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H. M. BOYLSTON, Cambridge, Mass.-We should feel greatly indebted to Mr. Miller for collecting this admirable series of photographs, but I cannot quite agree with his conclusions as to their significance. He apparently concludes that these needle-like constituents which he has shown in a good many cases, in the welded material at least, are cementite; that is, as we understand it, a carbide of iron. Now there seem to be

Jan 4, 1918

By R. Schempp

DURING the past few years, general interest in the steel-producing and steel-consuming industries has been centered on the so-called "inherent characteristics" of steels. While often vaguely described, these char-acteristics are known to influence the response to heat-treatment and the hardening characteristics of the material. Although most of the recent papers and discussions have associated the "inherent characteristics" with the austenitic grain size and empha-sized the importance of it, comparatively little is known of the variables that may affect the size of the austenite grain. The work to be described in this paper was carried out during the course of a study on the inherent characteristics of tool steel containing one per cent cart on. The discrepancies encountered in the determination and classification of the austenitic grain size led to in investigation of some of the variants influencing the austenitic grain size as determined by standard methods.

Jan 1, 1937

By R. E. Head, E. L. Tucker

In the metallurgy of precious metals, it has been standard practice for years to use cyanogen compounds, so it was but natural that early investigators in the field of flotation should consider these compounds as possible flotation reagents. In Australian Patent 9508, of 1913, alkali cyanides were described as suitable reagents for the separation of heavy sulfide minerals, the reagents being employed either in an alkaline or neutral circuit. In U. S. Patent 1236501, of 1917, to John M. Tibbet, the use of cyanide in conjunction with soda ash or lime is described. One of the claims of this patent reads, "An improvement in the cyanide process for the treatment of ores comprising, mixing the ore with cyanide solution and oil and alkali: emulsifying the oil in the presence of the ore, the alkali and the cyanide solution, floating a portion of the values in the pulp by producing gas bubbles in the mixture and removing the values floated." More recently, Sheridan and Griswold, in U. S. Patents 1421585 and 1427235, describe a somewhat similar process and have successfully introduced it in the mill of the Timber Butte Milling Co. U. S. Patent 1429544, of 1922, to Stevens, describes the use of double cyanides of copper, zinc, and lead. The success of cyanide as a reagent in the differential flotation of lead and zinc sulfides in highly complex ores is proof that these patents have a solid foundation. Although the technique of their application to particular ores has been worked out in many cases, no one, so far as is known, has attempted to describe the nature of the action of the cyanide or to determine the ideal conditions for its application. It was the purpose of the present investigation to gather information on these points. Naturally this would have been an exceedingly ambitious program had the attempt been made to study the effect of cyanide

Jan 1, 1926

By A. Eilers

(Butte Meeting, August, 1913.) A NUMBER of the copper refineries in this country have lately separated some of the rarer metals from the slimes in the refinery tanks One of these has furnished me the following table of recoveries from given amounts of blister. I publish . this to show the proportions, to gold and silver and to each other, in which these rarer metals may be expected to occur in copper from certain localities.

Jan 6, 1913

THE following paper has been prepared to meet a demand for a concise review of the California oil industry. It is based largely upon information secured during the course of the senior, author's professional activities, and upon data obtained during the course of investigations for the U. S. Geological Survey and the U. S. Bureau of Mines. Considerable information has been obtained from other sources, and to those who by publication or otherwise have contributed, the writers extend their thanks. GENERAL STATEMENT In 1912 the United States produced 63.25 per cent. of the world's production of petroleum, Russia, its nearest competitor, yielding only . about 19 per cent. The production in 1912 reached 222,113,218 barrels (or 29,615,096 metric tons), compared with 220,449,391 barrels in 1911. The average price per barrel in 1912 was nearly 74 c., as against nearly 61 c. in 1911. The total value, therefore, increased 22.20 per cent., or $163,802,334 above the value for the previous year. These figures of production include pipe-line runs, independent railroad shipments, oil piped direct to refineries, and the crude oil consumed as fuel in oil production. The production does not include oil in storage in the field which has not been sold.

Jan 3, 1914

By C. A. Heiland

Geophysical methods are playing an ever increasing part in various engineering fields. About ten years ago, geophysical exploration was first applied in civil engineering to the study of foundations and the location of construction materials and water. Its usefulness is now being extended into the field of structural engineering. Almost every structure has to be so designed that it will withstand any force to which it may be subjected. Such forces may result from its own weight, applied loads, pressures of various kinds, including those due to wind and water, ground subsidence and vibrations. The last two, problems involving the nature and dynamic behavior of surface and subsurface formations, are within the scope of geophysical investigations. In the design of any structure, the disposition and dimensions of its members as well as their materials must be so selected that they will withstand any or all of the forces enumerated above. In other words, its "resistance" to such forces must be sufficient, allowing for a definite margin of safety. Often a static treatment of the problem leads to satisfactory results, but the static method entails serious errors when vibrations are involved, as in resonance with an impressed vibration the displacements of a structure or parts thereof may dangerously exceed the allowable values. The principle of "dynamic design"† is, therefore, avoiding or reducing resonance by suitable selection of the natural frequency of a structure, or by the provision of damping. Methods of Investigation Dynamic design of structures is required where ground vibrations occur naturally or are produced artificially. Earthquake regions fall in the first group; areas of industrial activity where vibrations are produced by machinery, blasting, etc., fall in the second. In either case, dynamic

Jan 1, 1940

By C. A. Heiland

Geophysical methods are playing an ever increasing part in various engineering fields. About ten years ago, geophysical exploration was first applied in civil engineering to the study of foundations and the location of construction materials and water. Its usefulness is now being extended into the field of structural engineering. Almost every structure has to be so designed that it will withstand any force to which it may be subjected. Such forces may result from its own weight, applied loads, pressures of various kinds, including those due to wind and water, ground subsidence and vibrations. The last two, problems involving the nature and dynamic behavior of surface and subsurface formations, are within the scope of geophysical investigations. In the design of any structure, the disposition and dimensions of its members as well as their materials must be so selected that they will withstand any or all of the forces enumerated above. In other words, its "resistance" to such forces must be sufficient, allowing for a definite margin of safety. Often a static treatment of the problem leads to satisfactory results, but the static method entails serious errors when vibrations are involved, as in resonance with an impressed vibration the displacements of a structure or parts thereof may dangerously exceed the allowable values. The principle of "dynamic design"† is, therefore, avoiding or reducing resonance by suitable selection of the natural frequency of a structure, or by the provision of damping. Methods of Investigation Dynamic design of structures is required where ground vibrations occur naturally or are produced artificially. Earthquake regions fall in the first group; areas of industrial activity where vibrations are produced by machinery, blasting, etc., fall in the second. In either case, dynamic

Jan 1, 1940

By W. C. Elmore

THE magnetic powder method, long used. for roughly mapping mag-netic fields, has recently been refined 1,2 for investigating the microscopic variations in the surface magnetization of ferromagnetic crystals. Bitter2 first discovered regular powder patterns connected with the crystal structure of such specimens. Several other investigators3 have used Bitter's original technique, with slight modifications, to study the varia-tion of the patterns with variations in the magnetizing field applied parallel to the surface, and their dependence upon the state of strain, of polish and of crystal cut. All of the explanations of these patterns on metallic ferromagnetics have been couched in general terms. In a preliminary report we have described an improvement in the powder technique which led us to the discovery of a new effect throwing con-siderable light on the magnetic secondary structure of alpha iron4 and of nickels single crystals. We now report additional evidence confirming the existence and stability of a magnetic block secondary structure.

Jan 1, 1936

By E. A. H. Tays, F. A. Schiertz

In 1893 the Anglo-Mexican Mining Company, Limited, purchased the Guadalupe and adjoining mines, and, after opening up the Guadalupe, constructed a 20-stamp mill, which was started in August, 1894. Although the results were extremely profitable (the ore being very rich and carrying much free gold) they were not satisfactory, because the tailings were found to average about $20 per ton in gold. Early in 1895 the late Mr. James E. Mills made for the company a very thorough study of the subject, and decided that the tailings could be treated most advantageously by the cyanide process. In view of this opinion, Mr. Henry R. Batcheller, of Boston, was sent down in the winter of 1895-96 to experiment on a working scale. Mr. Batcheller was successful; and, during 1896-97, built a cyanide-plant with a capacity for treating 1500 tons per month. This was run until May, 1899, when all the sands suitable for the process had been treated. The mill was stopped about the same time for lack of ore; but no tailings from the mill had gone to the dump since October, 1897, as the values they contained after that date were far too low to warrant further treatment. When the cyanide-plant was stopped there still remained on the dump about 16,000 tons of slimes, consisting of about 75 per cent. of clay-slimes and 25 of sand-slimes. The successful treatment of this very unfavorable material is the theme of this paper. Fig. 1 is a view of the hacienda, taken in 1897.

Jan 1, 1902

By C. H. Mathewson

MICROSCOPIC. rnetallography has been exploited quite well enough to bring about a very general understanding that the typical metal or alloy is composed of minute crystalline particles blended into a coherent microstructural mosaic. One does not have to be a specialist in metallography to realize that the properties of such an aggregate are essentially a summation in appropriate form of individual effects derived from the shape, size, placement or orientation and cohesive characteristics of the component particles. It is clearly of great importance to consider the various forms of discontinuity which may occur at the boundaries between these crystalline particles. When a number of 'particles each possessing the same orderly arrangement of atoms are brought together into a close-fitting system of purely haphazard contacts, not unlike a handful of snowflakes compacted into a snowball, the particles are said to possess random orientation. There are no generally accepted views concerning the arrangement of the atoms or the constitutional reaction between atoms where one crystal meets another, but these contact regions are characterized by strength rather than weakness and it is customary to require the presence of many rather than few boundaries in preparing metal for useful service. Under certain circumstances all of the particles in a metal may be nearly alike in orientation. Other general tendencies of orientation may be associated with particular forms of mechanical and thermal treatment. In contrast with these cases of fortuitous or statistical diversity of orientation, we often find adjacent particles united along a plane which possesses a grouping of atoms belonging equally well to both structures. This, of course, determines a fixed relationship between the two orientations and it is always possible to derive one from the other by some form of rotation or reflection prescribed by the symmetry of the crystal structure under consideration. Particles united in this manner are known as twin crystals although the term refers to the form of association rather than the number of individuals concerned.

Jan 1, 1928

By P. A. Larssen, P. R. Gage, R. W. Bartlett

The kinetics of formation of intermediate sili-cide compounds from MoSi2/Mo and WSi2/W couples were studied using a cylindrical sample configuration. Concentration profiles of the constituent metals were deter mined from electron-microprobe analysis of cross-sectioned samples after isotlzernzal diffusion annealing. These data also yielded hand widths of phases. Growth of intermediate phases depends on diffusionin them and obeys a parabolic rate law. The rates of formation of the intermediate phases decrease in the order Mo5Si3 > W5Si3 > Mo3Si. Crowth rates. for the isomorphous phases Mo5Si3 and W5Si3 had the same activation energy. 43 kcal per mole. SILICIDE coatings employed to protect refractory metals from high-temperature oxidation are usually formed by a diffusion process requiring concurrent transfer of silicon to the refractory metal surface. For a simple binary system and a coating thickness of one or two mils, the coatings on molybdenum and tungsten are primarily the disilicides WSi2 and MoSi2, respectively. During use of the coated re- fractory-metal system at high temperatures, in the absence of the silicon source, further diffusion causes growth of lower silicide compounds and depletion of the disilicides. Recent investigations have shown that the lower silicides are less effective than the disilicides in forming a glassy oxide film which impedes oxidation.' Consequently, failure of coatings at high temperatures may coincide with complete conversion of the disilicide phase. The purpose of this part of the study is to investigate the growth kinetics of the intermediate compounds in the W-Si and Mo-Si systems. There are three intermetallic compounds in the Mo-Si system: MoSi2 with a tetragonal structure

Jan 1, 1964

By S. C. Sun, John A. L. Campbell

The surface properties exhibited by bituminous coal and bituminous coal lithotypes were ascertained by using streaming potential techniques. The electro kinetic prop-erties wereascertainederties of bituminous coal were found to be similar to those of anthracite. The principle electrokinetic properties of the coal and lithotypes, zero-points-of-charge (ZPC), and potential determining ions, were established. The effects of indifferent electrolytes, hydronium and hydroxyl ion sources, and polyvalent ions (cationic and anionic) were also evaluated. Location of the ZPC's with respect to pH is discussed in terms of chemical and mineralogical composition of the respective surfaces. To account for the observed electrokinetic phenomena, a generalized surface model and adsorption mechanism are proposed. Surface-dependent processes, such as froth flotation and flocculation, are important or potentially important techniques for combating some of the current major problems in coal preparation. In order to correctly apply or improve a surface-dependent process, it is of paramount importance to understand the interfacial phenomenon, especially the double layer properties, exhibited by the solid. The specific objective of this research was to determine the properties of the bituminous coal/liquid interface by an electrokinetic method, streaming potential, and to relate the findings, wherever possible, to the existing unit operations of froth flotation and floccula-tion tion. The electrokinetic properties of both the whole coal and its lithotypes were investigated. As part of the total investigation, the role played in the double layer by the reagents commonly employed in the surface dependent process was also established.' These data will be presented at a later date. Experimental Procedures The coal samples used in this research and their designations are listed in Table 1. The classical description of humic coal lithotypes as developed by Stopes" was used for the delineation of the lithotype samples. The samples were taken from the working face of a producing deep mine of the Pittsburgh seam in the area of Ellsworth, Pa. To avoid oxidation, only freshly exposed areas were sampled. The normal precautions against contamination were also exercised. Two types of samples were taken, specimens rich in a particular lithotype and a representative channel sample. The latter sample was prepared for analyses by grinding it to —35 mesh. It was screened repeatedly during the grinding to provide the largest amount of 35 x 48-mesh (standard Tyler sieves) material possible. The screened fraction was passed over a magnet and then washed several times with distilled water and finally with conductivity water. The resulting sample now termed "whole coal" was stored under conductivity water in a glass bottle. Pure lithotypes were obtained from the lithotype concentrates by hand picking, and were processed in the same manner as the representative sample. Maceral analyses, employing standard petrographic procedures," were performed on the lithotype samples to determine the purity of the samples. The results are presented in Table 2. Reflectance measurements of the vitrinites and fusinites are also reported in this table. Proximate and ultimate analyses of the samples are given in Tables 3 and 4. The electrokinetic properties of the coal samples were determined by streaming potential methods.'-' All of the chemicals used in the investigation were reagent grade (Baker analyzed). The conductivity water was prepared by doubly distilling the water in a pyrex Yoe-type still and passing the distillate through a mixed bed ion exchange column. Results In general, the electrokinetic properties of the investigated bituminous coal were found to be similar to the results of a previous study of anthracite by Camp-bell bell5 and are in accord with the suppositions of Brown." The zeta potentials of the coal and all the lithotypes were found to be negative in conductivity water. Jowett? in a study of slime coatings on coal also found bituminous coal to exhibit a negative surface. Fig. 1 shows that the negative charges, at neutral pH's, for both fusain and the gangue are very small, almost zero, while at the same pH, vitrain has the largest negative charge, almost 30 mv. Durain has a negative charge of 17.5 mv. The determination of the affect of pH on the charge of the coal surfaces revealed that hydronium and hydroxyl ions apparently behave as potential determining ions; however, they do not appear to be potential determining for the gangue. These results are illustrated in Fig. 1. As the pH of the solution was decreased, hydronium ions were adsorbed, causing the surface of the coal to reverse polarity and become

Jan 1, 1971

By A. H. Daane, A. S. Wilson

The U-Cr system is of the simple eutectic type with some solid solubility of chromium in r and ß uranium. The eutectic occurs at 20 atomic pet Cr and melts at 859°C. The maximum solubility of chromium in y uranium is 4 atomic pet at the eutectic temperature, and in ß uranium the solubility is estimated to be 1 atomic pet. y-ß and ß-a transformations were found to occur at 737°estimatedt° and 612°C respectively. DURING 1944 and 1945, the U-Cr constitution diagram was studied in this laboratory as a part of a research program on uranium metallurgy in the Manhattan Project, and the work was described in a Manhattan Project report issued in December 1945. This paper is based on that report, which has been declassified. Prior to this study, it had been shown by other Manhattan Project workers that the low Cr-U alloys could be quenched to retain the form of uranium. Experimental The uranium used in this work was massive metal prepared in this laboratory and contained less than 0.1 pct of other elements. The chromium was 200 mesh powder obtained from the A. D. McKay Co. and was found on analysis to be 99.5 pct Cr with 0.3 pct Fe the major impurity. Alloys, weighing 400 to 600 g, were prepared by induction heating the components to 1700°C in slip-cast ZrO, crucibles in a vacuum of 3x103 mm Hg. TO prevent too violent agitation of the melt by the induction field with subsequent crucible breakage and sample loss, the ZrO2 crucible was placed in a graphite crucible, which was surrounded by a layer of powdered carbon insulation 2 to 3 cm thick. Polished vertical sections of the alloys were examined microscopically to confirm their homogeneity. Heating and cooling curves were taken on the alloys by reheating them in ZrO, crucibles to 1200°C and inserting a mullite-protected chromel-alumel thermocouple into the melt by means of a slip seal in the vacuum head of the furnace. A recording potentiometer traced the curves which had a slope of from 3" to 6" per min. Samples of the alloys were prepared for metallo-graphic examination by conventional mechanical polishing techniques followed by an electrolytic polish in an ethylene glycol-phosphoric acid-ethyl alcohol bath. The structure of the alloys was brought out clearly by this procedure so that no further etching was required. Samples for chemical analysis were taken from drillings from the top, center, and bottom sections of the alloys. The uranium was determined by titra-tion with Ce(SO1)2, while the chromium was titrated with FeSO,; the uranium and chromium totaled at least 99.6 pct in all of the alloys prepared. X-ray samples were prepared by filing bulk specimens in a helium-filled glove box and annealing the resulting powder in a zirconium-gettered helium atmosphere. A 114.6 mm diam Debye-Scherrer camera and a Weyland nonsymmetrical self-focusing camera were used with filtered copper radiation to obtain the powder X-ray diffraction data. Results The data obtained in this study have been combined to construct the constitution diagram of the U-Cr system shown in Fig. 1 where the arrests observed in cooling curves are indicated by dots. The liquidus arrest was quite distinct in thermal data taken on alloys in the range 0 to 20 atomic pct Cr. The eutectic arrest was not observed in studies on the 2.5 and 4.5 pct Cr samples but appeared in the 7.5 pct samples, which suggested some solubility of chromium in y uranium. On quenching from 859 °C, the 2.5 pct sample showed but one phase while the 4.5 pct sample contained a small amount of the eutectic along the grain boundaries; see Figs. 2 and 3. From this the maximum solubility of chromium in r uranium has been set at 4 pct. X-ray studies on these samples showed that the r phase was not retained at room temperature by quenching, but in each case a pattern was observed .which has been identified with the ß phase of uranium. Thermal data show the y-ß transformation of uranium lowered to 737°C as a consequence of this solubility. On quenching from the ß range (660°C), precipitation of chromium in the primary uranium is observed in the 2.5 and 4.5 pct Cr samples (see Figs. 4 and 5),

Jan 1, 1956

By Lo-Ching Chang, Kenneth M. Goldman

INTRODUCTION THE kinetics and mechanism of transfer of a constituent across a slag-metal interface are fundamentally important because many metallurgical processes involve the existence of a slag phase and a metal phase. Industrial processes seldom proceed to equilibrium, and information of the rates and modes of reactions are therefore often of greater practical importance than equilibrium data. A study of the kinetics of sulphur transfer across a slag-metal interface under reducing conditions will contribute a great deal toward a better understanding of desulphurization in the blast furnace process. The general principles existing in the transfer of a constituent, such as sulphur, across a slag-metal interface can be extended to similar transfer phenomena in other metallurgical processes. The present paper will demonstrate how such studies will lead to fruitful results from both the practical and theoretical standpoints. EXPERIMENTAL METHOD The apparatus used was simple. A graphite crucible 1 5/8-in. id, a wall 1/8-in. thick, and a depth of 4 in., was packed in an outer fused silica tube with powdered magnesia. The crucible assembly was rotated at a speed of 235 rpm inside an induction coil. A charge of 250 g of Armco ingot iron was introduced into the graphite crucible and melted by induction heating. The melt was held at a desired temperature [ ] for 3-5 min., after which 7.5 g of granular ferrous sulphide was added and the bath was held for another 3-5 min. A metal sample was then taken by means of a fused silica tube and a rubber suction bulb. Immediately after the metal sample was taken, 30 g of a prefused and crushed slag were introduced. The slag reached the temperature of the furnace in 1 to 1 1/ 2 min. Slag

Jan 1, 1948

By Wei-Kao Lu, G. Bitsianes

An improved general rate equation for a one-ditnensional gas-solid system has been derived. Fov the veversihle interfacial chemical reaction, there are concentrations of gaseous reactant and product at the reacting zone to be considered. They have been calculated with the velations fuvnished by the constraints on the system, namely, quasi-steady state and equimolal counterdiffusion of the gases. The results of the diffusiori study of Evans, Watson, and ,Mason based on the "dusty gas" model have been applied here. The interfacial chemical reaction is taken as first-order with respect to the concentration of the gases involved. The equation has proper dependence on gas composition and on solid structure through the relative values of Knudsen and normal diffusivities. The existence of the total pressure gradient inside the specimen has been predicted and confirmed experimentally. In a previous communication' we introduced a general rate equation for gas-solid reactions by considering the contributions of chemical reaction at inter- phase boundaries and diffusion through the solid product layer simultaneously. These equations, for one-dimensional and spherical specimens, take care of the whole range continuously from purely diffusion control to purely chemical reaction control. In this paper we study only the one-dimensional system. The corresponding rate equation is reproduced here: Of the two terms on the right-hand side of Eq. [I], the first represents the contribution of interfacial chemical reaction and the second that of gaseous diffusion. The shortcomings of Eq. [I] are that in its derivation the interfacial chemical reaction was assumed to be irreversible and the diffusion rate of gaseous product was not considered. Any pressure effects building up within the porous media were also neglected. Evidently. these simplifying assumptions will limit the general applicability of these equations. The rate of reduction of iron oxide by hydrogen, for instance, is very sensitive to the concentration of water vapor in the main gas stream, as has been reported by cewan' and by Quets et a1.3 Furthermore, the gaseous phase at the reacting interface will contain an appreciable amount of the gaseous product of reaction. If this were not true, a sufficiently high concentration gradient for the outward diffusion of the gaseous product could not be maintained. With these shortcomings in mind, Eq. [1I cannot be rigorously ap-

Jan 1, 1967

By F. Hass, N. W. Lord

This paper gives the results of experiments conducted in the metallurgical laboratory of the Ohio State University with the objects of determining: First, the calorific powers of a number of coals in general use in Ohio; and second, how far ordinary analytical methods could be used as a basis for computing these values. Incidentally a test of the performance of the calorimeter was involved. The chemical work has been carried on in the department for some time, so that the whole investigation has extended over three or four years. The Mahler calorimeter was purchased from L. Golaz in Paris, and is practically identical with the one described and figured by Mahler in his monograph "Contribution a l'Etude des Combustibles," from the Bulletin de la Société d' Encouragement pour l'lndustrie Nationale. A figure and description is also given by William Kent in The Mineral Industry for 1892, page 97. There were furnished with the instrument three thermometers covering a range of from 7°.5 C. to 31° C. Thermometer "A" (17°.5 to 31°) was carefully calibrated by reading the ends of a thread of mercury in sixteen positions covering the whole scale, supplementing this by readings of longer threads and deducing the errors of scale by the method published by Prof. Holman in the Technology Quarterly of September, 1887. The maximum error of a single reading was found to be 0°.0042 C. Thermometer "B" (13° to 25°) was compared directly with " A " over the scale common to both, and a variation was found of 0°.0145 C. for 7°.5 (or 0°.002 for l°) of the scale. Thermometer " C" ('7°.5 to 19°.0) was omitted from the cornparison, as it was rarely used, being only required where measurements were made at low temperatures. From the

Jan 1, 1898

OF what use is the federation to me and why should I support it?" is a question that has been asked by many members of the constituent societies of the F. A. E. S. during the last year; a question that is asked because the speakers do not realize what the Federated is doing or what is the field of its activities. "What is it doing for the profession and for mankind?" would be a more appropriate question, the answer to which is found in the closing chapter of Prof. Cassius J. Keyser's "Mathematical Philosophy."' The chapter is entitled "Science and Engineering." Professor Keyser writes from the layman's point of view. He is looking at the profession and at engineers from the outside. We have in his thoughts the oppor-tunity that Burns sought when he wrote "Oh wad some power the giftie gie us to see oursels as ithers see us." With the permission of the author and the publisher, we quote the following paragraphs: A layman, viewing a profession from the outside, seeking thus to ascertain its proper relations to the common weal, may bring to the task a certain freedom, which, were he a member of the profession, he might have lost. "Men trained in a profession," said Prof. David Swing, "come by degrees into the profession's channel, and flow only in one direction, and always between the same banks. The master of a learned profession at last becomes its slave. He who follows faithfully any calling wears at last a soul of that call-ing's shape. You remember the death scene of the poor old schoolmaster. He had assembled the boys and girls in the winter mornings and had dismissed them winter evenings after sundown, and had done this for fifty long years. One winter morning he did not appear. Death had struck his old and feeble pulse; but, dying, his mind followed its beautiful but narrow river-bed, and his last words were: It is growing dark-the school is dismissed-let the .girls pass out first."' I shall not be so much concerned with the present status of the science as with its potency and promise. Of individual engineers the ideals may be high or low, worthy or unworthy; but of engineering itself the ideal is great and mighty. It is of that ideal that I intend to speak.

Jan 9, 1922

By Henry M. Stanley

The methods about to be described have been tested in practice, and are believed to be specially adapted to such extended topographical surveys as mining engineers in particular are sometimes called upon to execute. The assistance of Mr. H. 0. Flipper in the preparation of this paper, and his practical authorship of the second part, is hereby acknowledged. I. Photographic SuRveying. The writer was recently employed; together with Mr. H. O. Flipper, to survey the properties of the Plata-Reina de Sonora Mining and Milling Company, situated in the mining district of Las Planchas, District of Magdalena, State of Sonora, Mexico. These properties, now owned by an American corporation, of which M. W. Evans, of New Orleans, is president, and Richard A. Pomeroy is resident superintendent, are famous in the history of Mexican mining, as the place where planchus, or bolas de plata were foulld about the beginning of the last century. Ward, the English CILargh d7Affaires in Mexico from 1826 to 1828, writing at that epoch, says: "The idea [that the ores in the north of Mexico were richer than those in the south] probably originated in the discovery of the famous bolas de plata [balls of silver] of Arizona [Planchas de Plata de Arizona, a stock-ranch in northern Mexico], in the beginning of the last century, which was, and probably still is, believed in Europe to be one of those fables with which mining countries always abonnd. But the attention of the present government of Mexico having been drawn to the subject, a search was made in the viceregal archives, by order of the president, for the correspondence which was known to have taken place respecting it in the year 1736. This correspondence I have seen, and I have in my possession a certified copy of a decree of Philip the Fifth, dated Aranjuez, 28th May, 1741, the ohject of which was to terminate a prosecution, instituted by the Royal Fiscal, against the discoverers of Arizona, for having defrauded the treasnry of the duties payable upon the masses of pore silver found there. The decree states the weight of the balls, sheets and other pieces of silver discovered (bolas, planchas, y otras piezas de plata), to have amounted to 165 arroba, 8 pounds, in all, 4133 pounds; and mentions particularly one mass of pure silver, which weighed 108 arrobas (2700

Jan 1, 1892

Discussion of the paper of HOWARD N. EAVENSON, presented at the New York meeting, February, 1915, and printed in Bulletin No. 98, February, 1915, pp. 413 to 430. WILLIAM H. GRADY, Bluefield, W. Va.-Mr. Eavenson gave a comparison between accidents in the State of West Virginia and in the Pocahontas field. The figures quoted are, I presume, taken from the reports of the State Mine Inspector. There are no statistics available, in readily accessible form, giving a comparison between the Pocahontas field and the mines of the United States Coal & Coke Co. which are a part of the field. It occurs to me that the paper would be more complete with these data and I will say that the mines of the Pocahontas field produced during the year 1913 about 15,000,000 tons, about 3,000,000 tons of which was produced by the United States Coal &Coke Co. This gives an indication of the extent of its operations. The Pocahontas field lies largely in the counties of McDowell, Mercer, and Wyoming in West Virginia, and Tazewell in Virginia.: Without consulting maps, I should say that all of the acreage under operation at present by this company lies wholly in McDowell County and that the average conditions off roof top and bottom in its mines are the average of the county, but that the worst conditions in some of these mines are the worst to be found in the county. The average conditions in Tazewell County are about the same as in McDowell County, except that the average thickness of the seam is much greater. The average conditions of top and roof and bottom are better in Mercer and Wyoming counties than in the mines of the United States Coal &. Coke Co.; the worst conditions in these counties are not so bad as in McDowell and Tazewell counties and the best are better than those encountered in McDowell and Tazewell counties; also the thickness of seam is less in Mercer and Wyoming counties. THOMAS W. DAWSON, Scottdale, Pa. (communication to the Secretary*).-The H. C. Frick Coke Co., the mines of which are in Fayette and Westmoreland counties, Pennsylvania, in the Connellsville coke region, has been pursuing a safety campaign for a number of years and a short resume .of its practices will be of interest in connection with Mr. Eavenson's paper.

Jan 5, 1915

By B. G. Zambre, G. A. Parks, J. N. Roco

Automatic controls have long been a fact of technological life. Some understanding of control systems is rapidly becoming essential to the competence of mineral engineers. Students in undergraduate mineral engineering curricula, however, should not be expected to develop proficiency in the design and interpretation of control systems. They should be provided the opportunity to absorb some of the fundamental concepts and cant of such highly specialized peripheral fields as automatic controls. The present paper describes the components of a simple, flexible and relatively inexpensive control system designed primarily for the use of students in independent study projects. The control system is based on a continuous on-stream optical analyzer analogous to commercially available systems using X-Ray fluorescence analysis. The components can be easily adapted to control other separators and separations. As described here, they have been arranged to control the magnetic separation of a magnetite bearing specular hematite from quartz to produce a quartz product of fixed hematite content using a minimum of power. The control system consists of the magnetic separator* with a vibrating feeder, † a sampler, an optical scanner, a differential amplifier, a millivolt recorder ‡ and a motor driven, metered variable DC power supply for the separator electromagnet. An optional magnet current recorder is useful. The system as arranged for closed loop control is illustrated in Fig. 1. The elements of the loop are identified in automatic control jargon in Table I. The same components can be easily adapted for use in other control modes.§.1 * A Carpco Induced Roll High Intensity Magnetic Separator (Carpco Manufacturing, Inc., Jacksonville, Fla.); modified for external magnet power supply. A Jeffrey-Traylor Vibrating Feeder Type 1B (Jeffrey Manufacturing Co., Columbus, 0.). A Beckman Laboratory Potentiometric Recorder (Beckman Instruments, Inc., 619-A) fitted with adjustable limit switches for external circuit control (Beckman Instruments, Inc.. 71980). Terminology is taken from ref. 1. CLOSED LOOP OPERATION The separation is monitored through the optical reflectivity of the tailings stream which is proportional to the hematite content, THA. The difference, A, between the measured analysis (actually a proportional voltage) and a reference analysis (also a proportional voltage) is continuously recorded. The separation is controlled through changes in the electromagnet current, I, supplied from a motor driven variable source. The two primary variables, ? and I, are linked through adjustable limit switches on the

Jan 1, 1965