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By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By G. G. Gunther, C. L. Boeke

THE zinc deleading processes at the Parral and Santa Barbara mills are described separately to provide a basis for comparison. Although the two procedures are fundamentally alike, there are some differences in application to meet specific conditions. The Asarco mill at Parral in the State of Chihuahua is a flotation plant treating 1450 metric tons per day of complex sulphide copper-lead-zinc ores. In general, the procedure used for selective separation of the minerals into a copper, a lead, and a zinc concentrate follows the usual practice. First, a bulk copper-lead concentrate is floated and then separated into a final copper and a final lead concentrate by the sulphurous acid process. A small tonnage of high grade gravity lead concentrate is tabled from the bulk copper-lead cleaner tailing before it is reground so as to avoid undesirable over-grinding and sliming of this portion of the lead mineral. Next, a zinc concentrate is floated from the lead rougher tailing and, as described later, is separated into a final lead product and a final zinc concentrate. Finally, the zinc rougher tailing receives a strong scavenger float to remove all recoverable middling values for regrinding and return to the flotation circuits. The slime is separated from the scavenger flotation product, and only the sand portion goes to the regrind section. The minerals in the separated slime are extremely resistant to all methods of selective separation and pose one of the major problems awaiting solution. Nevertheless, the slime shows a profit when mixed with either the lead or the zinc concentrate, except when metal prices are very low, so it is accepted as a final product for lack of a more profitable method of handling it. In contrast, the minerals in the reground sands of the

Jan 1, 1953

By William Kent

In the paper by Mr. Fernom, on Red Charcoal, read at the first session of this meeting, it was suggested that this fuel might be used in the blast furnace with greater economy than ordinary or black charcoal. In the discussion which followed the paper, it was stated that the charcoal furnaces of the Lake Superior District have used imperfectly burned charcoal with success, and that these furnaces have given the best results in fuel economy on record. On consulting some of our well-known metallurgical authorities the writer finds that the question of the use of red charcoal, or other imperfectly burned charcoal, or charred wood, is not at all new. In Percy's late work on Fuel, pages 409-414, are given a few facts, which are here condensed, as follows:

Jan 1, 1879

By Joseph L. Gillson

IT is a somewhat curious circumstance that the newest of the Institute's several awards should be conferred in the oldest of our several professional fields—for there is little question that geology and mining have antedated metallurgy and petroleum. Perhaps so did geophysics. After all, one geophysical instrument, the magnetic compass, has been successfully employed for many centuries. Young in years the Jackling Award may be, but in distinction—whether in terms of the title it bears or in terms of the first three medalists (Reno Sales, E. D. Gardner, and the late Father MaceIwane)—the Jackling Award is already one of the ranking awards of the Institute. The name of the 1957 medalist will bring added luster to an already illustrious roll. J. L. Gillson was born and brought up in Evan-ston, Ill., in an area characterized by singularly flat and uninspiring topography, and devoid of ore deposits and even of bedrock—a most unlikely environment from which to expect a future Jackling medalist to emerge! On graduating from high school he enrolled as a chemistry major at Northwestern University. At the end of his frkshman year his scholastic prowess had won him a prize of two chemistry books. But these went unread, for about this time he came under the spell of U. S. Grant, that distinguished and enthusiastic geologist who for many years was head of Northwestern's geology department. From thence forward Joe was a dedicated geologist. After a Navy interlude in World War I, he went to MIT for graduate work, substituted for the late Professor Palache for one year at Harvard in mineralogy, received his doctorate at MIT and stayed on as a meniber of the MIT faculty, where the geology department was headed by that great dean of all economic geologists, Waldemar Lindgren. In 1926 Joe spent a summer looking into barite deposits for the du Pont Co., and since 1928 he has been du Pont's chief geologist. Do men who lead such active lives in our exploration organizations generally have permission to publish their observations? Do they generally find time to publish, even if they have permission? Alas, no. But in Joe Gillson's case, yes. His bibliography runs to well over two score papers, including one of the very first papers in this country on the applications of petrography to problems of Portland cement. He has written on such topics as the origin of talc and the genesis of ilmenite, fluorspar, and alkaline rocks. Each year for a number of years his annual reviews of industrial minerals in the Mining Congress Journal have been eagerly awaited. - Do men who do so much to advance their science have anything left to give to the advancement of their profession? In Joe Gillson's case, yes. He has been a vice president of the Mineralogical Society of America and has been active in the councils of the Society of Economic Geology, particularly in their research programs. This year he is president of the American Geological Institute, currently perhaps the most challenging post to which a geologist may be elected. His contributions to AIME scarcely need documentation, so I shall mention only three—his chairmanship of the Committee on Democratization of the Institute, a committee whose work and recommendations brought a new and hopeful leaven to AIME at a time when this was sorely needed; his chairmanship, a few years ago, of the Industrial Minerals Division; and his current place on the Board of Directors as Vice President of the Institute. Such' a catalogue of contributions and achievement, even as condensed as I have had to make it, certainly merits the Jackling Award. Yet, implicit although not often expressed in the conferring of most awards is the hope that besides recognizing a distinguished career, it will provide stimulus for further effort. In the present instance, such an expectation is already well on the way to fulfillment. Only recently Joe Gillson has undertaken the editorship of a new and greatly revised edition of the Institute's Seeley Mudd volume, Industrial Minerals and Rocks. And so, Mr. Chairman, it is with pleasure and enthusiasm that I present Dr. J. L. Gillson for the 1957 Jackling Award.

Jan 1, 1958

By William Kent

(Read at the Philadelphia Meeting, February, 1878.) IN the paper by Mr. Fernow, on Red Charcoal, read at the first session of this meeting, it was suggested that this fuel might be used in the blast furnace with greater economy than ordinary or black charcoal. In the discussion which followed the paper, it was stated that the charcoal furnaces of the Lake Superior District have used imperfectly burned charcoal with success, and that these furnaces have given the best results in fuel economy on record. On consulting some of our well-known metallurgical authorities the writer finds that the question of the use of red charcoal, or other imperfectly burned charcoal, or charred wood, is not at all new. In Percy's late work on Fuel, pages 409-414, are given a few facts, which are here condensed, as follows:

Jan 1, 1878

By R. J. Burgess, A. R. Ramey, A. R. Adams

During interpretation of pressure buildup tests on gas wells in a tight dolomite gas reservoir, peculiar behavior was noticed. Two straight lines were apparent. Effective permeability to gas taken from either straight line was about the same, and the Miller-Dyes-Hutchinson dimensionless time check for the straight line was proper for both straight lines. Geological data indicated the likelihood of scattered trending fractures in the reservoirs. Since the first straight Iine yielded permeability values close to the geometric mean permeability from core analyses, it was postulated that the reservoir model was that of an acidized well completed in the tight dolomite, but that widely scattered hairline fractures caused the mean permeability of the reservoir distant from the well to be higher than the matrix permeability. Because all other studies of fractured reservoirs to the authors' knowledge assumed that the fracture matrix was dense enough to communicate directly with the well, no interpretative methods were available. The Hurst line-source solution for a radial change in permeability for interference between oil reservoirs was adapted to pressure buildup testing. The result indicated that the first straight line should yield the proper matrix permeability and wellbore skin effect. The second straight line may be extrapolated to obtain static pressure. The time of bend between the straight lines was used to estimate distance to a fracture. Application to field test data is shown. It is believed that the methods developed and the case history presented will add to present tools available for pressure buildup interpretation. Introduction Since the pioneer studies by Miller, Dyes, and Hutchin-son1 and Horner' in 1950 and 1951, well test analysis has become recognized as one of the most powerful tools available to both production and reservoir engineers. Well test analysis serves as a logical basis for well stimulation and completion analysis, and for long-term reservoir engineering. Since the early 19501s, much effort has been placed on the development of well-test analytical methods. Reservoir and well conditions of increasing complexity have been considered systematically to provide the analyst with a catalog of causes and effects. Matthews and Russella state that some 200 papers dealing with this subject have been published in the last 35 years. Developments in well test analysis appear to have originated in one of two ways. Either a physically realistic field condition was anticipated and analytical solutions for the condition achieved, or anomalous field test behavior was recognized and interpretative methods sought for the anomaly. In recent years, it has appeared that the latter has inspired an increasing number of studies. The analyst today finds an increasing number of known cause and effect studies available for well test analysis, the classic of which is that of finding the specific flow problem that generated the answer — the well behavior. Although it may be impossible to achieve this goal uniquely, the analyst often is able to select a useful interpretation that combines all known performance and geologic data — or to show that various logical alternatives would not significantly affect the interpretation. During a recent reservoir study, we observed gas well test behavior that did not appear to fit behavior described previously. Although it cannot be said that we have found a unique interpretation, we shall present in this paper the peculiar behavior observed, and describe the reservoir and interpretative methods developed. Reservoir Description The subject gas reservoir is a 9-mile-long, narrow dolomite reservoir lying within a limestone of Ordovician age. (See Fig. 1.) The dolomitized rock in the field consists of dark brown to buff, dense to coarsely crystalline, vugular dolomite containing numerous hairline fractures, many of which may have been closed in the reservoir and parted when cores were brought to the surface. Larger fractures are also apparent in core, but usually are filled and sealed with euhedral dolomite crystals. Portions of the north flank of the reservoir are known to be cut by a sealing fault downthrown to the north. Gas wells located near the fault have higher open flow potentials than those more distant from the fault. This is believed to be a result of higher permeability near the fault due to more extensive and open fractures. Detailed coring and core analysis have been performed on several of the wells in this reservoir. Fig. 2 presents permeability variation' plots for both horizontal and vertical

Jan 1, 1969

By J. D. Grace

Screening by centrifugal force is a unique subject, for all vibrating screens, with but one exception, depend on gravity alone to pass material through a sizing mesh or screen cloth. Centrifugal screening is one of the greatest advancements made in screening since the development of vibrating screens. It makes possible sizing in a range previously im-practical by mechanical methods. The centrifugal screen is specially designed for fine sizing from No. 4 separations to finer than No. 100 separations. Centrifugal force provides a positive control of factors that make fine particle separation practical and effective as opposed to gravity which is a fixed force acting only in a fixed direction, The centrifugal screen provides a control of the force of material against the screening surface, and also controls the distance of departure of the material from the surface and its rate of return. The centrifugal screen has a rotating drum that becomes a natural fan blowing air outward through the material being screened and carrying float dust and fines through the apertures with it. Screening by centrifugal force is an unique subject, for with the exception of only one vibrating screen presently on the market, all vibrating screens depend upon gravity to pass material through a sizing mesh or screen cloth. This one screen that sizes by centrifugal force and utilizes gravity only to convey material along the screen, is the Symons V-Screen. The requirements of the industrial minerals industry to meet ever-increasing stringent fine sizing specifications by a practical mechanical method accentuates the weakness of gravity, a fixed force acting in a fixed direction, as a prime force for fine sizing. It was apparent a force other than gravity was needed. This led to the development of a centrifugal screen to meet modern demands for practical fine sizing operations. Gyratory-type screens in use today were originally designed in a day when a 1/4-in. separation was normally considered fine sizing and 1/8-in. separations were extremely fine sizing. Although gyratory-type screens are sometimes used for separating below 1/8-in., they are not practical screens for this purpose. They were not designed to do this type of work. A growing demand for a practical means of making positive mechanical separations in a range of from 1/8 in. downward led to the development of the vibrating screen. These screens utilize higher speeds and lower amplitudes of vibration than

Jan 1, 1967

Members whose deaths were reported from Apr 9, 1921 to Apr 7, 1923 Elected Died 1876 ABADIE, E R. 1923 1906 ADAMS, ARTHUR K 1920 1902 AHLES, ROBERT L 1921 1876 Akerman, Richard 0000 1884 ALEXANDER, CURTIS 1921 1918 ALLEN, CARL A 1923 1880 ALMY, WILLIAM F 0000 1893 AMSDEN, 0. B 1923 1917 ARGALL, P. H 1922 1917 ARNOLD, E C 1921 1914 ASANO, K 1921 1920 AUGUSTINE, ALBERT BEARSS 1922 1906 BAIRD, GEORGE A 1921 1921 BALDWIN, GEORGE P 1922 1920 BASKERVILLE, CHARLES 1922 1915 BENSEL, J A 1922 1890 BENSON, A J 0000 1912 BEST, WILLIAM NEWTON 1922 1892 BILHARZ, OSCAR M 1923 1890 BLACKSTONE, RICHARD 1922 1921 BLOOM, GEORGE BARNETT 1921 1905 BOSTWICK, WILLIAM A 1922 1884 BRANNER, JOHN C 1922 1920 BRIDGE, SAMUEL D JR 1921 1893 BROWNE, ARTHUR, 1922 1871 BUCK, STUART M 1921 1897 BURGER, C C 1922 1882 BURT, CHARLES S 1921 1921 BUTZ, Louis N 1922 1917 CAMPBELL, DONALD G 1921 1915 CAPLES, JAMES WATTS 1919 1892 CARLETON, JAMES G 1922 1914 CARUTHERS, A WAYNE 1922 1911 CHASE, FRED M 1921 1892 CLEMENT, F H 1922 1922 COAN, WALTER ERLING 1923 1872 COGSWELL, WILLIAM B 1921 1881 COLVIN, VERPLANCK 1920 1882 COOLIDGE, WALTER G 1922 1907 CORKILL, FREDERICK 1922 1912 COX, Guy H 1922 1883 CUNNINGHAM, JAMES S 1921 1873 DAGGETT, ELLSWORTH 1923 1916 DAULTON, THEODORE M 1921 1888 DICKERMAN, ALTON L 1921 1902 DIEFFENBACH, H M 1921 1911 DUNSTAN, SIMON P 1920 1917 DYNAN, ALAN E 1922 1920 EASTWICK, THOMAS H A 1922 1876 EDWARDS, J WARNER 1921 1914 ELDER, ROBERT B 1923 1885 EMMONS, ARTHUR B 1922 1911 ENGEL, GEORGE W 1920 1887 FERNOW, B E 1923 1879 FIRMSTONE, H1922

Jan 1, 1923

By J. G. Eenink, R. A. Cunningham

One phase has been completed of a laboratory invesrigation of formations with relatively high permeability under conditions of overburden, formation and mud coltrmn pressures. The following statements are based on these tests within the limitations described. Drilling rate decreased when mud column pressure was greater than formation pressure. The decrease was primarily due to a layer of cuttings and mud particles held to the hole bottom by the difference in pressure. Much of the force of the bit was wasted in this layer and was unavailable for penetrating virgin formation. Adequate jet velocities helped clean the filter cake and chips away and resulted in increased drilling rate — the higher the jet velocity the faster the drilling rate. Drilling rate increased slightly when formation pres sure was greater than mud column pressure. The i11(reuse resulted from cleaning the hole bottom as formarion fluid flowed into the borehole. Overburden pressure had practically no effect on drilling rate. INTRODUCTION Some formations are difficult to drill in a wellbore hole but are easily drilled under atmospheric conditions in the laboratory. The reasons for this apparent difference in drillability are not fully understood. An increase in formation compressive strength causes a reduction in drilling rate. It has been shown by Griggs1, Handin2 and others3-1 that formation strength increases under conditions of high hydrostatic stress. Based on these results, a decrease in drilling rate would be expected with increased drilling fluid pressure in formations of low permeability having low formation fluid pressure. Such a decrease has been shown by Murray. et a1 and Eckel" This effect holds even when using nitrogcn under high pressure as the drilling fluid (unrc-ported tests from the Hughes laboratory). Poor bottom-hole cleaning may account for decreased drilling rates. Even though it may not be easily explained, evidence of poor cleaning can easily bc seen. One evidence is the increased drilling rate that accompanies decreased balling obtained with addition of oil in some muds used to drill shales.4,7,3 Many variables can affect drilling rates. These may include mud composition and properties, formation properties, bit types and operating conditions, formation fluid, mud column and overburden pressures. These must be studied a few at a time under carefully controlled conditions which simulate actual conditions as closely as possible. The purpose of this work was to investigate effect of overburden, formation and mud column pressures on drilling rates in permeable formations. These tests were suggested by conditions shown in Fig. I. Represented is a borehole drilled into a formation with relatively high permeability. In the vicinity of the hole bottom there exists a mud column pressure, P a formation fluid pressure, P and an overburden pressure, The mud has low water-loss properties and sufficient weight to more than overbalance the formation pressure. Laboratory investigation included a range with formation pressure greater than mud column pressure. NOMENCLATURE Pm mud column pressure = pressure of drilling fluid or mud at hole bottom Pf, formation pressure = pressure of fluid in intersticies of formation

H. H. Hill.—I believe that as petroleum engineers you are all more or less interested in geophysical prospecting. A large number of the papers that have been written on that subject are too detailed or too much involved to be of much value to a person who is not familiar with the subject, so I suggested to Mr. Fohs that he might bring us something that we could all understand. As I take it, we are interested in learning something about the different methods, the places where they have been used, their limitations and in general whether they have given satisfaction in locating oil deposits. F. J. Fohs, New York, N. Y.—I will briefly summarize some of the results as I Bee them from my practical contacts with them and my discussion of the subject with some of the more important rnen both in this country and Europe. Geophysical Methods 1. Seismographs: A. 1. Sonic refracting seismographs of Karcher, McCullom and Reiber. For rapid reconnaissance and also for detail—perhaps, the best type of instrument. 2. Mechanical refracting seismographs of the Weichert-Mintrop type. B. I. Sonic seismographs using reflected sound from contacts of sufficiently unlike beds where latter are thick enough, being used for detail of both salt domes and ordinary structures where a good reflecting key bed occurs. 2. Torsion Balances: Made in three sizes with greater portability and loss of but 20 per cent. in medium size and loss of 40 per cent. efficiency in smallest size. A. Used to best advantage in detailing salt domes, in noting anomalies of deep-seated structures of the Edgerly, La., type (but not always certain here and dependent on interpretation which involves both experience and the human equation to a large degree). R. Used to advantage in mapping faults where a lime or other denser bed occurs upthrown, and the topographic irregularities are not too involved. C. Of use where buried granite plugs and buried-hill structures occur as in the Western Texas fields. D. Believed of little use for other types of structure. 3. Magnetometers or Variometers: Now built horizontal and vertical with declinometer combined in one instrument. A. Practical in mapping granite or basic igneous rock plugs and intrusions, or of detritus therefrom. Adams has recently demonstrated definite results in mapping the well known Panhandle arch.

Jan 1, 1928

By R. E. Carter, F. D. Richardson

Self-diffusion coefficients have been measured for iron in wustite (700° to 1000°C) and for cobalt in cobaltous oxide (800&apos; to 1350°C) by means of radio-isotopes. Both sectioning and decrease of surface-activity methods have been used and a particular shortcoming of the latter method has been disclosed for wustite. The effects of oxygen pressure on the composition of cobaltous oxide and on the diffusion coefficient of cobalt in the oxide have been established. The effect of the preparation conditions of the cobalt-oxide specimens on the diffusion measurements has been determined. It has been concluded that diffusion of cobalt occurs via vacant cation sites and that a cobaltous-oxide disk reaches equilibrium with its environment in a time which is very short compared with that needed for diffusion of the radio-isotope. THE availability of radioactive isotopes in recent years has permitted the measurement of many self-diffusion coefficients which were hitherto impossible to determine. With the advent of radioactivity, the method of measuring diffusion coefficients has also changed. The earlier sectioning method by which the concentration profile of the diffusing species was determined in the diffusion specimen has often been rejected in favor of the decrease of surface-activity method first developed by Von Hevesy,&apos; and extended by Steigman, Shockley, and Nix,&apos; and Raynor, Thomassen, and Rouse." With the experimental arrangement where an infinitely thin deposit of tracer is diffused into a semi-infinite cylinder, the decrease in activity of the active face due to diffusion of the tracer into the specimen is measured by counting the active face before and after diffusion. Under these conditions, the appropriate solution of the diffusion equation is R = e*(l-<K/Z) [1] where R is the ratio of the counting rates after-to-before diffusion, $& is the Gaussian error integral of \/Z, and Z is defined as Z = p2Dt, p being the linear-absorption coefficient of the detected radiation in the diffusion specimen, D the self-diffusion coefficient, and t the diffusion time. In the older sectioning method the concentration distribution of the tracer is found after diffusion by analysing thin parallel sections cut from the active face of the diffusion specimen. As seen from the solution of Fick&apos;s second law for the distribution of an infinitely thin source after diffusion into a semi-infinite cylinder the log of the concentration plotted against x&apos; will be a straight line of slope log e/4 Dt. The diffusion coefficient thus can be calculated directly. The units of the tracer concentration are completely arbitrary, since any change in units does not change the slope of the log c vs x2 lot. Although both of the above methods have been widely used, a thorough experimental comparison does not appear to have been made. Birchenall and Mehl,&apos; during an investigation of the self-diffusion rate of a and r iron by the surface method using Fe" tracer, diffused and sectioned one welded couple. The diffusion coefficient from this run agreed with those by the surface method. Buffington, Bakalar, and Cohen," during an investigation on a and y iron

Jan 1, 1955

By William A. Johnson

THE mathematical analysis of diffusion curves in solid metals is Carried out ordinarily by analogy with the flow of heat in a continuous medium and no account is taken of the fact that the materials involved are composed of discrete particles that move discrete distances at irregular intervals. It is possible to treat the problem on the basis of simple assumed atomic mechanisms, in which case, because of the small scale of the elementary process compared to the gross effects observed experimentally, the two procedures lead to the same expression for the variation of concentration with distance. Thus, for engineering purposes, the usual methods are quite satisfactory. If, on the other hand, our purpose is to go beyond the mere collection of data, however desirable this may be, it is necessary to recognize and understand the factors that are of fundamental importance. One factor that has not hitherto been considered when dealing with solid metals is the difference in atomic weights of the isotopes of a single metal. While all the atoms of a given element are alike chemically, their weights may vary by a small but significant amount, and atoms of different weights may have different diffusion rates. With gases this variation in isotopic weight produces a change in the rate of diffusion by a factor inversely proportional to the square root of mass. While, except for the lightest gases, this is not a large effect, it is, for example, sufficient to permit a considerable concentration of one isotope at the expense of others. If metals exhibit a similar phenomenon, some modification of the analysis of the diffusion process will be required, since the different isotopes of a given metal will have different probabilities of moving and the heat-flow analogy will contain a fundamental error. This situation cannot be rectified by using a diffusion coefficient based on the average probability of moving, and it can be shown that even when the diffusion coefficient is independent of composition, the diffusion curve will not agree with the simple theory except in the rare cases where only one isotope exists; e.g., gold. If, however, the mass effect in the solid state were no larger than in the gaseous, the errors arising therefrom in the analysis of ordinary diffusion curves would be quite negligible. Nevertheless, our desire to obtain all possible information concerning the details of the diffusion process, and the possibility of diffusion in the solid state as a means for separating isotopes are cogent reasons for undertaking an experimental study to determine whether isotopes of different masses diffuse at different rates. EXPERIMENTAL PROCEDURE If isotopes of different masses diffuse at different rates, the ratio of the concentration of one relative to another will vary with the distance from the diffusion inter-

Jan 1, 1946

By AIME AIME

A SYMPOSIUM on current. conditions in Mexico, particularly in the oil and mining industries, was a most successful feature of the May meeting of the New York Section of the A.I.M.E. Heath Steele, vice-president of The American Metal Co.. Ltd., with an intimate knowledge of Mexico gave the principal address, and asked that his analysis of the present situation he regarded neither as an endorsement of Mexico&apos;s policy nor as the criticism of a disgruntled operator. To explain the .attitude of the great mass of the Mexican people towards recent developments, he first described briefly the political, social, and religious beliefs and customs of tile Mexican Indian. In spite of their contact with foreigners these beliefs and customs have remained unchanged throughout many generations. The old communal spirit and the idea of common ownership of the land still persist especially in the rural districts and villages; the old custom of a council for local self-government is reflected in the present-day labor committee. Mr. Steele discussed in order land oil, and mines.

Jan 1, 1938

By Elmer W. Pehrson

The term "survival" in the title means the preservation of a society in which men are free from the political and economic restraints that characterize totalitarian systems, be they communist, socialist or facist. It means the ability to withstand the enemy&apos;s offensives in the fields of propaganda, commercial competition and, if necessary, war. The temptation to substitute "victory" for "survival" is great but a realistic appraisal of the creeping socialism and demagoguery that pervade our time indicates that we may have to be content with survival in status quo. "Mineral strength" means assurance that adequate supplies will be available to meet all the contingencies of cold and hot wars. The overall mineral position of the U. S. viewed in the light of these premises is far from secure. It is true that we are the leading producing and consuming nation of the world, but the Soviet Union is gaining and the Sino-Soviet Bloc confronts us with a sobering potential. The emergence of the Common Market in Europe as an economic and political unit places a third independent entity into the competition. Our total mineral output continues on an up- ward trend but the reverse is true in certain strategic commodities. Moreover, consumption is moving ahead faster than production so that there is increasing dependence on imports which has significant adverse geopolitical connotations. There is widespread belief that our resources can at least maintain present levels of self-sufficiency during this critical period in world history, but social dreamers, the labor monopoly, and trade and taxation policies have discouraged aggressive activity in exploration and development, and access to essential foreign sources is threatened by a variety of circumstances. Our stockpiles, belatedly built up to achieve minimum protection against shortages in time of war, are under. political attack and threatened with partial destruction on the basis of what are at best uncertain assumptions regarding the new: look of global warfare.

Jan 11, 1962

By Edgar Schweitzer

The original Dorrance breaker of the Lehigh Valley Coal Co. was erected in 1883. The coal beds were clean and dry, consequently a dry preparation system was used, consisting of revolving cylindrical screens for sizing and hand-picking, to remove the few impurities from the run of mine coal. The picking or cleaning room contained long parallel rows of chutes with seats mounted on them, for the use of the breaker boy, who bent over the chute and picked out the refuse material from the coal as it gravitated down the chute. The introduction of dry mechanical pickers, of, the sliding frictional type, in the early nineties lessened the number of boys, but hand-cleaning on the coal and refuse discharge ends of the mechanical picker was necessary. The Pardee spiral pickers, which were brought out about 1900, were better than the gravity pickers and gradually replaced them. In 1912 the breaker was entirely remodeled, although the original frame was retained. The revolving screens were replaced by shaking screens, and Pardee spirals were installed on all sizes of coal from egg to pea coal, inclusive. Hand-picking still was necessary on the coal and refuse ends of the spirals, although the changes did result in a reduction of the former breaker force. As mining advanced, and the thick clean bed became exhausted, it was necessary to mine veins containing a high percentage of impurities, which complicated the preparation problem. The most serious difficulty was the increase in the quantity of damp or wet run of mine, which could not be fully cleaned on the spirals. When this quantity exceeded approximately 5 per cent. of the feed, it was necessary to send the excess of the wet coal to the company&apos;s Prospect colliery for wet washing. This plan worked well for a time, but as the amount approached 15 per cent., with the prospect of a further increase, the company considered the building of a wet-washing plant. The Dorrance breaker was the only dry-cleaning plant operated by the company. At the seventeen other collieries, wet washing was employed, and jigs, both plunger and pan, were used. All the practical methods used in the anthracite fields were investigated, and it was finally decided to adopt the Rheolaveur system. The decision was due largely to the experience gained from the the operation of a Rheo-

Jan 1, 1931

By William Hutton Blauvelt

Coke is the product of dry distillation of bituminous coal, by which the volatile matter is driven off, producing a hard body of cellular structure. Not all bituminous coals will coke, and there has been much discussion regarding the substance which is present in coking-coals to distinguish them from dry coals. Professor Lewes says that the bituminous matter in coal is largely derived from the spores of fossil mosses. Resins are present in all soft coals, and contribute largely to the cementing of the coke. The resinates and hydrocarbons begin to distil out at moderate temperatures and leave the pitchy residual, which at 500&apos; C. forms a mass already well caked together, if the proportion of humus residual is not too great. This coke is soft, but if the heat be raised to 1,000° C. the pitch decomposes further, leaving carbon, and Professor Lewes is convinced that the coking bond is due to these liquid products which distil off, leaving pitch, which then carbonizes and binds the mass into coke. Professor Parr concludes that the structures of the organic compouilds of the coal Which furnish the cemeding-material for coke, and which are apparently attacked by oxygen, have not been determined and seen] to vary somesvhat in different types of coal. However, they yield, on oxidation, humic acids of varying composition which decompose into powdery residues. Because of the complex nature of these substances and the difficulty experienced in isolating and identifying them, the theory of coking is still an open problem and the explanations advanced are largely hypothetical. In the coking process the volatile matter driven off in the oven consists mainly of tar, ammonia, and gas, familiarly known as by-products. Both the quality and quantity of coke and by-products vary greatly With the composition of the coal.

Jan 1, 1913

By M. M. Leighton

THE engineers of Illinois have been submitting to the State Geological Survey an increasing number of requests for advice on their geological problems, including landslides, unequal settling of fills, laying pavements across peat bogs, shattering and heaving of pavement by frost action, etc. The authors discussed the behavior of landslides, their effects, their causes, a tentative classification, and remedial measures. In the latter connection the efficacy of drainage and how it should be handled in order to be most effective was considered. The principles and efficacy of other remedial measures, such as subsurface blasting, rock anchoring, installation of wood, concrete or steel piling, construction of retaining walls, construction of cribbing and reduction of slope were also discussed. Attention was also given to the matter of applying geological knowledge to avoid undesirable highway locations, and a specific example was cited.

Jan 1, 1929

By E. F. Poncelet

Forty years ago A. A. Griffith developed a theory explaining why brittle materials displayed such low tensile strengths.&apos; He based his views on two points. First, he found himself compelled to assume that all brittle materials are replete with flaws, cracks, and other defects that act, although quite invisible, as large stress raisers. Second, he applied the "theorem of minimum potential energy," which says that the total potential energy of a system must pass from the unbroken to the broken condition by a process involving a continuous decrease in potential energy. By this means he satisfactorily accounted for the noted low strength of such solids and also for the wide spread obtained in experimental measurement of these strengths. So successful has the theory been that it is favored by some to this day. Unfortunately this theory is of limited use beyond the explanation of these two noted phenomena and it is keenly felt that a better theoretical insight into the physics of the fracturing process is needed as the volume of experimental evidence accumulates. The author proposes in the following to build on the fundamentally sound concepts of Griffith and, with the help of increased theoretical knowledge over that available to Griffith, develop a mechanism for frac-ture which will provide far greater understanding of the experimental evidence accumulated to date than is possible from the original Griffith idea. THE GRlFFlTH THEORY Very little progress indeed can be made without accepting the first postulate of Griffith which supposes all brittle solids to be full of microcracks. It would be difficult indeed to find a better mechanism for the small strength of such brittle materials, in conjunction with the fact that the energy that must be expended for comminution is by no means small. The postulate of the existence of the microcracks permits the breakup of the various bonds a few at a time by concentrating the stress at the tip of the progressing crack, while the total energy expended is the same as if they all had been ruptured simultaneously. The only flaw in the argument is that no reasonable explanation has been proposed to account for the genesis of such cracks. Indeed their very presence is in violation of the Griffith second postulate, the potential energy theorem. This theorem is straightforward for isothermal processes, and, in spite of Griffith, there is some doubt that treating the problem isothermally is legitimate. The surface energy of bodies is a free energy, not a potential energy as stated by Griffith, and the production of new surface free energies is not necessarily an isothermal process. There is ample evidence to the contrary. Generally speaking, if heating a body increases its surface area, then, by virtue of Le Chatelier&apos;s principle, any increase of that area by other means will tend to lower its surface temperature. Lord Kelvin calculated the actual cooling that resulted in drawing out a film of liquid.2 R. A. Houston calculated the surface cooling that resulted in stretching a metal wire.3 These calculations were made by applying the Carnot cycle to the process and evaluating the thermodynamics thereof. IRREVERSIBILITY OF THE FRACTURING PROCESS While Griffith was very careful not to say so, the impression gained from studying his papers is that he considered the fracturing process as reversible, that is, a succession of quasi-equilibrium states. There is ample evidence that it is not. The indication that the new surfaces produced by the propagation of a crack are cooler than the original body points to an irreversible heat flow from the interior to the new surfaces to equalize the temperatures. If the process be reversible, any crack accidentally formed should immediately close up as, in the absence of any strain energy, the potential energy would thereby be lowered. The fact that they do not, constitutes a paradox. Such paradoxes are nothing new where certain phenomena that propagate from minuscule nuclei are assumed to be reversible. Such is, for instance, the condensation of a pure saturated vapor that is suddenly chilled by adiabatic expansion. At the beginning the tiny droplets that are formed should be only a few angstroms in size, but the vapor pressure at such droplets is so high that they should evaporate at once. A similar situation arises if a saturated pure solution becomes super-saturated upon cooling; the first tiny crystal nuclei should dissolve as fast as

Jan 1, 1964

By Charles C. Hawes

DETERMINATION OF SILICA OXIDE iron ores usually are found in intimate association with silica and phosphorus compounds. Their quantitative separation and purification sometimes present difficult problems to the chemist. Silicic acids may represent various degrees of dehydration. They are exceedingly weak, but combine with metallic acids and form some of the most stable oxides in nature, the silicates. When iron ores are treated with hydrochloric acid, they yield practically all their iron. However, apart from rare exceptions, varying amounts of insoluble residues of silica, alumina, lime, magnesia and compounds of phosphorus, sulphur, titanium, chromium and others will be left. If the oxides of silicon, aluminum and titanium are present in small quantities, the insoluble residue is generally very small, but the presence of these oxides more usual in larger quantities. Therefore, only a special treatment can break the bond between these elements. Ore Residues Acids remove the soluble constituent of the ore, leaving the insoluble residue, which chemically is rock or gangue and must be treated accordingly. Alkali carbonates are used frequently to break up the residue, but other fluxes have also been recommended, such as a number of lead and boron salts. The introduction of these salts, which offers certain advantages, requires, however, their removal before the other constituents can be analyzed, and this elimination is sometimes difficult. Usually in quantitative analysis silicates are dissociated by fusing them in a platinum crucible with sodium carbonate, thereby forming sodium silicate, Na2SiO3, sodium aluminate, Na2A1204, sodium titanate, Na2TiOs, and carbonates of other elements. All the carbonates are soluble in hydrochloric acid, but also some silicic acid is formed that must be rendered insoluble. To this end the solution is evaporated several times, as the first evaporation still leaves as much as 5 per cent of the silica soluble. Even after a number of evaporations, minute quantities of silica may be found with the iron and alumina present. Perchloric Acid as an Agent for Dehydrating Silicic Acid Perchloric acid, HCI04, (60 per cent), has been used for years as a solvent, but few chemists have used it to dehydrate silica. It is derived from anhydrous perchloric C1207, which is most unstable and dangerous. Perchloric acid is a strong oxidizing agent, which boils at 203°C. It is more effective in rendering silica insoluble than any other known agent, and most rapid in action. After perchloric acid is added to a mixture containing silicic acid, the resultant solution is

Jan 1, 1945

By AIME AIME

ON Tuesday afternoon, Feb. 17, a large and interested audience gathered in the auditorium of the Engineering Societies building to take part in the gold supply symposium that had been arranged for by the Mining Geology Committee. Waldemar Lindgren presided over the gathering and after brief introductory remarks on the international situation as regards lead, silver and gold, called on John Wellington Finch to present an oral abstract of the paper, "Sources and Trends in Gold Production," by R. J. Grant, director of the Mint, and. J. B. Knaebel. This &apos; paper reviewed the gold production of the world, by countries, since 1845, from the statistical viewpoint, leaving to the later speakers discussion of the statistics.

Jan 1, 1931