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By G. E. Goodspeed

The Cornucopia gold quartz veins form a parallel vein system traversing meta-morphic and granodioritic rocks. Field and petrographic evidence suggests that inetasomatism has played an important role both in the emplacement of the grano-diorite and in the formation of the veins. Structurally the veins appear to be related to the major tectonic features of the Wallowa Mountains and to be narrow shear zones rather than filled fissures. Petrographic studies indicate a complex history of formation starting from initial alteration along fractures or joints followed by recurrent fracturing and a quartz-forming stage, and closing with continued shearing and microbrecciation, which permitted the upward percolation of the later ore-forming solutions. The precipitation of ore minerals from these solutions formed ore shoots. Postmineral effects include the injection of Tertiary basaltic dikes, a shght amount of cross faulting, and some movement along the planes of the veins as well as oxidation. Introduction Cornucopia is in the southeastern part of the rugged Wallowa Mountains of northeastern Oregon. It was founded over 50 years ago following the discovery of its system of gold quartz veins. The major veins are roughly parallel and dip into the western side of Pine Valley, which drains the southern slope of the range. Previous operations had cut the upper portion of four major veins with two tunnels over 1000 ft. apart, when the present operating company drove a third tunnel, called the Coulter, at the level of the valley over 1000 ft. lower to intersect the most easterly major vein at over 6200 ft. from the portal. General Geology of District The oldest rocks in the vicinity are metamorphosed sediments and volcanics. These, for the most part, are presumably Mesozoic in age, although some black argillites outcropping along East Pine Creek are considered to be Permian.l,2 These rocks have been deformed and metamorphosed in general to hornfels at the close of the Jurassic. The series was then invaded by a granodiorite batholith, the origin of which is

Jan 1, 1941

By C. F. Wang

Manchuria in General Manchuria, called the "Three Eastern Provinces" in Chinese, forms the northeastern corner of China and is bordered by Siberia on the north and northeast, and by Korea on the east. It is a land famous in Chinese annals as the place of origin of the Ching dynasty, and in more recent times it has been an arena for diplomatic maneuvering and commercial competition between the Russians, advancing from the north, and the' Japanese from the southeast. It derives its name of "three eastern provinces" from the fact that it is divided into three provinces; Hei-

Jan 2, 1918

By G. E. Goodspeed

The Cornucopia gold quartz veins form a parallel vein system traversing meta-morphic and granodioritic rocks. Field and petrographic evidence suggests that inetasomatism has played an important role both in the emplacement of the grano-diorite and in the formation of the veins. Structurally the veins appear to be related to the major tectonic features of the Wallowa Mountains and to be narrow shear zones rather than filled fissures. Petrographic studies indicate a complex history of formation starting from initial alteration along fractures or joints followed by recurrent fracturing and a quartz-forming stage, and closing with continued shearing and microbrecciation, which permitted the upward percolation of the later ore-forming solutions. The precipitation of ore minerals from these solutions formed ore shoots. Postmineral effects include the injection of Tertiary basaltic dikes, a shght amount of cross faulting, and some movement along the planes of the veins as well as oxidation. Introduction Cornucopia is in the southeastern part of the rugged Wallowa Mountains of northeastern Oregon. It was founded over 50 years ago following the discovery of its system of gold quartz veins. The major veins are roughly parallel and dip into the western side of Pine Valley, which drains the southern slope of the range. Previous operations had cut the upper portion of four major veins with two tunnels over 1000 ft. apart, when the present operating company drove a third tunnel, called the Coulter, at the level of the valley over 1000 ft. lower to intersect the most easterly major vein at over 6200 ft. from the portal. General Geology of District The oldest rocks in the vicinity are metamorphosed sediments and volcanics. These, for the most part, are presumably Mesozoic in age, although some black argillites outcropping along East Pine Creek are considered to be Permian.l,2 These rocks have been deformed and metamorphosed in general to hornfels at the close of the Jurassic. The series was then invaded by a granodiorite batholith, the origin of which is

Jan 1, 1941

By N. H. Emmons

THE work of a consulting engineer or manager, when controlling mining-operations, requires that he have all the information concerning the mine in as concise a form as possible, and as the ore-reserves and their depletion and enlargement are the vital points to be studied, it is well to have them kept up to date and in some convenient form. The present paper describes a method adopted by me, which shows in a very clear manner the ore-reserves in a mine. The case illustrated is that of a vein near enough to the vertical for the vertical elevation of the mine to be the main working-map. A flat ore-body would be represented on a similar plat, but instead of the horizontal thickness of the vein being shown in the circles, the vertical thickness would be inserted. Fig. 1 represents an ideal longitudinal elevation of a mine, plotted in the ordinary way, using 100-ft. blocks and section-lines. In a mine where the block-numbers are posted by the engineer underground, the system of keeping the ore-tonnages extracted from the different blocks is easily maintained, and the actual tonnages of ore extracted can be kept so that the surveyor can have a check on his estimate from time to time. The ore-reserve sheet, Fig. 2, should be the same size as the map it is to accompany. Each square is used for the description of the ore-reserve in the block it corresponds to on the elevation. Where the section-lines cross the levels a circle is drawn, in which are written the widths of ore at that point, these widths being used in the calculations of each block cornering in the circle. It has been found convenient to show the figures in black in the lower half of the circle when the actual widths of ore are known, and when it is necessary to make up the figures of probable ore, as at the time of making

Jun 1, 1912

By R. F. Mehl, J. K. Stanley

THE recrystallization of cold-worked metals is studied ordinarily by determining the temperatures required for complete recrystallization to occur within a given arbitrary time period, usually within 15 min. to 2 hr. The results obtained are conventionally assembled in a three-dimensional diagram relating this temperature to the amount of cold-work (percentage deformation) and the resultant grain size, though sometimes other modes of representation are employed.1 Such three-dimensional diagrams are not complete, for the number of variables exceeds the number represented. The process of recrystallization is characterized by a time-rate, a fact that is not portrayed upon ordinary recrystallization diagrams. It is known that recrystallization consists in the formation of new nuclei and the growth of these nuclei, a process that continues until the matrix is completely consumed and the original set of grains entirely replaced by the new. This knowledge is old.2 Truly heterogeneous reactions invariably proceed by nucleation and growth; the decomposition of eutectoid solid solutions provides an example about which much is known,3 and freezing, originally studied by Tammann, provides the classic example. Although recrystallization is not a heterogeneous reaction .within the orthodox meaning of the term, the mechanism of the process is the same. As in eutectoid inversion and freezing, it should be possible to study the rate of isothermal recrystallization as a function of time, and it should also be possible to analyze the isothermal reaction curve into the component rates of nucleation and growth that determine them.* Other methods, not employing the rates of nucleation and growth, have been used to represent the rates of such reactions, but these in general have been artificial and have not led to progress.4,5? The theory of recrystallization is not in advanced state; if recrystallization data were obtained, in terms of the rate of isothermal recrystallization, and in terms of the rate of nucleation and the rate of growth of recrystallized grains, and in particular if the temperature coefficients of these rates were measured accurately, an adequate theory should be more readily developed.27 Such an effort requires proper experimental technique, but especially requires suitable methods of mathematical analysis to convert measurements made upon a surface of polish into values for the rate of nucleation and the rate of growth and to combine these into a rate of isothermal recrystallization. These methods are now

Jan 1, 1942

By Hans Lundberg

FOR the last 20 years, geophysical methods have been in practical use. The results accumulated during this time have been broad enough to enable us to formulate some general rules for conducting geophysical surveys to the best advantage. It is a well established fact that electrical and magnetic methods have aided the geologist to outline bodies of ore, to differentiate between various types of rocks hidden from view and also to determine the thick-ness of the layer of drift that covers the bedrock. Fundamental require-ments for a successful solution of a geophysical problem is the existence of physical differences between the various formations under investiga-tion. If such conditions exist, our problem becomes a physical, mathe-matical and geological analysis of the effects of these differences upon the structure of an arbitrarily produced, or already existing, field of force. Experience has shown that reliable and consistent results in analyzing such fields of force are obtained only if: (1) the methods and apparatus used are scientifically sound and designed to provide information with a maximum amount of accuracy, reliability, sensitivity, simplicity and speed of operation, and (2) the interpretation of the results of such an investigation is guided not only by rigid mathematical rules but also by common sense, based upon sound geological knowledge and imagination. Today, a number of methods are based upon sound principles, are highly sensitive and are well suited for field work. The instrumental developments have resulted in self-contained instruments, which permit the determination of field ratios and intensities with great accuracy. Magnetic surveys have almost become standardized. The electrical methods, mostly based on the determination of potential-drop ratios, or electromagnetic field ratios, are built as bridge circuits and it is easy to determine amplitude, as well as phase relationship of the various electrical and electromagnetic fields.

Jan 1, 1938

By L. W. McKeehan, W. C. Elmore

The magnetic powder method, long used for roughly mapping magnetic fields, has recently been refined1, "or 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 investigators:' have used Bitter's original technique, with slight modifications, to study the variation 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 ill the powder technique which led us to the discovery of a new effect throwing considerable light on the magnetic secondary structure of alpha iron4 and of nickel5 single crystals. We now report additional evidence confirming the existence and stability of a magnetic block secondary structure. Specimens The following list describes the specimens used in the present investigation. Designation Description A1 Silicon ferrite furnished to us by Dr. W. E. Ruder, of the General Electric Co., for which lie gave the following typical analysis: C, 0.05; P, 0.038; S, 0.026; Mn, 0.15; Si, 3.24. Disk, 0.60 cm. diameter, about 0.05 cm. thick. By X-ray analysis angles between disk normal and [100] 75o, [0101 76" [00l] 21o. A2 Same as A1 except: diameter 0.75 cm. A, Same as A1 except: diameter 0.68 cm.

Jan 1, 1936

By W. R. Shimer

IN his valuable report on Finishing Temperatures and Properties of Rails, I Dr. G. K. Burgess, Chief of the Division of Metallurgy, U. S. Bureau of Standards, has begun a line of investigation which should be continued by those interested in the subject, and who have proper facilities for carrying put the work. For the past year or more the Bethlehem Steel Co. has been conducting experiments to learn the effect of rail finishing temperatures on their physical properties and microstructure and the results are here given for the consideration of those interested in the rail situation. . Considerable differences of opinion have been expressed by various authorities, in the past, as to the effect of large or small grain size and high or low finishing temperatures of steel rails on their physical properties and wearing qualities. Low finishing temperatures and, therefore, low shrinkage, have been advocated on the theory that the wearing qualities would be improved. Others have recommended high finishing temperatures. The generally accepted cause for rail failures, due to the development ,of transverse fissures, is excessive wheel pressure on hard rails. One of the causes advanced for hard rails has been that they contain too high per centages of carbon and manganese; another that the rails were finished at too low a temperature, i.e., at or near the critical point. In the experiments herein described the rails were rolled from reheated blooms. All the rail blooms were charged hot in a reheating furnace and brought up to about the original ingot-rolling temperature before rolling into rails. These rails gave better results in deflection, withstood a greater number of drops before breaking, and showed greater ductility, than. rails of identically the same composition and section which were rolled, direct from the ingot. Rails rolled from reheated blooms, finished at somewhat higher temperatures than when rolled direct from the ingot, have a different microstructure, which the writer does not believe is due so much to the difference in finishing temperatures, as to the difference in

Jan 3, 1915

By Joe B. Alford

Founding of the Institute The advance of population and civilization in the U. S. moved through the woodlands of the East, and reached the edge of the great central plains about the middle of the nineteenth century. There the advance paused for almost a generation - ahead were vast reaches of prairie country, uncharted, forbidding, and populated by hostile tribes of the native Indians. The turmoil of the Civil War, and the readjustments following it, further delayed the advance. By about 1870, the Nation was becoming stabilized again, the conflict with the Indians was closing, and the pressure of growth was forcing population to resume its westward movement. In addition to geography, the Nation had another frontier: the development of its immense natural resources. Conditions of the time brought into sharp focus the need for coal, iron, steel, gold, silver, and other minerals. The application of engineering and science was necessary for the production of these minerals and their manufacture into products to meet the needs of a growing nation. The requirements of the time were eloquently expressed in a paper by AIME member Edmund C. Pechin in 1872 : We find, the world over, the most intense activity everywhere displayed in enterprises requiring prodigious quantities of iron. Railways of colossal magnitude are projected. . . . The growing scarcity of timber is compelling the use of iron in buildings; bridges of wonderful size and strength; huge ocean steamships; barges and boats for lake and river traffic; churches; cars, and thousands of minor articles of every shape and size. . . . The time has come when scientific research is to assume its true position - the day of "sheer force and blind stupidity," whose only protection is a high tariff, has gone forever . . . the physicist, the geologist and mineralogist; the chemist, the engineer, are as essential to success as the [blast] furnace itself. . . . There is no merely practical man, no matter how varied may have been his experience, or how long his practice, that will not benefit from the results of scientific investigation. That there is a growing sense of the importance of having thoroughly prepared scientific men in every department of business is evidenced by the institutions [of learning] that are springing up in different quarters, provided with

Jan 1, 1971

By L. W. McKeehan, W. C. Elmore

The magnetic powder method, long used for roughly mapping magnetic fields, has recently been refined1, "or 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 investigators:' have used Bitter's original technique, with slight modifications, to study the variation 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 ill the powder technique which led us to the discovery of a new effect throwing considerable light on the magnetic secondary structure of alpha iron4 and of nickel5 single crystals. We now report additional evidence confirming the existence and stability of a magnetic block secondary structure. Specimens The following list describes the specimens used in the present investigation. Designation Description A1 Silicon ferrite furnished to us by Dr. W. E. Ruder, of the General Electric Co., for which lie gave the following typical analysis: C, 0.05; P, 0.038; S, 0.026; Mn, 0.15; Si, 3.24. Disk, 0.60 cm. diameter, about 0.05 cm. thick. By X-ray analysis angles between disk normal and [100] 75o, [0101 76" [00l] 21o. A2 Same as A1 except: diameter 0.75 cm. A, Same as A1 except: diameter 0.68 cm.

Jan 1, 1936

By Harry V. Welch

Early in the development of the art of metallurgy, it was noted that a distinct difference existed in the character, collection possibility and health hazard of the "smoke" from lead furnaces and those from copper plants. Zinc-plant fumes, although not so detrimental to health, were closely allied in nature to those of the lead works. In Cottrell plants, there are sufficiently distinct differences in operation and amount of construction between those for lead and copper to justify their consideration under separate headings; therefore, while the application of the process at copper-reduction works was covered by the writer some two years ago in the Transactions1,† this discussion will confine itself more distinctly to "fume" collection. General information on the process has been presented in numerous articles and by many authors: Cottre112, Schmidt3, Bradley4, Anderson6, Labbe6, Shiga7, Rathbun8. "Fume" may be defined as material, metal or nonmetal, elemental or compound, evolved as a vapor from a furnacing or chemical reaction and condensing, chilling or reacting within the gas stream to yield a solid form, and in this definition liquid particles are solids in a sense as distinguished from gases or vapors. Such condensed particles are of minute form, on the order of "smoke," and, for example, on the order of a few hundredths of 1 micron (1 micron = 1/25,000 in.) to perhaps 3 microns, with agglomerates, in relatively small proportions of many particles. Metallurgically typical fume products are lead compounds, oxides, carbonates and sulphates; elemental zinc, more commonly encountered as a fume particle of zinc metal with a surrounding "skin" of zinc oxide; arsenic, both metal and oxide and some of its more complex salts such as added sulphates as found in flue dusts; antimony, more particularly its oxide forms; and elemental sulphur, sometimes a troublesome product, in Dwight-Lloyd sintering-plant fumes. These products, particularly the elemental or lower oxide forms, have relatively appreciable vapor pressures at the existing operating temperatures as reported by Welch and Duschak9, Ingold10, Johnstonll, Millar12,13.

Jan 1, 1937

By Persifor Frazer

The subject of Egypt, to use the words of perhaps the second of modern writers on the subject [Deodat. de Dolomieu, in Observations sur la Physique, etc., January, 1793, vol. xlii., pp. 41+, 108+; Abbe Rozier, J. A. Mongez, and J. C. Delametherie, Paris], is one which strongly excites our interest, and everything relating to it demands our respect. "Thus," he continues, "the Greeks appeared to the Romans," ..." thus Egypt appeared to the Greeks, and thus all three appear to us." This writer, in the three parts of the memoire given above, speaks of Norden as the modern pioneer of Egypt, and does not seem to have made original observations himself; nevertheless he seems to have rendered the same service to his authority that Playfair not very long afterward rendered Hutton. The limitations of a paper will permit little else than citations, but these are so numerous that, unless much compressed, they would supply a chapter of moderate size. A great deal of the very interesting memoire of Dolomieu is taken up with Quixotic tilts

Jan 1, 1883

By Stuart Croasdale

Not long ago I was called upon to conduct some experiments on the treatment of ores from the New Cornelia copper mine, Ajo mountains, Arizona, for the Calumet & Arizona Copper Co. The problem was a very interesting one and contained some unusual features. Incidental with this problem was the utilization of a large amount of low-grade pyrite in the Bisbee mines of the company, provided this could be accomplished by any feasible method. The New Cornelia mine is situated 45 miles south of Gila Bend, the nearest railroad point, on the Southern Pacific Railroad. It is about 160 miles, almost due west, from Tucson. This section is one of the most arid in the United States. The normal annual precipitation, as given by the United States Weather Bureau covering a period from 1870 to 1901, is 3 to 5 in. During June and July, 1913, the records kept by the company gave the following results. These are all I have available, but they show the enormous evaporation that can be expected, which may be a factor in leaching operations on a large scale. Temperature, Degrees F. High Low Average June...................... 112 62 84.0 ' July...................... 115 71 87.8 Evaporation June July Concrete tank, inches............ 11.7 10.72 Iron tank, inches.............. 14.8 13.07 Rainfall, inches................ None 0.77 Cloudy days................... None 10.00 Aside from several springs about 10 miles from the property, the nearest known water in quantity at the time these experiments were made was the Gila river at Gila Bend, 45 miles distant. Part of the developinent of the property of course included drilling for water in the valley, which was in progress at the conclusion of my experiments. The ore deposit itself is unusual. It consists of of intrusive plug of monzonite or granite porphyry. Chalcopyrite, bornite, and magnetite are finely disseminated throughout the magma in sufficient quantities to make the greater part of the mass commercial ore to a certain depth.

Jan 1, 1915

By J. E. Johnson

Discussion of the paper of Mark A. Amnion, presented at the Cleveland meeting October, 1913, and printed in Bulletin No. 70, October, 1913, pp. 1167 to 1 79. J. E. JOHNSON, JR., Ashland, Wis.:-Mr. Amnion's paper is of great value and it is not with any desire to reflect. on it that I wish to make some comments on the use of the scleroscope. We obtained one on trial some months ago and made very extensive tests with it, but without getting very satisfactory results. The readings on good car-wheels and bad ones were just about the same, but the factor in its use most likely to produce erroneous results is a variation in the thickness of the specimen being tested. In order to find out something on this subject we cut a thin disk, about -1,: in. thick, off a brass rod; then one 0.25 in. thick, and another about 1 in. thick, put the surfaces of all in about the same condition and tested them with the scleroscope. The readings varied widely; the resilience of the anvil evidently entered to a very high degree on thin pieces. By putting a soft cushion between such a thin specimen and the anvil, and forcing it up against the tube, the softness of the cushion cut off the resilience of the anvil and the results were more like those of the thick specimens. After a thickness of 1 in. was passed, the specimen seemed to have mass enough so that the resilience of the anvil no longer played an important part, and above that thickness results on different materials would be comparable, even though the thicknesses differed. But in order to get comparable results on thin specimens the thickness of those being tested should be the same. I should like to ask how the variations introduced in this way were overcome, so as to get strictly comparable results. Mr. AMMON :-.I have not had much experience in that, but the scleroscope is simply an indication of the surface harden-

Dec 1, 1912

By C. R. Ince

THE term "differential flotation" is used to denote a flotation operation in which separation is effected between two or more minerals of the same class; e. g., lead sulfide from zinc sulfide, pyrite from blende, chalcopyrite from pyrite, chalcopyrite from blende. At present, so far as published work shows, there seem to be two theories as to the mechanics of differential flotation. The earlier and more generally accepted theory is that the so-called depressing agents alter the surface of one or more of the sulfides in the ore, either by chemical action or adsorption, so that it is no longer amenable to flotation, but that these depressed sulfides can be revived, after the unaffected sulfide has been floated, by reagents which react chemically with the altered surface and make it amenable to flotation. More recently, Professor Taggart1 has advanced the theory that slime adsorption is an important factor in differential flotation. He believes that, with the proper use of a class of agents, which he calls .dispersion agents and which include practically all the depressing agents, one can cause the slime to adsorb differentially on sulfide surfaces. A gangue-slime coated sulfide surface will act as a gangue particle and will not float. If, subsequently, an agent that will remove the gangue-slime coating is added, the sulfide again assumes its original surface and can be floated as an ordinary sulfide. This-is the basis of the slime theory of differential flotation. Timber Butte mill at Butte, Mont., is a typical lead-zinc flotation concentrator. Neihart ore, chosen for investigation in this work, is one of the custom ores treated at that mill. Practice at Timber Butte mill in February, 1928, was as follows: A combined lead-zinc concentrate was first made using 0.2 lb. per ton on the ore of potassium xanthate and 0.03 lb. per ton of Cleveland Cliffs oil after 1.5 lb. per ton of lime and 1 lb. per ton of calcium chloride has been added just before the ball mill. The concentrate was then thickened to 70 per cent. solids. Potassium cyanide to the amount of 0.3 lb. per ton and zinc sulfate in the quantity of 0.5 lb. per ton were added to the thickened pulp and the whole

Jan 1, 1929

By O. W. Ellis

THE question of the influence of gases upon the properties of copper has received the attention of a number of investigators, among whom Sieverts,1 Iwasé,2 Lobley and Jepson3 stand preeminent. SOLUBILITY OF . GASES IN. COPPER Sieverts and Iwasé concerned themselves with the solubility of a variety of gases in the metal in the solid and liquid states. They determined the absorption coefficients of these gases and in all cases found a sharp change in solubility at the melting point of the metal. In this respect they disagree with Lobley and Jepson, who have based their opinions upon the appearance of small ingots of the metal which had been fused in an atmosphere of one or other of three gases and had then been rapidly cooled, while surrounded by gas, to the freezing point (rate-possibly 30° to 60° C. per sec.). The ingots that had been fused and cooled under nitrogen and carbon monoxide were free from blowholes and it was assumed that these gases were not absorbed in amounts much in excess of those which would dissolve in the solid metal; the ingots similarly treated under hydrogen were full of blowholes and it was assumed in this case that gas was ejected on solidification of the copper. The effect of varying the rate of freezing upon the character of the test ingots was not examined by these investigators; otherwise, it is felt, their views might have been subject to modification. Sieverts' most important contribution is that the solubility of a gas in any metal is proportional to the square root of its pressure or concentration. Knowing then the absorption coefficients of the various gases in copper, it should be possible to determine the analysis of the

Jan 1, 1928

By J. W. Bolton, S. A. Weigand

This paper discusses some fundamental metallurgical principles involved in production of sound cast bronze. In a previous paper the writers advanced the theory that "oxidation" in bronze castings is due to incipient shrinkage, and showed the effect of reducing melting atmospheres.' In the present paper the effects of certain impurities and of actual oxidizing conditions are shown. The appendix deals with the appearance of various inclusions. For many years the prevailing opinion has been that unsoundness, dark colored fractures and other phenomena accompanying porosity and weakness in bronzes are due to oxidation. The actual troubles are caused by fissures of intercrystalline type, which are often mistaken for intercrystalline films. These weaken the metal and make it porous. Grave doubt regarding the accuracy of the oxidation theory appears when several research papers presented within the last 10 years are reviewed critically. In 1919, Comstock2 conducted metallographic researches, attempting to identify "oxides" in synthetically prepared metals. He found that oxides of tin, aluminum, zinc, etc. are different from the intercrystalline films (or cavities) to which porosity is due. Apparently he believed that these "oxide films" may be caused by volatile oxides of zinc or of phosphorus or by dissolved gases thrown out of solution during solidification of the metal. In 1923, Woyski and Boeck3 definitely questioned the accuracy of the oxidation theory and indicated the danger from reducing atmospheres. They say that "oxidation, gassing and shrinkage may produce effects very similar." In 1926, investigations by Iwasé4 showed marked change in absorp-tion coefficients for various gases in copper above and below the liquidus.

Jan 1, 1930

By F. F. Peng, A. D. Walters, M. R. Geer, J. W. Leonard

INTRODUCTION Washability characteristics derived from float-and-sink analysis in Chapter 4 demonstrate that coal is intrinsically heterogeneous, and this heterogeneity is also evident in the proximate, ultimate, and size analyses. A range of particles from high to low specific gravity is usually seen in the run-of-mine coal. One objective of coal preparation is to recover the high quality float material (the particles of lower specific gravity) such that the recovered product meets certain quality specifications, as well as to reject or recycle low quality particles of higher specific gravity. The maximum recovery of cleaned coal at the required quality is of major concern to plant operators. However, the quantity and quality of products of coal cleaning, determined in the operation of actual commercial cleaning plants and by theoretical calculation based on run-of-mine washability studies, are known to be different with each coal. Therefore, during the last half century, coal preparation engineers have repeatedly sought methods to predict the technical and economical efficiency of separation of cleaning equipment and systems. Many formulas have been proposed by international investigators to evaluate the efficiency of various coal cleaning operations, primarily based on the yield and/or ash of the various products of coal cleaning. Performance criteria in use today are capable of defining all of the important aspects of a given concentrating operation; however each criterion has certain restrictions or limitations. It is important, therefore, to understand how such formulas can be used and the problems involved in their construction. Technical Measure of Plant Performance Conventional means for evaluating a preparation plant's performance are generally approached through the use of equipment performance mea-

Jan 1, 1979

The Sub-committee on Coal Mining, since its appointment, has been collecting data about subsidences in coal mines in this country, and thinks that almost all of the available data about occurrences of this sort in bituminous mines has been collected. Similar data is being compiled for the anthracite regions, which it is hoped will be ready for the 1927 meeting. As most of the bituminous seams are nearly level, the records obtained give the problem in its simplest form, without complications due to the pitch of the seam. Copies of the questionnaire, Appendix A, were mailed to all of the coal operators' associations, to most of the large operating companies and to many engineers, with the request that any data on the subject be returned to the committee, or that advice of any subsidences known be given: the replies to most of the questionnaires were general, although some specific cases were given. Many of the companies were unable to reply to all questions, as they lacked the necessary data, but in nearly every case where accuratc data was available, it was cheerfully furnished, and any additional information requested was secured. All specific cases of subsidence were followed up by correspondence, and in several cases by personal inspection. Figs. 1 to 31 were made from the information furnished. Table 1 gives measurements of elevations taken in one case at intervals from October, 1913, to May, 1918. With one exception, where the evidence cannot be released on account of a lawsuit, it is believed that the cases submitted with this report include practically all that have happened in bituminous coal mining in this country of which actual measurements were secured. Some of these have been published by Young and Stoek,l and some have been secured from other publications. In collecting these data, the subcommittee had the Engineering Societies Library extend its bibliography to date; this list is given in Appendix B. To assist in the study of the problem, all of the subsidence literature in English was examined for cases in which spccific measurements were given, and the essential data for each case are shown in Appendix C.

Jan 1, 1927

By Carl A. Zapffe, George A. Moore

IN a previous publication from this laboratory1 the conclusion was drawn that the embrittling effect of occluded hydrogen on iron and steel must result from the precipitation of the gas within small openings through the crystal structure. A review of the literature then published indicated the real existence of crystal sub- structures of the mosaic type and gave presumptive evidence that the "rift openings" associated with hydrogen occlusion are the same as the "disjunctions" of the mosaic theory. Inasmuch as no clear conception of the actual nature of the crystal fragments and openings inherent in these theories has been established, it was considered desirable to obtain direct micrographic evidence of their true configuration. In this direction the standard methods of metallographic attack have proved useless. Recourse was had, therefore, to the direct examination of the surfaces upon which failure by cleavage had resulted from the presence of hydrogen. It was expected that such a surface, un- affected by chemical attack and undistorted by polishing, would reveal the fine openings penetrated by the gas and thus indicate the real nature of the substructures. MATERIALS STUDIED In commercial steels, defects caused by hydrogen take various external forms ac- cording to such factors as structure and purity, and to the extent to which hydrogen either occludes or produces chemical changes. The present work relates only to the well-known transcrystalline hydrogen embrittlement-"pickling brittleness"-in which elemental hydrogen occluded within the grain develops cleavage characteristics. For example, hydrogen embrittlement resulting from hydrogen reaction products is excluded from detailed study. It was also desirable, as far as possible, to have the study uncomplicated by other elements which themselves cause brittleness. Three types of iron were used. These included ingot iron, decarburized free- machining steel, and a specially prepared, aluminum-killed, electrolytic iron. This , choice allowed a comprehensive selection of unavoidable minor impurities and inclusions, which could subsequently be shown to have no specific effects on the structures within the grains. Carbon, and any other impurities free to react with hydrogen, were first removed by a preliminary annealing treatment in hydrogen. Subsequent treatment in vacuo extracted much of this hydrogen and its gaseous reaction products. The resultant ductile iron was then embrittled either by a second anneal in hydrogen, followed by rapid cooling, or by cathodic electrolysis. Group I: Prepared from Armco Ingot Iron As shown in Table I, the principal impurity in this iron was oxygen, which survived the purifying treatment to a large extent. Two series were prepared. The first (Nos. SIO-24) was purified only one day in hydrogen and dehydrogenized one day in nitrogen. Containing both hydrogen and its

Jan 1, 1943