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By Ole Singstad

The legislatures of New York and New Jersey, determined in 1919 that a vehicular tunnel should be built under the Hudson River. On July 1, 1919, an engineering staff was organized with the late Clifford M. Holland as chief engineer. After preliminary investigation it was decided to build the tunnel from Canal St., New York, to 12th St., Jersey City, which is the center of the heaviest traffic across the Hudson River. It was also decided to build two tunnels—one for west-bound traffic and one for east-bound—the tunnels to be of cast iron, built up of segments and bolted together, each tunnel to have a roadway 20 ft. wide and a clear head room of 13 ft. 6 in. The tunnels have an exterior diameter of 29 ft. 6 in. The interior lining is of concrete, the sidewalls, tiled with a vitreous white tile, and the roadways are paved with granite block. The entrances and exits at both ends are separated by two blocks so as to reduce traffic congestion. Basis of Ventilation It was recognized very early that one of the most important problems confronting the engineers was a proper ventilation system. It was estimated that each tunnel as planned would have a traffic capacity of 1900 vehicles per hr. The tunnels are 8500 ft. long between portals, and it was considered that the ventilation should be based on all of these vehicles being operated by gasoline engines. That presented a problem in ventilation unlike any other either in magnitude or character. There have been vehicular tunnels built in Europe, principally in London, but they are shorter and have a smaller traffic capacity. Up to the present time, at least, they have handled a very large percentage of horsedrawn vehicles so that the necessary ventilation has been provided for by the natural draft through the portals and open shafts. Within the last few years, however, a small mechanical ventilating plant has been installed in the Blackwall Tunnel, which has been in operation about 27 years. I might mention that at the time this work was started, it was considered by many that the problem of ventilation was insuperable and it

Jan 1, 1927

By H. Landsberg

In a previous report1 it was pointed out that a successful attack on roof troubles has to be preceded by extensive scouting. As Lord Kelvin once said, scientific progress can be made only if accurate data are available: "unless you measure, you do not know." The Convergence Recorder For the observation of roof movements in mines the convergence recorder has shown that it will enable us to get some of the necessary information. Results with convergence recorders were first published by Winstanley and other English investigators for rapidly moving longwall faces. In their investigations the speed of work and the heavy overburden produced a considerable amount of absolute values of convergence in a short time. Under the conditions frequently encountered in our investigations in Central Pennsylvania, under shallow, overburden and in mines with slowly proceeding extraction, the movements observed were much less in absolute value, for an equal interval of time. This mas partly because the mines in which our studies were carried on frequently had idle days, sometimes four or five in succession. Therefore continuous records were not employed and a simple convergence gauge was built. In its first models, it consisted only of two telescoping tubes pressed against roof and floor by a coil spring. At the side of the lower tube a rule divided into 1/2-mm. divisions mas fixed and a knife-edge, which was attached to the upper tube, mas slid over the scale in case of convergence between roof and floor. While the larger motions could be read on this device, it seemed to be desirable to increase the accuracy by inserting between the two tubes a dial meter reading in 1/1000 in. Such a gauge was first built in April 1937 and installed for experimental purposes in a bituminous coal mine in Pennsylvania (Fig. I). It was read at least once daily, 24 hr. apart, and if feasible at shorter intervals. After several months of experience it can be said that this type of gauge answers the scientific as well as the practical needs. It is easier to handle than the recorder; no clock is used, there are no pen troubles. The price of

Jan 1, 1938

By H. Landsberg

In a previous report1 it was pointed out that a successful attack on roof troubles has to be preceded by extensive scouting. As Lord Kelvin once said, scientific progress can be made only if accurate data are available: "unless you measure, you do not know." The Convergence Recorder For the observation of roof movements in mines the convergence recorder has shown that it will enable us to get some of the necessary information. Results with convergence recorders were first published by Winstanley and other English investigators for rapidly moving longwall faces. In their investigations the speed of work and the heavy overburden produced a considerable amount of absolute values of convergence in a short time. Under the conditions frequently encountered in our investigations in Central Pennsylvania, under shallow, overburden and in mines with slowly proceeding extraction, the movements observed were much less in absolute value, for an equal interval of time. This mas partly because the mines in which our studies were carried on frequently had idle days, sometimes four or five in succession. Therefore continuous records were not employed and a simple convergence gauge was built. In its first models, it consisted only of two telescoping tubes pressed against roof and floor by a coil spring. At the side of the lower tube a rule divided into 1/2-mm. divisions mas fixed and a knife-edge, which was attached to the upper tube, mas slid over the scale in case of convergence between roof and floor. While the larger motions could be read on this device, it seemed to be desirable to increase the accuracy by inserting between the two tubes a dial meter reading in 1/1000 in. Such a gauge was first built in April 1937 and installed for experimental purposes in a bituminous coal mine in Pennsylvania (Fig. I). It was read at least once daily, 24 hr. apart, and if feasible at shorter intervals. After several months of experience it can be said that this type of gauge answers the scientific as well as the practical needs. It is easier to handle than the recorder; no clock is used, there are no pen troubles. The price of

Jan 1, 1938

By W. Tovote

This paper is based upon 12 years' experience in the Southwest, including three years that were spent in constant traveling as examining engineer for the Phelps-Dodge Corporation. The material was gathered during rather extensive work in Bisbee, Clifton-Morenci, Globe, and Tombstone, and also on short and rapid trips into most of the mining camps and prospect fields of New Mexico, Arizona, the desert country of California, and as much of Sonora as was safe at the time. My methods of observation and my deductions are not put forward as new or scientific; they are simply rough field methods, based upon short notes, rough sketches, and largely upon memory, which I have found useful for coördinating geological data for the purpose of passing quick judgment on mining possibilities in certain districts exhibiting uniform characteristics. The opportunities for observation have been better these last few years than ever before, due to the unprecedented activity in mining, which has caused the reopening of hundreds of old mines and the starting of even more numerous prospects all over the mining states. Possible Systems of Classification By Geological Provinces There are a number of well defined geological provinces in the territory under discussion, and a study of their individual features is of interest. The following are a few of those that are most striking in their uniformity. 1. The "Desert province," extending roughly from Wickenburg, Ariz., to and beyond Barstow, Cal. In its north-south extent it reaches up to the Colorado River and down into Sonora, but overlaps other provinces. It is characterized by a worn-down basement of schistose and granitic rocks, on which rest remnants of Paleozoic and pre-Paleozoic sediments, including very old limestones. The sediments are disrupted and contorted. Alteration in the mineralized areas is very prominent, especially in the schists and limestones. Cenozoic volcanic rocks, principally of semi-basic composition, have been intruded into this complex and sometimes cover it as lava flows. 2. The "Yavapai schist" province, similar to the one first mentioned, consists of metamorphosed basic and semi-basic rocks. It lies in northern

Jan 1, 1920

J. C. WRIGHT.-The problem of organizing and maintaining a vocational class for those employees who are engaged in the mining industry depends on several most important factors. The first is the sympathetic cooperation of employer and employee; the second is to find the subject matter that must be presented to these men; and the third is to find the instructor who can present that subject matter. This is perhaps the most difficult, for we usually find a man who knows the material that is to be presented but is not a teacher or does not know how to organize his material. The man must know the subject matter from the standpoint of absolute contact with industry in order to be a successful teacher. I have come into contact with two kinds of schools organized in connection with mining occupations. In one type the instruction leans very largely toward elementary subjects, arithmetic, reading and writing and spelling; it is not of such a character as to help or improve the working man in his occupation in the sense that we are attempting when we speak of vocational education. In the other type of school, an engineer is usually employed as a teacher. He immediately begins to give the things with which he is most familiar and the instruction becomes such as only those who possess a high-school or college education, perhaps, are able to receive. In between these two schools is the school we are trying to, promote, a school that will meet the needs of those employed. MARGUERITE W. JORDAN,* Altoona, Pa. -Vocational education has become the business man's problem; for he is the keeper of that white elephant, labor turnover, and anything that will decrease the size of the monster is worthy of serious consideration. This vocational education can do; for it can supply many of those deficiencies in upbringing and. environment that make for the discontent and restlessness of our varied classes of unskilled labor: the Anglo-Saxon mountaineer; the Southern negroes who have crossed Mason & Dixon's line by the thousands, "searching satisfaction for our minds;" and the still greater number who have sought across the sea America, "the promised land.

Jan 4, 1919

By William Phillips

THE possible sources of potash salts in the United States have been considered from many points of view during the last several years, but it is only within the last two or three months that the situation has become acute. We import from Germany, the only source of large supply, more than $10,000,000 worth of potash salts annually, and this business has been badly crippled by the European war. If there was ever a time in our industrial existence when the necessity of providing for our own needs was more acute than it is now, we are not aware of it. One has only to study the price, lists of chemicals sent out by the large supply houses to see the change wrought within a very short time. Whether or no these prices are to maintain for a considerable time, no one can say; but it appears to be probable that we shall not see prices materially lower for a period of uncomfortable length, to say the least. It is not my purpose at this time to discuss the various sources of supply of potash salts that have been suggested or recommended. Some of them might afford a pleasing relief but all of them combined would not affect the situation seriously. If we are to have our own sources of potash salts, they will have to compare, in some efficient manner, with the sources upon which we have drawn during the last 20 or 30 years; i.e., they must exist-in minable quantities. It seems to me to be quite idle to speculate upon our domestic sources of potash if those sources are not of a character similar to those upon which we have so long depended. A few thousand or, perhaps,, a few hundred thousand dollars' worth of chemically derived 'potash may be produced under the stress of present conditions, but when we consider that each year demands more than $10,000,000 worth, we must look to underground sources; we must look to mines similar to the famous Stassfurt and Halle deposits. If we cannot mine potash salts, we shall have to do without them for a while.

Jan 2, 1915

By L. D. Frink

THOSE actively interested in mining are fully aware of the ever-increasing difficulty of making conditions such that efficient work can be clone in underground openings, especially as higher rock temperatures are encountered in depth. This is also true where an effort is being made to cut down the burden of overhead expense by working headings 24 hr. in a day if blasting is done as often as is possible in that time. That the conditions resulting from both these causes have driven the native-born Americans from the mines and that their places have been taken by less efficient foreigners is a fact that we must all admit. The great war now being fought in Europe and the educational qualification clause written into our immigration law by the last Congress will probably limit very materially the supply of labor, such as we are now using in our mines, and will force upon mine operators the necessity of making this work appeal again to Americans. Metal tubing, with blower or exhaust fans, has long been used in supplying air to dead ends where natural ventilation is impossible, or in driving the smoke from such places, or in doing both, as the need might be. Here in Butte we have now come to use canvas tubing very extensively and find that it has many advantages not possessed by the metal. The use of flexible tubing is not new, but it has not been generally used in mining operations. Recent improvements, however, in the canvas itself and in the jointing of sections and manner of suspension have so increased its usefulness that it promises to add much to the efficiency of mining. There is now on the market a product that is impervious to air, is fireproof, and has a system of jointing which, permits it to be put up or taken clown in a few seconds. In this article an effort will be made to explain the manner in which canvas tubing is being used in the North Butte company's operations at Butte, Mont. The accompanying photographs will, I hope, help make clear what may be done with this material.

Jan 1, 1918

By Dr. O’Neil Thomas J., Donald W. Gentry

"We should be concerned about the future be- cause we will have to spend the rest of our lives there. " -Charles Kettering INTRODUCTION Since the early 1970s, there has been no economic phenomenon that has been more widely discussed or experienced in the United States than inflation. Al- though its precise definition and measurement are elusive, inflation has had pro- found and extensive impacts on the manner in which nearly everyone lives. It is painfully obvious to consumers that inflation is characterized by a continuing up- ward spiral of prices. In a capital-intensive industry like mining, those increases can be positively breathtaking. An interesting example is shown in Table 1. Table I shows that on a unit basis, the equivalent 1980 capital cost of Cuajone was over six times the cost of the adjacent and quite similar Toquepala operation completed in 1959. Such sobering statistics weigh heavily on the minds of executives who are contemplating major investments in new mining facilities. In spite of its monumental presence, inflation has usually been either inadequately covered or totally ignored in textbooks on engineering economy. The reasons for this are not entirely clear, but a contributing factor is the inherent difficulty in accurately predicting inflation. However, under certain conditions, inflation may become the most important factor in a mining investment, and it can rarely be safely ignored in capital investment analyses. DEFINING AND MEASURING INFLATION Defining inflation and related terms is relatively easy. Its measurement, how- ever, is the source of almost endless debate in economic and political circles. How- ever, much of that debate is not relevant to the scope of this book, so that only those issues which impact directly on the capital investment decision are covered in this section. Inflation is the general decline in the value of money as measured by what it will buy. It is clear, then, that the rate of inflation varies with the particular currency under consideration as well as the type of goods and services being purchased. One would find, for example, that the general rate of inflation relative to German marks

Jan 1, 1984

By J. L. Gillson

Andre Hubaux: In the writer's opinion, more stress should be put on field and microscope observations, as J. L. Gillson does. His discovery of relics of big labra-dorite feldspars from the Marcy anorthosite in all the other rocks is proof enough that previous field observations have been inadequate. The writer's field experience with anorthositie massifs is limited to the Egersund-Sogndal district in southern Norway; however, this is a very large and well exposed area. It seems to have so many points in common with the Adirondack region that a detailed comparison should be beneficial. This comparison was not possible 20 years ago, owing to the scarcity of geological data, at least for Norway. Both regions are now far better known—the Norway district because of the work of Professors Bugge and Barth 33-35 and especially because of the extensive field and microscopic research of P. Michot,30-35 who introduced me in the field to the problems of that region. In a particular unit of the Egersund district, a sodi-fication of the plagioclase, very similar to what Gillson calls "andesinization," has taken place. 12' The percentage of anorthite in the plagioclase has dropped from 42 to 43 pct in the original norite down to 27 pct, but never below that level. This metasomatical transformation is a part of a whole series of processes of mig-matitization which have produced, above the level of granitization, concentrations of Mg, Fe, and Ti and among them, patches and parallel bands of ilmenite and magnetite. Thus both regions present somewhat comparable features and the theories to explain them have several points in common. However, as there seem to be differences between some American conceptions and the views commonly accepted at the University of Liege, I would like to make some comments about J. L. Gill-son's article. The author speaks of the garnet as being an anti-stress mineral. However, garnet may be found in schists, where its helicitic texture, when present, demonstrates its formation during differential movement. Furthermore, the whole concept of stress and anti-

Jan 1, 1959

By Theodore P. Holt

The Mines Operating Co.'s plant at Park City, Utah, was designed to treat the low-grade fillings in the old stopes of the Ontario mine. These fillings carry 6 to 14 oz. of silver, 1 to 2 lb. of copper, 0.01 to 0.015 oz. of gold, and a small percentage of lead and zinc. The treatment consists in mixing the crushed ore with coal dust and salt and then roasting in a new type of furnace by combustion of the contained fuel. The roasted ore is leached with an acid salt solution to dissolve the silver, gold, copper, and lead. At present these metals are precipitated together on scrap iron and the product sold to a refinery. The only new feature of importance in this scheme of treatment is the roasting process, which makes possible the chloridizing of ores without any loss of the valuable metals, and at a very low cost. History of the Development of the Process The roasting process- had its beginning in connection with research work at the Utah State School of Mines. N. C. Christensen, Jr., who held one of the School of Mines' fellowships, was engaged in some experimental work on blast roasting. At the same time I was doing some work on the insoluble gold in Mercur base ores. Mr. Christensen roasted some of this base gold ore in his pot furnace, and found that when he mixed a sufficiently low percentage of fuel with the ore, it did not sinter but roasted to a leachable product. We considered this a new application of blast roasting, and proceeded to test out a large number of ores in several different types of small roasters which we constructed.. This experimental work continued well into the summer of 1911. In August, 1911, the Consolidated Mercur Gold Mines Co. installed a small roaster of our design, which we proposed to operate on the counter-current principle, feeding mixed ore continuously on top, and at the same time drawing off the roasted ore from the bottom. By proper adjustment we hoped to maintain a permanent roasting zone near the center of the column, the ore moving downward as roasted. However, we

Jan 1, 1915

By Eric J. Bradshaw

For several hundred years the petroleum industry has flourished in Burma and at the close of the eighteenth century there were over five hundred producing wells in the Yenangyaung field. These were laboriously dug by hand and were exceedingly primitive, yet even today a small part of India's total production is obtained from hand-dug wells. The Indian Empire, the cradle of the oil industry, today produces but an unimpressive fraction of the world's supply of petroleum, not because the size of her contribution has diminished, but because it has remained more or less stationary while other countries have far outstripped her during the prodigious increase in the world's production of petroleum in recent years. Though for the past 10 years the total production in India has been remarkably constant, it has become increasingly difficult to maintain this output and at any rate from the older fields a slow decline may be anticipated unless new productive horizons are discovered. Production figures for the 10 years 192&1929 (the last year for which figures are available) are given by fields in Table 1. Crudes of Burma and Assam The bulk of India's production comes from the Yenangyaung and Singu fields, from which the crudes are very similar, the only important difference being that the oil from the Singu-Yenangyat structure contains a higher percentage of lighter fractions. The Burma crudes resemble that of the Panhandle of Texas and have a high content of solid paraffin, though strictly speaking the oil is of mixed base with a low content of asphaltum. With the exception of the negligible production from Sabe, the Burma crudes do not require dehydration; the sulfur content is very low and is innocuous. A small amount of naphthenic acids occurs in the kerosene and intermediate oil fractions while the lubricating fraction is practically free from acid. The ash content is low and the average A.P.I. gravity of mixtures of Yenangyaung and Singu oil is 36.4. Burma crudes require only light refinery treatment and practically dl the fractions are merchantable. Part of the gasoline supply is stripped

Jan 1, 1931

By L. A. White

IN this paper it is proposed to follow the developments in the design of the lead blast furnace at Port Pirie from the time The Broken Hill Associated Smelters Pty. assumed control in 1915 to the present time, with special reference to the development of the system using two superimposed rows of tuyeres as is now in operation. Lead smelting operations first commenced in 1889, when the British Broken Hill Pty. Ltd. started its first furnace. This was followed by installing two more furnaces during the same year and another the following year. In 1892, Broken Hill Proprietary Co. Ltd. acquired the smelting works and combined operations with those at Broken Hill, New South Wales; by 1897, the whole of the smelting operations had been transferred to Port Pirie and thirteen blast furnaces were built to treat the Broken Hill ore production. In 1915, The Broken Hill Associated Smelters Pty. Ltd. took over from the Broken Hill Proprietary and have carried out operations since that time. From its inception, the present company started on a long range program of reconstruction, in which the development of the lead blast furnace has played a prominent part. A definite trend in plant development has been towards the simplification of plant control by a reduction in the number of operating units. The great advantages of technical control which resulted from the very simplified flowsheet established in the continuous refining process stimulated the desire to extend the principle to the smelting operation. Thus in the sequence of furnaces described here, it will be noted that the trend has been towards larger and, of course, fewer units. With each such development it is significant that the operating conditions and metallurgical results have shown steady improvement. Standard Furnace In 1920 there were seven furnaces operating, five of a type subsequently called the standard furnace and two of the original thirteen smaller furnaces, the latter type being used for the treatment of drosses, etc. produced from the refinery section, while the standard type carried out the main, lead-smelting operations. The standard furnace (figs. 1 and 2) had the dimensions given in table I.

Jan 1, 1951

By A. H. Hand

When considering the question of future demand for crude petroleum in California, one must first decide whether it is to be approached in the light of the definition of "demand" when used in economics; i.e., "The quantity of any commodity required or sought in the market," or in the light of markets developed to dispose of total supply. Therefore, is the California demand of future years to be predicated on a continuation of supplying markets developed following the surplus production commencing in 1922, or predicated on supplying what would be termed economic markets ? If the latter, what are economic markets ? Obviously, the Pacific Coast States and Canada, Alaska, Hawaii and probably the Pacific side of Central and South America, can be considered as normal markets for California petroleum products. While there have been small quantities of gasoline shipped into the PacSc Coast from East Texas, transportation costs, plus import taxes in the case of foreign oil, are a sufficient barrier to justify considering that these markets will be retained. But how about our participation in Atlantic and Pacific foreign and intercoastal markets? During the five years preceding 1931 California shipped substantial quantities of gasoline to the United Kingdom and to France, Germany and Italy. During recent years our business in European markets has been restricted to occasional shipments of gasoline and Kettleman crude. This loss of business is occasioned by the development of production in the Mid-Continent, principally East Texas, and in Iraq, Rumania, Venezuela and other closer producing areas, which makes it impossible at the prevailing crude-oil prices for California to be competitive in supplying any substantial portion of these markets. It is therefore apparent that under a stabilized price structure that will return the California producer a reasonable price for his oil, future Atlantic foreign -business will be restricted to occasional spot cargo sales. As to Pacific foreign shipments which, in addition to Central and South America, consist principally of shipments to Japan, China, Australia and New Zealand: A considerable portion of the business we had with Australia and New Zealand until four or five years ago is now being

Jan 1, 1937

By Edmund B. Kirby

This meeting marks the point at which the long-standing dissatisfaction with the mineral-land laws, the innumerable protests against them, and the many isolated efforts to obtain relief, have developed into a general movement for their revision. That part of the mining industry which is affected by these laws has three general organizations which are able to speak for it: the American Institute of Mining Engineers, the Mining and Metallurgical Society of . America, and the American Mining Congress; all of which are represented in this meeting. In the series of able and thoughtful papers presented here, prominent men have discussed the evils of the present laws and some of the reforms which should be made in them. We all appreciate fully the ultimate value of these studies; but we are also painfully aware of the fact that discussion of this kind has been going on for a quarter of a century without any other effect than a steady increase in the mass of printed records stored on library shelves. In order to get any practical result we Gust induce an indifferent government at Washington to act, and to do this we must unite in pushing some practical plan whereby it may act in a simple and effective way and with the least possible amount of criticism or opposition. The actual question before us is not whether the mining laws are bad; for their evils and absurdities are not only beyond discussion but also beyond the resources of a temperate and dignified vocabulary. It is not what particular changes ought to be made; for it is premature to make . specific recommendations until there is some one to listen to them. Moreover, we all know that there are wisdom and experience enough available, and awaiting that time, for the creation of a code which would be a model to the mining world. The practical question now is, how to obtain the revision; and since the American Mining Congress has of late restricted its attention to this phase of the problem I wish as one of its representatives here to present its views upon the matter.

Jan 1, 1915

By E. E. Carpenter

Believing that the results accomplished in the mill of the Churchill Milling Co., Wonder, Nev., during the fiscal year ended Sept. 30, 1914, will be of interest, I am presenting the more prominent facts and figures showing the progress made in treating this ore with especial reference to tonnage, supplies, costs, and extractions. The mill is situated at Wonder, Nev., in the Wonder mining district, 55 miles east from Fallon, Nev., the nearest railroad point. All supplies are hauled this distance by freight teams, this method of transportation having been found more reliable for continuous service than truclis, the price paid for hauling being slightly under one cent per pound. In this mill are treated the ores of the Nevada Wonder Mining Co. Ore is Unusually Hard The company which tested this ore before the mill was built reported "This ore is an unusually hard, tough, oxidized quartz, carrying a small percentage of high-grade sulphides, containing good values in both gold and silver. None of the rebellious silver minerals appear to occur in appreciable quantities." ... "In regard to the mill tonnage this ore is unusually hard and tough, and a high stamp duty cannot be expected. Using a 20-mesh screen and 1,050-lb. stamps, our best work was three tons per stamp per 24 hours." It is very probable that the ore delivered to the testing plant was harder than the regular mill run has proved to be. However, at present the mine is developed to a depth of 1,000 ft., and still shows hard ore in places at this depth in about the same proportion as on the upper levels from which the test ore came; during this year's work, ore was treated from nearly all levels. Together with this hard ore in the mill feed a considerable proportion appears to be broken down and tending to crumble, thus making an ideal mixture for stamp milling. A small proportion of talc is also noticeable, which sometimes increases in amount to the point where it is very troublesome in the thickeners.

Jan 1, 1916

By B. K. Asdell

Crude kaolin exhibits a wide particle size range in which kaolinite is the predominant mineral. Bene-ficiation by wet processing produces high-brightness white pigments. The wet processing techniques peculiar to kaolin beneficiation are emphasized in this article in some detail. Included are discussions of long-distance pipeline transportation, centrifuga-tion, flotation, spray drying and shipment as 70% solids slurry. Georgia, a state seldom considered to be an important mineral producer, has one surprising feature — it is the nation's largest producer of kaolin. Kaolin is a highly important raw material in the paper, rubber, ceramic whiteware, paint and chemical industries. In 1965, more than 2.7 million tons of kaolin were produced in this state, a 150,000-ton increase over the preceding year, and production continues to climb. Strictly defined, the term "kaolin" applies to a group of hydrous aluminum silicates in which kaolinite is the predominant mineral. Kaolinite is inherently white, non-abrasive, chemically inert, and of a very fine particle size, ranging from sub-micron to 40-microns equivalent spherical diameter. An electron-micrograph of kaolinite is shown in Fig. 1. The particles finer than about 2 microns are thin, elongated plates, hexagonal in outline. The larger particles, coarser than 2 microns, are predominantly vermicular in outline with a foliated structure. Table I shows a typical chemical analysis of commercial, wet-processed kaolin compared to pure kaolinite. The sedimentary Cretaceous deposits of the Coastal Plain are the source of most of the kaolin produced in the Southeast. These deposits are of relatively high purity, and it is not uncommon to find the clays running greater than 90% kaolinite. Beneficiating plants using wet processing techniques are most numerous in an area within about 50 miles east of Macon, Ga., in a band approximately 15 miles wide. Kaolin may vary widely in quality from one deposit to another, or within the same deposit. The qualities critically examined are brightness index as measured by reflectance, viscosity of water suspensions, bleachability and particle size distribution. Crude kaolin always contains sand and mica in varying amounts, along with small amounts of many other minerals. These are classed collectively as "grit" because; they are generally coarser than 325

Jan 1, 1968

By C. C. Koch, M. L. Picklesimer

PHYSICAL metallurgists interested in the alloying behavior and phase transformations in rare-earth metals and alloys require a strain-free polished and etched surface for both metallographic and X-ray examination. However, the rare earths have presented a problem in this respect since they are difficult to polish free from strain and are very reactive to the atmosphere. Their tendency to oxidize readily even at room temperature necessitates careful preparation and rather elaborate protection if their surface is to be examined for any length of time. The "light" lan-thanides (i .e., atomic numbers less than 63), especially lanthanum and cerium, are particularly bad in this regard; they oxidize very rapidly at room temperature. To eliminate the problem of plastic deformation remaining on the surface after mechanical polishing, electropolishingl and chemical polishing techniques2 have been developed. The electropolishing technique requires the specimen to be immersed in an electrolyte at -77°C and thus obviates a metallographic study of, for example, the fcc —double-hexagonal close-packed (dhcp) transformation in cerium which begins at -10°C. The chemical polishing solution has been used only on several of the "heavy" rare-earth metals. However, a convenient method for protecting the polished and etched surfaces from atmospheric corrosion has not been available. Our interest in the superconducting properties of lanthanum, and in the phase transformations in lanthanum and cerium, has led us to develop a technique for the metallographic preparation of lanthanum and cerium which clearly reveals the microstructure and preserves the etched surface for days. The specimens are chemically polished and anodized. The chemical polishing is performed at room temperature, the anodic oxide film provides the required protection from the atmosphere, and colors produced in the film provide a simple positive technique for phase identification. Lanthanum and cerium metal ingots obtained from Johnson Matthey and Co., Ltd., were remelted to suitable shapes and heat-treated to produce various microstructures. The samples were placed in epoxy mounts and, after a small hole was drilled in the back of the mount for electrical contact, were ground on silicon carbide

Jan 1, 1968

By William Sharp

DISCOVERY of new ore in the Eureka district, Nevada, as a result of bold and persistent exploration based on a geologic interpretation of structure has recently aroused wide comment in mining circles. It may therefore be of interest to the profession to have a summary of the historical background and an account of the recent program of development. The mines of Eureka, discovered in the late 1860's, were the first important silverlead mines in the United States. They have a production record of more than fifty-one million dollars.1 After the ore bodies were apparently bottomed in the 1880's, repeated attempts to find new ore were unsuccessful until 1940, when a diamond-drill hole cut a 40-ft width of sulphide ore 1409 ft below the 841-ft level of the Locan shaft. The next hole cut 30 ft, of ore and three additional holes drilled in 1943 and 1944 showed the ore body to be continuous, Shaft sinking to reach and open up the ore body has been in progress since 1945. GEOLOGY Stratigraphy The ore in the Eureka district occurs in a series of Cambrian sediments which is exposed through a thickness of over 6000 ft. The stratigraphic column is as follows:2 [THICKNESS, FI ORDOVICIAN Pogonip limestone (upper part). Thin bedded limestone with some chert. UPPER CAMBRIAN: Pogonip limestone (lower part). Thin-bedded limestone (with shaly limestone and chert).... 425+ Dunderberg shale. Shale (clay and calcareous shale) and thin bedded limestone340+ Hamburg dolomite. Dolomite and limestonegoo+ MIDDLE CAMBRIAN: Secret Canyon shale. Shale and thin-bedded limestone1,035 Geddes limestone. Carbonaceous, flaggy limestone with some shale partings 335 MIDDLE (?) AND LOWER CAMBRIAN: Eldorado dolomite. Dolomite and limestone2,000 LOWER CAMBRIAN: Prospect Mountain quartzite. Quartzite with occasional inter calated conglomerate and shale 1,660+ The Prospect Mountain quartzite has been subdivided into two formations: Upper part, Pioche shale. Shale, quartzite with some intercalated limestone (Lower Cambrian fossils)-200 ft. Lower part, Prospect Mountain quart zite proper-I,460+ft. Total thickness6,695+] Much the most productive of these formations has been the Eldorado dolomite, which yielded more than $42,000,000 at Ruby Hill and an additional amount

Jan 1, 1947

By Robert B. Sosman

ONE of the most neglected fields for physicochemical education as well as for research is that of high-temperature phenomena. Few universities or technical schools give instruction in the physical chemistry of substances at high temperatures. On the contrary such instruction is almost entirely confined to the region between the freezing and boiling points of water. This field should be extended to a much wider range of temperatures, both low and high. Such an extension is logical, sound, feasible, and practical.

Jan 1, 1943

By H. M. Warrren

IN the past, steam engines were used in practically all cases for driving the machinery, in and about an anthracite breaker, and hence little or no accurate data were available as to the power requirements for starting and operating the individual machines, which make up the complete equipment. It was impossible to segregate the power necessary to drive each individual machine, first, because the equipment was driven in groups, and second, because it was impracticable to obtain graphic, integrated, or instantaneous records of the horsepower used. As a result of these conditions, it was found, when individual electric motors were applied to the various machines, that more accurate and complete data were needed in order to provide motors of the proper power and design for the particular services to be rendered. In order to obtain the desired information, the writers made and collected a number of tests, from time to time, on the individual motor drives in- electrically operated breakers, and as these tests have been of great value, it occurred to them that a paper giving the results might be of service to other engineers interested in similar installations. Table I shows the .results of these tests. All the motors tested were of the three-phase, 60-cycle, 440-volt, induction, squirrel-cage type, except a few, which, on account of size and starting conditions, were of the wound-rotor type. The instruments used in making these tests were: An integrating watt-hour meter, a graphic ammeter, and a graphic voltmeter. These instruments were connected in each motor circuit, and a record of a day's run of 9 hours was obtained from each machine. From these tests, the running light load, the average all-clay load, and the instantaneous peak readings in amperes, volts, and kilowatt input, were obtained. By means of the characteristic curves obtained from these motors at the factory, the power factor, the efficiency, and the horsepower output were calculated for each particular test. Starting tests were made by the brake-arm method, in which the torque in pounds was measured directly on a spring balance.

Jan 2, 1916