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Prior to any detailed discussion, I'd like to say that Dr. Aplan has made direct hits on two important considerations: 1) The most demanding need in Fine Coal research is to develop improved methods of sulfur reduction. 2) The areas of particle (impurity) liberation and froth flotation hold real near-term promise as techniques for improved sulfur removal. Digressing for a moment, I thin kwe can all remember the time when the biggest problem facing coal research was simply defined - "No money!" In the mid 70's we suddenly found ourselves dealing with a product worth five to seven times the value it carried in the mid60's. All of a sudden, we're talking about a high-profile, high- value commodity. The coal industry still hasn't made the complete psychological adjustment - especially in the operating areas (prep plants included). We have a valuable material at hand which is, in' many cases still being processed as though it were a two or three dollar per ton item. Simply put, I think that while the industry has made some major strides during this transition, a stronger commitment of attitude (and finances) needs to be made toward deeper definition of beneficiation work. Back to specifics - Dr. Aplan has really highlighted three areas where strong research efforts are needed. 1) Liberation processes - not limited to mechanical comminution - must be more fully studied.The industry certainly needs a better handle on value returned (improved ability to beneficiate) for dollars spent on improved liberation. 2) Flotation processes probably hold the most promise for near- term improvement in fine coal beneficiation technology. Dr. Aplan’s.

Jan 1, 1979

By G. K. Manning, C. H. Lorig

TWO metallurgical tools have acquired wide use within the past several years as a means of studying the transformation characteristics of steel. One is a technique used first by Bain and Davenport for determining the transformation characteristics of a steel at constant temperature; the second is the end-quench hardenability test. Constant-temperature transformation curves like those of Bain and Davenport have done much to rationalize the metallography of steel; however, in commercial practices, constant-temperature transformation is seldom encountered, therefore only rarely can such curves be directly applied. The real reason for the determination of such curves lies in the fact that they provide a way of thinking about transformation that is both convenient and productive. The end-quench hardenability test is a more practical means of studying transformation, for, by correlating positions on the hardenability bar with shapes of different masses, an almost direct application of the results can be made. Unfortunately, the end-quench test, though practical, can do very little toward improving the metallurgists' way of thinking about transformation. These two metallurgical tools, dealing with precisely the same phenomenon, should be very closely associated in metallurgists' minds. Actually, they are frequently pushed into separate mental corners and considered as being more or less distinct and unrelated. The reason for this is that no strong connecting link between them has been developed. An attempt is sometimes made to relate these two tools by projecting the critical cooling rate on the isothermal transformation plot as illustrated in Fig. I. The critical cooling rate is considered as a constant rate-though in practical applications, cooling rates are never constant—and this constant cooling rate is given uniform significance from the Ae temperature down to the temperature of initial transformation. A little thought indicates the errors of such a procedure. Certainly the time interval spent just below point A of Fig. I cannot be as effective in promoting nucleation as is the time interval spent just above point B. Yet the procedure represented in Fig. I considers all the time spent between temperatures A and B to be just as effective in promoting nucleation as though all the time were spent at temperature B. Furthermore, change the shape of the isothermal curve between points B and C in any way desired, and the required critical cooling rate is not changed one iota. This cannot possibly be true. Such a way of thinking about critical cooling rates not only is incapable of giving any results that are quantitatively satisfactory but is likely to give very misleading qualitative results.

Jan 1, 1947

By G. K. Manning, C. H. Lorig

TWO metallurgical tools have acquired wide use within the past several years as a means of studying the transformation characteristics of steel. One is a technique used first by Bain and Davenport for determining the transformation characteristics of a steel at constant temperature; the second is the end-quench hardenability test. Constant-temperature transformation curves like those of Bain and Davenport have done much to rationalize the metallography of steel; however, in commercial practices, constant-temperature transformation is seldom encountered, therefore only rarely can such curves be directly applied. The real reason for the determination of such curves lies in the fact that they provide a way of thinking about transformation that is both convenient and productive. The end-quench hardenability test is a more practical means of studying transformation, for, by correlating positions on the hardenability bar with shapes of different masses, an almost direct application of the results can be made. Unfortunately, the end-quench test, though practical, can do very little toward improving the metallurgists' way of thinking about transformation. These two metallurgical tools, dealing with precisely the same phenomenon, should be very closely associated in metallurgists' minds. Actually, they are frequently pushed into separate mental corners and considered as being more or less distinct and unrelated. The reason for this is that no strong connecting link between them has been developed. An attempt is sometimes made to relate these two tools by projecting the critical cooling rate on the isothermal transformation plot as illustrated in Fig. I. The critical cooling rate is considered as a constant rate-though in practical applications, cooling rates are never constant—and this constant cooling rate is given uniform significance from the Ae temperature down to the temperature of initial transformation. A little thought indicates the errors of such a procedure. Certainly the time interval spent just below point A of Fig. I cannot be as effective in promoting nucleation as is the time interval spent just above point B. Yet the procedure represented in Fig. I considers all the time spent between temperatures A and B to be just as effective in promoting nucleation as though all the time were spent at temperature B. Furthermore, change the shape of the isothermal curve between points B and C in any way desired, and the required critical cooling rate is not changed one iota. This cannot possibly be true. Such a way of thinking about critical cooling rates not only is incapable of giving any results that are quantitatively satisfactory but is likely to give very misleading qualitative results.

Jan 1, 1947

By Andrew Mayer

Early in 1942 National Lead Co. was requested by the War Production Board to construct and operate a plant for the Government to produce magnesium by the ferrosilicon process which had been developed by Dr. E. M. Pidgeon in the laboratories of the Canadian National Research Council. A contract with the Defense PlantCorporation was concluded in May 1942 and Magnesium Reduction Co., a wholly owned subsidiary of National Lead Co., was formed to carry out this project. The capacity of the plant was rated at I0,000,000 lb. of magnesium per year, equivalent to an average production of about 14 tons per day. The Process The process, in brief, is as follows: The raw materials are dolomite and ferro-silicon, 75 per cent grade. The dolomite is calcined, the calcine and ferrosilicon are ground and mixed and the mixture is briquetted. The briquets are charged into tubular retorts of chrome-nickel steel set horizontally in a furnace with the open ends projecting outside the front wall. The retorts are then closed and evacuated. Magnesium is liberated according to then reaction 2(MgOl CaO) + Si = 2Mg + zCaO, Si% It is distilled from the charge and con- densed on a removable sleeve in the throat of the retort. Sodium and potassium, if present, are also liberated, distilled and condensed on a "sodium condenser" in the end of the retort. At the expiration of the distillation period the retorts are discharged and the cycle of operations is repeated. For the rated daily capacity of 14 tons of magnesium there are required approximately 170 tons of dolomite, equivalent to about 85 tons of calcine, and 16.5 tons of ferrosilicon. The retort residue, a bulky powder which at present is waste, amounts to about 87 tons. Choosing the Site The investigation to select the location of the plant was conducted by the Research Laboratories of National Lead Co. This work included geologic and economic surveys of a number of districts, examination of dolomite samples by chemical, spectrographic and petrographic methods and large-scale tests of dolomite from several of the more promising localities. in the last-named tests 2-ton samples were put through the ferrosilicon process in the pilot plant of the Canadian National Research Council, under the guidance of Dr. Pidgeon. The conclusions drawn from the investigation, in regard to the quality of dolomite to be used in the ferrosilicon process, were: First, the dolomite should contain not less than 21 per cent MgO and not more than 2 per cent acid-insoluble material. Second, the dolomite should

Jan 1, 1944

By R. S. Cartwright

Two types of automatic drilling controls, the Halliburton and the Hild, are now available and are coming into more or less general use in deep drilling. The primary function of both is to maintain a safe limit of torque on the drill pipe, this being accomplished by automatically controlling the weight or pressure on the cutting tool. Neither type will necessarily increase drilling speed, but by permitting advantage to be taken of "breaks" in the hole higher average cutting speed may be maintained. The control is essentially a safety device, and should be considered as such. It is not the purpose of this paper to discuss the merits of drilling controls, although the advantages over manual feed at the brake drum are obvious, but rather to point out some of the limitations. The Halliburton Control The Halliburton control is designed to operate during drilling through the agency of the draw works. Automatic and constant control. of the torque on the bit is governed by clutches on the control itself, and the line shaft to drum shaft drives on the draw works. In operations other than drilling the control is simply a jackshaft between prime mover and draw works. It is, of course, adaptable to any type of power. Because control of the torque on the bit is dependent upon the various ratios or clutch combinations available on the Halliburton control and the draw works, it follows that there are certain limitations in points of control. Table 1 shows the possible ratios which can be obtained with the control and a popular type of three-speed draw works, it being assumed that the highest possible gear combination-the combination which when engaged will suspend the least amount of weight-has a value of 1.00.

Jan 1, 1928

By P. T. Carter, A. B. Murad, H. B. Bell

N. A. Gokcen (Michigan College of Mining and Technology, Houghton, Mich.)—The activities of silica, represented in Fig. 5 for the systems MnO-SiO2 and CaO-SiO2, are in disagreement with the established binary phase diagrams. At Ns102 = 0.50 in MnO-SiO2, and at Ns102, = 0.65 in CaO-SiO2, each binary system is saturated with respect to silica at 1550°C, and therefore as102, is unity in each case. The curves for as102 (FeO-SiO2) and as102, (MnO-SiO,) should nearly co-

Jan 1, 1953

By Owen F. Devereux

Two discrete types of microstructure me seen in cermets formed by the reaction: 4Al (liquid) + 3SiO2 (glass) — 2A12O3(a) + 3Si (solid) Relatively coarse-grained macroscopically isotropic specimens resulted from reaction with aluminum containing appreciable silicon, while macroscopically anisotropic fine-grained specimens were formed by reaction with aluminum low in silicon. Optical microscopy, electron microscopy, and X-ray diffraction suggest that the anisotropic material contains gross areas in which submicroscopic grains of a A12O3 are oriented along radial lines drawn from the specimen surface. These lines are presumed to originate at defects in an otherwise protecting surface layer. A unique cermet is formed by the reduction of high-silica glass by molten aluminum according to the reaction: 4A1 (liquid) + 3SiO2 (glass) — 2A12O3 (a) + 3Si (solid) The free-energy change accompanying this reaction is -150 kcal at 800°C; the volume change (volume of A12O3 and silicon minus volume of SiO2) is +6 pct. The reaction product, however, contains aluminum metal as well as Al2O3 and silicon because some of the product silicon is dissolved in the aluminum bath and is replaced by aluminum in the structure. The product is a hard gray solid that retains the external dimensions of the original silica article. The system has been studied in the past, the investigations culminating in patents to George1, 2 and Saw-chuk., The former emphasize that this reaction is but one of a relatively broad class of such systems, while the latter demonstrates that a marked improvement in the gross physical properties of the cermet can be obtained by dissolving appreciable quantities of silicon in the aluminum reactant. The system has also been studied by workers at Rolls Royce Ltd.,4-6 who have patented the addition of small quantities of arsenic, antimony, bismuth, or phosphorus to the reactant bath to SO impede the reaction that glass fibers may be metal-coated by immersion in molten aluminum.

Jan 1, 1969

By M. C. Smith, W. V. Green, D. M. Olsen

The creep-rupture behavior of commercial powder-metallurgy molybdenum rod is reported in the temperature range 1600" to 250O°C, at stresses up to 9000 psi and times up to 1 month. The effects of temperature, stress, and grain growth are discussed. Rupture time is fitted to the Larson-Miller parameter and compared to lower-temperature and higher-stress results reported by pugh.1 BECAUSE of its high melting point, molybdenum should retain useful strength to relatively high temperatures. Combined with its ready availability in the United States, this makes it attractive for many applications in missiles, rockets, and so forth—wherever its susceptibility to oxidation can be tolerated or overcome. The mechanical properties of molybdenum rod in the temperature range —200" to 1540°C have been reported by pugh,' Bechtold,' Parke,3 and Carriker and Guard.4 Madden and chen5 have measured the tensile properties of molybdenum single crystals in vacuum up to about 2500°C. As one further step in evaluating its mechanical usefulness, the constant-load creep-rupture properties of commercial powder-metallurgy molybdenum rod have been investigated in the range 1600" to 2500°C. MATERIAL TESTED Creep specimens were machined from 1/2-in. round commercial molybdenum rod, manufactured from powder by pressing, sintering, and swaging. Spectrochemical analysis of the rod showed "traces" (less than 0.01 pct) of silicon, aluminum, chromium, iron, and zirconium, and "faint traces" (less than 0.001 pct) of manganese, magnesium, cobalt, and nickel. Carbon content was 130 to 200 ppm, nitrogen was 110 to 180 ppm, and oxygen 30 to 35 ppm. A typical microstructure of the as-received rod is shown in Fig. 1. Room temperature tensile properties for five specimens strained at about 0.015 in. per in. per min are shown in Table I. CREEP SPECIMENS USED The specimens used for creep-rupture testing are illustrated in Fig. 2. The 1/4-in.-diam gage section was 3/4 in. long, and terminated at shoulders 5 mils high. These shoulders served as fiducial marks for optical strain measurements. Surface finish on the gage section was 16pin. r.m.s. One specimen, for a "long-time" test described below, was modified by dividing the 3/4-in. gage length into three 1/4-in. long sections with individual diameters of 0.250, 0.230, and 0.210 in., each terminating in a pair of fiducial shoulders. TESTING PROCEDURE The constant-load creep-testing machine used has been described by Smith, Olson, and Brown.6 In it the specimen is held vertically on the axis of a cylindrical tantalum or tungsten heater tube by threaded molybdenum or tungsten grips. Both specimen and grips are heated by radiation from the heater-tube, which is heated by its own electrical resistance. The bottom specimen grip is held at its lower end by a clevis pin. The testing load is applied to the specimen through the upper grip by means of hanging weights, a constant force-multiplication lever system, and a pull rod sealed to the chamber lid by a bellows. The incandescent specimen is viewed by an external optical system through slots in the heater-tube and radiation shielding, and an enlarged image of it is projected on a ground-glass screen. Gage-length measurements are made on this image with a pair of cathetometers. Thorium oxide coatings were applied to the threaded ends of most specimens, to prevent diffusion-welding of specimens to grips during testing. Without such a coating welding usually occurred, and grips were often broken by subsequent efforts to remove the tested specimens.

Jan 1, 1960

By George Sachs, S. M. Clark, George Espey

he tendency of a commercially drawn cartridge case to crack in the mercury test and the relation of cracking tendency to residual stress retained after drawing were studied. The fourth drawpiece (next to the final) of caliber 0.30 cartridge cases produced by Frankford Arsenal were selected as test pieces. These exhibited an exceptionally high cracking tendency, making a detailed study possible. To obtain fast cracking in the mercury test, about 0.0015 to 0.003 in. must be removed from the wall thickness of the drawpiece by pickling, and it must be subjected to the mercury test immediately after washing. Removal of the adhering mercury by annealing and subsequent squeezing of the case in a vise was used to reveal definitely the presence or absence of cracks. Various lots of apparently identically fabricated cases were shown to possess a different cracking tendency. Machining off or boring a hole in the base gradually reduced and eventually eliminated the cracking tendency. On the contrary, shortening of the wall (body) reduced the cracking tendency only if the wall became so short that the cracking zone was directly affected. By boring out the base and pickling from the outside and then splitting the resulting rings, it was possible to determine the approximate stress distribution in the base and in the adjacent part of the wall. Small compression stresses were present in the core and the major part of the base, while the surface of the base and the adjacent wall contained high circumferential tensile stresses. On the contrary, the wall when parted from the base contained only insignificant residual stress. The conception is advanced, that the stress distribution in a drawn cartridge case corresponds fundamentally to that of a tube (wall) shrunk on a disk (base). Such a stress distribution results from the tendency of the base to recover elastically by an increase in diameter from the biaxial compression during drawing while the wall exhibits little tendency to change its diameter after progressing through the die. This is confirmed by measurements which show the base diameter to be slightly larger than the wall diameter.

Jan 1, 1945

By C Gunther

The classification here used is one of convenience only; it is not intended to include all known types of ore deposits. The characteristic features of the several well-marked types of primary mineralizations are described without reference to the ultimate source of their metals. The minerals of many deposits of obscure origin were probably introduced through fissures that are now healed, or are due to the migration of metals from such deposits. It is not within the scope of this book to enter into a general discussion of the genesis of ore deposits but, in view of the progress being made in our comprehension of the conditions under which ore deposits were formed, mention should be made of recent work. J. E. Spurr's two volumes, "The Ore Magmas," are recommended as crystallizing the views of those who are inclined to ascribe the origin of most ore deposits to a differential precipitation from magmatic rock masses and to the migration and precipitation of the viscous, liquid or gaseous exhalations from those masses. He has especially emphasized the role

Jan 1, 1932

By Moore, Richard B

PROBABLY no other metal excites as much interest, among both scientific men and the general public, as radium. This is due partly to the high cost of radium salts and partly to the peculiar properties of the element. Since radium-bearing ores were discovered in the United States, the interest of American scientific men has been stimulated and, at the present time, more radium is extracted and refined in this country than in all the rest of the world together. HISTORY The property of radioactivity was discovered, partly by accident, by Henri Becquerel, the French physicist, in 1896. He was experimenting with certain fluorescent substances in order to find, if possible, a connection between fluorescence and the recently discovered Y-rays. Among other chemicals which possess the property of fluorescence, he was using

Jan 8, 1918

By B. R. Queneau

[ ] B. R. QUENEAU-One of the difficulties in metallurgy has always been a lack of precision in measurement, and I think the authors are to be congratulated on developing a method which will give us an accurate and dependable quantitative estimate of the amount of retained austenite. O. ZMESKAL*-As Chairman Queneau said, this is indeed an ingenious and needed determination. We have seen figures presented of 1/2 pct retained austenite determined, and I would like to ask the authors the lower limits of this method. How far down do they feel they can go in improving the technique still more?

Jan 1, 1948

By A. F. Taggart

THE following notes represent significant excerpts from a mass of records of experimental work done in the ore-dressing laboratory at the Columbia School of Mines during the years 1926 to 1928-inclusive. CLASSIFICATION OF EXPERIMENTAL WORK The experiments performed may be grouped for purposes of description under the following general -headings: I. Collecting agents. a. A method for quantifying collecting effect. b. Coating with undissolved collecting agents (oils) c. Action of dissolved collecting agents. II. Frothing agents. a. A method for quantifying frothing effect. b. Relation between frothing effect and chemical composition. III. Inorganic reagents. a. Methods of studying the effects of these reagents. b. Effect on slime dispersion. c. Effect on sulfides. SUMMARY OF THE ORIGINS OF PRESENT-DAY FLOTATION PRACTICE The first practicable, foolproof method of froth flotation was described in U. S. patent 835120, issued in 1906 to Sulman, Picard and Ballot, and in the equivalent patents in other countries. A number of less simple methods of producing the same result had been described previously in patent publications and otherwise.1 The reagents specified in all of these early patents were "oils" and, in addition, some inorganic substance, usually an acid. The quantities of reagents recommended and added were enormous when' compared with those used today.

Jan 1, 1929

[A Aall, Christian H., M49 B VP, Dir of Smelt & Refin, Am. Metal Climax Inc., 1270 Ave. of the Americas, N.Y. Aaroe, Stanley L., A54 B VP, The W. S. Tyler Co. of Can. Ltd., St. Catharines, Ontario, Canada Abalos, Toodulo Q., J57 A Prod Foreman, Lepanto Cons. Mng. Co., Mt. Province, Philippines Abbass, G., M55 P. O. Box 680, Hong Kong, China Abbitt, James M., A54 770 Sole Blvd., Bartow, Fla. Abbott, Raymond C., J59 3442 Greenwich Ave., Columbus 24, Ohio Abdullah, N. Y., J53 Dept. of Mines, Res. Div., P. O. Box 1016, Tiger Lane, Ipoh Perak, Malaya Abel, John F., Jr., J53- 100 Maple, Littleton, Colo. Abell, Leo M., M31 B Conc Supt, Phelps Dodge Corp., Morenci, Ariz. Abendroth, Harry E., A57 A Geol, Union Carbide India, 183 Brabourne Rd.. Calcutta. India]

Jan 1, 1961

By V. H. Gottschalk

THE solubility of gases in metals has been of interest since Graham's time in 1866, but, although the subject was actively studied by iron and steel metallurgists during the eighties, the era of painstaking laboratory investigation begins in 1907 with the publication of Sieverts'1 thesis on the occlusion and diffusion of gases in metals. Since then, Sieverts has worked almost continuously in this field, and his views on the subject are the prevailing ones at the present time.2 Probably the most important result obtained by Sieverts, and frequently verified since by other observers, is the discovery that at a constant temperature the solubility of almost all gases in both the liquid and solid state of most of the metals is proportional to the square root of the pressure (for pressure above 100 mm.). The obvious explanation of this fact is that the gas dissolves as atoms and not as molecules, although it has been pointed out a number of times, first by Donnan and Shawl in connection with their work on the solubility of oxygen in silver at 1075° C., that the formation and solution of a compound of the metal and gas would also be indicated by a variation of the solubility with the square or higher root of the pressure. Sieverts4 himself raised the question whether the usual explanation (i. e., that the gas dissolves as atoms) may not be wrong, when he found that the square root law held also for the solubility of sulfur dioxide in molten copper; in which case dissociation into simpler molecules or atoms does not take place. Stubbs5 subsequently showed that Sieverts and Krumbhaar's "constant" for sulfur

Jan 1, 1932

By J. Spotts McDowell

INTRODUCTION The magnitude of the thermal expansion of silica brick, and its inability to withstand rapid temperature changes, present problems of considerable importance in the manufacture of siliceous refractories. In the study represented by the experimental data herein described, these problems are considered from the point of view afforded by the results of recent investigators: Fenner and his associates of the "Geophysical Laboratory, Washington, D. C., who have established the stability relations of the silica minerals, and Endell and co-workers in Berlin, who have studied the changes brought about in the constitution of siliceous refractory materials upon the application of heat. In the process of manufacture, the quartzite from which the brick is made changes in part into cristobalite and tridymite. The attempt is herein made to determine by microscopic methods the degree of transformation in various specimens of test bricks manufactured at slightly varying temperatures of burning, with varying coarseness of grain, and to determine the effect of repeated burning. The effect of variations

Jan 10, 1916

By Thomas Fraser, Alvaro Abreu

The work described in this paper was carried out under the sponsorship of the Foreign Economics Administration and in cooperation with the Departamento Nacional da Produggo Mineral, Rio de Janeiro. The project was undertaken to obtain complete data on the variations in washability of coal to be used for coke manufacture in the steel industry and to determine the economy of preliminary hand-sorting operations. The coal-producing industry of Brazil is in that pioneering stage in which operating practices and methods are just being developed. Increased wartime demand for fuel, coincident with a drastic curtailment of foreign supplies due to lack of shipping facilities, has put a tremendous pressure on the national industry to furnish more coal. Under this incentive, production facilities are being -expanded- and new methods of operation are being tested. Such changes are being developed both by improvement of existing methods that originated in the field and by adaptation and modification of methods introduced from the United States and Europe. These mining conditions and mining practices in Brazil are typical of what the American mining engineer will find in many instances when he goes pioneering into the developing coal fields of the Southern Hemisphere. The producing coal fields of Brazil are all in the southern states of that country. The coal measures are in a band roughly paralleling the coast and extending in a generally southwesterly direction from northern Sao Paulo through the states of Paraná, Santa Catarina and Rio Grande do Sul to near the Uruguayan border in the vicinity of Bajé. The accompanying map1 (Fig. I) shows the general location of these fields and also the principal routes of movement of both national and imported coal in a late pre-war year (1940). Statistical data on production by states up to that year are given in Table I. Rio Grande do Sul is still the largest producer among the coal states; but wartime

Jan 1, 1947

By Alvaro Abreu, Thomas Fraser

The work described in this paper was carried out under the sponsorship of the Foreign Economics Administration and in cooperation with the Departamento Nacional da Produggo Mineral, Rio de Janeiro. The project was undertaken to obtain complete data on the variations in washability of coal to be used for coke manufacture in the steel industry and to determine the economy of preliminary hand-sorting operations. The coal-producing industry of Brazil is in that pioneering stage in which operating practices and methods are just being developed. Increased wartime demand for fuel, coincident with a drastic curtailment of foreign supplies due to lack of shipping facilities, has put a tremendous pressure on the national industry to furnish more coal. Under this incentive, production facilities are being -expanded- and new methods of operation are being tested. Such changes are being developed both by improvement of existing methods that originated in the field and by adaptation and modification of methods introduced from the United States and Europe. These mining conditions and mining practices in Brazil are typical of what the American mining engineer will find in many instances when he goes pioneering into the developing coal fields of the Southern Hemisphere. The producing coal fields of Brazil are all in the southern states of that country. The coal measures are in a band roughly paralleling the coast and extending in a generally southwesterly direction from northern Sao Paulo through the states of Paraná, Santa Catarina and Rio Grande do Sul to near the Uruguayan border in the vicinity of Bajé. The accompanying map1 (Fig. I) shows the general location of these fields and also the principal routes of movement of both national and imported coal in a late pre-war year (1940). Statistical data on production by states up to that year are given in Table I. Rio Grande do Sul is still the largest producer among the coal states; but wartime

Jan 1, 1947

By Frederick T. Fischer

INTRODUCTION Post-Lower Ordovician karstification on a continental scale produced a wide-spread paleoaquifer in the upper portion of the Knox Group of the Southeastern United States. The presence of economic zinc deposits in the Knox of Tennessee is considered to be a con- sequence of this paleoaquifer(1). During The New Jersey Zinc Company's initial exploration of the middle Tennessee region the known artesian nature of modern Knox water and its potentially adverse effect upon mining activities was a matter of concern. This concern intensified as a mining situation appeared imminent and a program of hydrologic investigation was begun in early 1969 and continued through August 1972. The preliminary findings of this work were reported at the AIME World Symposium on Mining and Metallurgy of Lead & Zinc in 1970(2). This paper presents additional data acquired during subsequent stages of the program and relates the hydrologic relationships to the overall geologic framework of the area. PHYSICAL GEOGRAPHY The Elmwood mine is 85km east of Nashville and 8km southeast of Carthage in Smith County, Tennessee (Figure 1). Its physiographic location is in the Central Basin of Tennessee, a basin resulting from erosional breaching across the Nashville Dome of the Mississippian strata which now form the bordering Highland Rims. Both the Central Basin and Highland Rims are divisions of the Interior Low- lands Province. Outcropping rock units of the Central Basin are predominantly Middle Ordovician limestones with scattered high hilltops capped by Devonian and Mississippian strata. One outlier

Jan 1, 1977

By G. Barbery

Since the original paper, two methods have been introduced to compute the parameters of the three parameter size distribution equation: [ ] Both of them are based on graphical means, which are time-consuming and of little statistical significance. A program has been developed, using the Gauss-Newton method to compute by nonlinear regression analysis the parameters of the equation. Although the method is quite general in curve-fitting applications, it does not appear to be used in the field of size analysis, and a brief description is given. As applied here, the Gauss-Newton method involves the minimization of the least squares: [ ] where n is the number of sieves used. The second member of Eq. 2 can be approximated by a multiple Taylor's series expansion of first order about a starting value [ ] The minimization of Q (r,s,Xo) means: [ ] Putting Eq. 3 into Eq. 2 and differentiating, we obtain a system of equations which can be represented in matrix symbolism (box) The system can be solved for: [ ] and the operations repeated with new values: [ ] The starting values for r and s are taken as 1, for Xo, a value higher than the maximum sieve opening value. Applied to the data given by Herbst 5,6 for batch grinding of 7 X 9 mesh dolomite, the parameters given in Table 1 were obtained. The discussion of the significance of the residual sum of squares is a difficult subject in multiple nonlinear

Jan 1, 1972