reads closer to R.. and the latter closer to Rt. Thus, it has been observed that the ratio of the 16-in. normal to the induction log readings can be used as a basis for the interpretation in terms of saturation, with the help of appropriate charts. The purpose of the present paper is essentially to explain this procedure and to provide the corresponding charts. On the other hand, when a formation is deeply invaded, the response of any log (in particular the induction log) depends upon the radial distribution of formation resistivities behind the wall of the hole, which itself is a function of the arrangement of the fluids saturating the formation pore spaces. This paper, accordingly, will begin with a schematic description of the distribution of fluids and resistivities in the invaded zone. Next, some essential characteristics of the induction log will be reviewed. Finally, the determination of the interpretation charts and their application will be explained. The discussion will be confined to the case of fresh muds, i.e., muds whose resistivity is at least five times as great as that of the formation waters. With the present equipment the induction log is not well adapted for logging in salty mud. The Laterolog and guard electrode log are at their best under conditions of low resistivity mud. Accordingly, when these tools were introduced a few years ago, the use of salty mud was recommended. Now, with the introduction of induction logging, spe-

Jan 1, 1958

By Arthur Boynton

IN THE preparation of this paper the writer has been influenced by the fact that descriptions of various means of cleaning blast-furnace gas have been published and that further descriptive treatment of the subject will probably be less interesting than a statement of conclusions with regard to preferable methods which have been reached by him as a result, of experience and observation in this country and also as a result of somewhat detailed investigation of the subject made toward the end of the year 1927 on the Continent of Europe and particularly in. Germany. Owing to various circumstances, including a cost of fuel that is extremely high in relation to the wages of labor, the German iron and steel industry has accumulated experience in gas washing which is as yet in part lacking in the United States of America. The paper begins with a statement regarding the economics of the use of blast-furnace gas, then considers the principle's and practices employed in its purification. USES OF BLAST-FURNACE GAS For many reasons having to do with the utilization of coke-oven and blast-furnace gases in steel manufacture and with the use of hot metal, the blast furnace is now usually a part of a steel-producing unit, which also includes coke plant and rolling mill. Therefore both blast-furnace and coke-oven gas are usually applicable to any of the iron and steel-making processes, including the generation of power, and their allocation in any given works should be considered as a single problem. The uses to which blast-furnace gas, either alone or mixed with coke-oven gas may be put, include the following: Regenerative Heating of Air for the Blast Furnace.-This is the oldest and metallurgically the most important of all uses. It is universally performed with unmixed blast-furnace gas and under proper conditions should require not over 23.5 per cent. of the total gas generated for a blast temperature of 1350° F. For Steam-raising Purposes.-This is almost universally done with unmixed blast-furnace gas. From the standpoint of quantity used, it is at the present time the most important application in American steel-works practice.

Jan 1, 1928

By Thomas W. Dawson

THE H. C. Frick Coke Co. has used belt conveyers for handling coal for the last eighteen years but, until recently, only for small tonnage and over short distances. The first installations were outside the mines for distributing coal to various parts of plants. A belt conveyer was put in service at Colonial No. 4 Mine in November, 1906, to carry coal from the main hoisting shaft to a storage bin serving two blocks of beehive ovens on the other side of the valley; it was in constant service until the Colonial No. 4 ovens were abandoned less than a year ago. This conveyor was in an overhead gallery that spanned our sidings and yard tracks and the main line of the Pennsylvania Railroad. It was a crude installation, from the viewpoint of present conveyor engineering practice. It had no mechanical feeding device, the coal simply ran through a gate in the side of a bin on to the belt; but one belt on this conveyor lasted eleven years. This conveyor is about 300 ft. long center, to center of pulleys. It operated at a speed of 250 ft. per min. and carried about 400 tons per day. On this basis, the belt life of eleven years means that not over a million and a quarter tons were carried by the belt. While this is not a large tonnage, the cost per ton was much less than by any previous method in use for supplying coal to ovens located at a distance from the main shaft. The next belt conveyor was installed at Bridgeport Mine in 1907. It carried about the same daily tonnage as the first, delivering from the hoisting shaft to a coke-oven bin. Very few data were kept on this conveyor. It also operated until the coke ovens at the plant were put out of blast and the coal taken to the Clairton byproduct plant by river. In 1916, work was started to equip the Bridgeport, Palmer, Gates, and Ronco mines to load their entire output on, the river for transportation to the Clairton byproduct plant, which was then being built. These mines were all operating at that time and had a large area of coal available for river shipment. The Monongahela Railroad was located between the hoisting shaft and the river at each of these plants and,, therefore, had to be crossed at each location to deliver coal to the river.

Jan 6, 1925

By Walter Renton Ingalls

IN SEVERAL papers and addresses during the past two years, I have dwelled upon some of the economic consequences of the war. The fundamental thought that I have sought to convey is that the world became immensely poorer by the war, not only in material wealth and population, but also in the psychology and morale of the people. I do not see how there can be any intelligent dissent from that statement. All the ideas of post-war prosperity were manifestly fallacious, manifestly fallacious from the outset. If there had been any truth in them it would have followed logically that a great war, with all its destruction of wealth, health and life would be a good thing. Therefore, let us have a great war every ten years or so. Such an idea would be both monstrous and absurd. Assuming then the acceptance of my premise, I have tried to show that the losses by the war could be made good in a short time, i.e., in a relatively short time, only by doing things a great deal better than formerly, and that the accomplishment of such a result called for greater transparency in industry, for industrial cooperation, for thinking in terms of industries as a whole, and for the greater exercise of engineering functions. All of this introduced, of course, the position and psychology of labor. I say frankly that I do not look for labor to contribute any constructive thought to the upbuilding. I neither expect it nor hope for it. This is a pity, for it could do so much for its own economic advancement if it would. However, it never has done so, but rather has benefited only from the exercise of the talents of the few, and the main hope now is to bring it into a passive state, dispelling the resistive fallacies that developed during the war. Let us briefly examine the nature of these.

Jan 1, 1921

ALABAMA Aldrich -Thomas, D A Altoona -Cain, J Anmston-Cowie, L K Walmsley, W N White, H E Bankhead -Terentieff, V E Bessemer -Abbott, C E Ball, E M McKenzie, W C, Jr Mitchell, F R Morgan, C Thompson, N E Birmingham -Adams, J H Adler, J E Aldrich, T H Aldrich, T H , Jr

Jan 1, 1923

ALABAMA Altoona.-Cain, J. America.-Foreman, J. T. Anniston.-Cowie, L. K. Foster, R. N. Rogers, R. F. White, H. E. Ashland.-Sturdevant, J. C. Bessemer. Ball, E. M. McKenzie. W. C., Jr. Morgan, C. Birmingham.-Abbott, C. E. Adler, J. E. Aldrich, T. H. Aldrich, T. H., Jr. Ashton, J. J. Burgin, G. E.

Jan 1, 1923

By S. V. Krusiewski, J. W. Gabelman

Regional metallogenic zones and areas of equal paragenetic range have been interpreted from a compiled metallogenic map. of Mexico. Mineralization gradients of the pattern subsequently identified extend inland from coastal zones of high-temperature mineralization, and join in a central longitudinal zone of relatively low-temperature mineralization, apparently leaving no zonal room for lowest temperature deposits. The striking regional zoning pattern can be correlated with regional deformation gradients of similar position and orientation. The gradients represent at least three major orogenic cycles in two structural belts. Paleozoic structural belts existed along each coast with deformation gradients diminishing inland toward a narrow, central peninsular craton. The Mesozoic-Tertiary Mexican (Cordilleran) belt covered the entire country with a gradient oriented toward the Gulf of Mexico. Most ore deposits in this belt are of Tertiary age, although Tertiary mineralization gradients seem to have "inherited" the pattern left by Paleozoic tectonic gradients. Mineralization gradients can be used to identify the regions most favorable for the occurrence of selected metals. A metallogenic province is characterized by particular proportions of various metals, and the relative proportions can vary from province to province; but within any province the same intensity of mineralization would produce similar deposits in different places. Declining intensity of minetalization produces different kinds and sizes of deposits in zones that are concentrically arranged around sites of strongest rock alteration. On a regional basis, districts of similar average intensity of mineralization occur in zones that generally parallel some tectonic grain with the result that tectonic deformation has been designated a principal cause of mineralization. Variations in the type and intensity of deformation would determine the type as well as size of metal deposits. Mexico is especially favorable for such a study be- cause of its great abundance and variety of epi-genetic mineral deposits in various lithologic, structural and tectonic environments. The concept is also useful in recognizing portions of Mexico favorable for the occurrence of specific metals. METALLOTECTONIC ZONING IN MEXICO Theory: In studies of individual districts and groups of districts throughout North and South America, areal zoning of metal deposits generally seemed to respond to the paragenetic sequence of iron, gold, copper, zinc, lead, silver, antimony and arsenic, gold and fluorite. However, the definition of district zones is greatly obscured by contemporaneous or rhythmic deposition of metals, especially in the middle of the paragenetic range, and by the common superimposi-tions of different generations of metals. Zones could usually be distinguished only for groups of metals, such as early precious metals, base-metal sulfides, sulfosalts and late precious metals. The best defined zoning in a district is normally the spatial separation of the greatest volumes of altered and metallized rocks.' Exceptions are districts representing the high- and low-temperature extremes of the mineralization range where the former creates a matrix for the latter. In most districts the total quantity of alteration products is greatly in excess of, and appears to be roughly proportional to, the total quantity of metallization products. Subsequent to the bicomponent nature of each district, the most important mineralogical feature is the great excess of one to several metals or minerals which results in a district identifiable as one of predominantly gold, copper, lead-zinc, fluorite, etc., although a great variety of other elements may be present. The para-genetic range for the abundant elements in any district is only a portion of the entire possible range for all the elements representing the complete process throughout the region. Early during investigations of this type, it became apparent that the consistent bicomponent character of districts allows two methods for studying epi-genetic mineralization patterns. One is to identify and plot altered rock "pipes,"* which are easily recognizable in the landscape by their anomalous

Jan 1, 1969

By R. M. Asimow

The magnetization curves for specimezs containing superparmagnetic particles are considered. It is shown that the curves may differ from a Langezlin function because of particle anisotropy, particle interactions , and the presence of a size distribution of particles. The various causes of particle anisotropy are considered, and magnetization curves for specimens with cubic and uniaxial anisotropy are presented. The magnetization curves depend on the In the particle-size below 100A it is quite difficult to obtain quantitative size and shape information on precipitate particles. All of the available techniques have their limitations; however, quantitative applications of superparmagnetism have not been developed as fully as possible due to a lack of analysis of the complete magnetization curve. With such an analysis it appears possible to obtain from a single magnetization curve of a specimen containing randomly oriented SPM (superparamagnetic) particles a quantitative volume distribution and a description of the particle shape.* sign of the anisotropy energy and in the case of a negative uniaxial anisotropy (prolate spheroids) the resulting curves may differ very considerbly from a Langevin function. A graphical technique is developed whereby it is possible to separate out the effects of the size distribution, the particle interaction, and the particle anisotropy. Thus it is possible to obtain quantitative values for both the particle shape and the size distribution. Langevin function2 I/Is = ctnh(HVIs/k T)-k T/HVIS [ 1 ] where I, is the saturation magnetization, V the particle volume, H the applied field, T the particle temperature, k the Boltzmann constant, and I the magnetization in the direction of the applied field. Such behavior is rarely if ever observed in actual systems. One explanation for this is that the SPM particles do possess a significant anisotropy and thus the magnetic energy associated with the particle depends on the direction of magnetization in a more complicated way than for the isotropic particle of Eq. [I]. In general the magnetic energy E of an isolated SPM particle embedded in a nonmagnetic matrix can be expressed as a sum of several contributions: E = Eh + Ed+Es+Ec [2] where Eh is the external field energy, Ed the energy resulting from the particle demagnetizing factor, E, the magnetostriction energy, and E, the crystalline anisotropy energy. In each term we consider only the part dependent on the orientation of the magnetization vector and the particle axes as the shape of the magnetization curve will be determined by these contributions. Following the same procedure used in deriving the Langevin function,

Jan 1, 1965

New York LOUIS D. HUNTOON, Chairman. ARTHUR S. DWIGHT, Vice-Chairman. THOMAS T. READ, Secretary, Woolworth Bldg., New York, N. Y. E. MALTBY SHIPP, Treasurer. GEORGE F. KUNZ, W. De L. BENEDICT. Boston ROBERT H. RICHARDS, Chairman. ALBERT SAUVEUR, Vice-Chairman. AUGUSTUS H. EUSTIS, Secretary-Treasurer, 131 State St., Boston. Mass. TIMOTHY W. SPRAGUE, HENRY A. WENTWORTH.

Jan 1, 1917

By T. Yoshioka, Paul A. Beck

SILICON, germanium, and tin occur with both the white tine-type structure and the diamond cubic structure. In the latter form these elements are semiconductors; in the former they are metallic. The metallic form of germanium and silicon is obtained only under high pressure.' For all three elements the transition from the semiconductor to the metallic state is accompanied by a decrease in the atomic volume of somewhat more than 20 pctily2 Table I. At such a large compression the widening of the s and p bands is sufficient to make the energy gap of 1.1 ev, or less, of the semiconductor disappear, giving rise to the metallic state.*

Jan 1, 1965

By John T. Dickman, Ralph E. O’Dette

Chemical Abstracts Service (CAS) is in the process of evolving a computer-based information system which will process all of the material selected for abstracting in the area of chemistry and chemical engineering and its related fields such as the earth sciences and technologies. This system is already operational to some extent and is expected to be fully utilized by 1971. The objective of CAS is to make chemical and related information more readily available, more usable and more used. Chemical Abstracts handle some 5000 abstracts weekly from 13, 000 journals and patents from 25 nations. These cover all of the 80 CA subject sections which relate to chemistry and also extend into areas of interest to geologists, mineralogists, and mining engineers. In this way, CAS fulfills its objective of complete coverage of its major fields, informative abstracting, and indexing to maximum specificity. The concept of a computer-based information system is that of a single machine-language data base into which the results of intellectual analysis of the literature are entered and from which computer programs produce a variety of publications and services applicable to the needs of a wide range of users.

Jan 1, 1969

By Charles H. Behre

This paper discusses education and training for economic geologists other than petroleum geologists. Candidates enter economic geology through liberal arts colleges, engineering schools and university graduate study. Whatever their backgrounds, rigorous courses are desirable—now conceded in theory, but not adequately recognized in practice. Besides basic sciences (each studied long enough to give a fair comprehension of its basic tenets), a functional command of English and two modern foreign languages is needed, as well as a broad understanding of mining, milling and metallurgy. A year of economics and finance is recommended. Surveying and drafting are essential skills. Yet geology should be represented in each term; otherwise the initial enthusiasm for the science, once contact is broken, may never be regained. A five-year curriculum is thus designed to take care of all major requirements and culminate in the M. S. degree. This curriculum reduces "cultural" courses below the average liberal arts requirements, but this is regarded as necessary. The pursuit of "culture" is assigned, as in most engineering and medical curricula, to extra college years or extracurricular time. To avoid the danger of over-crowding the schooling, the Doctorate in geology is preferred wherever possible. Its two added years should permit wider professional education; more browsing in "cultural" pastures; due attention to broader social implications; and some training in the research now increasingly required of the mineral industry. "In-course" training through cooperation between school and industry is especially advo- cated. The Institute should take the initiative in stimulating this practice. Introduction Training a student in geology for a career in the mineral industry is still a moot question, one that is likely to be looked at from many different angles, each of which will reflect the background of the individual considering it. From what follows, the training of petroleum geologists is omitted since, although theirs is an equally important phase of economic geology, it is based upon different essentials. The general subject was recently effectively discussed, but from a somewhat different viewpoint, by Professor McKinstry.' The practical problems that confront the young mining geologist are highly varied and in the eyes of his employer apparently almost any demands seem justified. The mining executive wants from the mining geologist results related mainly to overall operations, reports or forecasts that are largely recordable on paper and chiefly in terms of "discovery thinking." The local mining engineer may have many specific questions of his own, chiefly relating to details of geology that apply to mining practice, which he will address to the mining geologist; these usually deal with production quantities; frequently also they necessitate the immediate handling of pressing but apparently minor matters: shall the drill be moved; how soon will we encounter the watercourse which made so much trouble for us above? The client employing a consultant often wants advice or good judg-

Jan 1, 1949

By Charles H. Behre

This paper discusses education and training for economic geologists other than petroleum geologists. Candidates enter economic geology through liberal arts colleges, engineering schools and university graduate study. Whatever their backgrounds, rigorous courses are desirable—now conceded in theory, but not adequately recognized in practice. Besides basic sciences (each studied long enough to give a fair comprehension of its basic tenets), a functional command of English and two modern foreign languages is needed, as well as a broad understanding of mining, milling and metallurgy. A year of economics and finance is recommended. Surveying and drafting are essential skills. Yet geology should be represented in each term; otherwise the initial enthusiasm for the science, once contact is broken, may never be regained. A five-year curriculum is thus designed to take care of all major requirements and culminate in the M. S. degree. This curriculum reduces "cultural" courses below the average liberal arts requirements, but this is regarded as necessary. The pursuit of "culture" is assigned, as in most engineering and medical curricula, to extra college years or extracurricular time. To avoid the danger of over-crowding the schooling, the Doctorate in geology is preferred wherever possible. Its two added years should permit wider professional education; more browsing in "cultural" pastures; due attention to broader social implications; and some training in the research now increasingly required of the mineral industry. "In-course" training through cooperation between school and industry is especially advo- cated. The Institute should take the initiative in stimulating this practice. Introduction Training a student in geology for a career in the mineral industry is still a moot question, one that is likely to be looked at from many different angles, each of which will reflect the background of the individual considering it. From what follows, the training of petroleum geologists is omitted since, although theirs is an equally important phase of economic geology, it is based upon different essentials. The general subject was recently effectively discussed, but from a somewhat different viewpoint, by Professor McKinstry.' The practical problems that confront the young mining geologist are highly varied and in the eyes of his employer apparently almost any demands seem justified. The mining executive wants from the mining geologist results related mainly to overall operations, reports or forecasts that are largely recordable on paper and chiefly in terms of "discovery thinking." The local mining engineer may have many specific questions of his own, chiefly relating to details of geology that apply to mining practice, which he will address to the mining geologist; these usually deal with production quantities; frequently also they necessitate the immediate handling of pressing but apparently minor matters: shall the drill be moved; how soon will we encounter the watercourse which made so much trouble for us above? The client employing a consultant often wants advice or good judg-

Jan 1, 1949

By Gordon S. Duncan

(New York Meeting, February, 1912 THE U. S. Geological Survey, I believe, has almost completed a study of the Harney Peak quadrangle, preliminary to the publication of a report on that, district. As I was engaged for some months on an investigation of the mode of occurrence of the ore-bearing formation in this area, it has seemed to me timely to make public the results of my study, as a contribution to the consideration of this subject. It seems scarcely necessary to describe the locality and general geology of the Black hills of South Dakota, for since 1846 many have contributed information concerning this region, some of the reports bearing such well-known names as those of Walter P. Jenney, Henry Newton, S. F. Emmons, and C. R. Van Hise, while we have only to glance at Bulletin No. 4 of the South Dakota School of Mines, in which Prof. C. C. O'Harra, of that institution, has given us a bibliography of contributions to the geography and geology of the section, to find that other well-known men have studied the district, and have given us the benefit of their researches. The U. S. Geological Survey has made geological maps of nearly the whole of the Black hills, the only quadrangle yet to be completed being, as stated, the Harney Peak district. During the late summer and autnmn of 1910, it was my lot to examine and report. on a considerable area in this neighborhood, which once had been prospected, and in some cases exploited, for tin. This paper gives an account of certain geological phenomena, noted at that time, which greatly influenced my conclnsions. The predominating formation of the district is pre-Cambrian, represented by a highly-cleaved mica-schist, usually very garnetiferous, and sometimes hornblendic. Rising like an island from the surrounding schist is a large mass of granite, known as

Jul 1, 1912

By A. H. Geisler, R. F. Mehl, C. S. Barrett

The mechanism by which the supersaturated solid solution of 20 per cent silver in aluminum decomposes has been reported in two previous publications.1'2 The analysis of streaks in Laue photograms showed that thin platelike particles (the so-called Guinier-Preston aggregates) form upon matrix planes in the early state of decomposition.1 The size of these particles is larger, the higher the temperature at which they form in accordance with nucleation theory;³ at all temperatures they increase in size with aging.2 When they have grown thick enough to afford three-dimensional diffraction, powder X-ray photograms show that the structure is not that of the equilibrium precipitate but that of a transition lattice . Sincc this is also platelike in shape and also lies upon the (III) matrix planes with the [IIO] direction in the matrix parallel to the [II.O] direction in it seems likely that the original platelet particles are merely in an early stage of formation, and thus finely dispersed. The atomic spacing and pattern on the (00.1) plane in y' are identical with those on the (111) matrix plane to which it lies parallel, and since comparable directions in the two planes are parallel, the lattices are thus coherent at the interface; an analogous coherence has been found in aluminum-copper alloys.3 The structures y' and y are both close-packed hexagonal and are oriented alike; they differ only in interatomic distances. Consequently, y' is regarded as y strained from its ordinary dimensions by the lattice coherency between it and the matrix.2 The lattice movements that transform the matrix to the equilibrium precipitate appear to be very simple.2 The mechanism of precipitation in this system is simpler and is more precisely known than that in any other system hence the system should be a profitable one for the difficult task of correlating property changes with structural alterations. The present report provides additional studies on powder X-ray diffraction from alloys of 10 per cent, 20 per cent and 30 per cent Ag, and presents the correlation of crystallographic changes with changes in microstructurc, Brinell hardness and electrical resistivity of the three alloys. Preparation of Samples and Experimental Procedure The preparation of the 20.2 per cent Ag alloy has been described2 Alloys containing 9.9 and 29.7 per cent Ag were prepared from 99.97 per cent A1 and 99.99+ per cent Ag using a similar procedure. Rolled

Jan 1, 1943

By R. F. Mehl, C. S. Barrett, A. H. Geisler

The mechanism by which the supersaturated solid solution of 20 per cent silver in aluminum decomposes has been reported in two previous publications.1'2 The analysis of streaks in Laue photograms showed that thin platelike particles (the so-called Guinier-Preston aggregates) form upon matrix planes in the early state of decomposition.1 The size of these particles is larger, the higher the temperature at which they form in accordance with nucleation theory;³ at all temperatures they increase in size with aging.2 When they have grown thick enough to afford three-dimensional diffraction, powder X-ray photograms show that the structure is not that of the equilibrium precipitate but that of a transition lattice . Sincc this is also platelike in shape and also lies upon the (III) matrix planes with the [IIO] direction in the matrix parallel to the [II.O] direction in it seems likely that the original platelet particles are merely in an early stage of formation, and thus finely dispersed. The atomic spacing and pattern on the (00.1) plane in y' are identical with those on the (111) matrix plane to which it lies parallel, and since comparable directions in the two planes are parallel, the lattices are thus coherent at the interface; an analogous coherence has been found in aluminum-copper alloys.3 The structures y' and y are both close-packed hexagonal and are oriented alike; they differ only in interatomic distances. Consequently, y' is regarded as y strained from its ordinary dimensions by the lattice coherency between it and the matrix.2 The lattice movements that transform the matrix to the equilibrium precipitate appear to be very simple.2 The mechanism of precipitation in this system is simpler and is more precisely known than that in any other system hence the system should be a profitable one for the difficult task of correlating property changes with structural alterations. The present report provides additional studies on powder X-ray diffraction from alloys of 10 per cent, 20 per cent and 30 per cent Ag, and presents the correlation of crystallographic changes with changes in microstructurc, Brinell hardness and electrical resistivity of the three alloys. Preparation of Samples and Experimental Procedure The preparation of the 20.2 per cent Ag alloy has been described2 Alloys containing 9.9 and 29.7 per cent Ag were prepared from 99.97 per cent A1 and 99.99+ per cent Ag using a similar procedure. Rolled

Jan 1, 1943