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By J. Brett, L. Seigle, L. Castleman, T. Montelbano

Impurity-induced low-temperature recrystallization of cold-worked tungsten was inuestigated with emphasis on the influence of nickel on the reaction. Palladium, nickel, aluminum, manganese, platinum, and iron greatly lower the recrystallization temperature of doped tungsten, which zs normally very high, but the recrystallization temperature of electron-be am zone-refined tungsten wzre is slightly raised by conlacl with nickel. Recrystallization can be induced at low temperature by the presence of solid nickel on the surface of doped tungsten wire, but apparently not by exposure to nickel vapors alone. Approximately 200 ppm of Ni dijjused into 10-mil wires at 1200 from a deposit of nickel on the surface produced total recrystallization, whereas more than 600 ppm of Ni could be absorbed frotn a vapor source without altering the fibrous structure of cold-worked tungsten. Once initiated, nickel-induced recrystallization required a continued source of' nickel for propagation of the recrystallization front. The solubility of nickel in fibrous 10-mil W wire was approximalely 500 ppm at 1150' C, and the activation energy for penetration of the recrystallization front was 52 kcal per mole. In many applications the usefulness of tungsten depends on critical control of its structure. Cold-worked tungsten with the fibrous structure developed by suitable thermo-mechanical treatment has a low, but technologically significant, ductility. It has long been known1 that traces of nickel, and perhaps other metals, are profoundly deleterious in doped tungsten, because they induce recrystallization at low temperature, which produces a brittle, equiaxed grain structure. This effect appears to be an exception to the general observation that recrystallization is impeded and the recrystallization temperature raised by the presence of impurities.2"9 Previous studies7-'' of the annealing and recrystallization of tungsten wire have divided the phenomenon into prior recovery stages, primary recrystallization and secondary recrystallization. The present investigation is concerned principally with primary recrystallization which is defined here as the replacement of the fibrous structure of deformed tungsten by equiaxed grains. The objective of this study was to explore the nickel-induced recrystallization reaction in tungsten and attempt to elucidate its mechanism. As well, an effort to define which other elements give rise to low-temperature-induced recrystallization was carried out. EXPERIMENTAL PROCEDURE The procedure adopted for these experiments was essentially to bring nickel and other elements into diffusive contact with cold-worked tungsten wires. The process of recrystallization was followed as a function of time and temperature by light and electron microscopic observations. First the influence of nickel on the recrystallization temperature of arc-melted, zone-refined, and variously doped tungsten wire was determined by electroplating a deposit of nickel on the surface of the wire and annealing at a variety of temperatures for 3 hr. The chemical analyses of the tungsten wires used in this investigation are given in Table I. The surface of the tungsten wire was etched with Murakami's slution' and approximately 0.005 in, of Ni was deposited from a Watts-type low pH bath14 for the conditions of these experiments. Variations in plating thickness from about 0.001 to 0.005 in. had no discernible influence on the resulting structures. The wires were then annealed in an atmosphere of dry hydrogen to establish the recrystallization temperature. Concurrently, un-plated specimens were annealed to establish the recrystallization characteristics of nickel-free wire. The criterion of recrystallization was that the fibrous structure be completely replaced by equiaxed grains after a 3-hr treatment of temperature. This provided more reproducible results than use of the first recrystallized grain or a fixed proportion of re-crystallized structure as the critical observation. The structures encountered in longitudinal and transverse sections were examined by both light and electron microscopy at magnifications up to X32,000 using parlo-dion-carbon replicas shadowed with platinum for the latter method. Second, the influence of a variety of metals on the recrystallization temperature of 0.010 in. D alumina-silica doped tungsten wire, AW136-64, was determined. The elements were applied by electroplating whenever possible. Alternatively, they were vapor-plated on the tungsten wire and a greater thickness built up by coating with a dispersion of metal powder in nitrocellulose lacquer. Elements not amenable to either of these procedures were merely slurry coated on the tungsten. The recrystallization temperature was determined as above. Third, the nickel-induced recrystallization process in doped wire was studied more closely by electroplating 8 mils of Ni on 65-mil alumina-silica doped tungsten wire, AW153-NS10, and exposing the wire to temperatures of llOO°, 1200°, or 1300°C for various times in a hydrogen atmosphere. A circular recrystallization front, 'Onsisting of equiaxed grains, developed at the periphery Of the coated tungsten wire, and the advance of this front into the fibrous interior was studied. These experiments employed relatively coarse 0.065 in. D wire because the 0.010 in. D wire recrystallized too quickly to permit observation of the pene-

Jan 1, 1969

By J. W. Snavely

WITH all the advantages of handling bulk materials by means of belt conveyor also go some problems, one of the most persistent being that of cleaning. When sticky materials are being carried; the build-up of material on the return idler rolls results in difficulty of belt training. Much attention has been given to the problem of cleaning conveyor belts, and a great variety of cleaning devices have been developed. Even the best involve troublesome maintenance, and none can completely remove the fine particles imbedded in the belt cover, which cause rapid wear of the return idler rolls, and at the same time, of the belt cover as well. One of the major rubber companies has been promoting a two-way belt system, in which the conveyor belt is given two successive 90" twists at each end to enable it to carry material in both directions simultaneously. For many years the flat belt transmission industry has installed quarter-turn and half-turn twists in countless numbers of instances. While quarter-turn and half-turn twists in transmission belts is a familiar application, the 180" twist apparently has never been previously attempted with a conveyor belt. About a year ago, two officials of the National Iron Co. of Duluth, Lester and Lewis Erickson, proposed twisting the return run of a conveyor belt on an installation that they were designing for one of the major iron ore producers. Since then the soundness of the idea has been demonstrated, both in theory and by practical test, with the result that the installation of two conveyor belts involving the twisting of the return run is now under way. These two installations are designed to have the return run of the conveyor belt twisted 180" as it leaves the snub pulley at the head drive. The clean underside of the belt is thus placed against the idlers on the return run as well as on the carrying run. Just before it enters the tail pulley, the belt will be twisted an additional 180°, restoring it to its normal position. Because this twisting of the return run of a conveyor belt is a radical departure from accepted practice, an elaborate and extensive test was conducted early in 1950 to demonstrate that this twisting of the return run could be done successfully, also to establish application data for accomplishing this twisting, and to determine if any special equipment would be required. In studying this concept of twisting the return run of a conveyor belt, a number of problems need to be solved, primarily the ones brought about by deliberately introducing an unequal distribution of stress across the conveyor belt and controlling that maldistribution of stress, while confining it to the return run portion. The tension conditions existing in the return run of a conveyor belt are clear to all designers. First, the return run carries the initial or slack side tension of the conveyor belt, the tension that must be supplied to the return run to provide proper frictional contact between the belt and the driving pulley so that the necessary power can be transmitted from the driving pulley to the belt without slippage. This slack side tension is supplied to the belt by means of takeups, either of the gravity type, which can be vertical or horizontal, or by means of the screw type. With inclined or declined belt conveyors the slope tension also must be considered, which is the tension imposed by the weight of the belt hanging from the top pulley. This slope tension frequently can furnish part or even all of the initial tension required. The maximum value of the slope tension will be at the top pulley, and it decreases in direct proportion to the length. In addition to the foregoing, it frequently is desirable to impose arbitrarily additional slack side tension to provide sufficient tension at the loading point at the tail, so that the belt will adequately support its load between the carrying idlers. Design Conditions for Twisting A number of design conditions exist, which must be satisfied successfully to accomplish the twisting of the return run without exceeding normal working limits in any portion of the conveyor belt. It is obvious that the belt edge, in its relation to the center of the belt, must stretch in making a twist, because as the twist is accomplished, the belt edge travels through a longer path than does the center of the belt. It is further obvious that if the edge of the belt is stretched, a redistribution of stress in the belt is required to allow this edge stretching. Moreover, this stress will be unequal across the width of the belt, having a maximum value at the edges, with a minimum value at the- center of the belt. With correct initial tension in the return run of a conveyor belt, the existing slack side tension will be unequally distributed when a twist is introduced. A condition then exists in which the edge stresses,

Jan 1, 1952

By W. A. Hutchins

Water laws important to the mining industry are those which govern or affect the right to use water, to dispose of water after using it in mining or milling, and to discharge waste material into watercourses. They include statutes and court decisions having general applicability, as well as others that pertain specifically to mining. THE INDUSTRY'S CONTRIBUTION TO WESTERN WATER LAW Despite sharp differences of opinion, the water law the Spaniards brought to the Southwest appears to have included some form of appropriation of water. The Mormons, who settled in Utah in the mid-nineteenth century, also developed a system of appro-priative water titles. But by far the most profound impact on western water law was made by the gold-seekers who flocked to the Sierra Nevada foothills of California after the discovery of gold in 1848. Much of the gold was extracted from the ground by hydraulic or placer mining, and so the miners' rights to the use of water became fundamentally important. Since there was no organized government in the foothills and no laws other than those made by the miners, they helped themselves to the land, the gold, and the water needed to work their claims.1 They established and enforced regulations governing the acquirement and holding of mining claims and their rights to the water they needed.' In 1879 Justice Field, former Chief Justice of the California Supreme Court, spoke for the U. S. Supreme Court in saying that the miners were "emphatically the law-makers, as respects mining, upon the public lands in the State."" Rules of the California mining camps were based on two essential principles: 1) priority in discovering claims and appropriating water by diverting it from streams and putting it to use, and 2) diligence in working claims and applying water in mining. The customs so developed, which were copied in mining areas of other states and territories, were enacted into law in one western jurisdiction after another. They form the basis of what is called the arid-region doctrine of prior appropriation of water, which received the attention of Congress in legislation recognizing and protecting appropriations of water for mining, agriculture, and other purposes on the public domain.' In several western states a great number of water cases decided in the early years involved relative rights to the use of water for mining purposes or for milling connected with mining." The miner's inch, the customary unit for measuring water in the mining camps, is still used in various western communities, although its relation to the cubic foot per second varies from one area to another. Undoubtedly, the miners of a century ago made the major contribution to the appropriation doctrine as it is now recognized and applied throughout the West. What inspired the California gold-seekers to develop these principles? Thoughtful writers have pointed out that their regulations and customs were strikingly characteristic of much earlier mining enterprises in the Old World.D It is said that the right of free mining and free use of flowing water therefor —so similar to the California conditions and practices—-was a part of the customs of Germanic miners in the Middle Ages, that it spread from middle Europe to other countries and colonies, and that the doctrine of prior appropriation was widespread in the important mining regions of the world. Certainly the Forty-niners came to California from many countries. It does not tax the imagination to consider that they may have brought with them some knowledge of the old Germanic customs and applied this knowledge in their new environment. RIGHTS TO USE OF WATER IN GENERAL In the West, rights to the use of water of watercourses fall into two categories—appropriative and riparian. The doctrine of prior appropriation is recognized in each of the 17 western states. The riparian doctrine is recognized concurrently with the appropriation doctrine in some of these states but has been abrogated in the others. The riparian doctrine prevails generally throughout the East, although there is now considerable interest in developing something else. Generally speaking, the appropriation doctrine has been highly developed in the West, whereas the principles of riparian doctrine have been comprehensively established in only a few states throughout the country. The subject of water rights is a big one. Space permits no more than a brief discussion of aspects that bear upon the title of this article. RIGHTS OF PRIOR APPROPRIATION Fundamental to the doctrine of prior appropriation is the principle first in time, first in right. Although in some states there are statutory exceptions. the original and still generally prevailing rule is that the first one who initiates a right to divert and use water of a stream, and who completes his undertaking with reasonable diligence, acquires thereby the first right of appropriation of the specific quantity of water involved. Each succeeding right in point of time is junior to all earlier rights but senior to all later ones. The practical effect of this priority system is that when the water supply is not enough for all, the earliest rights must be fully satisfied before any water may be taken by those later in time. Acquirement of Appropriative Rights: Each of the 17 western states has a statute under which water may be appropriated pursuant to a prescribed procedure. Generally, the first step to be taken by the intending appropriator is to file application in the office of the State Engineer for a permit to make the appropriation. In most but not a11 states, valid ap-

Jan 1, 1961

By M. L. Bleiberg, L. J. Jones

THE changes induced in metals by subjecting them to heavy particle bombardment have received widespread attention in recent years and results of such investigations have been reviewed by Slater, Dienes, Seitz, Siegel, and Seitz and Koehler.1-5 Of particular significance are the property changes that occur in uranium-base alloys due to neutron bombardment. These changes are generally very severe since fission occurs within the sample, resulting in the formation of heavy, highly energetic fission fragments, as well as additional neutrons born in fission, which serve to intensify the damage generally associated with fast neutron bombardment of nonfissionable metals. The property changes in uranium and uranium alloys due to neutron bombardment have been summarized by Paine and Kitte16 and Billington.7 It has also been shown that neutron bombardment of

Jan 1, 1959

By W. E. Horst

Flotation feed was hell constant for batch laboratory tests and continuous pilot and commercial plant tests on a spodumene ore to determine the relation.ship between flotation behavior and the size and type of flotation machine. Results. showed that additional retention time would be needed in the plant flotation circuit to duplicate laboratory or pilot plant performance when operating Dariables of the. plant flotation machines remained unchanged. During the past few years of operation at Kings Mountain, N. C., full-scale flotation has generally yielded poorer metallurgical results than those obtained in the laboratory or pilot plant. After 2 min in each size of Denver flotation machine in the spodumene rougher circuit, pilot recovery (41.7 pct) was almost three times that of the plant (13.6 pct) and about twice that of the laboratory (21.0 pct). Pilot and commercial plant data are based on continuous operation, and laboratory results on batch testing of rougher performance. The ore is a pegmatite containing spodumene, feldspar, quartz, mica, and amphibolite. Data were accumulated to evaluate the scale-up relationships between laboratory, pilot plant, and plant flotation cells. Flotation rate constants and dimensional analysis were used to define the relationship existing between flotation behavior and scale of operation. Measuring Flotation Rates: Efficiency of the rougher stage was measured by flotation rate, defined as the recovery that can be attained within a given time." • The problem of measuring flotation rates has been studied by many investigators, whose methods have varied. Published studies an flotation kinetics have been summarized recently by Gaudin.l When comparing flotation rates, it is more satisfactory to compare straight line relationships between recovery and flotation time than exponential curves resulting from plotting cumulative recovery vs cumulative flotation time. To convert the exponential curves into straight line relationships, rate equations were applied similar to those used in chemical kinetics to study the velocity of chemical reactions. Two rate equations have been used in this investigation to measure efficiency of the various cells: 1.5 order Rate Equation dR/dt=k (A-R)1.0 [Eq.1] Second Order Rate Equation dR ---- - K(A - R)2 [Eq. 2] dt Upon integration Eq. 1 becomes 1/(A-R)1/2=k/2 t+1/A1/2 [Eq. 3] and Eq 2 becomes: or fEq. 4] t/R=1/A2K+t/A [Eq. 4] where R = cumulative recovery [percent recovery of total value (spodumene) in flotation feed]. A = initial concentration, pct (100 pct of mineral to be separated). t = flotation time (minutes). k = flotation rate constant for 1.5 order rate equation [units: 1/(percent) 0.5 (min)1. K = flotation rate constant for second order rate equation [units: 1/(percent) (min) 1.

Jan 1, 1959

By Harrison Everett Ashley

Prof. Hofman's diagrams, Figs. 5 and 7 of his paper, which are reproduced as Figs. 1 and 2 of the present contribution, confessedly fail to show comprehensively the properties of the silicates investigated. Each curve is carefully discussed, and the author has evidently drawn all the conclusions that can be thus reached; but he says :* "The curves do not show, as was hoped, any simple connection between silicate-degree, percentage of lime, and minimum of formation-temperature." There is, therefore, in this case, an excellent opportunity of

Jan 1, 1902

NEW MEMBERS The following list comprises the names of those persons who became members during the period May 10 to June 10, 1915: Members ANDREEN, HARRY MAYO, Millman: and Assayer Thane, Alaska. BANKS, HUBERT RAYMOND, Min. Engr., Mill Staff, Consolidated Arizona Smelting Co., Humboldt, Ariz. BASSETT, ARTHUR F., Min. Engr., Care Consolidated Arizona Smelting Co., Humboldt, Ariz. BLACKNER, LESTER A., Slope Engr.... Care Ray Consolidated Copper Co., Ray, Ariz. BUSHNELL, C. E., Draftsman Butte & Superior Copper Co., Butte, Mont. CAVAGNARO, DAVID AMILE, Min. Engr., Genl. Supt., Wisconsin North Fork GravelMines, Forest, Sierra Co.; Cal. COGHILL, WILLIAM HAKES, Met., Ore Testing Laboratory, 3705 Hueco St., - - El Paso, Tex.

Jan 7, 1915

By T. S. Mohibatsela, R. V. Ramani, C. V. Manula

The Mineral Engineering Department of The Pennsylvania State University has developed a suite of computer models for anthracite open pit mining (Fig. 1)1 Individual sub-systems have been developed to (a) interpolate geologic field data to obtain coal tonnages, waste volumes, and strip ratios; (b) simulate equipment performance on selected pit profiles to generate data required to choose coal and waste removal equipment; and (c) evaluate selected cost factors to determine either a rate of return for a specified selling price or vice-versa. This paper describes the application of two of these subsystems, namely, the Reserves Model (GEOL) and the Open Pit Materials Handling Simulator (OPMHS), and how these may be applied for the selection of equipment for a prime anthracite mining site.2

Jan 1, 1981

By N. E. Norman, R. Stier

The mining industry is continually seeking out new and better underground mining techniques. One of the most recent-also, perhaps, the most significant-of the new concepts in underground mining is the use of mechanical rock-boring machines. And one of the problems that concerns us all in this matter is the cost of mechanical rock tunneling. To help answer the oft-quoted question "What will it cost me?" the following pages deal with the operating costs of so-called "medium to medium hard rock" boring machines-i.e., those designed to meet the drilling requirements in 8000 psi to 25,000 psi rock. A few machines are capable of drilling hard rock above 25,000 psi, but the economics of mechanical tunneling in rock that hard is limited at the present time. [ ] For mechanical rock tunneling, there are five main cost factors influencing the expense: Capital Investment, Cutters, Labor, Power Requirements, and Maintenance. These factors give us a good basic picture of the cost of excavation, although muck handling, erecting supports, and other costs directly related to conventional tunneling and mechanical boring enter into the final picture.

Jan 6, 1967

By Clifford Frondel

THE aluminum oxide known as corundum has several varieties that have been used as gem materials since ancient times. These include the red variety called ruby, the blue variety sapphire, and the asteriated types of ruby and sapphire. Asteriated sapphire was known to the ancients under the name of astrios, and descriptions of this gem were given by Pliny and other early writers. The relation of these gem materials to each other as varieties of a single species, corundum, was first clearly established by Haüy in 1805 and J. M. Güthe1 in 1809. Natural gem corundum is obtained principally in Ceylon, Siam, Burma, India, and Australia. Star sapphires and rubies always have been highly prized and in recent years have become particularly popular in the United States. Natural star rubies of large size and fine quality are extremely rare and rank with large and fine emeralds and diamonds as the most valuable of gem stones. Interest thus attaches to the recent success in commercially synthesizing star sapphires and rubies of a size and perfection unmatched by nature.

Jan 1, 1954

By Robert G. Van Nostrand, John H. Henkel

TRANSIENT potentials obtained in resistivity prospecting can be separated into two classes. The first is electromagnetic, has a comparatively short time constant, and increases in relative amplitude as the electrode separation is increased. These electromagnetic transient potentials, of which an excellent theoretical treatment is given by Yost: are the result of changes in the current and can be classed as differentiated signals. The second class is electrochemical, has a comparatively long time constant, and decreases in relative amplitude as the electrode separation is increased. The electrochemical signals are generated by the current flow itself and can be classed as integrated signals. The transient potentials due to electrochemical factors are the subject of this article. The phenomenon is referred to as induced polarization. Schlumberger" was the first worker to observe induced polarization, but he was unsuccessful in attempts to apply the principles of induced polarization in electrochemical prospecting. Other workers, notably Bleil; have studied polarization and in some cases pointed out its possibilities, but no theory has been presented that describes polarization and its time dependence adequately. It is the purpose of this discussion to present the essence of a theory to geo-physicists and to show that it leads to results consistent with experimental evidence. The theory on which this analysis is based has existed in electrochemical circles since 1910."

Jan 1, 1958

By S. S. Clarke

THE opening of zinc-lead ore bodies in the lower chert beds of the Tri-State district, locally called sheet-ground deposits, [ ] presented several new economic operating problems to be solved before the low-grade deposits could be mined profitably. Drilling was the first high-cost problem and loading and haulage difficulties followed. At this time, the sheet-ground mines are producing about 2000 tons per day. GEOLOGY The geology and ore deposits of the Tri-State district have been covered in detail by [ ] Fowler and Lyden.* Briefly, the sheet-

Jan 1, 1942

By E. Werchowsky

FOR over four years, since the revolution of 1917, Russia has been cut off from the Western world. Political and general economical reforms have attracted the attention of the public and business world, but mining men have had no information as to the situation in their branch of industry, as various articles which have appeared in the European and American press gave little information as to actual conditions in our country. When the Soviet system of government was estab-lished and private ownership abolished, it affected the FIG. 1.-ORGANIZATION OF THE COUNCIL OF MINES. mining industry very little at first. The power of the Soviets did not affect the Ural provinces nor Ukraine or Asiatic Russia (Siberia, Turkestan, etc.) during 1918 and 1919, and, as is well known, the mineral wealth of the republic lies within those boundaries. In the Ural Mountains are copper, gold, and platinum; in Siberia, silver, lead, zinc, and gold, and the coal deposits in Koushetz district; in Ukraine, there are the coal fields of Donetz and the iron mines of Krivvy Rog, and silver, lead, zinc, copper, oil, etc. in the Cauca-sus. The mineral resources of Central Russia are the coal fields of Moscow (low-grade and brown coal), turf deposits, iron mines in Tula and Kalonga provinces, and quarries of granite and other building materials.

Jan 8, 1922

By Earl R. Hoskins, James E. Russell

The electrical resistivity of rocks has been studied quite extensively, in particular, the effects of temperature and confining pressure on resistivity. References 1 through 6 at the end of this chapter pertain to electrical resistivity of rock and contain further references on the same topic. The present study is motivated by an interest in determining the in-situ properties of rock as well as the stress state of the rock and how these quantities are changing with time. Most of the previous work on the electrical resistivity of rocks has been directed toward saturated rocks at relatively high confining pressures and temperatures. The present study was oriented towards air-dry surface rock that might occur in mine pillars. The mean stress and temperature under such conditions are comparatively low. It has been demonstrated that the resistivity of rock is highly dependent upon the porosity. In fact, for saturated rocks, a relationship referred to as Archie's law has been established between porosity and electrical resistivity. In the case of saturated rock, the property that is actually being measured is the resistivity of the solid/fluid system. Since the resistivity of the fluid alone is usually much lower than that of the dry rock, it is understandable that the resistivity of a saturated rock is in general several orders of magnitude lower than the resistivity of a relatively dry rocli. For dry rock, it seems reasonable that the electrical resistivity should increase as microcracks open within the material. Since microcracks open as material is stressed closer and closer to its failure point, it appears that there should be a correlation between electrical resistivity

Jan 1, 1970

By G. S. Ansell

RCENTLY, in investigating the high-temperature creep properties of an aluminum, SAP-type alloy, MD 2100, fabricated by Professor F. V. Lenel of Rensselaer Polytechnic Institute, Ansell and Weertman1 found unusually low creep rates. These creep rates are 4 or 5 orders of magnitude lower than is predicted by the slowest creep mechanism based upon dispersion-hardened alloy theory. They ascribed these results to a lack of both normal active dislocation sources and a continuous three-dimensional dislocation network. If one couples these results with the following factors of production and microstructure: 1) The compacted and sintered aluminum powder compact is hot-extruded, with an extrusion ratio of 25:1.2 2) The alyminum oxide particles are approximately 140A units thick, and have a spacing varying from 0.05 to 1.5 1. 3 3) The alloy has plate-shaped grains with minor axes of about 5 X 10 -3 mm and major axes several orders of magnitude greater than this.'

Jan 1, 1960

By L. F. Mondolfo

An aluminum-copper 4 pct Cu alloy aged at room temperature for times increasing up to 78,000 hr was annealed at 170°C and the hardness and electrolytic potential determined during retrogression and subsequent aging. It was found that there is a change of behavior with increasing time of aging at room temperature which indicates that, given sufficient time, retrogression disappears and the room-temperature aging tends to progress directly into the high-temperature aging. WHEN an age-hardenable alloy is aged at low temperature after proper quench, changes of properties and structure take place. If this material is then heated to a temperature higher than the previous one, but still well below the solution-treatment temperature, the properties and structure changes produced by the low-temperature aging disappear and the material apparently reverts to the as-quenched condition, ready to undergo aging from the start. This phenomenon is termed reversion or retrogression. First discovered by Cayler3l it has been extensively investigated, as shown by the number of publications listed in the bibliography. From all the information available the following facts emerge: 1) All aeg hardenable alloys can be retrogressed.9 13, 19) 24, 33, 41, 42, 44, 47, 53, 54, 61, 63, 64, 66, 73, 78 2) All the properties changes that take place during aging at low temperature can be retrogressed to a smaller or larger extent.4,5,7,12,19,32,49,50,57,58,60,67,75,76 67, 75, 76 3) Retrogression requires that the temperature be well above the preliminary aging temperature. If the difference between the two temperatures is small, Little or no retrogression takes place.7,20,32,33,41,49 57. 65 4) The larger the difference between the preliminary aging and the retrogression temperature, the faster and more complete is the retrogression.20, 33, 41, 48, 65, 67 5) Retrogression can be produced several times in the same alloy.23, 35,41,57,59 6) The amount of retrogression that can be obtained depends on the aging temperature. Alloys aged at the lower temperatures can be retrogressed the most. The higher the preliminary aging temperature the less retrogression can be produced.20,25,33,37,44,49,54,58 7) Appreciable retrogression after aging at elevated temperatures is possible only if the preliminary aging has lasted a short time. After a certain time of aging at high temerature retrogression does not take place any more,:5,6,9,10,11,21,40,58 8) During retrogression the Guinier-Preston zones redissolve and disappear. The other precipitate

Jan 1, 1960

DISCUSSION, A. Y. Bethune presiding M. E. Wadsworth and W. M. Fassell (University of Utah, Salt Lake City)—The authors of this paper should be complimented on the experimental techniques they have employed to investigate the rate of solution of galena in sodium hydroxide solution. Studies of this type are important not only as a practical means of leaching normally non-leachable substances, but also to determine the mechanism of solution at the solid-aqueous solution interface. There is some question, however, as to the conclusions which have been drawn by these authors concerning their proposed mechanism. Unfortunately, the contribution of OH- was not definitely established in their work, and concentrations less than 0.5 N NaOH evidently were not investigated. The pressure data at 123°C and 0.5 N NaOH were used to determine pressure dependency and the subsequent model proposed was taken as correct on the basis of the three points presented in Fig. 5 of the paper. In developing the

Jan 1, 1954

By Frank Van Horn

INTRODUCTION IN June, 1911, the writer spent a few days in studying the economic geology of the vicinity of Park City. During this rather hurried visit a number of specimens of ore were collected, which have since been examined. The results of these investigations show that bournonite (PbCuSbS3) is present in the ores in greater or less quantity. This fact has never before been reported, as far as can be learned. The failure to recognize this mineral is due to its similarity to tetrahedrite, with which it has probably been confused during a long period of years. Jamesonite (Pb2Sb2S5) has been reported from the region in a rather doubtful manner, but the writer has seen it in notable amounts from several mines, and can offer the first analysis of this mineral from the district. Calamine (H2Zn2SiO6) was found at one mine and has never been recognized and reported from the district.

Jan 8, 1914

By R. R. Sayers

VENTILATION may be defined as the process by which vitiated air of an inclosed or partly inclosed space is continuously replaced by fresh air. Fresh air has been defined as invigorating pure air. Pure dry air at sea level contains the following gases:1 Analysis of Air at Sea Level PER CENT. Oxygen 20.94 Nitrogen 78.09 Carbon dioxide 0.03 Argon 0.94 Helium, krypton, neon, xenon, hydrogen, hydrogen peroxid, ammonia, ozone traces CARBON DIOXIDE LIMIT For many years carbon dioxide was used as an index of the purity of the air vitiated by the metabolism of people. It was, however, well known that the untoward effects produced on those exposed to such air was not due to the concentration of the carbon dioxide. It has been found that the untoward effects on the comfort and efficiency of those so exposed are due to the increased temperature and humidity. It has been found that men can breathe air containing many times the amount of carbon dioxide found in our worst ventilated theaters and assembly halls, which, according to Rosenau, do not contain above 0.5 per cent. carbon dioxide.

Jan 7, 1926

By Guy Bjorge

IN recent years the Homestake mine has been served by three shafts, the B. &. M., the B. & M. No; 2 and the Ellison, supplemented by an inside shaft, the Milliken, extending from the 2000-ft. level to the 3200-ft. level. In 1932, when a new operating shaft was under consideration, the bottom of the mine was at the 3200-ft. level. The B: & M. and the B. & M. No. 2 shafts were down to the 1550-ft. level and the Ellison was being deepened from the 2600 to the 3200-ft. level. All ore was hoisted at the B. & M. and-Ellison shafts. Levels below the 2600 level, which were under development only, were served by the Milliken shaft. Below the 1550-ft. level, the mine was served only by the Ellison shaft from the surface. Within a few years, when ore reserves above the 1550-ft. level would be depleted, operation would be limited to the Ellison shaft and the auxiliary underground shaft. The Ellison shaft alone was not adequate for hoisting the entire output from the deeper levels and also handling all men and supplies. Further-more, assurance of safety and uninterrupted operation required- two fully equipped shafts to the deeper levels. Therefore a new operating shaft was authorized in November, 1932, and was named for A. J. M. Ross, the mine superintendent.

Jan 1, 1935