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By W. F. Hosford

W. F. Hosford, (Massachusetts Institute of Technology) —evelopment of methods for predicting the plastic anisotropy of textured metals is an important step toward the improvement of properties by texture control. The engineering value of the present analysis is indicated by the good agreement between prediction and experimental findings. The purpose of this discussion, however, is to point out the weakness of the assumptions on which the analysis is based. The authors state that "the relative width and thickness strains are believed to depend only on the slip direction" and accordingly they disregard the orientation of the active slip plane. where E,, cW, and et are the tensile, width, and thickness strains, A,, A,, and At are the angles between the tensile axis x, the width direction w, and the thickness direction t, respectively; and G,, GW, and 4 are the angles between the slip-plane normal and x, w, and t, respectively. Therefore, the ratio of width to thickness strains resulting from slip on a single system would be These relations hold regardless of whether the slip plane is a crystallographic plane of the {110}, (1121, or (123) type or whether noncrystallographic slip occurs. If noncrystallographic slip occurs, it might be reasonable to assume that the effective slip plane is the most highly stressed plane containing the slip direction. In this case the slip direction, S.D., the slip plane normal, S.P.N., and the tensile axis, x, are coplanar (Fig. 19) and the angles are related by following expressions: where 9 is the angle between t and the projection of the slip direction in the w-t plane (igs. 1 and 2). The normal strains, Eq. [9], become

Jan 1, 1963

By John Jermain Porter

THe value of any particular ore, coke, or limestone, for iron-making, depends upon its effect, first, upon the quality or value of the resultant product; and second, upon the cost of smelting. The factors under the first head are the percentages of phosphorus, manganese, and other elements, which remain in the pig-iron ; while those under the second head are the percentages of iron, carbon, or lime, the slag-forming constituents, which must be fluxed, and any other ingredients which give rise to variations in cost of fuel and flux. The first of these criteria of value is perhaps not capable of being reduced to a general formula embracing all cases, since it must vary to a great extent with market-fluctuations. For example, Bessemer pig is worth sometimes more and sometimes less than foundry-pig; and the premium paid for high manganese varies within wide limits. The second, or smelt-ing-value, however, can be expressed numerically with a fair degree of accuracy; and it is with this phase of valuation that the present paper is concerned. The utility of a means of comparing numerically the relative smeltiug-values of difierent ores, cokes, and limestones, is self-evident, although it may not have importance in Northern practice, where materials are largely standardized. On the other hand, there are, especially in the South, many furnace-managers who must use a great variety of materials of widely varying grade; and it is with special reference to this district, and in connection with the efficiency-methods which I have elsewhere proposed,' that the methods herein described were devised.

Jan 1, 1913

By Richard McCaffery

THE statistical analysis of blast-furnace data was undertaken to determine some of the relations which exist between the variables involved in furnace operation, and particularly to show the effect of variation of slag composition on such economically important factors as coke consumption, daily tonnage of pig iron and sulfur elimination. It was desired to correlate the results obtained in- commercial practice with those predicted from a study of the quaternary system lime-alumina-silica-magnesia. This paper presents the results of a preliminary study of blast-furnace daily operating reports, and is intended to indicate the suitability of our method of attack and something of the results that may be expected from an extended statistical examination of such data. It has been shown that blast-furnace slags are not composed of oxides, as reported by chemical analysis, but are actually composed of several compounds, each made up of two or more of the oxides present.1 These compounds persist in the liquid state, and the properties of a slag are the properties of a mixture of these compounds, and not of a mixture of the ultimate oxides .2,3 The oxides lime, alumina, silica and magnesia make up 94 to 96 per cent. of the usual blast-furnace slag, and assuming that we may neglect the remainder of the components, we may determine the minerals present, and their relative proportions, from a study of the quaternary system involving these four oxides. Operating reports from 15 furnaces were available for this investigation. Complete slag analyses for one slag per day were available, permitting the calculation of the mineral composition of the slags used. Basic, malleable and foundry irons, with silicon varying from 0.75 to 4.50 per cent. were included in the reports for this examination.

Jan 1, 1931

By J. A. M. van Liempt

Since the discovery of von Laue, that a crystal forms a natural grating for X-rays, our knowledge of the structure of solids has gone forward with rapid strides. This progress is not only of purely scientific interest, but has also yielded direct technological results. One of the most valuable results is the broadening of our knowledge of the structure of pure metals and alloys. To promote these studies it is often desirable to have at our disposal pieces of metal consisting of one single crystal. As is so often the case in the natural sciences, we obtain the best results by making our earliest experiments on pure, simple materials and avoiding unnecessary complications. The Cryogen Laboratory at Leyden followed this method with much success, because the work was done at such low temperatures that the heat movement of the atoms was almost absent. Similarly we can simplify the studies of metals by leaving out of consideration the influence of the grain boundaries and the mutual influence of the crystals by using unicrystalline instead of polycrystal-line metal. Methods of making single crystals have been scientifically studied during the past few years. Some methods were already known in the arts, but these have been improved and new methods have been developed. The methods for making metallic single crystals may be divided into the following groups: A. From the liquid state B. From the gaseous state C. Electrolytically D. By recrystallization in the solid state Method A 1. Tamwmnn's Method1—Tammann succeeded in making bismuth single crystals of a maximum length of 20 cm. by undercooling the molten metal 0.1 to 0.3' G. below its melting point in glass tubes of a maximum

By Horace Williams

IN VIEW of the frequent occurrence of petroleum in other parts of the world, it seems odd that so large an area as is contained within the borders of Brazil should be without this product. This apparent deficiency may be due, however, to our ignorance of the regions in which-it, may exist. In some places, indications point to the probable existence of petroleum in ages gone by; and while the presence of petroleum pools may be problematic, in several regions conditions not unfavorable to their occurrence exist. Yet, Brazil has enormous oil resources in the rich oil-shales in different parts of the country. Many of these shales are very rich and only suitable processes for the extraction of the oil are lacking. At the present time, only a few small experimental plants are producing oil by distillation from these shales. These plants have been the subject of recent investigations by the Geological and Mineralogical Survey, a. pre-liminary report of which is in the hands of the printer. The only regions where studies have not been made are the upper Amazon, the Acre, the Rio Negro, and the Peruvian frontier, which really seems to be the most promising field for, explorations of any in the country. In the vast plateau region of the interior north of the 20th parallel of latitude, granites, gneiss, mica schists, and, very old metamorphosed sedimentaries predominate. Later, sedimentaries occupy a minor position and, where found in the interior, represent a thin veneering resting on the older rocks. At several places near the coast they have a greater development and contain considerable beds of oil-shale and may, in some cases, offer conditions favorable for the occurrence of oil. Such deposits are found in the Permian rocks of central-and southern Maranhão; in the Tertiary and Cretaceous beds along the coast of Alagôas Sergipe, Bahia, and perhaps farther south in Espirito Santo; and in the Parahyba embayment north of Cape Frio and in the interior Tertiary basin of eastern Sao Paulo.

Jan 9, 1920

By George S. Ramsay

The Appalachian system contains the largest area of all known Carboniferous coal-fields. Beginning near the north line dividing Pennsylvania and New York, it extends southwest through West Virginia, southeastern Ohio, Kentucky and Tennessee and terminates in Alabama—a distance of about 950 miles. The northeastern part of this field will be considered in this paper. The general dips of the measures are toward a trough about parallel to the Ohio river, from the Allegheny mountains and ridges on the west. The Potonlac field is an exception; the dip in this case being northeast, the folding to the east of the Allegheny mountains in Pennsylvania being of a greater degree and diminishing southwestward. The cause of the general dip to the west of the mountains seems to be the westward movement of the thrust east of the mountains, with the large Nittany fold including other folds to the east of the escarpment, raising the mountains high above the coal-fields to the west, making a general slope toward the Ohio river southwest, and crossing waves of anticlinals west ward. The synclinals contain the coals, while in many cases on the top of the folds or anticlinals some of the veins (or, in some cases, all) are eroded. The Coal-Measures of this field are generally divided into three principal divisions, known as the Upper, the Barren, and the Lower Coal-Measures, but there is a tendency to divide them into five groups, which is more convenient. Beginning at the bottom, the first would be the Conglomerate ; second, the Lower Coal-Measures; third, the Barren; fourth, the Upper Coal-Measures, and fifth, the Upper Barren or Permian Measures.

Jan 1, 1896

By Wallace Ralston

DuRing the year of 1937, the East Texas district produced 211,194,467 hbl. of oil and marketed more than 22,329 million cu. ft. of gas; 3377 oil and gas wells were completed. During this same period 106 exploratory wells were drilled, discovering three new oil fields and one gas-distillate field. Fields East Texas Field.—The East Texas field again led the district as to production and number of wells completed. During the year, 2420 oil wells were completed, making a total of 24,382 producing wells, which produced 171,336,854 bbl. of oil, for a total of 1,156,352,834 bbl. since the beginning. During the year the average bottom-hole pressure dropped 49 lb., making the average bottom-hole pressure 1119 lb. Approximately 3500 wells are making salt water, 20 per cent of them making over 80 per cent of the water. During the month of December, the daily average production of salt water was 119,000 barrels. Talco Field, Titus and Franklin Counties.—The Talco field produced 9,780,948 bbl. of oil during the year, from 637 wells. During the year 472 wells were completed. All of the wells are pumping and 241 are making salt water. This field has followed a normal development and did not exceed the estimated number of acres reported last year. Rodessa Field, Cuss and Marion Counties.—The Rodessa field was extended about 13 miles southwest into Marion County, which added approximately 4000 acres to the field. During the year 260 wells were completed, making a total of 416 producing wells, which produced 12,646,-970 bbl. of oil. The author was unable to obtain figures for the amount of gas produced. The field has two gasoline plants, which had a daily average of 16,558,000 cu. ft. of gas during December, averaging 0.83 gal. per M cu. ft. As of Jan. 1, 31 wells were making salt water. The bottom-hole pressure varies greatly, depending upon the pay from which the well is producing. The average bottom-hole pressure from the Young

Jan 1, 1938

By Charles W. Sweetwood

THE Western phosphate field, virtually ignored for 40 years, has been undergoing a rapid climb to economic importance. Until World War II there seemed to be no reason for developing the phosphate rock region of the Intermountain Empire. But the tremendously increased demand for food production and the needs of many branches of the chemical industry changed all that. Quite suddenly a report made by the U. S. Geological Survey at the turn of the century became important. The survey showed that 60 pet of the nation's phosphate reserves were in the western phosphate field. Simplot Fertilizer Co. was one of the first to become actively interested in the development of the area. In August, 1945 the company began exploration of the Phosphoria Formation on the Fort Hall Indian Reservation. The result was the Gay Mine, about 18 miles east of Indian Agency Headquarters at Fort Hall, Idaho, developed to supply high grade phosphate rock for processing into superphosphate fertilizer at the company's Pocatello plant. Six ft of high grade oolitic phosphate rock (ranging from 32.5 to 34.5 pet P2O5) were discovered at the base of the Phosphoria Formation by diamond drilling and dozer trenching. High quality and thickness, plus the fact that the formation lay flat and near the surface made strip and open pit mining possible. In one year of mining, starting June 1946, a total of 53,000 tons of main bed oolitic phosphate rock was hauled to Pocatello for processing into supersulphate. The first year's operation was in

Jan 1, 1952

By F. E. Crane, H. A. Kendall, G. H. F. Gardner

Two effects of a difference in density may be observed in miscible displacement. As the difference is increased from zero there is first a change in mode from multiple fingers to a single finger. A further increase results in a more rapid growth of the single finger. Miscible displacement with multiple fingers has been discussed by Blackwell, et al, whereas miscible displacement with a single finger has been discussed by Craig, et al. In the present paper experiments are described which bridge the gap between these extreme cases. INTRODUCTION Craig, et al,1 investigated the effect of gravity on frontal displacements for circumstances in which the gravity forces were significant. Blackwell, et a1,2 dealt with the other extreme in which gravity forces were negligible. The considerable difference between their results is illustrated in Fig. 1 where the breakthrough recoveries are plotted against the mobility ratio. The experiments described in the present paper were conducted to examine how the transition from the one extreme case to the other occurs when the gravity forces are gradually reduced. The transition is well illustrated by the production history after breakthrough. Fig. 2 shows how the number of pore volumes which must be injected at a constant rate to displace 98 per cent of the original fluid depends on the gravity force. For each mobility ratio there is a transition range, and a very significant change in the number of pore volumes occurs when this range is traversed. This range of the gravity force is physically linked with the formation of viscous fingers. A single finger is predominant for larger gravity forces; a multiplicity of fingers is formed for smaller gravity forces. Improved recovery and the occurrence of multiple fingers is concomitant with a large increase in the amount by which the fluids are mixed within the porous medium. The transition range depends on all the dimension-less groups which characterize the problem; but this dependence has not been exhaustively studied as yet and only fragmentary results are discussed in this paper.

By Douglas Bunting

With the gradual exhaustion of the upper veins in the anthracite coal-fields, the problem of mining at greater depths acquires increasing importance and demands the consideration .of a number of important factors, one of which is the greater earth-pressure and the consequent necessity of stronger support for the roof. Under the pillar-and-chamber system, almost exclusively followed in the Northen anthracite-field, the highest economy in mining is generally secured by leaving, on first mining, pillars only sufficient to support safely the overlying strata. As to the necessary size of such pillars, the opinions of mining experts are widely divergent. In establishing the width of chambers and pillars, the thickness of vein and its depth below the surface have received little consideration. For instance, it has been quite usual to work both overlying and underlying veins with the same width of chambers and pillars, when the lower vein was two and one-half times as thick, and twice as far below the surface, as the upper. In view of the generally-accepted theory that the crushing-strength of coal-pillars of the same base-area becomes less with increased height, it is probable, in this instance at least, that the moat economical mining has not been secured. This question of adequate pillar-support is economically less important down to about 800 ft. than at greater depths; and it is with reference to mining at these greater depths that the study of the subject here presented has been prompted. The necessity of leaving larger pillars, involving greater mining-costs per ton and also smaller yields per acre, is one of the troubles of deep working. To mine without leaving adequate pillar-supports will result, sooner or later, in a squeeze. Limited areas, it is true, have been mined at certain widths of

Jan 1, 1912

By Carl Swartz

ALTHOUGH a number of articles appeared during the war advocating the use of cadmium in lead-tin solders, very little information of value can be found in the literature regarding the properties of solders containing cadmium. In most of the published articles the cadmium seems to have been considered merely as a partial substitute for tin in a tin-lead alloy rather than as an essential constituent of a ternary alloy. The primary object of the substitution of cadmium for tin was to lessen the amount of tin required, at a time when the latter was scarce and high-priced, and thus to produce a cheaper solder. While this object was accomplished, the new properties resulting from a change from a binary lead-tin alloy to a ternary lead-tin-cadmium alloy were not given proper consideration in many cases. For the past few years, the American Smelting & Refining Co. has been marketing a very considerable amount of cadmium in the form of lead-tin-cadmium alloys for use as solders for certain special purposes, and the successful use of these solders suggested that if more extensive knowledge were available concerning the properties of lead-tin-cadmium alloys of various compositions their field of usefulness might be materially extended. The investigation described in the present paper was undertaken to obtain this information and, by means of tests under conditions approaching those of practical use, to determine the suitability of cadmium solders for various purposes.

Jan 1, 1928

By D. V. Carter, Dan C. Williams, Franklin M. Hackbusch

During 1939 little of consequence happened in East and East Central Texas in the way of oil discoveries. At the end of the year, there were 47 oil and gas fields in the district. Twelve other fields, 11 oil and one gas, have been abandoned. The ranking fields in order of the number of completions for the year were East Texas, Talco, and Rodessa (Texas portion). There were 511 oil wells (distillate wells included), 32 gas wells, and 257 dry holes completed in the district. Exploration, Discoveries and Extensions During the year, 113 exploratory wells were drilled, the same number as in 1938; four oil fields and one gas-distillate field were discovered. Perhaps the most important discovery, which has been named Barron field, was that of M. Samuel et al., No. 1 Barron in Limestone County. The wells in this field are of the gas-distillate type. Other than the Talco and Sulphur Bluff fields, which produce oil from the Paluxy sand (Upper Trinity), this is the first field on the Corsicana-Mexia fault zone to obtain commercial production from deeper Trinity strata. This "pay" is the Petit lime of the Lower Glen Rose of the Trinity group. The four oil discoveries were: Redland, Angelina County; Bazette, Henderson County; Rowe and Baker, Henderson County; and Marion County Shallow in Marion County. It is believed that the Bazette field, Navarro County, represents an extension of the Flag Lake field. For details concerning discoveries, extensions and important wildcat wells drilled during 1939 see Table 2. Production and Proration The district produced 175,053,729 bbl. of oil (distillate production included) which is a decrease of 4.0 per cent from the 182,369,484 bbl. (distillate production included) produced during 1938. The district's production for the year 1937 was 208,594,453 bbl. The East Texas

Jan 1, 1940

By B. B. Zavoico, J. G. H. Crump, P. P. Gregory

West Texas was the scene of greatly increased oil activity during 1937, producing 75,743,000 bb1.l in that year as compared with 61,901,-000 bb1.2 in 1936, an increase of 22.36 per cent. The annual total of wells completed increased from 15863 in 1936 to 28062 in 1937, an increase of 76.92 per cent. Of the total completions in 1937, 2464 were oil wells,2 11 gas wells2 and 331 dry holes.2 The marked increase in the number of oil wells completed in West Texas during 1937 had a substantial effect upon the daily average production per well, which decreased 20.84 per cent from December 1936, when a total of 5310 wells3 produced 5,236,467 bbl.3 for an average of 31.81 bbl. per well per day to December 1937, when 7571 wells2 with a total production of 5,910,257 bb1.2 averaged 25.18 bbl. per well per day. Drilling blocks and checkerboard acreage were being acquired following geophysical work in the northern end of the Permian Basin area, composed of Bailey, Cochran, Hockley, Yoakum and Terry Counties, presaging extension of active development northward. During 1937, at one time 30 geophysical crews were working in West Texas, and an average of 15 to 20 crews was active in this area throughout the year. Discoveries Wasson-Denver Field.—Wasson-Denver field in Gaines and Yoakum Counties was the outstanding field discovery of the year. Production is from porous limestone found at about 5000 ft., and an average well is good for from 300 to 500 bbl. of crude oil per day through 3/4-in. choke. The discovery well was drilled by A. G. Carter and others on the Wasson Ranch, Gaines County, and the field has since been extended into Yoakum County. At the year's end 21 wells had been completed, producing

Jan 1, 1938

By R. S. Barneyback

Not much more is known about concrete today than was known to the Romans. For all the research only better tools have resulted to measure the quality of the materials that go into it." In this paper "some of the materials for lightweight concrete and their characteristics are considered and effort is made to indicate their effect on the end result — a structure of lightweight concrete." Lightweight concrete had noble beginnings. It is believed that the first specification for lightweight concrete was written by the Roman Emperor Hadrian in the early years of his reign, 117-138 AD. Hadrian, was an engineer by trade and an Emperor by adoption. He took considerable interest in the structures sponsored during his reign, even to the point of working out the structural details and preparing working drawings for some of the more prominent works in the vicinity of Rome. In order to reduce the dead weight of the 140 ft diam dome of the Pantheon he specified that the lightweight structural concrete members supporting this concrete and tile composite dome were to be fabricated from a concrete containing pumice and scoria. Still standing after 18 centuries of abuse, this structure has been described as the master effort of a great structural genius, the ultimate achievement of Roman engineering skill.' The Romans were the first to employ many concrete techniques we think of as modem innovations. Some unnamed superintendent noted that when a carefully measured amount of pigs blood was measured into each batch of concrete during mixing, the concrete was more durable and exhibited much better resistance to freezing and thawing climates. He no doubt, attributed this success to the appeasement of one of the gods who in return provided protection for the building containing this sacrificial offering in its walls. It is known today that the blood-entrained air in the concrete tends to make mixtures more workable, resistant to moisture penetration and more resistant to frost damage.

Jan 1, 1964

By L. R. Jackson, W. T. Lankford, K. F. Smith

COMMERCIAL steel sheet is prepared by a combination of hot and cold rolling and annealing. This treatment usually results in more or less pronounced anisotropy. The [ ] anisotropy may manifest itself both as preferred orientation and in the manner in which impurities, segregations, and the like, are aligned in the sheet. The type of preferred orientation and the organization of impurities or segregations may affect the elastic moduli, the yield strength, the tensile strength, and almost always the amount of ductility in different directions. In any case, the most important directions concerned in the anisotropy are along the rolling direction, along the width direction, and along the thickness direction. Considerable data exist on the anisotropy of sheet steel as demonstrated by conventional tensile tests; however, few attempts have been made to measure the constants of plastic anisotropy and use them to describe the flow of anisotropic sheet under combined stresses. [ ] In this paper, evidence is presented indicating that plastic flow in anisotropic sheet can be described by the shear-strain energy flow theory provided that the anisotropy is properly taken into account. MATERIALS USED IN THE INVESTIGATION Table I lists the sheet materials used in this investigation and describes the condition in which materials were tested. DESCRIPTION OF TESTS AND TEST METHODS Two types of tests were run-tensile tests and hydraulic-bulge tests. Characteristic parameters of anisotropy were determined from the tension tests by methods which will be described later. In all cases, the tensile test pieces were cut from the same quarter line and adjacent to the bulge test pieces in the sheet in order to minimize

Jan 1, 1948

By G. W. Garside

In order to render my descriptions more intelligible, I have compiled a general map of this section of Alaska, showing accurately the relative positions of the most important districts where valuable deposits of minerals have been discovered (page 819). Upon inspection of this map, it will be observed that the chief metalliferous belt in this mineral field is in close proximity to the mainland shore, the trend of which it follows for more than a hundred miles in a northwest and southeast course, while the mineral croppings on the adjoining islands are much shorter in extent, and more irregular with respect to their strike and continuity. This principal metalliferous zone, which I will call the main-land system of lodes, contains gold, silver and lead, besides traces of copper, zinc and iron, gold being found extensively in a free state and also associated with sulphur, and with many of the sulphides of iron, lead and other substances. On the line of this belt, as shown on the map, there are a number of distinct mineral districts. Beginning at the southerly extremity, they are named as follows: Sumdum, Snettishham, Grindstone Creek, Sheep Creek, Gold Creek, Lemon Creek, Montana Creek and Berners Bay districts, each deriving its name from the hay or creek on which it is situated. Harris mining district, as legally organized under the local customs, rules and regulations adopted by the miners of Juneau, embraces, within its exterior boundaries, Grindstone, Sheep, Gold and Lemon Creeks, and all of Douglas Island. The limits of this immense metalliferous horizon are becoming definitely known through the exposures made by prospectors. The belt, as now recognized, varies in width from one to several miles, the lateral measurement being greatest at Juneau in Harris district, where the famous Treadwell mine, with its slate foot-wall, marks the westerly boundary of the zone, while the eastern side of Silver Bow Basin, with a granite hanging-wall, defines its easterly border.

Jan 1, 1893

By A. F. Lucas

EACH day, the fact becomes more evident that the ever-growing demand for oil is farther outstripping production, regardless of the increase in output throughout the past twenty years. The development of known oil fields and the prospecting for new ones along present lines are not resulting, in, and cannot bring forth, supplies large enough adequately to meet the oil needs of the country. The usual methods of prospecting-for new supplies are insufficient to meet the exigencies of the situation which threatens, in the not distant future, to reach a critical stage. Were it not that within the last two years new and prolific oil fields have been discovered in northern Louisiana, central Texas, and California, this crisis would undoubtedly be now at our door. Stocks are being exhausted in spite of the rapid growth of imports. The time is therefore fast approaching when some radical departures must be made in the method of prospecting and developing old and new fields in order to increase our oil supplies. Methods and chances, that have seemed unwarranted will not only be given serious consideration, but, according to the results promised, will be put to the test. Meanwhile, however, nearly all the oil fields are responding to the stimulus of higher prices, whereby enormously growing capital is attracted to this important industry, both here and abroad; the increase in our petroleum production at the present time is due to this circumstance. Yet, although a most active search is being made for possible sources of additional supply, one section of our country is not yielding the results that, in my opinion, it is capable of producing: I allude to the coastal dome belt of Texas, Louisiana, and Mexico. The United States Geological Survey has estimated that three-fourths of a billion barrels are available in the ground in the Coastal Plain of the two states just mentioned. Numerous papers have been written on the subject of the salt domes of the Coastal Plain and more or less attractive theories have been advocated by leading geologists to account for their origin and the presence of the oil, sulfur, and salt associated in them. However, owing in part to the generally monotonously level country in which the coastal

Jan 9, 1920

By J. Howard Boyce

INTRODUCTION The Tsumeb Mine is situated in the northern part of South West Africa, approximately 335 air miles north-east of the port of Walvis Bay on the Atlantic Coast, and 240 air miles north of Windhoek, the capital of South west Africa. The mine came into operation in the early 1900's and has operated continuously since then except during the two world warm and the depression years of the thirties, Tsumeb Corporation purchased the property in 1947, installed a new plat, and ham built a modern tom. In addition to the concentrator which began operations in 1948, a copper smelter was started in 1962 and a lead smelter in 1963, Tonnage of ore treated in the concentrator has varied through the years, reaching a maximum of 70,000 tons per month with a current mined tonnage of approximately 50,000 tons per month. Copper concentrates, lead concentrates and zinc concentrates are produced, and for a number of years the production of a germanium enriched concentrate was an important feature of the operation, Both copper and lead concentrates are smelted in Tsumeb, while the zinc concentrates are shipped overseas. Ore change, and the installation of the smelters in Tsumeb have necessitated modifications in the concentrator operation. This paper will describe current plant practice in some detail and will touch briefly on the techniques used from 1954 to

Jan 1, 1970

By Charles J. Moore

It seems a duty incumbent on the older members of the Institute to set forth in permanent form some of the results of their experience for the benefit of the younger members; this is the principal object of the present paper, which is the result of a recent examination requiring somewhat unusual geologic investigation. History. The London vein mas first discovered by float and occasional outcrops in the year 1873, four years before the great lead carbonate discoveries of Leadville, but the mine was not definitely located and opened until two years later, when the present locations, Mother, Paris, London, and Hard to Beat, were surveyed for patent. Since 1875 the London mine has been worked almost continuously until 1911, when the force was reduced to a few men only. In its early life the ore was assumed to be free-milling gold-quartz, although lead was a constituent of the vein throughout, and much useless expenditure was made in the erection and operation of a free-gold stamp-mill, with plates and tables for saving concentrates. The vein then opened was in the porphyry-limestone contact, a siliceous lead-ore, clearly most amenable to reduction by lead-smelter. The losses due to this process led in time to the close of the mill. For 20 years past, the mine has been worked under lease and the ore shipped to the lead-smelters in Denver or Salida. In January, 1912,I examined the mine to ascertain whether it was advisable to run a cross-cut tunnel some 4,200 ft. in length to intersect the main vein at a depth of 650 ft. below the present lowest workings. Finding a greatly-faulted zone, a close determination of the geological conditions became necessary to the solution of the problem.

Jan 1, 1914

By H. H. Stoek

A STUDY of American coal mine practice shows two of its distinctive features to be: A greater number of accidents per thousand employees than in any of the other leading coal-producing countries; a much greater percentage of the coal lost than is the case in any of the other leading coal producing countries. Although our subject is mainly concerned with the second feature, any consideration of mining methods should include safety, efficiency, and economy or costs. If in defense of our wasteful mining the argument could be offered that it was necessary on account of safety, and that it is carried out with less loss of life than is the case in other countries the plea for conservation of coal could not be so strongly urged. But when we are wasteful of both life and property, the subject merits more consideration than it has received. Some coal operators will doubtless say that the unit of accidents should be the number per million tons produced rather than per thousand employees, for by adopting this unit America probably stands in the lead rather than the lowest among the countries. However, vital statistics are not usually so expressed by other governments, by life and accident insurance companies, or in other industries, and it is merely begging the question and attempting to bolster up a bad condition to adopt a peculiar unit for the statement of our accidents. For many years the statement was made by various agencies, and was unchallenged, that "For every ton of bituminous coal mined in the United States a ton had been lost in the way of pillars left in the mines." This statement was undoubtedly true for many years, and although some progress has been made in the past decade looking to a higher extraction, and in some districts very decided progress, the loss is still great; and, although no exact data can be given, it is probable that for the United States as a whole at- least one ton is lost for every two mined.

Jan 2, 1922