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By Vincent P. Gianella

Barite deposits are of widespread occurrence in Nevada but there are few producing properties; most of the latter are in northern Nevada. The production of the state is small at present—in the neighborhood of 15,000 tons annually—but is steadily increasing. The barite occurs in veins and also as replacement deposits in limestone. The bulk of the production has come from the replacement deposits. It is thought that the barite was deposited from rising hot waters similar to—and probably contemporaneous with—those responsible for some of the metallic ores of the state. This paper discusses only the deposits in northern Nevada. The commercial mining of barite did not begin in Nevada until 1916 but although the production has been small there has been a rapid increase in tonnage during the past several years. Barite is widely distributed in the state and production comes from at least nine of the seventeen counties. Apparently this is not generally known, as only two counties arc mentioned in a recent publication6 dealing with barite. The increase in output is due largely to recently discovered barite deposits in northern Nevada. The principal production has come from the northern portions of Lander and Eureka counties; smaller amounts from Elko County. The discussion in this paper is confined largely to the deposits in these counties. Most of the producing area is tributary to the Western Pacific and Southern Pacific Railroads, whose tracks lie along the Humboldt River. Barite is known from other northern counties but so far the production has been small. The output has come entirely from veins and replacement deposits, the latter largely in sedimentary rocks. In general, the barite from veins is white; that from the replacement deposits usually is dark gray to black, although some is light gray or white. Most of the veins contain sulphides and many barite-bearing veins have been worked for their content of base or precious metals. Production The recorded production in Nevada to the end of 1938, according to the U. S. Bureau of Mines,3 is 66,424 short tons, of which 57,157 tons

Jan 1, 1941

By Nelson W. Taylor

With the extensive deposits of potash minerals which have been discovered in the southwestern states, and their rapid development, a permanent American supply of potassium compounds is now assured. The 325-year history of the potash industry in this country has been told by H. I. Smith1, of the U.S. Geological Survey, and the more recent activities of the Survey and of American potash companies were described last year by the same author2. In fact, it may be stated that so great is the productive capacity that two mines in New Mexico and one in California are able to supply more than half a million tons of crude and refined salts over and above that produced for agricultural purposes. The era of scarcity has given way to an era of superabundance. This situatiori makes it desirable for the potash producer to look for other applications for his product, and it is with this in mind that the writer presents some information pertaining to present and possible future uses for potassium compounds in the ceramic industry. Ceramic Products Ceramic products are essentially solid materials containing one or more oxides such as SiO2, Al2O3, CaO, MgO, FeO, K2O, Na2O, TiO2, which are the oxides of greatest abundance in the earth's crust. The typical ceramic process is that of firing or burning the batch, and the product may be glassy, crystalline or mixed. In the glassy or vitreous group come glass, porcelain enamel and glazes; in the crystalline group, refractory materials such as silica brick, or chromite or magnesia; and in the mixed group, porcelain, chinaware, stoneware, tile, brick, etc., which contain both a vitreous and a crystalline phase, in variable proportions. The ceramic industry of the United States is a billion dollar industry, and is important not only because of its magnitude but also because of the key position occupied by certain ceramic products in the whole manufacturing structure. From the standpoint of use of potash, the field of refractories is of no great interest, since K2O lowers the melting point of a refractory oxide and

Jan 1, 1938

By Kendall E. Born

Production of crude oil in Tennessee during 1941 was slightly more than 15,000 bbl., about the same as in the preceding year. Two thirds of the total was from the Mississippi limestone pools in Scott and Morgan Counties. About a dozen small scattered wells in Clay, Pickett, and Fentress Counties, pumped irregularly, produced approximately 5000 bbl. Natural gas was marketed from wells in Morgan and Fentress Counties for consumption in the Sunbright and Jamestown areas, respectively. The production by counties is shown in Table I. Drilling activities in the state fell to the lowest stage since 1933. Twenty-seven wells were spudded in during 1941, of which six were drilling or only temporarily suspended on Dec. 37, 1941. Of the 22 completions, four were gas wells of undetermined quantity, but are classed as commercial, and 17 were dry or near-dry holes. One well encountered oil, but it has not been tested. The total footage drilled during the year was 29,916 ft.; the average depth of wells was 1359 ft. The more important wildcats are listed in Table 2; the distribution of tests according to physiographic divisions is given in Table 3. East Tennessee.—One well was drilled to 3480 ft. in northwestern Anderson County, in the highly disturbed Appalachian area, a region long considered the most unfavorable in the state for the accumulation of oil and gas. Another test is now drilling below 2000 ft. in this general area. Cumberland Plateau.—There were two completions in the Cumberland Plateau area. One test, drilled in northwestern Scott County in an area of former Mississippi limestone production,' encountered a considerable amount of free oil at 850 ft., about the same horizon as in the old abandoned wells. No pumping tests have been made to date. A well at Oneida, Scott County, found gas at 1579 ft. in a sandy limestone of lower Mississippian age. The volume was reported doubled by a shot, although no open-flow measurement is available. Eastern Highland Rim.—Six completions on the eastern Highland Rim resulted in two small gas wells in Fentress County, which will be used to augment the supply for Jamestown. The producing horizons are shaly limestones of Ordovician (Trenton) age. Two wells in this area tested the upper part of the Knox dolomite group, one of which encountered some free oil in a sandy dolomite at 1670 to 1681 ft. A test high on a well-defined structure in Clay County found a considerable amount

Jan 1, 1942

By R. E. Head

Under existing economic conditions, the treatment of gold ores occupies an outstanding position in metallurgical activity. The increased price of gold has automatically brought about a reclassification of old dumps and low-grade orebodies, and many that formerly were considered valueless are now being vigorously investigated and worked. This situation has developed problems that have taxed the ingenuity and ability of metallurgists to the utmost. Some gold ores give a high extraction of gold by standardized methods of treatment; other ores of apparently similar character yield but a relatively small percentage of their gold when treated by the same processes. Surface Contamination The experience gained by microscopic study of numerous gold ores and tailings has shown that there are pronounced differences in the physical characteristics of the minerals composing them, more especially of the gold. Repeated studies of tailings from flotation and cyanidation of gold ores has established the fact that surface contaminations on gold particles are often directly responsible for high gold losses; comparison of gold particles isolated from flotation concentrates and the resulting tailings have showed that the clean gold has been recovered and the tarnished or contaminated gold invariably lost in the tailing. Obviously, it is not possible to make such a comparison of gold ores treated by cyanidation, as the clean gold has been taken into solution; but when the gold found in cyanide tailing has a tarnished or coated surface, one may infer, with a reasonable degree of certainty, that the clean gold has been extracted. This premise is supported by experimental evidence obtained by isolating particles of tarnished gold and exposing them to cyanide solution in small parting cups. In one such experiment, tarnished gold particles picked from a cyanide tailing showed but slight evidence 01 dissolving at the end of 27 days. In this test, a cyanide solution of 1.6 11). per ton was used and the leach solution was decanted arid renewed every

Jan 1, 1939

By F. W. Bloecher, A. M. Gaudin

THIS paper describes the results of a series of tests carried out to determine the partition of dodecylamine between distilled water and the surface of quartz at various concentrations of dodecylamine acetate in solution. An adsorption-column technique was utilized for this purpose. Ralston and Harwood, of Armour and Co., had synthesized marked dodecylamine acetate for us.' In their preparation which we employed, 0.0007 pct of the total carbon was the radioactive isotope, carbon fourteen. Unmarked dodecylamine acetate of high purity was also prepared by them for our use. The presence of carbon fourteen in the dodecylamine enabled us to analyze quantitatively for dodecylamine on the surface of quartz, using a radioactive-tracer technique. The method used was that known as internal gas counting of carbon dioxide, formed by oxidation of the amine. This method has already been described, "3 ' and the reader is referred to these papers for details of the analytical method and procedures. and surrounding liquor, a technique analogous to chromatographic columns was utilized. The experimental setup is shown in fig. 1. The dodecylamine-acetate solution was made up in a volumetric flask and poured into the glass funnel shown. It was allowed to drip slowly onto the quartz bed, the rate of flow from the funnel reser- voir being controlled by a hose clamp. The quartz column was contained in a small, fritted-glass filter (size 20 mm, C). The beaded top edge of the filter was cut off to enable the holder and contents to fit into the open end of the 30/45 joint on the combustion tube. This combustion tube is used in the analytical train described in a previous paper.' A piece of gum-rubber tubing joins the bottom of the fritted-glass filter to a filter flask, which in turn is connected to a vacuum line, or water aspirator. The rate of flow of amine solution through the bed was

Jan 1, 1951

By H. T. Byck

The plastering properties of six representative California drilling muds were studied over a temperature range of 70 to 175 F. at several mud weights, using a high-pressure circulating filter press with full size consolidated cores. In all tests, with untreated as well as with chemically treated muds, the filtration rates at elevated temperature were higher than at low temperatures and in nearly every case this increased filtration rate was notably larger than could be attributed alone to the decreased viscosity of water—the flowing medium—at elevated temperatures. It is concluded that no existing method will permit even an approximate determination of the filtration rate at high temperature from data at room temperature. It is necessary to measure filtration at the temperature actually anticipated in the well, or to make a sufficient number of tests at various lower temperatures so that a small extrapolation of these data to the anticipated well temperature may be applied. Such tests should be carried out on the mud as actually used in the well. The viscosity of each of the muds was determined over the same temperature range. While no relationship was observed between mud viscosity and plastering properties, it was found that chemical treatment of the muds for viscosity reduction shifted the temperature of minimum viscosity to appreciably higher values than for untreated muds. Importance of Plastering Properties A survey of the literature on rotary drilling muds clearly shows the growing realization of the importance of plastering properties,'-5 not only from the point of view of the successful completion of the mechanical operation of drilling the well but also from the point of view of minimum impairment of the natural flow possibilities of a given well. Poor plastering properties with attendant high filtration rate (large water loss to the formation) and thick mud sheath, lead to stuck drill

Jan 1, 1940

By David A. Keys

Applied geophysics is the youngest child of that old branch of learning that has been known from Aristotle's time as physics—the constitution and laws of nature. The mother science, with the help of mathematics, has given birth to many children, who, on becoming of age in the scientific sense, wedded more practical applications which later became known as electrical engineering, physical chemistry and acoustical engineering. Some vigorous sons still retain the family name, among which the most recent to take its place as a division of science is geophysics, which deals with the physics of the earth. Geophysics in its broad sense has many departments—meteorology, oceanography and seismology, to mention only three. Within the past 20 years, however, a special interest has arisen in the application of physical principles to problems in geology, mining and civil engineering, with the consequent rapid growth of what has now been called "applied geophysics." Applied geophysics in this narrower sense is the application of experimental and theoretical physics to determine variations and discontinuities in underground structures that cannot be ascertained from surface inspection. It seems evident, then, that the physics department is the natural place in a university where the principles and methods involved should be taught and developed, for the physicist will also have had the requisite training in mathematics that the proper understanding of many methods now used will require. A knowledge of the procedure and principles, however, is not sufficient for the successful application of geophysical methods. One may know the dynamics of flight of golf balls and of impact and yet not play a par game of golf! The proper selection and use of the right club to suit the circumstances of the lay of the ball and an acquaintance with the possibilities and limitations of the strokes as well as the practical execution of the play is essential to a successful game. So, also, in the application of geophysical methods, it is important for the geophysicist to use the best device under the conditions presented, to know the limitations of the conclusions deduced from his physical measurements and to make the proper interpretation of the results. A knowledge of geology will be of great aid in coming to the correct con-

Jan 1, 1940

By Alec M. Crowell, C. H. Thigpen

Continuing the increase in production of crude oil and condensate started in 1937, the oil fields of South Arkansas reached a 13-year peak with 26,570,704 bbl. for the year 1942. The stability of the production branch of the industry in the area is demonstrated by Fig. I, which reflects the fact that although the number of producing wells in the state has declined from 3280 in 1931 to 2957 at the end of 1942, total production has continuously increased since the beginning of 1937. This is because all fields discovered since Jan. I, 1937, have observed spacing patterns up to one well to each 160 surface acres, the dual completion of wells where there is more than one producing horizon Eight new pools were brought into production in South Arkansas during 1942 (Fig. 2) They increased the state's crude oil and condensate reserve by 121,000,000 bbl., bringing the total recoverable reserve figure to 450,000,000 bbl. (Table 3) as of Jan. I, 1943. Abandonment of wells in the stripper areas of the state increased by 32 per cent over the preceding year, there having been 142 wells permanently abandoned in 1942. For economic reasons 279 wells were temporarily shut down as of Dec. 31, 1942. A price increase may start these wells to pumping again and also be the incentive toward the commencing of several secondary recovery projects in the fields discovered between 1922 and 1937. There were 149 wells brought into production in 1942 as against 119 for the

Jan 1, 1943

By P. G. Shewmon, F. R. Winslow

An experimental method is describedfor Ihe determination of the derivative of the surface free energy (y,) with surface orientation using symmetric bicrystals. The method measures the equilibrium root-angle of grain boundary grooves for the same grain boundary on two different surfaces. In contrast to previous methods, the presence of annealing twins is not necessary. Results on silver at 900°C indicate that ??s/?3 is 0.014y, on the (loo), 0.075y, on the (111), and < 0.004?s on the (110). DURING an investigation of the kinetics of grain-boundary grooving on silver&apos; values of the derivative of the surface free energy ?s with respect to orientation were needed. Previous investigations of these so-called torque terms show that, for low-index planes in copper2 and nickel,&apos; a finite derivative exists even near the melting point. These two studies give the only previously published values of the torque on low-index metal surfaces. These investigators measured the equilibrium root angles, both greater than and less than 180 deg, along the lines where a twin boundary intersects a free surface. The technique described here is suitable for materials which do not have annealing twins, and enables the surface for study to be chosen instead of having to work in a direction normal to the twin trace on the surface. The purpose of this paper is to describe this new technique and to report the values found for the (111): (100), and (110) surfaces of silver. To check the technique proposed above, a series of 99.99 pct Ag bicrystals were used. These bicrystals were grown from the melt by a modified Bridge-man technique so that a low-index direction was parallel to the growth direction. Two orthogonal faces were studied on each bicrystal. One of these contained the low index or simple plane normal to

Jan 1, 1963

By William Glenn

In their account of chromium, Roscoe and Schorlemmer (Treatise on Chemistry, London, 1879) state that "In 1762 Lehmann, in a letter to Buffon, de nova minerœ plumbi specie crystalline rubra, described a new mineral from Siberia, now termed crocoisite." In 1786 Lehmann analyzed it (Nicholson&apos;s Jour., Dee., 1798) and found that it contained chiefly lead, and that the " mineralizers " were arsenic and sulphur. It was next examined in 1189 by Macquart and Vauquelin, who stated that it contained an intimate mixture of iron, alumina, and lead peroxide. The account of their work was published over the name of Macquart. Vauquelin (Louis-Nicolas) was a Norman peasant, who had studied in the village school, and at the age of fourteen was a laboratory-boy in a pharmacy at Rouen. Later, he found his way to Paris, and in 1789 was assistant to Fourcroy, a pharmacist and a teacher of note. It was here that he met Macquart, with whom he did the work on Siberian red lead, and at this time his friend Cheradame taught him his Latin.

Jan 1, 1896

By R. G. Knickerbocker

THE copper smelter and refinery of The Messina (Transvaal) Development Co. Ltd., at Messina, South Africa, was erected in 1920 and 1921, but initial operations were deferred until late in 1922 on account of the collapse of the copper market in the interim. Because the anticipated production was to be only 20 tons of copper per day from a high-grade matte containing 60 per cent copper, and because the ore did not contain gold or silver in quantities sufficient to pay for separation from the copper bullion, it was decided to design the plant along lines quite different from the modern smelteries treating large quantities of sulfide ores carrying appreciable amounts of gold and silver. The plant was built, therefore, for the production of copper by the Nicholls-James process. By this method two-thirds of the copper matte produced was roasted in a Merton calciner and charged into a bath of the remaining one-third portion of unroasted matte in a reaction furnace. The original design was not only novel in providing for the Nicholls-James process, but also in comparison with new plants built elsewhere, because of factors inherent in the locality. Sources of supply for machinery were very remote; it takes three months after the placing of an order to accomplish delivery of machinery into Messina from the United States. Native labor was available at 30 to 40¢ per 8-hr. shift. These factors permitted plant design which provided no overhead cranes, no matte ladles, no slag pots or other usual mechanical means of transportation between departments. The design resulted in a compact simple plant with furnaces arranged close together and. terraced so as to provide for gravity transfer of molten material from one furnace to another and for manual disposal of products. Fig. 1 shows the relative location of furnaces. The three furnaces are parallel on successively decreasing elevations. A superimposed feed floor was provided above the furnaces. All three furnaces were provided with coal-dust burners served from a Bonnot system of coal-dust transportation, and the waste gases were discharged into waste-heat boilers.

Jan 1, 1932

By G. Pomey

Heat-resisting chromium steels and alloys treated at 825° or 9.50°C (1527° or 1742°F) in a carburizing atmosphere exhibit an extensive carbide precipitation. This carbide precipitation may be succeeded by the FeCr a phase or by a carbide with a higher carbon content. Point analyses carried out with an electron mi-croanalyzer make it possible to study the depletion of chromium in the matrix after precipitation has occurred and to determine the chemical composition of carbides. In particular the content in the carbides of Fe, Ni, and W, elements which substitute Cr, can be accurately determined. HEAT-resisting chromium steels and alloys employed in the construction of gas carburizing and carbonitriding furnaces are subjected to a succession of oxidizing atmospheres during heating and cooling and to carburizing atmosphere during isothermal stage. Such a sequence of thermal cycling causes embrittlement and corrosion in the furnace materials. A quantitative study of the structural changes induced in the furnace materials has not received much attention in the past. However, utilization of the electron probe microanalyzer and other modern techniques has permitted a point analysis of the various phases formed and to follow their relative evolution. This paper gives results as regards the nature and composition of the carbide precipitation and the distribution of chromium in the matrix during only the carburizing periods. The structural changes subsequently produced during oxidizing periods will be presented eventually. METHODS AND MATERIALS Metallographic, X-ray diffraction and Castaing electron-probe microanalysis1 techniques have been employed to study carbide precipitation and evolution and the changes in the composition of the matrix in heat-resisting steels and alloys.

Jan 1, 1961

NEW MEMBERS The following list comprises the names of those persons who became members during the period of Apr. 10, 1918, to May 10, 1918. BALLARD, JOHN I Supt., Cable Mining Corpn., Cable, Mont. BURKMAN, JOHN M. F., Constr. Engr., U. S. Smelt. Refin. & Min. Co., Care -University Club, Mexico City, D. F. CALLEN, ALFRED COPELAND, Head, Mining Engineering Dept., West Virginia University Morgantown, W. Va. CHADWICK, LAWRENCE, Chem., Mt. Elliott Copper Co., Ltd., Selwyn, via Townsville, North Queensland, Australia. CODY, FRANK W., Skimmer, Reverberatory Furnace, Arizona Copper Co., Clifton, Ariz. COOLBAUGH, MELVILLE F., Prof. of Chem., Colorado School of Mines, Golden, Colo. DODGE, ALLAN WAYNE The Dodge Agency, 104 East Iron Ave., Salina, bans. DONNELLY, LEONARD G., Pet. Geol., Sinclair Oil & Gas Co., Sinclair Bldg., Tulsa, Okla.

Jan 6, 1918

By L. W. Saperstein, W. W. Kaufman

Stimulated by the hearing protection clauses in the 1969 Coal Mine Health and Safety Law, attempts were made to determine what safety hazards, in terms of warning signal discrimination, are attendant upon the wearing of hearing protectors. Warning signals of dangerous roof conditions were collected and analyzed from 11 different coal mines in four different coal seams. Primarily, signals of audible level emanating from roof, floor, or coal were recorded. The interpretations of these signals were seen to be very dependent upon coincident visual and tactile signals. Acoustic character of such signals is shown to be dependent upon the spectral energy distribution of the pulses. Roof talk signals generally have broad-band spectra concentrated below 5 kHz. Reverberation times of acoustic pulses are generally less than 0.5 sec in duration. Indications have developed which link the coal mine entry dimensions with the nature of noises recorded there. Related experiments suggest that roof talk can be discriminated from background noise equally well when wearing protection as when not. This conclusion is only appropriate when noise levels warrant the wearing of protection. When quiet, the wearing of protection somewhat reduces discriminatory ability.

Jan 1, 1976

By P. H. Griffin

WHEN a subject, such as the manufacture and service of chilled car wheels, as has been fruitlessly discussed for ten or fifteen years, it is difficult to revive interest and action by the mere repetition of statements and arguments that have been made before. And when a situation involves serious responsibilities for conditions that have grown up under circumstances beyond the control of any particular individuals or authority, it is even more difficult to deal with. But there is one phase of every subject that need not involve these particular points if presented in a, proper manner; and that is, " the future state." I will try to present the subject of this communication from the latter standpoint and with the hope that all of those interested will feel disposed to give the matter attention from the basis that it is a, vitally important one to all that travel on railroads, whether as employees or officials, or as dependent on those in charge of the operation, or in the matter of materials and equipment used. The conditions of chilled wheel service have been changed so radically in the past ten or fifteen years by the use of freight cars of 40 and 50 tons capacity, that it is fair to say in the interest of all concerned in the use and in the manufacture of such wheels, that the increased strains and loads have been quite sufficient to account for much of the service results that have transpired. That proper provision was not made for increased possibilities of strength and wear, in fact that previous factors of the kind were allowed to deteriorate, is no proof that such wheels cannot be made equal to heavy service conditions as shown in the data given herein.

Jan 10, 1913

By Herbert Johnson

DURING the past 10 or 12 years very little information has been made generally available concerning the commercial possibilities of separating materials by means of static electricity; and yet during that same period important improvements have been made in various branches of the science of electricity, which, when taken together, and applied to electro-static separation, have resulted in important improvements in that art as well. For example, much improvement has been made in high-voltage electrical equipment such as full-wave vacuum-tube rectification and improved mechanical rectification. Great strides have likewise been made in the development of insulators for high-voltage work, not only in the materials used but also in the design of the insulators themselves. Again, in another field, the development of air-conditioning equipment has improved the technique of controlling the surface condition, through drying or humidifying, of the various materials that are passed through the electrostatic separator. In many authoritative publications and textbooks, the electrostatic separation process is declared to require a balance far too sensitive for general commercial application. For example, one publication1 in the past has referred to an unfavorable effect on the process caused by varying atmospheric conditions such as humidity. Some2 have even gone so far as to state that sunlight and shadows may seriously affect the separating efficiency of the process. Such statements may have been true in the early development of the art, when the source of static elec-tricity was derived from a friction disk machine, such as the Wimshurst. The Blake Mosher equipment and the work of Huff in applying motor-generator sets, transformers and mechanical rectification overcame much of this kind of objection to the commercial application of the elec-trostatic separating process.

Jan 1, 1938

By R. L. Curfman

In May 1960, six months after conversion of one- half of the Uranium Reduction Co. mill from acid to alkaline leach, severe corrosion was encountered in the 112 stainless steel wash baskets in the resin- in-pulp portion of the uranium circuit. Fortunately the corrosion was limited to the stainless steel screen cloth and bolts. The frames were not affected. Each resin-in-pulp wash basket serves as a container and a vehicle for approximately 40 cu ft of ion-exchange resin. Four baskets are installed in each tank through which uranium-rich solution flows as the baskets move up and down mechanically in the tank. The ion-exchange resin has an affinity for the uranium in the solution which causes it to be deposited on the resin in solid form. By reverse action with different chemical solutions, the uranium may be stripped from the resin for further processing and purifying. This section is the first step in the actual recovery of the uranium.

Jan 9, 1962

By William A. Kennedy, Jonathan R. Stahl

This paper deals with the phenomenon of water held in a leach dump due to capillarity. Water is shown to be retained in the fine pores of the ore as well as in the interstices between the rock and soil particles. Upon drainage, Chino leach dump material shows two distinct capillary systems and a double capillary curve is often obtained. Both the igneous and the sedimentary rocks composing the leach material are shown to have appreciable porosity but little permeability. Fluid flow is, therefore, restricted to the interstices between the rock and soil particles. The irreducible water saturation for the aggregate is found to be 884 for the -48 mesh material and 235 for the448 mesh to one inch material. The composite sample of minus one inch dump material had an irreducible water saturation of 52 percent. The irreducible water saturation in the fine pores of the ore was found to be between 73 and 76 percent. Very coarse pores or channels between large rocks exhibit essentially zero capillary retained water. The presence of fine material in a dump can cause high water saturations to be retained and these saturations may be mistaken for perched water tables. Perched water tables can be drained but capillary water will be retained. Capillary pressure data can aid in distinguishing between perched water tables and capillary retained water.

Jan 1, 1974

Discussion of the paper of L. A. DELANO, presented at the St. Louis meeting, October, 1917, and printed in Bulletin No. 129, September, 1917, pp. 1267 to 1286. L. A. DELANO.-Since this paper was written, our daily mill tonnage has increased, from 2100 tons to 2700 tons a clay. We now use 11,000 lb. of chrome-steel balls of 2 ½ -in. maximum diameter, for an average crushing capacity of 275 tons per 24 hr., this giving a much higher crushing efficiency. I wish to call attention to two typographical errors in my paper as published. On page 1271, Table 1, the screen analysis of ore at the Bonne Terre mill should be stated in inches instead of mesh. - On page 1272, "the rolls average 185 tons per 24 hr., and have shown by test that 250 tons per hour can be maintained" should, of course, read "250 tons per 24 hours." THE CHAIRMAN (0. M. BILHARZ, Miami, Okla.).-Is the increased mill capacity due to improvement in the re-crushing of middlings or to keeping middlings out of circulation and treating them separately? L. A. DELANO.-AS was shown in Mr. Rabling&apos;s paper (Bulletin No. 128, p. 1161) the tonnage was raised by about 400 tons by simply changing the arrangement of screen openings in the jig bed and using punched plate instead of woven-wire screen. Then, by adding a ball-mill, we are taking from the jigs a much larger tonnage of middlings than before or as much as the ball-mill will crush. By sending the ball-mill product to tables and flotation, the jig capacity for original ore is increased. CHAIRMAN BILHARZ.-In your opinion, the satisfactory operation of a Hancock jig on a given ore requires adjustment of the length of the different screens and careful selection of screen openings? L. A. DELANO.-I think it does. In order to decide what screen openings to use on the jigs, we did a great deal of experimental work, making screen analyses of the various hutch products, and then hand-sorting the galena, middlings and chat from each size screen to determine the percentage of galena in each. Then adjusting our jig screens, we gradually worked the process up to a very efficient basis. ERNEST GAYFORD, Salt Lake City, Utah.-I would like too ask Mr. Delano whether the work of the Allen cone has been quite as satisfactory as the manufacturers claim for it.

Jan 1, 1918

By Edgar Bain

IN STUDYING the structural characteristics of martensite it is desirable that a clear conception of the material from which martensite is produced should first be obtained. Any theory of its formation and structure incompatible with the facts of its parent substance, austenite, can be eliminated with little consideration. Austenite is the name applied to solid solutions of carbon and other elements in gamma iron. At temperatures above about 900° C. (1650°, F.), pure iron exists in a system of crystallinity1 entirely different from the crystal structure below that temperature. This high-temperature allotrope of iron is of an atomic structure associated with great ductility, having very manifold symmetry and an abundance of easy slip planes. The exceptionally ductile and malleable metals (gold, silver, platinum, copper, aluminum, and nickel) have this same atomic arrangement-the face-centered cubic. The low-temperature allotrope of iron, alpha iron, the solid solutions of which are known as ferrite, has a body-centered cubic arrangement of atoms. Like it, in crystal structure, are the less ductile and malleable metals, molybdenum, tungsten, titanium and chromium. Fig. 1. shows the two atomic arrangements known in iron; the diagrams are drawn to scale. Either of these modifications of iron may dissolve other elements in the solid state; by so doing, the temperature of the transformation is changed. In general2-7, it appears that a solid solvent metal dissolves a metal solute by substituting foreign atoms in its own space lattice. Thus, iron may dissolve nickel in either of its crystalline forms by permitting an atom of nickel here and there to occupy the normal position

Jan 2, 1924