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By H. W. Gillett

Unlike most previous Howe lecturers, I had not the good fortune to be associated with Henry Marion Howe, nor to be directly one of his students. Yet, through his writings, he has been my teacher, as he has of all American metallurgists. Instructive as his writings are—I use the present tense because Howe thought so keenly and reasoned so surely, seeing clearly, as if by intuition, what was hazy to lesser minds, that his writings are still vital—it is not those books and papers, nor even the minds he trained in his classes, that were his most outstanding service. It was the spirit of Howe in his approach to the problems of metallurgy, his broad-mindedness and fairness, his recognition of the need for theories and hypotheses to explain metallurgical phenomena, his willingness to use them as servants, as well as his questioning attitude—his refusal to accept them as masters—that comprise his greatest service. This most thoroughly warrants the honor the Institute pays each year to his memory. These traits I so respect and honor in any man that I glory in this opportunity to do reverence to him in whom they were so notably united. Howe's Discussion of a Creep Problem I have often wished that Howe were still with us to turn his keen insight upon the problems of the use of metals at high temperatures, a field much studied but still very hazy. Indeed, 53 years ago, in a paper1 before this Institute, Howe stated a problem closely allied to some that still perplex metallurgists and engineers dealing with the high-temperature field. Howe was intrigued by a report2 from another old master, Robert Henry Thurston, on the behavior of annealed vs. cold-drawn iron wire, and in order to broaden the foundation for metallurgical generalization, Howe made experiments of his own on copper and silver. In these tests by Thurston and by Howe, the wires were rapidly loaded to determine the

Jan 1, 1939

By American Institute of Mining Engineers

David J. Mack (University of Wisconsin, Madison, Wise.)—Have the authors considered that the effects reported in their paper are readily explainable on the basis of equilibrium grain boundary segregation rather than ordering? It seems to the writer that all of their experiments and observations correlate well with known behavior associated with equilibrium grain boundary segregation. Although at first glance one would tend to dismiss such a possibility because of the similarity of the gold and copper atoms, their sizes differ by 12.8 pct which is in the range where segregation at grain boundaries would be expected. Then, too, the electrochemical differences between the copper, the Cu3Au, and the gold strongly suggest that a segregation mechanism is involved in the corrosion of the Cu-Au alloys. R. Bakish and W. D. Robertson (authors' reply)—The authors would like to thank Dr. Mack for his consideration of the problem of grain boundary segregation as an explanation of the observed phenomena. We had considered the problem in the following terms: Assuming a pure binary Cu-Au alloy and an ideal solid solution, the surface excess, T2= N25 — N2, of the second component (gold) may be expressed in the following way20 1 —exp (—da/kT) where 8 is the difference in surface tension of copper and gold, and a is the surface area per atom. In the present case, 6 is positive which implies that the component in excess at the boundary is gold. Since the only chemically active component in ferric chloride is copper, it does not appear that the segregation of gold is likely to increase the boundary activity. A small concentration of a third component could profoundly affect the situation. Analysis indicated only spectrographic traces of impurities, all of which are soluble in both copper and gold. Quenching experiments, reported in the paper, also tended to eliminate significant effects attributable to a third component.

Jan 1, 1958

By John C. Branner

Shales rich in oil are found at several places along the coast of Brazil. The material has been prospected at several places, and samples have been examined and reported upon by competent authorities. So far as I am acquainted with them, these oil-bearing beds are of Tertiary age. A glimpse at the distribution and character of the Tertiary rocks of the region should give us some idea of the possible distribution of these oil-bearing shales. Tertiary rocks skirt the northeast coast of Brazil from the northern part of the State of Espirito Santo almost or quite to the Amazon valley. Here and there this narrow strip is cut in two by the encroachment of the sea, and the underlying gneisses, granites or other crystalline rocks are exposed upon the beach. In other places, the Tertiary belt widens out until it is 80 kilometers or more in width. Fig. 1 is a sketch-map of a part of the coast-area referred to. Along the coast from Prado, in the State of Bahia, northward to Natal, there is a line of bluffs from 15 to 90 meters high, interrupted here and there by stream-valleys. As seen from the sea, these bluffs are rather conspicuous and highly colored yellow, brown, red, white, black, and purple. These colors are often so mingled as to give the beds a mottled or parti-colored appearance. Fig. 2 shows a characteristic bit of the coast in the State of Parahyba do Norte. In some places, especially in the southern part of the State of Sergipe, and in the northern part of Rio Grande do Norte, the immediate coast is covered with sand-dunes. Here and there these sanddunes have been carried inland over the top of the Tertiary beds, and the subsequent encroachment of the sea has exposed the Tertiary rocks again, where they form the bases of the bluffs. This is well shown in Fig. 3, from a photograph taken at Bahia Formosa, on the coast of Rio Grande do Norte.

Jan 1, 1901

By K. D. McBean, W. H. Hannay, B. A. Stimmel

The electrolytic plant at Trail, B. C., was erected by the Consolidated Mining and Smelting Company of Canada, Ltd., for the treatment of zinc ores and concentrates, particularly those of the Sullivan mine at Kimberley, B. C. It began operations in 1916 at a rated capacity of 60 tons of cathodes per day, which has been steadily increased to the present production of 400 tons per day. The Sullivan has furnished the greater part of the zinc so far produced, although notable tonnages of customs zinc concentrates have been treated. The maximum yearly tonnage of customs concentrates, 25,000 tons, was treated in 1926. Practically no customs concentrates hale been treated since 1929. The total bar zinc production to the close of 1935 was 1,092,782 tons. The zinc mineral in the Sullivan ore is marmatite of somewhat variable composition, ranging between 6ZnS.FeS and 8 ZnS.FeS. Practically all the zinc ores tributary to this plant are marmatites; and the iron content of the zinc mineral varies considerably. The formation of zinc ferrite during roasting is now a matter of common knowledge, so the possible extraction from any zinc concentrate is largely a function of the iron content; the progress made in concentration is reflected directly in zinc-plant recovery. The Trail plant operafes on the low-acid system, as do all the other major plants on this continent at present operating, except the electrolytic plant of the Sullivan Mining Co. at Kellogg, Idaho. The new Magdeburg plant, in Germany, occupies an intermediate position between high and low acid. Plant operation at Trail will be treated in this paper under five main sections: roasting, leaching and purification, electrolysis, cadmium recovery and melting. The oxide section of the plant, treating zinc fume from re-treatment of lead blast-furnace slag, is practically a separate zinc plant; this is necessary because of the presence of fluorine in the smelter zinc fume. Cadmium is recovered electrolytically from the purification residues of both the sulphide and oxide leaching plants.

Jan 1, 1937

By L. H. Levenson, Charles S. Barrett

Since 1925, when the preferred orientations in compressed aluminum were first determined1,2 the orientations have been described as a fiber texture in which a face diagonal, [110], of the face-centered cubic lattice is parallel to the compression axis. Subsequent experiments have seemed to confirm this texture,3-5 and a number of theories (recently summarized in references 6 and 7) have been proposed to explain it and to relate it to the behavior of single crystals during compression.3,8-11 The experiments reported in this paper prove that the orientations are not adequately described as quoted above—i.e., as a [110] fiber texture—although this is a first approximation to the actual texture. They also show that the texture cannot be thought of as a stable orientati011 that is reached and maintained after a sufficient amount of deformation. The actual texture, when studied in detail at successive stages of compression, indicates that a hitherto unsuspected range of orientations is present, both in the polycrystalline metal as a whole and in various individual grains in its interior, and that a state of dynamic equilibrium exists within this range. The reasons for the failure of previous theories to predict the actual texture become obvious when the heterogeneous nature of the flow is considered. In addition to the deformation texture, the manner of its development, and its theory, this paper presents data on the following related subjects: the identity of strain markings in aluminum; the orientation changes in aluminum single crystals during compression and a comparison of these with the conditions in individual grains of a polycrystalliile specimen; the origin of asterism ill deformed single crystals, which heretofore has been regarded as a distortion localized at the surfaces or slip planes; and the relation of plastic strain in individual grains ill all aggregate to the strain of the whole.

Jan 1, 1940

By Charles S. Barrett, L. H. Levenson

Since 1925, when the preferred orientations in compressed aluminum were first determined1,2 the orientations have been described as a fiber texture in which a face diagonal, [110], of the face-centered cubic lattice is parallel to the compression axis. Subsequent experiments have seemed to confirm this texture,3-5 and a number of theories (recently summarized in references 6 and 7) have been proposed to explain it and to relate it to the behavior of single crystals during compression.3,8-11 The experiments reported in this paper prove that the orientations are not adequately described as quoted above—i.e., as a [110] fiber texture—although this is a first approximation to the actual texture. They also show that the texture cannot be thought of as a stable orientati011 that is reached and maintained after a sufficient amount of deformation. The actual texture, when studied in detail at successive stages of compression, indicates that a hitherto unsuspected range of orientations is present, both in the polycrystalline metal as a whole and in various individual grains in its interior, and that a state of dynamic equilibrium exists within this range. The reasons for the failure of previous theories to predict the actual texture become obvious when the heterogeneous nature of the flow is considered. In addition to the deformation texture, the manner of its development, and its theory, this paper presents data on the following related subjects: the identity of strain markings in aluminum; the orientation changes in aluminum single crystals during compression and a comparison of these with the conditions in individual grains of a polycrystalliile specimen; the origin of asterism ill deformed single crystals, which heretofore has been regarded as a distortion localized at the surfaces or slip planes; and the relation of plastic strain in individual grains ill all aggregate to the strain of the whole.

Jan 1, 1940

By Gifford White

CONSIDERABLE attention has been directed in recent years to methods of electric prospecting other than the conventional direct-current tech-niques. It has been extensively recognized that electrical data of a more general nature than that possible by direct-current methods might be useful in geophysical studies. To this end, a number of different types of electric currents have been employed, such as single-frequency alter-nating currents, square-topped periodic current waves,4 periodic surges of a less specific nature,8 and suddenly applied direct current.1,2 Yet, to the author's knowledge, little analysis of these different types of driving currents has been made from the standpoint of network theory to determine just what type of currents would give the most useful data, and, most important of all, to determine the relation of the data taken by one method to those of another. Without touching on the actual theoretical problem of how currents flow in the earth under specified boundary conditions, some very useful information can be obtained from the study of the fundamental integral equations of electrical networks, throwing light on the problem not ordinarily appreciated by the field worker. Some manipulation of the standard network equations will be made, with the sole purpose in mind of developing expressions leading to practical results. Suppose that four points in the earth have been located and it is wished to obtain the most useful type of electrical data by inserting current into two of them and measuring the potential developed between the other two. The first problem that arises is that of which pair of the four shall be chosen as current grounds. In the direct-current case, where only steady potentials are measured, the selection is of little consequence, but as soon as currents varying with time are used at the current grounds, a new effect arises. The fact that a varying current is flowing in the current-carrying conductor between the current grounds means that magnetic and electric fields varying with time will be produced

Jan 1, 1940

By P. H. Brace, N. A. Ziegler

The study of the relations between gases and metals is one of pcren-nial interest to all who are connected with the production of high-grade metallurgical products. The data reported here are the outcome of work of which the object is to determine the effects of dissolved gases upon the properties of metals and to gain a more detailed knowledge of the reactions between gases and molten metals, particularly iron, under definitely controlled conditions. We have attempted to reduce our margin of error by dealing with relatively large quantities of metal, from 4 to 13 Ih. (2 to 6 kg.), and keeping the ratio of refractories to metal as small as practicable. The ingots produced are large enough to provide adequate material for making determinations of magnetic and other physical properties. In choosing the bell-jar type of furnace we were influenced by the results of considerable experimentation along the same general line which indicated that, for the scale on which we were to work, it was important to have the furnace structure independent of the vacuum enclosure. The use of a bell-jar surrounding the entire furnace accomplishes this and also gives great freedom of observation during operation and ready accessibility for the replacements which are necessary after each run. Our choice of analytical method was made in the light of the results secured by H. M. Ryder, who used a method similar in principle for the analysis of very small quantities of gas extracted from strips of metal heated electrically in high vacuum. We have presented some selected preliminary experirnental data as being illustrative of the quantity and nature of the gases which occur in iron of different origins, but do not urgc any hypothesis at this time. The Furnace Our furnace may be described as "a high-frequency induction furnacc of the bell-jar type." It is similar in a general way to that described by Cain and Peterson1 though we have introduced certain refinements of

By George Comstock

Results are given of scleroscope and Brinell tests on specimens of cast 10-per cent. aluminum bronze, quenched and reheated at various low temperatures. The scleroscope was not found as reliable as the Brinell machine for measuring the hardness, for the size of the piece tested seemed to affect the scleroscope results. The maximum hardness was obtained by quenching and reheating to between 315° and 370° C. Softening was produced by reheating above 370° or 400° C. A series of polished and etched microsections showed a more reddish color in those that had been reheated above 400° C., and a change in microstructure above 500° C. IT HAS been known for many years that the alloy containing 90 per cent. copper and 10 per cent. aluminum can be hardened, like steel, by quenching from a suitable temperature, and that the hardened alloy can be softened again by annealing or drawing the temper. It does not seem to be generally appreciated, however, that the effect of the first slight reheating after quenching is actually increased hardness, the softening effect not taking place until a certain temperature of "drawing" has been exceeded. This paper gives the results of a few experiments on various specimens of cast 10-per cent. aluminum bronze, quenched for maximum hardness, and subsequently annealed at different temperatures. The hardness measurements were made with both a scleroscope and a standard Swedish Brinell machine; some peculiarities of the scleroscope test on this material are described. The author is not aware of many previous investigations of the hardness of this alloy when quenched and drawn, but two important papers on the subject should be mentioned. The earliest was by Portevin and Arnou,1 in which it was stated that tempering quenched 10-per cent. aluminum bronze at 400° C. increased the hardness as compared with the quenched untempered alloy and that reheating above that temperature was necessary to obtain any softening effect.

Jan 7, 1924

By Robert E. Hoffman, John B. Hudson

The self-diffusion coefficient of pure lead has been measured at five pressures between atmospheric and 40 kb. over a temperature range of about 150°C near the melting point at each pressure. Measurements were made using a radiotracer technique, samples being sectioned electrochemically after the diffusion anneal to determine the diffusion penetration curve. Pressure was applied in a "belt" type pressure device similar to that used by Hall et al., in the diamond synthesis. The self-diffusion coefficient, D, can be represented by an equation of the form at constant pressure, and an equation of the format constant temperature. An apparent correlation between the effects of pressure on self-diffusion and on the melting point of the material observed by Nachtrieb et al., at pressures below 10 kb. was found to be only approximate as measurements are carried to higher pressures. OVER the course of the past 30 years a large number of studies1-' of the rate of atom movements in solid metals have been carried out. These studies have in general been aimed at increasing the understanding of the detailed atomic process by which atom movements in metals can take place. The largest portion of these studies consisted of measurements of the self-diffusion coefficient, D, as a function of temperature. From such studies con- siderable information regarding the energetics of the motive process has been deduced. Recently such measurements have been extended to the pressure dimension. However, the existing work in this area is scanty and has in the past been limited to the pressures attainable in oil or gas bombs—i.e., up to about 10 kilobars (kb). In the present work, the self-diffusion behavior of pure lead has been investigated using the "belt" type high-pressure apparatus designed by Hall7 over a pressure range from atmospheric to 40 kb at temperatures extending over about a 150°C range close to the melting point at each pressure.

Jan 1, 1962

By J. L. Rodda

The desirability of a uniformly sized abrasive for metallographic polishing has probably been recognized in a general way for a long time. Certainly all metallographers have recognized the damage that can be done to a polished surface by a piece of grit, especially if one of the softer metals, such as zinc or aluminum, is being polished. It is to be doubted, however, whether many metallographers have had any adequate idea of the particle size of the abrasives they were using or of the range of sizes encountered in any given grade of abrasive. At any rate, the descriptions of abrasives for metallographic work found in the literature are generally very meager. It was with the idea of securing an abrasive with a limited range of particle size that a study of this problem was commenced. Commercial abrasives, even when recommended for metallographic work, are made up of particles of varying sizes. One such abrasive contains some particles so fine that they remain in suspension for days and other particles so coarse that they settle at the rate of 3 in. per minute. It is evident that the coarsest particles are over 100 times the diameter of the smallest ones, or over 1,000,000 times the volume. The hopelessness of avoiding scratches under these conditions is evident. Vanderwiltl has described a laboratory method for grading abrasives in which the elutriator is used. Le Chatelier's method, described by Goereq2 also makes use of an elutriator. However, the elutriator is too slow for this purpose and requires too delicate a control for the range of sizes desired. The method of stirring up the abrasive in water, allowing it to settle for a given time, then drawing a measured depth off the top of the suspension, has been finally adopted as the simplest procedure. The largest particle in a given portion is then determined by Stokes' law:3

Jan 1, 1932

By Chester T. Sims, Robert I. Jaffee

The thermoelectric behavior of the Pt—Pt-Re thermocouple and the resistance of rhenium to attack by certain molten metals is discussed. In addition, data are presented on the stress-rupture behavior of drawn wire, the tensile characteristics of rolled sheet, the variation of Young's modulus with temperature, and the effect of specimen size and fabrication method on the work harden ability. Mechanical properties of thoriated rhenium are discussed. This includes data on the effect of thoria in rhenium on tensile properties, ductility, work hardening, and recrystallization. RECENT work by the authors', has described methods of fabrication and some of the physical and mechanical properties of rhenium. Rhenium was established as a high melting, dense, refractory-type metal with favorable mechanical properties. In addition, Todd and co-workers' and others" have studied such properties of rhenium as the work function, specific heat, and the resistance of rhenium to the water cycle. Revelation of these and other properties has led to serious consideration for application as electrical contacts, high temperature thermocouples, and wear resistant materials. chanical properties reported previously,' several additional examinations have been conducted. The stress-rupture behavior and the Young's modulus of rhenium have been investigated at elevated temperatures. Tensile data have been obtained for rolled sheet, and a study of the relative work hardening characteristics of rod, wire, and sheet has been conducted. Variation of Modulus of Elasticity With Temperature—The Young's modulus of a % in. diam annealed rhenium rod was determined from room temperature to 880"C (1620OF). The rod, approximately 6 in. in length, was activated in a transverse vibration apparatus suspended in a furnace. The resonance frequencies of the rod were measured and used to calculate the moduli values. The driven frequency was 569 cycles per sec, and a protective helium atmosphere was used. The data, plotted in Fig. 1, show that the modulus decreases in an approximately linear manner with temperature over the range tested.

Jan 1, 1957

By H. A. Coy, James A. Noble

The Mascot mines of the American Zinc Co. of Tennessee are situated at Mascot, Tenn., 14 miles northeast of Knoxville, on the Southern Railway. The district is centrally located in the Great Valley, or Appalachian Valley Province. Prior to 1900, a small output of zinc was obtained from oxidized ore mined in open pits. In 1900, a shaft was sunk to sulfide ore, and in 1903, a second shaft was put down, neither being as deep as 200 ft. The American Zinc Co. of Tennessee began drilling in 1911, and outlined an ore-body to which its No. 1 shaft was sunk, to a depth of 365 ft. Since that time, the American Zinc Co. of Tennessee has been the only operator in the district. The Federal mining laws have never been in operation in Tennessee and mining lands are as irregular in boundary and area as farm lands. Ownerships are generally held in fee. In most cases the surface and mineral rights are transferred together. Electric power is supplied at 66,000 volts by the Tennessee Power Co., from a hydro-electric plant at Parksville, Polk County, Tenn., 100 miles from Mascot. No other power is used, but an emergency steam plant is held ready in case of interruption of service. Labor is all native and non-union. Negroes are employed for most of the shoveling, and for a few miscellaneous jobs, but for almost no other work. Exploration Exploration is carried ahead of mining largely by surface drilling. Both churn and diamond drills are used. Holes are not spotted according to geometric plan, but to block out ore outlines with the least number of holes. Churn-drill cuttings from each 5-ft. run are mounted for formation record, and in ore ground, all the bailings from each 3 ft. of advance are sampled and assayed. Diamond-drill cores are sampled and a specimen core filed for formation record. In ore ground, all the core

Jan 1, 1925

By Jay R. Burns

Two magnesium sand-casting alloys are commonly favored in the United States. These are referred to as H and C alloys (Dow Chemical Co.) or AM265 and AM260 alloys (American Magnesium Corporation). Both are of an aluminum-zinc-manganese type. H alloy contains 6 per cent aluminum and 3 per cent zinc and is characterized by relatively good toughness. C alloy contains g per cent aluminum and 2 per cent zinc and is employed where high yield strength and pressure tightness are required. Examination of magnesium castings poured in Europe and England,1,2 however, demonstrates that H and C alloys are replaced by A8 and AZ91, respectively. That is, A8 represents a magnesium alloy having superior toughness while AZ91 is suitable for high yield strength and pressure-tight applications. The basic difference between the American and European alloys is that the foreign alloys employ a somewhat higher aluminum content and less zinc than is found in H and C alloys. The mechanical properties of the alloys, when divided into high and low-aluminum groups, are quite similar, as determined from separately cast foundry-control type test bars.3 In this paper the decrease of mechanical properties caused by any given amount of microporosity is measured for H, C, A8, and AZ91 alloys. The relative susceptibility of each of the four alloys to microporosity is also determined. Typical mechanical properties and nominal chemical analyses are reported in Table I. [ ] The apparent similarities between the two alloys in each group have led to considerable discussion as to the relative merits of each of the compositions.2 Popular points for comparison between the alloys have been the relative susceptibility of each of the four alloys to microporosity5 and the effect of this microporosity on their mechanical properties. It is primarily intended, in this paper, to show the

Jan 1, 1946

By Frederick Laist

While remodeling No. 1 section of the concentrator at the Washoe Reduction Works of the Anaconda Copper Mining Co. during the summer of 1912, for the purpose of ascertaining what additional metal recoveries could be made by improvements in concentration practice which had been developed by the staff of the Boston & Montana Reduction Department, at Great Falls, it was deemed advisable to carry on some experiments on the treatment of the regular mill tailings by roasting and leaching, to see whether the losses of metal values might not be still further decreased. In the course of these experiments about 5,000 tons of tailings were roasted, and of the resulting calcine about 200 tons were leached. The results were so satisfactory that it was decided to continue the work on a larger scale, particularly as regards the leaching end of the process, and construction work on an 80-ton roasting and leaching plant was accordingly commenced during the latter part of February, 1913, and is being pushed as rapidly as possible. 80-Ton Leaching Plant. This plant will consist of one 20-ft. roasting furnace of the Mac-Dougall type, specially adapted to the work of roasting for leaching; two leaching tanks, 32 ft. in diameter by 12 ft. deep, together with the necessary solution tanks, air lifts, precipitating launders, etc. It has been decided to precipitate the copper from solution on scrap iron, so as not to hamper the roasting and leaching departments by any weakness that might develop in the precipitating department. It is, however, the intention to experiment with a number of different methods of precipitation; for example, by electrolysis and by hydrogen sulphide. The acid required for the operation of this plant will be purchased, ad the quantity required is not sufficient to justify the installation of an acid plant. An acid plant will, however, be established in con-

Jan 1, 1914

By Henry Hebley

IN recent years, especially in the last decade, great interest has been shown and many advances have been made in the preparation and clean-ing of coal. In the major coal-producing countries, the percentage of tonnage cleaned has been increasing ever since 1924. As separating media, both liquids and gases are used, these generally being water and air respectively. Some systems, instead of obtaining separation by the velocity of the medium in which the coal is cleaned, depend on the density of water mixed with sand, or coal dust and shale, or with chemicals such as calcium chloride. In studying the results of coal-cleaning equipment, it will be observed that the efficiency of the cleaning apparatus lowers as the size of the coal decreases. This inability to obtain any marked improvement in the fines has been partly responsible for the installation of dedusting equipment, to remove the fine sizes from the raw coal prior to cleaning. When considering the possibility of installing dedusting equipment, many factors must be taken into account. Very often, but not always, both the ash and sulfur content of the coal increase as the coal size decreases. When bituminous coal, containing soft powdery fusain, is subjected to a wet washing process, the porous fines of the fusain remain in the small coal or in the wash water and delay the dewatering of the washed coal and increase the difficulty of clarification in settling tanks or thickeners. When a dedusted coal is cleaned by a wet process, the sludge recovered from the settling tank often runs so high in ash that the sludge can be discarded without further treatment and still the loss is small. Where treatment of the sludge is desired, however, froth flotation may be used to advantage if the size of the feed is below 1/10 in. Dust from the deduster can be treated in a similar manner. Fusain, which is usually found in the fine sizes, has often a much larger ash content than other coal.

Jan 1, 1933

By A. D. Hodges

The great mining region of Peru is a mountainous belt of country, running nearly the whole length of the republic, and comprising the two grand ranges of the Andes with the elevated table-lands between them. On the east of this belt are the extensive plains and fertile valleys of the Amazon and its tributaries. On the west is a narrow strip of coast 20 to 50 miles wide, for the most part a sandy desert, but producing abundant crops where irrigated ; and here are found petroleum (Department of Piura), salt (at Huacho and elsewhere), nitrate of soda in enormous amounts at the south, silver in a few localities (Province of Tarapaca), copper and other mineral products. The Western Cordillera, running nearly parallel with the shoreline, rises like a wall on the eastern side of the coast-belt, with passes from 15,000 to 18,000 feet high and peaks attaining 18,000 to 20,000 feet. Further east, at a varying distance, is the Eastern Cordillera, composed of broken mountain ranges which, considered as one group, have a general parallelism with the western chain, but individually vary greatly in direction, sometimes running nearly east and west, in places projecting out into the Amazonian lands, or here and there curving around to unite with the western ridge, and with this enclosing immense inter-alpine plains. These general features are indicated in Fig. 1. The surface of these plains is uneven and traversed by lower ranges of hills which surround large lakes, or rolling pampas, or fertile valleys; and through many of these last run rivers of considerable size. The whole country has a high altitude (averaging up to 15,000 or 16,000 feet), and slopes gradually north and east towards the Amazon, into which drain all its waters. Its bounding mountain chains are scored on all sides by narrow, picturesque and pre-

Jan 1, 1888

By W. Henry Weimer

A successful surface coal operation requires the combined efforts of engineering and operating personnel. In the planning for a mine, machines should be selected to do the best work in getting the coal uncovered, loaded, and transported to the preparation plant. The best system and extent of cleaning will be determined by the market. After the fundamentals of operation have been established, the operating personnel should see they are carried out. There is no simple solution to some of the every day problems facing the operating officials. Here the production engineer with the technical approach, time studies, control methods, past experience, and available records can help in detecting causes of inefficient phases of the operations. With these studies, a careful analysis can be made in setting up the expected standards to be followed. Management can then compare the job under study with the standards and make corrections to solve the problems. 5.2-1. Annual or Daily Coal Production. Once the production cycle has been established, it is paramount that coal sales keep the productivity of the mine as high as possible. A successful company does this by what they call "the control approach." The daily tonnage report is one of the things that is a potent control tool in attaining the goals to be achieved. If production is falling short of the goal, the daily tonnage report will reveal what has to be done in the remaining days of the month or year to achieve the expected schedule. When goals are reached or exceeded, then budgeted tonnages and costs will be reached or exceeded and thus assure attainment of a profit. Failing to keep to the scheduled pace shows up quickly and prominently, facilitating any necessary action to get things back to the projected plans. The sales target is usually set a little higher than the operating production. The sales tonnage is scheduled and sales are made accordingly, slightly

Jan 1, 1968

SANTA Rita del Cobre Grant, as the present Chino property was known in the early part of the nineteenth century, was the scene of the first copper-mining operations of consequence in the territory now included in the United States. As early as 1801, the mines afforded the principal supply of copper for coinage by the Mexican Government. According to an estimate made from old records by H. A. Thorne, now superintendent of mines for the Chino company, about 41,000,- 000 lb. of copper had been produced prior to 1845, when the exploitation of the native copper deposits of the Lake Superior district was started for the first time by white men. B. S. Butler, in Mineral Resources of the United States for 1913, estimated the production from Grant County, New Mexico, from 1845 to 1913, at 134,353,963 1b.-an amazingly precise figure, considering the character of the data that he must have used. As "Grant County" may be interpreted for practical purposes as the Santa Rita district, it seems fair to credit the Chino group with a production of 165,000,000 lb. of copper prior to the time when the modern operations commenced. Unlike Morenci, which, by the way, lies only about 80 miles westerly across the Arizona-New Mexico line, Chino offers no problem as to when its production might properly be classified as coming from a Porphyry Copper. The time is definitely fixed by the starting of the new mill at Hurley in October, 1911. The interval from 1903 to 1913 had witnessed little production of any kind; and prior to that time operations had been confined entirely to the mining of narrow veins or lenses of ore assaying 10 to 15 per cent copper or even more. Such orebodies frequently are encountered today, when the electric shovels, working in broad daylight, eat away rock that once was buried

Jan 1, 1933

By S. Andrew Kulin, L. Kaufman

A general treatment of the broadening of X-ray double-crystal spectrometer rocking curves due to distributions of tilts and strains has been carried out. The results of this treatment have been applied to the case where dislocations in a crystal give rise to both tilts and strains. On this basis it is found that the rocking-curve halfwidth due to imperfections in the crystal, ßC , increases with increasing Bragg angle, 8. These considerations predict linear relationships between & and tan2 , and ßCand tan 8, for Gaussian and Cauchy distributions of dislocations, respectively. The zero intercept of the ßC us 8 curve, which is a measure of the degree of imperfection of the crystal, is found to depend directly on the distribution rather than the number of dislocations. In addition, the slope-intercept ratio for the ßc - ? curve has been calculated for both the Gaussian and Cauchy distributions. Experimental determination of the - 8 curves for a series of copper single crystals prepared by the Bridgeman and Czochralski methods yields results in agreement with the calculated slope-intercept ratio for a Cauchy distribution of dislocations. CERTAIN X-ray techniques have been used to study the perfection of single crystals. Gay, Hirsch, and Kelly have considered the spreading of spots into arcs on Debye-Sherrer rings due to imperfections. The Double-Crystal Spectrometer has also been applied to this problem.2 The characteristics of Double-Crystal Spectrometer Rocking Curves have been described in the literature by various workers.2-4 By assuming a random spacing of dislocations which give rise to a Gaussian distribution of misorientations relative to some mean orientation in a crystal Gay, et al.,1 arrive at the conclu- sion that the most probable misorientation is given by where h is the spacing between dislocations, and 8 and are the relative misorientations of neighboring regions. If ßC is the halfwidth of the rocking curve (the width at one-half the peak intensity) due to dislocations in the crystal then5

Jan 1, 1960