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By Edwin Ludlow

EDWIN LUDLOW, president of the American Institute of Mining and Metallurgical Engineers for the year beginning Feb. 15, 1921, is a well-known figure in the state that was the birthplace of the Institute-Pennsylvania-although he was born and educated in New York and is again one of its residents, after years of active work in the field. Mr. Ludlow was born at Oakdale, Long Island, and was graduated from the School of Mines at Columbia University with the class of 1879. After graduation, he became a civilian worker with the U. S. Engineer Corps under General William Ludlow, his brother, and for two years did river and harbor surveying along the New Jersey coast.

Jan 1, 1921

By J. A. Kitchener, J. P. Anfruns

Measurements have been made of the rate of capture of single particles of strongly hydrophobic, surface-methylated, quartz, of sizes ranging from 12 to 40 µm diam., by single rising bubbles of diam. 0.5 to 1.1mm. The results agree closely with the theoretically calculated hydrodynamic collision rates, indicating that, in this system, every collision results in capture and retention of a particle.

Jan 1, 1976

By William F. Blake

The discovery of tin-ore in the Black Hills of Dakota dates from June, 1883, and short preliminary notices were published in September of that year.* The discovery-point is known as the Etta Mine, in the central portion of the Hills, about six miles east of

Jan 1, 1885

By LOWELL LAWRENCE

MAGNETITE minim and milling in the Eastern States continued at a low rate of production during 1934. The year's output was 50 per cent greater than in 1933, but when one considers that the 1934 output was only 1.5 per cent of the combined plant capacities of the eastern iron ore producers, the far-reaching effect of unrestricted importation of foreign ores and pig iron is apparent. The Chateaugay Ore and Iron Co., at Lyon Mountain, N. Y., produced 1.00,136 gross tons of concentrated and sintered ore up to Nov.1, when operations were closed clown. At Mineville, the Witherbee, Sherman Corp. confined its productivity to part-time operation of its Old Bed and Harmony mines front May 1 Lo Oct. 27. This period of activity was brought about by the use of Mineville ores in the recent blast made by the Green Island furnace at Troy, N. Y. The Forest of Dean property at Fort Montgomery, N, Y., has continued closed down during the year.

Jan 1, 1935

By Harrison Schmitt

DURING the past decade the writer has studied and mapped certain ore deposits and their structural associations in the states of Chihuahua, Durango, New Mexico and Arizona, and he believes that these deposits, with the exception of the manto-chimney, are representative of the principal types in the area of the states named. In this paper the deposits are described; then generalizations are drawn so far as seems appropriate. HANOVER, NEW MEXICO The Hanover; New Mexico, zinc deposits were briefly described by Lindgren and others,1 Paige2 and recently in more detail by Schmitt.3 These, the kind ordinarily called contact metamorphic, border the southern end of an oval area of granodiorite intrusive 3/4 mile wide and 2 1/2 miles long (Fig. 1). The granodiorite has intruded, folded, and metamorphosed sedimentary and igneous rocks, which range in age from pre-Cambrian to Upper Cretaceous. About 90 per cent of the ore has replaced coarse, recrystallized, pure, fossiliferous, lower Mississippian, nonmagnesian limestone (Hanover limestone) 110 ft. thick;4 about 75 per cent of it occurs in the upper 50 ft. of this horizon just below an 18-ft. lower Pennsylvanian shale bed, which lies on a locally inconspicuous unconformity representing upper Mississippian time. The orebodies show five shapes or attitudes, each dependent on a special structural situation: 1. Most of the ore occurs as podlike; thick lenslike or other "three-dimensional" shoots extending from top to bottom of the Hanover limestone and lying adjacent to the outer contact of a silicate zone largely of andradite, which follows the intrusive contact (Figs. 1 and 2).

Jan 1, 1933

By M. W. Clegg

The application of the Laplace transformation to problems in the flow of compressible fluids in porous media has provided a large number of exact solutions. For plane radial flow, however, these solutions are either complex integrals or infinite series and are of little value to the field engineer. In the case of production at constant well pressure, the available approximate solutions me valid for large times only. In this paper it is shown that an approximate inversion formula for the Laplace transform, developed for the solution of viscoelastic problems, is applicable to radial flow problems and provides simple analytical solutions to constant terminal pressure problems. The method may be used to obtain approximate solutions to many problems, including media with radial permeability discontinuities, multi-layer formations and pressure buildup in wells after shut-in. The results are compared with the few available computer solutions as well as the large time solutions, and it is shown that this approximate method greatly extends the time interval over which a simple analytical solution is acceptable. INTRODUCTION The study of transient problems in the flow of fluids through porous media has benefited greatly from the application of transform methods. The use of the Laplace transformation for solving parabolic equations has been widely discussed in the field of heat conduction and diffusion as well as in the petroleum literature. Removal of the time variable with the Laplace transformation generally reduces the problem to a boundary value problem which may be solved by standard techniques. A much more formidable problem then faces the engineer, however, for frequently the transform does not possess a simple inverse. The result is that the general inversion integral must be used and this leads to either an infinite integral or an infinite series, both of which are difficult to handle from a computational standpoint. Asymptotic approximations for the inverse have been known for some time and these yield approximate inverse functions that are valid for very large or very small times — but frequently the times of interest lie somewhere between these two extremes. Therefore, some acceptable approximation valid over a larger interval of time is desirable. During the past few years a number of methods for achieving this have been developed and some of these are discussed briefly in this paper. The relative merits of the various methods are not evaluated here, but some general conclusions reached by other authors are given. One of these methods has been applied to problems associated with the radial flow of compressible liquids to producing wells. In the case of production at constant well pressure, the method leads to simple analytical solutions for a number of standard problems; e.g., homogeneous formation, permeability discontinuities, pressure buildup. These solutions greatly extend the range of validity of the asymptotic ones (valid for large times only) and should be of value in studying the behavior of wells producing under constant pressure conditions. METHOD FOR THE APPROXIMATE INVERSION OF LAPLACE TRANSFORMS Much of the work that has been done on the approximate inversion of Laplace transforms has originated in viscoelastic problems. Apart from the asymptotic approximations,1 one of the first approximate methods was due to Alfrey.2 If (s) is the Laplace transform of f(t) defined by

By Richard H. Rein, John Chipman

The activity of SiO2, in the entire liquid system SiO2-CaO-Mg0-A12O3 at 1600°C is calculated from the distribution of silicon between these slags and Fe-Si-C alloys saturated with either graphite or silicon carbide, the activity coefficient of silicon in these alloys, and the requisite thermodynamic data. The activities of the other components in the ternary systems SiO2-CaO-A12O3, SiO2-MgO-CaO, SiO2-MgO -A12O3 are computed from these data by the IrON blast-furnace slags can be regarded as consisting of the four major oxide components, SO2, CaO, MgO, and A12O3 along with minor proportions of other oxides and of sulfur. The purpose of this study is to measure the activity of silica in the liquid solutions of these four oxides at iron-making Gibbs-Duhem equation with the aid of the known free energies of several of the interoxide compounds and the accepted phase diagrams. Based on these activities, new data are Presented for the free energy of formation of a number of the interoxide compounds. The free energy of mixing the liquid metasilicates of CaO and MgO shows slight positive deviations from the ideal. temperatures and to obtain activities of the other components by application of the Gibbs-Duhem equation and the properties of several interoxide compounds. Recent investigations on the activity of silica in the SiO2-CaO-A12O3 system1-3 and recogntion of a serious error in older data for the free energy of formation of SiO2 (Ref. 4) have succeeded in bringing a fair degree of concordance into the results of different investigators. In the present study, the activity of silica is obtained from the silicon-distribution experiments described in a previous paper,' the revised activity coefficient of silicon

Jan 1, 1965

By C. S. Smith

The solubility of tantalum at 1100°C is 0.025 pct in pure copper, 1.2 pct with 20 pct Ni, and 2.7 pct with -30 pct Ni. The solubility decreases with temperature, and the alloys are precipitation hardenable. A 79/20/1 Cu-Ni-Ta alloy reaches maximum hardness after aging at about 750°C and, if cold worked, does not recrystal-lize below that temperature. The alloys have good tensile properties at moderately elevated temperatures and, since they can be hot and cold worked nearly as easily as cupronickel, they are suggested for service at temperatures above the usual limits for copper alloys. MASSIVE tantalum dissolves extremely slowly in copper-rich alloys, and tantalum powder forms refractory surface layers which prevent its solution unless special precautions are taken. After many trials, an 80 pit recovery was consistently obtained by using a mixture of a finely divided tantalum powder with two or three times its volume of potassium tantalum fluoride (K2TaF1,-melting point about 750°C) poured in a slow stream directly on to the surface of the molten copper alloy, so that each particle would remain coated with flux and be immediately and individually wetted by the molten metal. A 50-50 nickel-tantalum alloy has a melting point of about 1400°C and small lumps of it slowly but satisfactorily dissolve in molten copper-nickel alloys as does commerical "ferro-tantalum." The high affinity of tantalum for carbon makes it necessary to avoid carbonaceous crucibles. COPPER-TANTALUM ALLOYS Castings with good shrinkage resulted when 0.1 pct Ta or more was added to copper melted under charcoal and cast in air. Copper in two-pound melts to which 0.1, 0.15, and 0.2 pct Ta had been added retained residual amounts, by analysis, of 0.025, 0.023 and 0.026 pct, respectively. The solubility of tantalum in molten copper at about 1200 °C is therefore about 0.025 pct. The electrical conductivity of these three samples was 100.48, 100.00 and 100.20 pct IACS in the annealed condition, and 98.24, 97.98 and 98.08 in the cold-drawn condition. Wires 0.080 in. in diam withstood from thirteen to nineteen reversed bends after annealing for 30 min in hydrogen at 850°C and the metal was therefore completely deoxidized. The annealing temperature corresponding to 50 pct loss of work hardness in 1 hr in a strip cold rolled 77 pct reduction was 175C, compared to 230°C for equivalent undeoxidized material. It is unusual for a decrease of recrystallization temperature to result from an alloying addition, and the tantalum probably combines with and removes some minor impurity in the original copper that restrained its recrystalliza- tion. No difficulty whatever was encountered in hot or cold rolling or drawing these ingots, and were tantalum not so expensive it would make an excellent deoxidizer for copper. COPPER-NIcKEL-TANTALUM ALLOYS Studies were made of the solubility of tantalum in a large number of copper-rich alloys, but of these significant solubilities were found only in the case of an iron alloy (which, however, separated into two immiscible liquid layers) and alloys of copper and nickel, in which tantalum is freely soluble and which were found to have interesting properties. The latter alloys are the subject of U. S. Patent No. 2,430,306 (1947). They are not at present available commercially. The Ternary Constitution Diagram—The copper-rich corner of the constitution diagram was constructed on the basis of microscopic examination of samples of various composition and treatments. The alloys were hot rolled to 0.25 in. from castings 0.625 in. thick, then annealed for 1 hr at 1000°C, quenched, cold rolled to 0.10 in. and finally annealed for various periods of time at temperatures between 800" and 1100°C in a nonoxidizing atmosphere and quenched. When the solid-solubility limit had been transgressed, particles of a compound believed to be Ni2Ta*were

Jan 1, 1960

By W. F. Chiao, R. B. Gordon

Tile sharp-yield point found in magnesium crystals in the solulion-treated and aged condition is studied by dislocation internal-friction experiments. The results show that the sharp yield is not file to the sudden release of pinned dislocations hut is movc likely due to the rapid multiplication of an initially small number of dislocations. Recovery or the dislocation internal friction after deformation is also studied. This yecovery results from the re-pinning of dislocations by a solute, presumably nitrogen, which moves with a relatively small activation energy. SHARP-yield points, when they occur, are a striking feature of the stress-strain curve generated during a tensile test. Although commonly associated with steel, sharp yielding has been found in a variety of metallic and nonmetallic crystalline materials. In particular, sharp-yield points have been found in zinc"' and cadmium3 containing nitrogen. With this background, Geiselman and Guy4 investigated the tensile properties of magnesium single crystals containing nitrogen to see if sharp yielding also occurs in this system. They found that sharp yields did indeed occur in solution-treated and aged specimens tested at elevated temperature but were not able to give conclusive proof that the sharp yield was caused by nitrogen, a yield drop being observed even in their purest crystals. Sharp-yield points have also been found in various polycrystalline magnesium alloys.7'8 In the study of the sharp-yield phenomenon it is desired to observe the behavior of dislocations in the earliest stages of the deformation process. Internal-friction experiments are useful for this purpose because dislocation damping is sensitive to the mobility of free-dislocation segments. At low strain amplitudes the damping, A, due to the the forced vibration of dislocation segments of average length L is ? =KAL4 [1] where A is the dislocation density and K, if the applied frequency is well below the resonant frequency of the dislocation segments? is a constant for the sample under observation.5 Dislocation damping, because of the fourth-power dependence on L, is particularly sensitive to the creation of free-dislocation segments during deformation. Since sharp yielding is associated with the sudden release of pinned-dislocation segments, marked changes in the dislocation damping are expected at the yield point.6 The use of the dislocation-damping observations to help elucidate the incompletely understood mechanism of yielding in magnesium is the primary objective of the experiments reported here. PROCEDURE Many investigations have shown that very marked and rapid changes occur in the dislocation damping of of a deformed material as soon as the straining is stopped.5 It was quite essential, then, for the purpose of this investigation, to make the damping measurements during the deformation of the samples. This can only be accomplished through the use of the ultrasonic-pulse method. In this method traveling sound-wave pulses are used and, in contrast to resonating-bar methods, only the sample ends are set in vibration. Thus, the sample can be gripped along its sides in the tensile-test machine without disturbing the damping measurements. In the pulse method, the decrease in the amplitude of a sound pulse is measured as it travels back and forth through the sample. If A is the amplitude after traversing a distance x and A. is the initial amplitude, A=Aoe-ax [2] and a is called the attenuation. It is commonly measured either in units of cm-I or as db per µ sec. The observed attenuation in a metal sample is due to a number of causes. These include scattering by grain boundaries and impurity particles, thermo-elastic damping, diffraction effects, stress-induced ordering of solute atoms, and dislocation damping. The total observed attenuation in a given sample usually cannot be resolved into these various components, but changes in a due solely to changes in dislocation damping can be accurately determined, provided the experiment is arranged so that all other sources of damping are held constant. It is desired to reduce the extraneous sources of attenuation to a minimum and for this reason the experiments are done on single crystals of high purity. Magnesium crystals offer the further advantage that, when properly oriented, only a single set of slip planes is active during deformation. Crystal Preparation. The method of sample preparation is similar to that of Geiselman and Guy.4 The starting material was high-purity, sublimed magnesium rod supplied by the Dow Chemical Co. Melting under Dow 310 flux was used to reduce the nitrogen content of the starting material: the fluxing was done under an argon atmosphere and the

Jan 1, 1965

By D. Turnbull, J. H. Hollomon

THERE is a large body of evidence'" indicating that solidification during the liquid-solid transition is usually induced by heterogeneities present in the liquid. By dispersing liquid metals into small droplets, the impurities responsible for catalyzing solidification are isolated within a small number of these droplets. The effect of the foreign body therefore is restricted to a single drop by this technique. Thus upon cooling below the melting temperature, solidification is initiated by homogeneous nucleation in the majority of the droplets that do not contain impurities. In the case of solidification of liquid metals, the activation energy for nucleation is so great that its rate changes by orders of magnitude for a change in temperature of only several degrees centigrade.' Effectively homogeneous nucleation occurs at a critical temperature upon continuous cooling. Thus by microscopic observation of single particles during cooling, a temperature at which the rate of homogeneous nucleation becomes sensible can be determined.3 since at the temperatures at which nucleation occurs in the absence of impurities the rate of crystal growth is extremely rapid, the temperature at which the entire particle solidifies is very nearly the temperature at which the nucleation of the solidification occurs. Thus for liquids that freeze at high temperatures the onset of nucleation can be established by simply observing the temperature at which the marked heat evolution and increase in brightness of the particle occur. For liquids that freeze at lower temperatures the onset of nucleation can be determined by a rumpling and change in shape of the particle resulting from its solidification. The microscopic technique for observing the solidification of small particles has already been described." In earlier papers the nucleation of solidification of pure metals 5,6 and of alloy systems7 showing complete liquid and solid solubility have been described. In the present paper, the observations are extended to a simple eutectic system (Pb-Sn) where the possibility of the formation of two solid phases exists. Metals for the investigation were obtained from the American Smelting and Refining Co. in the form of pure lead and pure tin, 99.8 and 99.9 pct purity, respectively. An ingot of each of the pure metals was made into shot by heating the metals at a temperature about 50 °C in excess of the melting point and pouring the liquid slowly into a container of water at 15°C. Samples of the shotted pure metals were weighed out to make alloys containing 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, and 90 atomic pct Pb. Samples of each alloy were then melted in separate beakers. Each melt was poured through a pyrex funnel into a cylindrical mold (% in. ID). The casting solidified in 10 to 20 sec. The inside of the mold as well as the funnel through which the metal was poured were coated with graphite to eliminate adherence of the metal. Analyses were performed on some of the compositions and are given in Table I. The compositions also were checked for these samples and for those that were not analyzed by determining the spread between the liquidus and the solidus upon melting the small metal particles. These measurements agreed as well with the nominal compositions as the analyses listed above. Results The results of the supercooling experiments for the several alloys are summarized in Table II and plotted on the constitution diagram in Fig. 1. Data for the pure lead and pure tin were taken from earlier investigations. The values for the maximum supercooling of the several alloys are the average of several determinations on a number of drops of each alloy. The maximum value in any determination was within about 2 pct of the average. For the alloys containing from 20 to 60 atomic pct Sn, inclusive, two marked changes of the surface structure were observed upon cooling. At the higher temperature, after the first appearance of the solid phase it continued to grow slowly at a constant temperature and then stopped. At the lower temperature the alteration of surface structure was abrupt. For the alloys containing from 70 to 95 atomic pct Sn, inclusive, an abrupt change in surface structure was observed at a single critical temperature.

Jan 1, 1952

By John B. Farish

This brief paper is designed to place on record some interesting occurrences, recently observed during an examination of the Golden Age Mine, in Boulder county, Colorado. Leaving the little village of Jamestown—or Jimtown, as it is more generally called—located in the canon of James creek, the road winds up a steep mountain composed of the coarse gray granite, with occasional belts of gneiss, common to all the mineral-bearing sections of Boulder county, to the summit of the front range of the Continental Divide. Here are located the mines known as the Golden Age and the Sentinel, the relative locations of which are shown in Fig. 1. The Golden Age location covers the outcrop of a quartz-porphyry dike, which cuts through the granite country-rock with a strike of about N. 70' E. This dike varies in width from a few feet, as at a point between the main shaft and the Hill shaft, to about 50 feet,

Jan 1, 1891

By K. E. Beu

IN the measurement of retained austenite concentrations in steels using the integrated intensity method,1 Averbach has pointed out" that the absorption factor A(0) for a flat sample making a glancing angle 4 with the incident X-ray beam can be combined with his constant factor R to obtain our constant factor" G provided that "1—There is no preferred orientation in the sample, and 2—The geometric requirements [for the sample, film, and X-ray beam] have been met precisely."' If A(0) can be combined with R to give G according to the equation G = R . A(0) [14] then the possibility for making non-compensating errors in the austenite determination has been eliminated. This has been described previously in a technical note." Because of the brevity of the previous note,3 it was impossible to emphasize the fact that the two conditions on preferred orientation and geometry can be easily met experimentally, contrary to Aver-bach's statement that: ". . . the necessary conditions must be tested experimentally for each determination, and this is done most easily by observing whether the apparent absorption has the form of Eq. 2 [the theoretical equation for A(0)]."" he way in which these two conditions can be met experimentally will be discussed briefly to help clear up this point. In addition to these two conditions, other factors such as sample shape, homogeneity, and grain size which also affect A will be included in this discussion. A (0) depends on sample shape. The theoretical function for A was derived originally for a flat surface.' In general we have found that a flat sample surface is readily obtainable." If such a surface can * The effect of surfaces which are not flat on the measurement of retained austenite will be discussed later. be obtained, it has the following advantages: 1—it is easily reproducible from sample to sample, 2—it is the form required for metallurgical examination —this type of examination being frequently desirable for this work, and 3—it is an efficient shape for diffraction purposes. Perhaps the most important of these features is that a flat sample surface is easily reproducible; hence, this requirement on the repro-ducibility of A from sample to sample is met for all such samples. Fig. 1—Schematic diagram of the quartz crystal monochromator diffraction unit. The centerline of the main beam is at 6' to the target face. The tangent to the crystal face is at 16.8' to the moin beam. The centerline of the monochromatic beam is at 33.6 to the main beam. The sample surface can be rotated in its own plane. The angle of the sample surface and the monochromatic beam can be adjusted by rotating about the vertical axis, The film holder can also be rotated about B so that the film can be exposed over the desired angular range. For Fe K, X = 1.932A. 1011 planes of quartz have d = 3.35A. A(0) depends on homogeneity and grain size. If the sample is badly segregated or the grain size is large, the effect of micro-absorption and primary extinction1. ' must be considered. It has been shown, however, that for most plain carbon or low alloy hardened steels, neither micro-absorption nor primary extinction effects are present.' A (0) depends on camera geometry. For a given angle 0, A remains theoretically constant from a geometrical viewpoint only if the following factors are kept constant: 1—the angle of inclination .+ of the sample to the X-ray beam, and 2—the centering of the sample with respect to the film cylinder. These are mechanical problems which can be solved readily if the facilities of a good machine shop are available. The arrangement used to insure that the angle 4 remains constant and the centering of the sample is reproducible is indicated schematically in Fig. 1. The sample is clamped against a thin plate with a hole in it by means of a spring-loaded pres-

Jan 1, 1954

By John Hays Hammond

IT was but a few years ago that the mining engineer, and his confreres, the civil, mechanical and electrical engineer, were stigmatized by politicians of the parish? pump variety as advance agents of unprincipled exploiters of backward countries. Today he is recognized as a most important missionary of civilization in opening up new territory to contribute its mineral wealth and incidentally its other resources for the needs of mankind. An engineer, it is now conceded, is not only a benefactor of the world at large, but is a primary factor in the betterment of conditions of the inhabitants of those countries developed by his skill and indomitable courage-for courage is requisite in pioneering and his indefatigable industry. The engineer will, I believe, become a real "Ambassador of Good Will," when the slow-consenting academic mind realizes as it must that beneficent deeds are more enduring and more convincing than mere gestures of professed amity.

Jan 1, 1929

By Fred S. Mulock

THE principal operating and producing properties covered by the Western Operations of the United States Smelting Refining and Mining Company are the U. S. and Lark mine in the Bingham district of Utah, the Bayard department in the Central mining district of New Mexico, the Midvale mill and smelter near Salt Lake City, the lead refinery of its subsidiary, U. S. S. Lead Refinery, Inc., at East Chicago, Ind., and the coal operations of its subsidiary, United States Fuel Company, at Hiawatha, Utah. Operations of lesser importance at this time are conducted either on company account or by lessees in the Centennial, Bullion Beck, and Eagle and Blue Bell mines in the Tintic district of Utah, the Hidden Treasure and Ophir mines in the Ophir district of Utah, and the White Knob mine in Custer County, Idaho. The Richmond-Eureka Mining Company, in which the Company owns a controlling interest, has leased its properties near Eureka, Nev., to the Eureka Corporation Limited. The Gold-road property at Goldroad, Ariz., has been shut down since 1942, and due to high costs of labor and supplies, consideration is now being given to removal of all surface and underground improvements. The mine and mill im¬provements at the Sunnyside property in Colorado, recently purchased by the Sunbank Corporation, a subsidiary of the Company, are now being dismantled.

Jan 1, 1948

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

Jan 1, 1930

By Frank Hall

THE needs of the World War showed the necessity of a metal stronger than cast iron which would supplement the supply of steel. So patriotic metallurgists were spurred to new efforts to improve the status of that half-breed of the metal world that had been, more or less erroneously, christened semisteel. As a result, it was developed that for certain purposes semisteel was superior to steel in the manufacture of shells. Steel, because of its greater strength and toughness, is able to carry a greater charge of explosive, weight for weight; consequently, a steel shell can be expected to cause greater destruction when used against fortifications or other inanimate objects, while semisteel, because of its comparative brittleness and its resulting greater fragmentation, is capable of inflicting more serious loss of life when used against opposing forces of men. Therefore, each has its proper place in the economy of war. For the present purpose, steel may be defined as a comparatively pure iron whose physical nature is modified by small amounts of carbon, silicon, sulfur, phosphorus, manganese, and possibly other rarer elements; while cast iron generally is limited to approximately 93 per cent. of iron, the remainder consisting of larger percentages of carbon, silicon, sulfur, phosphorus, and manganese. Semisteel may be defined as cast iron in which the carbon and silicon have been reduced to as low a point as is consistent with maintaining the nature of gray iron, and in which the remaining elements are manipulated so as to give the greatest strength.

Jan 1, 1920

Magazine Advertising $ 62,564 83 Magazine Sales 3,591 44 Total 66,156 27 Dues, Arrears 7,032 88 Dues, Current 96,839 74 Dues, New Members 6,525 00 Dues, in advance 1,907 02 Initiation Fees 7,584 00 Sale of Transactions 3,909 03 Sale of Binding .. 7,845 05 Sale of Special Editions 338 20 Sale of Year Book 76 20 Sale of Pamphlets 1,189 06 Sale of Authors' Reprints 867 54 Miscellaneous Receipts 62 93 Interest on Bank Balances 1,712 89 Interest on General Reserve Fund 337 50 Interest on Life Membership Fund 557 84 Interest on James Douglas Library Fund 5,491 89 Total Receipts $208,433 04

Jan 1, 1923

By S. R. Mitchell, M. Weissman, J. H. Brown

It has been demonstrated that for fine grinding operations, the energy input (E) and the product size modulus (k) are related by an equation of the form E = Ak1-n (1) where "A " and "n" are constants.(1) Also, it was suggested that "A" is determined by the comminuting device and that "n" depends primarily on the rock. It was the purpose of this investigation to study these constants by determining the form of an energy-size reduction relationship over an extreme range of energy inputs, and at the same time, to evaluate the minimum particle size produced during grinding. The comminution system consisted of a stainless steel laboratory ball mill in which quartz was ground at 60% solids for times ranging from 1 minute to 700 hours. The mill which measured 10" diameter by 12" long was loaded with about 60 pounds of balls ranging in diameter from 3/8" to 1-1/8" and was driven at 55 r.p.m. Quartz was selected for the tests because it is a brittle material for which size distribution data were expected to show a constant distribution coefficient regardless of product size.(1) This permitted specification of product size by a size modulus alone. The quantities measured were the time of grind (measure of energy input) and the specific surfaces of the products. Since no accurate method is available yet for determining particle size directly in the very fine size ranges specific surface data were used for this purpose. The relationship between these two quantities may be expressed as where Cis a constant which includes a shape factor, p is the specific gravity of the solid,_S is the specific surface and D is an equivalent particle diameter. For a material in which the distribution coefficient does not change with size the term (l/S) may be substituted for k in equation L if the proportionality constant "A" is changed correspondingly. This substitution was made in this work but in addition, screen analyses were made on several products to verify the equivalence of the two methods of size specification. EXPERIMENTAL DETAIL QUARTZ Quartz from two sources was tested. One series of tests was made on a clear, high purity crystalline quartz from Brazil and Arkansas, and another series was run on massive quartz fromNewHampshire. Grinding charges of the high purity material consisted of 2000 gram samples of -3-8 mesh particles, while the charges of the New Hampshire quartz were 500 gram samples of a -35+48 mesh screen fraction. The difference in the sizes of these two series of charges was not significant in view of the extreme size reduction accomplished, and the New Hampshire samples were smaller to permit ginding to finer sizes in shorter times than required for 2000 gram lots. SAMPLING AND ANALYSIS Separate charges were ground for all tests in which the grinding times were less than one hour and for all tests on New Hampshire quartz since these products were difficult to sample accurately without affecting the entire charge. During the long time grinding tests the mill was

Jan 1, 1961

By James F. Magee

There is nothing new about dragline dredging for placer gold. The use of the separate unit for excavating preceded the large barge with excavator mounted upon it, which has reached a high state of perfection through use in every part of the world. But at present there is a vogue for a small, inexpensive plant combining a dragline excavator on caterpillar mounting and a gravel-washing plant on a floating barge. The most efficient ones use a bucket of 1 to 2 yd. capacity with boom from 40 to 70 ft. long. The barge varies from 20 by 30 ft. to 36 by 48, and carries the trommel screen, pump, riffle sluices and power engine. Plants in Oboville District In the Oroville district eight such plants have been built since 1933, and have been operated with varying success. The most successful of these is the plant of the Wyandotte Gold Dredging Co. This organization of six active partners constructed its first plant on Wyandotte Creek in the autumn of 1933. To September of 1935 about one million cubic yards of gravel was dredged for an output of about $225,000 in gold. The operation has been successful from the beginning, because of wise management, which was based upon good plant design and proper principles of operation. All the partners have taken a more or less active part in the operation. Usually there is one at work on each shift, and they have conducted their own prospecting and building also. They elected H. F. England as manager, with wide power of control, and he carries out this responsibility energetically and successfully. One of the other plants, started shortly before the Wyandotte, finally abandoned its operation and sold its ground to the latter company, which successfully worked it for a profit. The failure of the other plant was due principally to poor excavating equipment. Another organization that built a plant some months later than the Wyandotte company had considerable difficulty in management and was unable to keep ahead of expenses. Finally, late last summer, it entered into an agreement with the Wyandotte company to have the latter supply

Jan 1, 1937