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By L. T. Larson, M. L. Picklesimer

The relationship between the apparent angle of rotation of monochromatic plane polarized light and the tilt of the basal pole from the surface normal has been experimentally determined for zirconium over the wavelength range of 500 to 655 mp. This relationship allows the determination of the spatial orientation of the basal pole of an individual grain in a polycvystal-ling zivrconium specimen to within ±3 deg by three simple tneasurements with a polarized-light metallurgical microscope. The method of measurement is discussed in detail. THE optical anisotropy of materials having noncubic crystal structures has long been used to reveal features by polarized-light microscopy. Petrographers have used measurements of certain optical properties to identify and classify transparent or translucent minerals. More recent work (i.e., Cameron1) has extended such measurements to opaque minerals in reflected light. Few attempts have been made to make similar measurements on noncubic metals. Couling and pearsall2 have reported that a sensitive tint plate can be used in a polarized-light metallurgical microscope to determine the position of the basal-plane trace in a grain of polycrystalline magnesium. Reed-Hill3 has reported that the same technique can be used for zirconium. We have found that the precision of measurement can be increased to about ±0.5 deg by using a Nakamura plate4,5 to determine the exact extinction position after the sensitive tint plate has been used to locate approximately the basal-plane trace. This report describes a method for measurement of another optical property, the apparent angle of rotation. This measurement permits determination of the angle between the basal pole of a grain of a hcp metal and the normal to the surface of the specimen. When the two measurements are combined, the orientation of the basal pole in space can be determined from three simple measurements on a single surface. One to two hundred such determinations will permit plotting of a basal-pole figure for the polycrystalline material with reasonable accuracy. When normally incident, monochromatic, plane-polarized light is reflected from the surface of an optically anisotropic material, the light may be converted to elliptically polarized light, the plane of vibration may be rotated, or both may occur. The el- lipticity, the angle of rotation, and the reflectivity can be related to the indices of refraction and the absorption coefficients of the material.6,7 Ellipticity values can be determined with an elliptical compensator, but not with the ease and precision desirable for the present purposes. Measurement of the angle of rotation requires only the determination of the angle from the crossed position (90 deg to the polarizer) that the analyzer must be rotated to obtain extinction when the trace of the optical axis in the surface is at 45 deg to the vibration direction of the polarizer. The angle of rotation of the analyzer is approximately 6/5 that of the true angle of rotation of the light as reflected from the specimen because there is a small amount of additional rotation produced during the passage of the reflected light through the mirror of the microscope. Since we are presently interested only in determining the tilt of the basal pole, the angle of rotation of the analyzer (the apparent angle of rotation of the light, i.e., uncorrected) can be used. Precision of the measurement can be increased substantially by the use of a Nakamura plate4,5 in determining the extinction position. In an optically uniaxial material (hcp or tetragonal crystal structure) the angle of rotation depends only on the optical properties of the material and the orientation of the optical axis of the grain relative to the plane of incidence of the plane-polarized light.7,8 Thus, in a metal such as zirconium, the apparent angle of rotation at the 45-deg position in any given wavelength of light is a direct measure of the tilt of the basal pole from the normal to the surface. If the optical properties vary with wavelength, the apparent angle of rotation for any given tilt of the basal pole will vary. None of the required information exists in the literature for zirconium nor for any other non-cubic metal. MEASUREMENTS ON SINGLE-CRYSTAL ZIRCONIUM A single-crystal sphere of zirconium 9/16 in. in diam was spark-cut from a single-crystal rod grown from iodide bar by an electron-beam zone-melting process.9 The damaged surface was removed by chemical polishing in a 45/45/10 mixture (by vol) of water, concentrated HNO3, and HF (48 pct) and then electropolishing at 50 v in a bath1' of methyl alcohol and perchloric acid (95/5 by vol) at -70-C. The single-crystal sphere was mounted in a five-axis goniometer stage having a removable eucentric X-ray diffraction goniometer head for the two inner orientation axes. The basal pole of the single-crysta sphere was aligned parallel to a third axis of the goniometer stage by using the sensitive tint method to determine the basal-plane trace at several rotational positions of the sphere. The alignment was then checked by removing the sphere and eucentric gonio-

Jan 1, 1967

By William D. Klopp, Joseph R. Stephens

A substantial reduction in the 300°F ductile-to-brittle transition temperature for unalloyed chromium was achieved in alloys from systems which resemble the Cr-Re system. These alloy systems include Cr-Ru, Cr-Co, and Cr-Fe. Transition temperatures ranged from -300° F for Cr-35 at. pct Re to -75°F for 0-50 at. pct Fe. The ductile alloys have high grain gvowth rates at elevated temperatures. Also, Cr-24 at. pct Ru exhibited enhanced tensile ductility at elevated temperatures, characteristic of superplas-ticity. It is concluded that phase relations play an importarlt role in the rhenium ductilizing effect. The ductile alloys have compositions near the solubility limit in systems with a high terminal solubility and which contain an intermediate o phase. The importance of enhanced high-temperature ductility to the rhenium ductilizing effect is not well understood although both may have common basic features. CHROMIUM alloys are currently being investigated for advanced air-breathing engine applications, primarily as turbine buckets and/or stator vanes. The inherent advantages of chromium as a high-temperature structural material are well-known1 and include its high melting point relative to superalloys, moderately high modulus of elasticity, low density, good thermal shock resistance, and superior oxidation resistance as compared to the other refractory metals. Additionally, it is capable of being strengthened by conventional alloying techniques. The major disadvantage of chromium is its poor ductility at ambient temperatures, a problem which it shares with the other two Group VI-A metals, molybdenum and tungsten. For chromium, the problem is further amplified by its susceptibility to nitrogen em-brittlement during high-temperature air exposure. In cases of severe nitrogen embrittlement, the ductile-to-brittle transition temperature might exceed the steady-state operating temperature of the component. The low ductility of chromium would make stator vanes and turbine buckets prone to foreign object damage. The present work was directed towards improvement of the ductility of chromium through alloying, with the anticipation that any improvements so obtained might be additive to strengthening improvements achieved through different types of alloying. The alloying additions for ductility were selected on the basis of the similarity of their phase relations with chromium to that of Cr-Re. The reduction in the ductile-to-brittle transition temperatures of the Group VI-A metals as a result of alloying with 25 to 35 pct Re is well established.a4 the temperature range -300" to 750° F. This phenomenon is commonly referred to as the &apos;<rhenium ductilizing effect"; this term is also used to describe systems in which the ductilizing element is not rhenium. Other alloy systems which have recently been shown to exhibit the rhenium ductilizing effect include Cr-Co and c-Ru.= In order to explore the generality of this effect, alloys were selected from systems having phase relations similar to that of Cr-Re, primarily a high solubility in chromium and an intermediate o phase. The following compositions were prepared: Cr-35 and -40Re; Cr-10, -15, -18, -21, -24, and -27 pct Ru; Cr-25 and -30 pct Co; Cr-30, -40, and -50 pct Fe; Cr-45, -55, and -65 pct Mn. Seven other systems were also studied which partially resemble Cr-Re. These systems have extensive chromium solid solutions or a complex intermediate phase, not necessarily o. The compositions evaluated include the following: Cr-20 pct Ti; Cr-15, -30, and -45 pct V; Cr-2.5 pct Cb; Cr-2.5 pct Ta; Cr-20 pct Ni; Cr-6, -9, -12, and -15 pct 0s; Cr-10 pct Ir. The compositions of alloys in these systems were chosen near the solubility limit for the chromium-base solid solutions, since in the Group VI-A Re systems, the saturated alloys are the most ductile. These alloys were evaluated on the basis of hardness, fabricability, and ductile-to-brittle transition temperatures. In addition to the studies of alloying effects on ductility, an exploratory investigation was conducted on mechanical properties at high temperatures in Cr-Ru alloys EXPERIMENTAL PROCEDURE High-purity chromium prepared by the iodide deposition process was employed for all studies. An analysis of this chromium is given in Table I. Alloying elements were obtained in the following forms: Commercially pure powder — iridium, osmium, rhenium, and ruthenium. Arc-melted ingot — titanium and vanadium. Electrolytic flake — iron, manganese, and nickel. Sheet rolled from electron-bearn-melted ingot — columbium and tantalum. Electron-beam-melted ingot — cobalt. Sheet rolled from arc-melted ingot — rhenium. All alloys were initially consolidated by triple arc melting into 60-g button ingots on a water-cooled hearth using a nonconsumable tungsten electrode. The melting atmosphere was Ti-gettered Ar at a pressure of 20 torr. The ingots were drop cast into rectangular slabs and fabricated by heating at 1470" to 2800° F in argon followed by rolling in air. Bend specimens measuring 0.3 by 0.9 in. were cut from the 0.035-in. sheet parallel to the rolling direction. The specimens were annealed for 1 hr in argon, furnace cooled or water quenched, and electropolished prior to testing. Three-point loading bend tests were conducted at a crosshead speed of l-in. per min over

Jan 1, 1969

By John C. McDonald

CONTROLLED cold work is used between solution heat treatment and precipitation heat treatment for producing certain tempers of the commercial aluminum base alloy 2219 (designation of the Aluminum Association, U.S.A.) which contains 6.3 pet Cu as the major ingredient responsible for the age hardening. The complete composition limits for this alloy are listed in Table I. The alloy has been described in detail,&apos; and the control of the heat treatment has also been published.2 Beneficial effects of such cold work in other alloys have also been pointed out.3&apos;4 NO data have been published on the effects of varying amounts of cold work under fixed aging conditions. In connection with an investigation of the possibility of providing the desired cold work by explosively generated shock waves, it became desirable to investigate the effect of variable cold work, and to compare the re -sults with those obtained from explosives. The general principles of explosive hardening are well-described in the literature.&apos; All material used was guaranteed by the supplier

Jan 1, 1968

By C. W. George, Bruce Chalmers

The authors enumerate the factors which appear, from their observations and practical experience of failure of aircraft components in Great Britain, to be responsible for causing a metal or alloy to fail by stress corrosion. The essential conditions for promoting failure by stress corrosion are: (I) tensile stress at the surface of the component, (either residual or applied), and (2) an attacking medium that may be a solution or a liquid metal. Particular attacking agents are effective only on certain metals. In all instances of stress-corrosion failure experienced, cracking of an intercrystalline form has occurred and examples of such failure in aluminum alloy, steel and copper alloys are described and illustrated. The relation between microstructure and stress corrosion is mentioned and methods of investigating the susceptibility to stress-corrosion failure of metallic materials are described. The precautions to be taken in selecting materials for particular aircraft components and the importance of adequate protection against chemical attack are considered. The authors have given a factual survey of stress corrosion and have made no attempt to advance any scientific explanation of the phenomenon.

Jan 1, 1945

By Lawrence Adler

A lag apparent in the mining engineering field. While mining will continue as an essential industry, a revitalized profession will be required for national well-being. Specific problems facing the profession include: - a conflict between its design, production and management components, which affect the engineers on a daily basis; - a credibility gap in public matters that is so extreme, government action approaches punitive in degree, and - historical decreases in the number of degree-offering departments in the face of an increasing demand for graduates. A turnaround in these areas could result in attracting into the industry, highly creative, capable, and socially concerned engineers. By improving the quality of undergraduate education, the effectiveness of each entering engineer would be multiplied. This is another way to combat the chronic shortage of trained mining engineers. At the same time, it would set a significant example for other professions in the throes of overspecialization. A revival of the mining profession can be accomplished only during the formative training years of its future practitioners. An educator&apos;s role would be pivotal in this effort.

Jan 3, 1975

By Howard N. Hall

The compressibility of reservoir rock is a factor which is generally neglected in reservoir engineering calculations. This is due in part to the fact that there is little published information on rock compressibility values for limestones and sandstones. Omission of rock compressibility is undoubtedly justified in calculations for saturated reservoirs; however, in under-saturated reservoirs,* expansion of the rock accompanying decline in the reservoir pressure may be of such magnitude as to affect materially the prediction of reservoir performance. The effect of rock compressibility will be of most importance in: (1) calculation of oil in place by pressure decline data in undersaturated volumetric reservoirs when the limits of the field are unknown or indefinite, and (2) studies of natural water drive performance. To estimate its importance in such cases, a series of laboratory tests were made to obtain usable values for reservoir rock compressibility. The total, or effective, compressibility of any reservoir rock is a result of two separate factors, namely, expansion of the individual rock grains, as the surrounding fluid pressure de-

Jan 1, 1953

By A. F. Baker, E. R. Palowitch, A. W. Deurbrouck

As air-pollution regulations become increasingly more stringent, increased significance is being placed on the amount of sulfur present in coals used for steam generation. These regulations are aimed at minimizing the pollution of the atmosphere with noxious gases such as the sulfur oxides that are formed and emitted when coal is burned. Two meet these future requirements, a definite need exists to reduce the sulfur content of some of the coals used for steam generation. Reducing pyritic sulfur involves liberating the pyrite from the coal and then removing it. The specific gravity of pyrite is high (5.0) compared to that of coal (about 1.2, mineral-free), and standard coal-washing devices, such as wet concentrating tables, will efficiently remove pyrite particles larger than about 100 mesh. Particles below this size will be entrained in the table water and will be carried into the clean coal product. Techniques such as froth flotation are of little benefit for pyrite reduction because the flotation characteristics of pyrite are similar to those of coal.

Jan 6, 1966

By V. R. Garfias, R. V. Whetsel, J. W. Ristori

World consumption of petroleum and related fuels for civil purposes in 1939 was close to 2,024,000,000 bbl., or approximately 110,000,000 bbl. more than in 1938, the United States accounting for 96,000,000 bbl. of the increased amount. With the annexation of Czechoslovakia and part of Poland, civil consurnption in Germany during 1939, notwithstanding sevre rationing in the last four months of the year, was 54,000,000 bbl., or only 1,600,000 bbl. less than in 1938, and domestic production of pctroleum and related fuels was some 34,000,000 bbl. short of civil consumption. The mounting petroleum requirements of the military forces of greater Germany are, of course, not included in these figures of civil consumption. To supply this deficiency Germany now must rely almost exclusively on the Rumanian fields, which in 1939 produced about 35,000,000 bbl in ewes, of the Rumanian civil consumption. However, these fields arc supplying and have supplied for years the oil requirements of the neighboring

Jan 1, 1940

By J. W. Ristori, R. V. Whetsel, V. R. Garfias

World consumption of petroleum and related fuels for civil purposes in 1939 was close to 2,024,000,000 bbl., or approximately 110,000,000 bbl. more than in 1938, the United States accounting for 96,000,000 bbl. of the increased amount. With the annexation of Czechoslovakia and part of Poland, civil consurnption in Germany during 1939, notwithstanding sevre rationing in the last four months of the year, was 54,000,000 bbl., or only 1,600,000 bbl. less than in 1938, and domestic production of pctroleum and related fuels was some 34,000,000 bbl. short of civil consumption. The mounting petroleum requirements of the military forces of greater Germany are, of course, not included in these figures of civil consumption. To supply this deficiency Germany now must rely almost exclusively on the Rumanian fields, which in 1939 produced about 35,000,000 bbl in ewes, of the Rumanian civil consumption. However, these fields arc supplying and have supplied for years the oil requirements of the neighboring

Jan 1, 1940

By Francis J. Dennis

Many factors govern the value of dredging-ground, and much capital can be wasted by the mistaken policy of contracting for the purchase of property arid the installation of machinery before a thorough examination has been made. To the uninitiated investor the presence of gold is generally the criterion, and very superficial evidence is necessary to satisfy him as to this point. he couuiclers the comprehensive report of a competent engineer as a wasteful extravagance, aild cannot understand why the engineer requires so much time and money to ascertain the information on which to base his conalusions, when the promoter can furnish him such pleaaing and satisfactory data with but little expenditure of time aud money. The uninitiated investor will often optimistically risk capital for purchase and equipment, and riot uiitil the veuture comes to grief does he learn that the condition8 are wholly unsuited for dredging. In many instances, a short preliminary examination by a competent engineer would have disclosed these facts. The mere presence of gold is by no means suficient; sonie of

Jan 1, 1912

By F. D. DeVaney

IT is of great interest that the various organizations engaged in the search for a cheap and efficient agglomeration process for fine magnetite concentrates-essential if the taconites are to be utilized-have ended up with processes that are basically different. This paper describes the development and the present status of the shaft-type furnace as now utilized by the Erie Mining Co., which is managed by Pickands Mather & Co. The shaft furnace has always had an appeal to metallurgists because of the simplicity of the design and the possible low fuel consumption. Work done on pelletizing at the University of Minnesota Mines Experiment Station by E. W. Davis and his associates determined that it was possible to roll up fine magnetite concentrates in a balling drum, and that, if such balls were fired at a sufficiently high temperature, a hard, indurated pellet, well adapted for use in a blast furnace, could be made. Early furnaces had no heat recuperation and the heat consumption was in the order of 2 million BTU&apos;s per long ton.

Jan 3, 1958

By J. Donald Graham, John G. Kuhn

The goal of any development drilling program is the drilling of the exact number of holes necessary to adequately determine grade and dimensions of an ore body, no more and no less. Any technique which eliminates unnecessary drilling costs produces beneficial results, both to the company and to the person who can claim the savings. The method for controlling development drilling programs to be described was developed during the latter part of a major development drilling project at the Christmas mine of Inspiration Consolidated Copper Co. in Gila County, Arizona. It was used to test the need for drilling individual holes but could be expanded to control an entire project. Application of this method involves an evaluation of geological conditions present and a good bit of common sense. Projects involving large disseminated, rather homogeneous ore bodies of the porphyry-copper type would be the most likely candidates for application of the technique. Discontinuous ore bodies would not be amenable. The method is based on the measurement of the linear correlation between the spatial distribution of two sets

Jan 1, 1973

By A. L. Senkayi, L. R. Hossner, J. B. Dixon, J. S. Ahlrichs

Chemical and physical properties of soils and overburden materials must be evaluated prior to strip mining activities. This information can be used to assess whether subsurface overburden can be equal in quality to the native soils, especially when these soils are classed as prime farm lands. In northeast Texas, lignite primarily occurs in the Calvert Bluff formation which is underlain by the Simboro and Hooper formations. These formations are in the Wilcox group (early Eocene). The Carrizo formation, that unconformably overlies the Calvert Bluff formation, consists of thick layers of sand with poor water and nutrient retention capabilities. These materials are least suited for placement on the surface of reclaimed land. The oxidized, medium textured overburden of the Culvert Bluff and Simboro formations possess adequate water and nutrient retention properties and are better suited for sustained plant growth when compared to the existing native soils. Non-oxidized Calvert Bluff and Hooper sediments generally have acceptable properties for reclamation although acid forming sulfides occasionally occur. Materials high in sulfides must be buried during mining or appropriately treated prior to reclamation.

Jan 1, 1984

By Harold M. Mooney

RESISTIVITY measurements for determining depth to bedrock, water table, and other geo- logic discontinuities have had only limited success. Many of the difficulties can be attributed to complex geology and to basic limitations of the method; current flow through a continuous medium is a diffusion phenomenon, emphasizing irregularities near the source and smoothing out those at a distance. Some of the failures, however, are due to careless field work and incompetent interpretation. A forthcoming publication1 may help to reduce difficulties of this sort. The writer here attempts to bring order into the multiplicity of interpretation methods and, to a limited extent, to evaluate them. For all methods, the field data to be interpreted consist of apparent resistivity values plotted against electrode separation, Fig. 1. The interpretation should give depths to one or more geologic horizons. Direct currents and the Werner four-electrode configuration will be assumed, since these are widely used, although the interpretation problems remain essentially the same for other electrode configurations. Alternating currents higher than, say, 20 cycles per second introduce complications beyond the scope of this paper.

Jan 9, 1954

By J. M. Lohr

A COMMERCIAL development requiring a suitable alloy or alloys for sealing into various grades of glass made it desirable to have a more exact knowledge of the expansion characteristics of the nickel-iron alloys than appeared in the published literature. The expansion of the more common. FIG. I.-EXPANSION CURVES OF SEVERAL FIG. 2.-EXPANSION CURVES OF TWO TYPES OF GLASS. (Courtesy of R. C. A.) TYPES OF GLASS. (Courtesy of R. C. A.) types of glass under consideration varies from 2.7 to 10.4 X 10-6 per degree Centigrade, over the range 20° to 400° C. For reference, the thermal expansion curves f several types of glass used for sealing by the lamp and tube industries are given (Figs. 1 and 2). This paper covers a detailed investigation of the thermal expansion of a series of nickel-iron alloys in which the nickel content varies from 30 to 70 per cent. Particular stress is laid on the alloys that contain between 40 and 55 per cent Ni.

Jan 1, 1938

By W. B. Tijmann

Maintaining safe, yet economical, slope geometries in a mining operation is paramount. When design analysis and engineering judgement have dictated conservative and usually more expensive problem solutions, monitoring has often proven to be a valuable method in dealing with potential slope instability. A well planned and executed monitoring program can allow operation at a lower theoretical margin of safety. Monitoring provides a valuable check on design parameters and can measure effects of remedial improvements. Warning of impending failure can often be established well in advance. The monitoring problem situations in civil engineering works and open pit mining are much alike. Instruments used for monitoring in both industries are often the same. In this paper, geotechnical instruments for measuring deformation and groundwater pressure in rock and overburden are discussed with a broad-brush approach. Results obtained over extended time periods are presented in a graphical presentation for a case history. Descriptions of various types of instruments, mostly used to monitor stability of rock slopes, are discussed, and data analysis and approximate costs are presented.

Jan 1, 1983

By James B. Vance, Parviz Mottahed

An extensive research program has been carried out at PCS Mining for some time into the use of high frequency microseismic emissions in the range of 30-200 kHz for roof fall warning in the mines. A laboratory investigation on loaded samples of potash has established a close correlation between acoustic emissions and the applied load. The tests also indicated the occurrence of the Kaiser effect. The positive and encouraging response from underground testing and controlled laboratory testing has lead to the extension of the investigation into correlation of the high frequency microseismic emissions and the change in stress distribution due to mining. Hydraulic borehole pressure cells were installed at different depths ahead of the advancing boring machine. The output due to the stress change and the microseismic event count was monitored by a continuous chart recorder. This paper discusses the results of this instrumentation. The results confirm the strong correlation between the two measured parameters and outlines future areas of research for the use of the high frequency microseismic emission techniques in quantifying the changes in stress distribution.

Jan 1, 1984

By T. Nakao

Fujiwara quarry had been operated by the glory-hole benchcut mining system, but as it became difficult to meet expanding demand with this system, a central-shaft mobile crushing plant (MCP) system was introduced in 1979. This MCP is equipped with a hydraulic walking system manufactured for the first time in Japan. Central-shaft mining is now the common mining method of Japanese limestone quarries. With this method, crushing facilities are usually installed at the bottom of the shaft. But at the Fujiwara quarry, MCP was adopted and installed on the quarry surface. Many MCPs are operated in foreign countries, but few examples exist in Japan. Normally, Japanese limestone deposits lie in high mountain, obviously making it inconvenient for MCPs to walk in and around the quarry. This difficulty, however, was overcome, and the MCP has operated satisfactorily and efficiently for two years since its installation. To overcome difficulties in the central-shaft MCP mining system, two mining methods are employed: the slice-down method and the block-cut method.

Jan 1, 1985

By Joseph Kuti

ROOF SUPPORT DEVELOPMENTS IN LONGWALL (1) European longwall mining technology developed towards its modern form in relatively deep mines. With increasing depth the stability of openings driven for ventilation, travel or transport becomes paramount in mine design considerations. As a result the number of roadways and entries, as well as their width must be a minimum. (1) Another important aspect of European mining is the high density of mineable seams, as opposed to the wide lateral extension of a single seam in the U. S. A. Multi-seam mining requires strict planning and near 100% extraction, since with increasing depth, the effect of remnant pillars can be devastating. As a result the face layout of a modern European longwall panel is based on single panel entries of moderate width and great height. The mode of extraction is generally a mixture of the advance and retreat system which is called a 2-system. It is obvious, therefore, that the supports developed for the entries and for the intersection areas are more complex than those in the U. S. A.

Jan 1, 1981

By Chauncey Berrien

THE Hawkesworth detachable drill steel shank and bit were invented by A. L. Hawkesworth; while he was a mechanical foreman for the Anaconda Copper Mining Co., at Butte, Mont. Mr. Hawkesworth died on June 16, 1925, at the time that his invention was practically a proved success. The first application for patents was made by him in November, 1918, and the bit is now being manufactured under patents issued in 1922 and 1923. The credit, for its development in the early stages belongs to A. L. Hawkesworth, Roy S. Alley, Harry A. Gallwey, E. J. Bowman and various officials of the Anaconda Copper Mining Co. Later improvements, manufacturing problems and the direct usage in the mines were originated and perfected by the mechanical department under C. D. Woodward, E. R. Borcherdt, head of the Rock Drill Equipment Department, Robert E. Kelly of the Mechanical Department, and various operating department heads of the Anaconda Copper Mining Co. The author wishes to acknowledge the assistance of these officials in the preparation of this paper.

Jan 1, 1930