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By Perry Olcott .

THE Taka oil field is in the northern part of Titus and Franklin Counties, in north- eastern Texas. The small town of Talco, from which the field derives its name, is on the P. & Mt. P. R. R., about 15 mi. north of Mt. Pleasant, the county seat of Titus County. The oil field extends east and west from the town of Talco, the approximate center. In May, 1924, R. L. Cannon, while doing surface geology for the Humble. Oil & Refining Co., mapped the surface trace of this fault structure as evidenced by Upper Midway faulted down against Lower Midway. In the interval of sixteen years between the original surface work and the recent productive well completion, approximately eight wells were drilled into the Woodbine sand without success. The structure was well defined by those tests and all of the wells en-

Jan 1, 1936

By J. D. Ridge

The geologic setting and mineral relationships of seven European massive sulfide deposits that more or less conform to the bedding of the largely noncal-careous sedimentary rocks and/or bedded volcanics in which they are found are considered here. These orebodies consist largely of massive beds or lenses of sulfides usually surrounded by halos of disseminated sulfides and distorted by tectonic activity. The formations containing these deposits have been metamorphosed in varying degrees at times subsequent to their lithification. The ore-forming process is thought to be essentially volcanic, with the ore constituents being brought to the shallow-water site of deposition through tectonic fissures from magma chambers at depth as gases or relatively concentrated hydrother-mal solutions. Certain European ore deposits of base metal sulfide have previously been considered to be of hydro-thermal or magmatic origin, but today a number of European mining geologists consider them to be syngenetically produced. In an effort to provide American geologists with some idea of the reasons behind this change in thought, the geological settings of seven of these deposits have been studied. These are: Ldkken, Meggen, Rammelsberg, Ergani-Maden, Outokumpu, Boliden and Roros. These deposits lie in bedded rocks that have undergone metamorphism from causes not universally agreed upon; most of the formations were originally shales, and may have been intercalated with limey and occasionally quartzitic beds, volcanic tuff, agglomerate, extrusive lavas and usually basic intrusives. Deposits of the conformable type, however, are not confined to these rock types but may be in calcareous and associated igneous rocks or almost entirely in volcanics. These deposits may be closely associated in space with igneous rocks that, again, are usually basic types. Although the ages of the enclosing rocks range from mid-Precambrian (Boliden and Outokumpu) to Eocene (Ergani-Maden), the bulk of them are Paleozoic, with two (Meggen, and eammelsberg) being upper middle Devonian and two (LØkken and RØros) being Cambro-Ordovician. Geographically, two are in West Germany, four in Scandanavia and one in Turkey. Of the seven deposits, six are mined for copper, with three of these also producing zinc, and two lead; one is mined for zinc and minor lead. In the discussions of the seven conformable deposits that follow, I have attempted to present as uniform a treatment as their varying characters will permit. For each deposit, I have considered the stratigraphy of the area, its major structural characteristics, the form of the orebodies, their mineral content, and the origin of the ore. In the last of these subdivisions, I have presented only the viewpoint of those who believe the ores to have been formed by syngenetic processes, processes that went on at the same time as those which produced the beds that enclose the ores but that are not, in the deposits in question, thought to have been sedimentary in the strict sense of the term. The materials of which these orebodies are composed, it is suggested, did actually collect by falling through sea water to the floor of that portion of the sea in which they accumulated. The ore constituents, however, are believed by a considerable number of European geologists to have been added to the sea water from intratelluric sources, probably igneous magma chambers, as exhalations — hydrothermal solutions or volcanic gases. The effect of the encounter with sea water on these ejected gases or water-rich vapors was to precipitate their potentially solid constituents with great rapidity; they were deposited so quickly, in fact, that the amounj of normally accumulated mechanical or chemical sediment deposited over the same period of time was essentially negligible. The ores formed in this manner, however, are generally interbedded with normal sediments or with lava flows, or with any combination of these two types of rock-forming materials. Such departures as these deposits may have from their original mineral content and attitude are thought to be directly related to the degree of dynamic or static metamorphism that they may have undergone after their accumulation. I have not attempted here to present alternate hypotheses to that of so-called exhalative sedimentation although, of course, such exist and, in my

Jan 1, 1963

By R. F. Jones, N. E. Truitt, M. Prats

In most published discussions and theories of in situ combustion, the combustion fronts are assumed to be vertical. However, evidence from field tests leaves no doubt that combustion fronts often advance more rapidly along the top than near the bottom of a formation as a result of difference in density between injected air and formation liquids. The approximation proposed in this paper to determine the movement of the resultant tilted combustion surfaces states that the vertical rate of movement of combustion surfaces is proportional to the horizontal oxygen flux. Where self-ignition is possible, the proposed method demands that a secondary combustion surface exist around production wells which produce some oxygen. These secondary combustion surfaces may be formed long before the primary combustion surface can advance from injection to production wells. Heat liberated near production wells at these secondary combustion surfaces can contribute to an early increase in production rate. Results indicate that significant oil recoveries cannot be obtained from the usual flood patterns (five-spots, seven-spots, etc.) without producing large volumes of unused oxygen. Ideally, to increase oxygen- consumption efficiency, well patterns should allow oil production from a first line of production wells and gas production from more distant lines of producers. However, it may be desirable to produce some gas at all wells to support (and benefit from) active secondary combustion surfaces. Results indicate that the well spacing through which combustion can be advanced is larger than that predicted by other methods. A large number of production wells may still be desirable to take quick advantage of gravity drainage. From a comparison with results at South Belridge field, California, it appears that this method adequately describes oxygen concentration and temperature histories and combustion-front shapes. However, this method does not accurately locate the most advanced point of the combustion surface. There is some field evidence to substantiate the actual presence of secondary combustion surfaces at South Belridge. Use of the proposed method appears warranted at this time when lay-over of the combustion surface can be anticipated. INTRODUCTION The assumption of vertical combustion fronts has been embodied in all previous publicationsl-6 which use the movement of combustion fronts away from injection wells to determine the temperature and fluid distributions in the reservoir. The only paper concerned with a mathematical model of the combustion process in which a nonvertical combustion front is used was written by Gottfried.11 Actually, nonvertical combustion fronts have been observed in most in situ combustion field tests for which adequate data are available.7, 8, 6 In practice, the typical vertical extent of the burned zone decreases with distance from the injection well, and this burned zone is at or near the top of the sand body. In some cases, such as at South Belridge field near Taft, Calif., the combustion surface is almost horizontal over a very large area.8 Thus, for some years an obvious and serious gap has existed between theory (vertical fronts) and practice (tilted fronts). This is indicated in Fig. 1. Tilted combustion fronts such as observed at South Belridge8 sometimes result from the natural tendency of injected gases to rise to the top of an oil sand. An initially present gas cap, even if thin, would make apparent the effect of gravity segregation from the first, particularly since formations considered for in situ combustion field operations are generally selected for their

Jan 1, 1969

By R. B. Tippin, J. S. Browning

The feasibility of multistage heavy liquid cyclone beneficiation of spodumene was successfully demonstrated in this investigation. The indicated recovery for the multistage circuits was mathematically estimated as continuous test runs would be necessary to determine the true influence of a middlings recycle. In the three-stage circuit, both the concentrate analysis and spodumene recovery exceeded 90%. The two-stage circuits were unable to simultaneously yield an acceptable produce with a satisfactory recovery. With the Nation's growing industrial mineral requirements, the U.S. Bureau of Mines has undertaken the task of investigating new mineral dressing techniques and improving the existing concentrating methods of ore beneficiation. One such project is the gravity concentration of minerals using heavy liquid separation (HLS).1-3 Heavy liquid separation is based on the simple principle that a material, whose specific gravity is less than the density of a solution, will float on top of the liquid and a material with a greater specific gravity will sink. Heavy liquid separation techniques were developed in the laboratory over half a century ago but the process has yet to be commercially adopted. In the past, commercial operations have failed because of numerous problems.4 Industrial interest has recently been reactivated because of engineering advances. The number and quality of the heavy liquids suitable for mineral processing has increased while the cost has sharply dropped. New and improved liquid recovery systems5,6 are under consideration with present emphasis on 1) solvent extraction, 2) thermo-evaporation, and 3) water washing. The toxicity of the heavy liquids7 presents a problem, but throughout the chemical and mining industries, many similar hazardous materials are safely handled. A distinct advantage of using heavy liquids is its ability to provide a near perfect separation of fine-sized mineral particles even when the specific gravities are close. Effective separations have been made on minerals down to 200 mesh and with a density

Jan 1, 1968

By Auguste J. Rosh

The use of titaniferous ores in the blast-furnace has been the subject of much controversy for many years. Divers objections have been raised against them, and, for one cause or another, the verdict

Jan 1, 1893

By George W. Neumann

The mines and concentrator of Brunswick Mining and Smelting Corporation are located in the northern part of the province of New Brunswick, approximately 20 miles distant from the City of Bathurst. Discovery of the No. 6 orebody by diamond drilling in 1952 was followed by the finding in March 1953, of the larger and higher- grade No. 12 orebody, approximately six miles to the north of the No. 6 deposit. Original development was financed by St. Joseph Lead Co., and included a small open-pit operation with a 10C ton per day pilot mill at No. 6 orebody, shaft sinking and underground development at No. 1; orebody, and an extensive program of laboratory and pilot plant metallurgical research on No. 12 ore. These operations were suspended in May 1958, and remained in standby condition until June 1961, when the equity of St. Joseph Lead Co. was purchased by a group headed by M. J. Boylen, K. C. Irving, Maritime Mining Corporation, and the Patino Corporation. Construction of a mine plant and concentrator at the No. 12 mine commenced in October 1962 and the concentrator was placed in operation in March, 1961b. Preparation of the open pit mine for production, construction of the No. 6 Concentrator to produce bulk Pb-Zn-Cu-Ag concentrate from No. 6 ore, and construction of an Imperial Smelting Process smelter at Belledune were started in 1964 and placed in operation in September 1966.

Jan 1, 1970

By Albert Sauveur

(New York Meeting, February, 1913.) IT is delightful to read a technical paper like that of J. E. Johnson, The Effect of High Carbon on the Quality of Charcoal-Iron, presented in October, 1912, at the Cleveland meeting of the American Institute of Mining Engineers.1 The clear, simple, and straightforward manner in which he describes his experiments and results makes you feel as if you had been, so to speak, at his elbow during the course of his investigations, while his method of procedure is so rational that you can fairly anticipate each step in the logical sequence of the tests performed. The following notes suggested by Mr. Johnson's paper are presented here in the hope that they may help, if only a mite, towards the final solution of a problem of considerable scientific and industrial importance.

Jan 3, 1913

By H. E. Cook

The Ising model for the internal energy of a binary alloy has been used to obtain a general equation for the critical resolved shear stress of partially ordered crystals. The equation expresses the stress in terms of the Warren "alphas " and can be used to estimate the variation in strength with order without the assumption, present in the original formulation of this problem in terms of domain size, that order is complete within each domain and that the domains are of ungorm size and shape. In addition, it is the general equation, according to the Ising model, for strengthening by short-range order. Two applications of the equation are considered: One is an estimate of the variation in strength of CkAu with long-range order. The other is an estimate of the variation in strength of FeCo with quench temperature. Reasonable agreement is found with the variations reported in the literature. When the internal energy of an alloy crystal depends upon the distribution of solute, the strength of the crystal will also depend upon it because a portion of the applied stress for plastic deformation will be: where V is the volume of the crystal and E(E) is the energy change associated with the solute redistribution caused by the plastic strain, E. We expect T to equal zero for a crystal having a random arrangement of solute because the arrangement would remain random after plastic deformation. Likewise, we expect it to equal zero when the crystal is perfectly ordered because the motion of paired dislocations found in such crystals does not disrupt order. However, when short-range order exists or when long-range order is incomplete, plastic deformation will decrease the amount of order and additional work, proportional to the ordering energy, will be expended. Fisher' estimated T for crystals having short-range order by assuming an interaction energy between neighboring atoms and estimating the change in the number of unlike neighbors as a dislocation moved through the crystal. (His analysis was limited and several workers2"6 have since given more complete ones.) Fisher minimized the importance of a strengthening mechanism of this type for paired dislocations in a structure having long-range order. ~ottrell,' however, pointed out that T could be appreciable for ordered crystals having antiphase domains. He attributed the strengthening to the increase in surface energy of the domains as they were cut by paired dislocations. Ardley,' in his test of Cottrell's theory, found that r for Cu3Au crystals obeyed the equation: for 1 > t where 1 is the domain size, t is the domain wall thickness, and y is the surface energy of an antiphase boundary. His experiments represent the classic confirmation of the strengthening mechanism proposed by Cottrell. However, the assumptions involved in using Cottrell's theory are valid only for large domain size in CU~AU,~"~ i.e., when Eq. [2] reduces to: For small domains, ~linn~ has questioned Ardley's assumption that order was complete, and, indeed, Stoloff and ~avies" fpnd it incomplete until a size of approximately lOOA was reached. Even when the order within a domain is complete, it is not obvious how one determines the appropriate value for I in a structure where domains vary in size and are irregularly shaped. The purpose of this paper is to estimate T without restrictions upon the degree of order and domain shape. Our major assumption will be the use of a generalization of the model proposed by Bethe" (the Ising model) for the internal energy. This will in fact allow us to combine the theories for strengthening by short-range order and by antiphase domains into a single, general formalism. We will use the results to estimate the variation in strength of Cu3Au crystals with long-range order8 and the variation in flow stress of FeCo crystals with quench temperature.12'13 INTERNAL ENERGY For simplicity, we restrict our considerations to those binary solid solutions which can be described as an arrangement of atoms on a Bravais lattice. An atom site will be indexed by three numbers (PI, pz, p3) determined by the vector: from the origin fixed at atom (0, 0, 0) to the atom site where a', an, and a, are the lattice translation vectors. We write: For the energy of the crystal where pi(p) is the probability (either zero or one) of finding an atom of type i (i = 1, 2) at site (p), which is shorthand for (pl, pz, p3) and pj(p + r) is that for an atom of type j (j = 1, 2) at the site (p + r), which is shorthand for (pl + rl, The coupling parameter, resents the energy associated with the pair Pi(p), Pj(p + r). The crystal is assumed large enough so that surface effects can be neglected; therefore, trans-lational and inversion symmetry require the coupling parameters to obey the relations

Jan 1, 1969

By Julian M. Avery

In its dual role of pig-iron smelter and gas producer, the blast furnace is a remarkably satisfactory and efficient apparatus. Many metallurgists and engineers have pointed out, however, that since the primary function of the blast furnace is to produce pig iron at the lowest possible cost, its function as a gas producer should be subordinated to this primary purpose. During the past 10 years or more, improvements in blast-furnace technique and economy have, in fact, been directed primarily to increasing efficiency in the use of the reducing power of the gases produced by combustion of coke at the tuyeres, to reduce iron ore within the furnace. The net over-all result is a decrease in the fuel value of the top gas per unit of volume, and per ton of pig iron, which is evidently more than offset in value by the corollary saving in coke and the possibility of increased furnace capacity, for otherwise there would be no point in making such improvements. The purpose of the present paper is to suggest that, while progress has been made in this direction, there is another approach to the problem of increasing the chemical and thermal efficiency of the blast furnace in its primary role as a pig-iron smelter, which appears to offer possibilities of improvement in over-all ecorlomy of a different order of magnitude than results thus far obtained by the use of other expedients. The present argument is based in large part upon the hypothesis that the efficiency and economics of pig-iron smelting are seriously and adversely affected by the phenomenon known as "solution loss," and that the problem of solution loss call be successfully attacked by increasing the over-all pressure; i.e., the "top prcssure" under which the furnace is operated. It is indicated that pressure operation may also be expected to result in concomitant benefits, which may be summed up as generally improved operating conditions, together with a substantial saving in fuel and/or a substantial increase in furnace capacity. In a broad sense, the suggestion of pressure operation of the pig-iron blast furnace is not new, for operation under moderately increased over-all pressure was suggested as early as 1871, by no less an authority than

Jan 1, 1938

By Julian M. Avery

In its dual role of pig-iron smelter and gas producer, the blast furnace is a remarkably satisfactory and efficient apparatus. Many metallurgists and engineers have pointed out, however, that since the primary function of the blast furnace is to produce pig iron at the lowest possible cost, its function as a gas producer should be subordinated to this primary purpose. During the past 10 years or more, improvements in blast-furnace technique and economy have, in fact, been directed primarily to increasing efficiency in the use of the reducing power of the gases produced by combustion of coke at the tuyeres, to reduce iron ore within the furnace. The net over-all result is a decrease in the fuel value of the top gas per unit of volume, and per ton of pig iron, which is evidently more than offset in value by the corollary saving in coke and the possibility of increased furnace capacity, for otherwise there would be no point in making such improvements. The purpose of the present paper is to suggest that, while progress has been made in this direction, there is another approach to the problem of increasing the chemical and thermal efficiency of the blast furnace in its primary role as a pig-iron smelter, which appears to offer possibilities of improvement in over-all ecorlomy of a different order of magnitude than results thus far obtained by the use of other expedients. The present argument is based in large part upon the hypothesis that the efficiency and economics of pig-iron smelting are seriously and adversely affected by the phenomenon known as "solution loss," and that the problem of solution loss call be successfully attacked by increasing the over-all pressure; i.e., the "top prcssure" under which the furnace is operated. It is indicated that pressure operation may also be expected to result in concomitant benefits, which may be summed up as generally improved operating conditions, together with a substantial saving in fuel and/or a substantial increase in furnace capacity. In a broad sense, the suggestion of pressure operation of the pig-iron blast furnace is not new, for operation under moderately increased over-all pressure was suggested as early as 1871, by no less an authority than

Jan 1, 1938

By S. S. Clarke

ABOUT two years ago some of my friends were discussing the amount of drill-steel breakage that was permissible or not excessive, per month, per rock ton, per ton of steel or any unit of measure or output that would give a comparison between different kinds of drill steel. No one seemed to know what life to expect of steel, or what percentage of breakage might be termed excessive. In fact there were no operating data available to guide one in selecting the best steel for our mines, nor could any ideas or information be secured from the steel manufacturers. One was merely told that so and so used their steel and it was very satisfactory; or else one was given a highly technical lecture on their specific heat-treatment. Any estimates on expected breakage were just guesses, ranging from a fraction of a per cent to as high as ten per cent per month.

Jan 1, 1933

By O. I. Deschon, Ralph Arnold

Deep drilling was the keynote of the more important developments in the North Rocky Mountain region during 1929, with Montana recording the most important achievement through discovery of three new oil fields. Alberta produced 1,000,000 bbl. of 74 gravity naphtha, showing a considerable gain over 1928, developed a commercial oil pool in Turner Valley and extended that field 8 miles southward. Wyoming's discovery field was deepened to a second producing horizon, giving impetus to deeper drilling, and practically every Wyoming oil field will have a deep test either this year or in the near future. Whereas Montana prospecting has been confined to the shallow plains structures, since the discovery of Kevin-Sunburst field, the coming year will see an active search for new oil and gas pools in sharp-dip structures, following the success of prospecting in the Sweetgrass Hills during 1929. A dozen or more structures have been mapped in North Central Montana, several of these straddling the Alberta border. Four structures tested thus far have all shown commercial oil or gas or both. Sweetgrass Hills The first important development in the Hills area was the Rogers-Imperial gasser, which had an initial of 51,000,000 cu. ft. of dry gas per day, with a rock pressure of 1080 lb. This well is located on a sharp nose running north from the hills into Alberta. Several wells drilled by independent operators on the American side, on the west flank of reserve structure, have developed a total open flow capacity of 30,000,000 cubic feet. The third structure tested in the Hills area is known as Bears Den, where commercial oil was found at the base of the Cretaceous at 2470 ft. The existence of oil in three lower sands has been established by two wells on the top of the structure, these two wells finding gas flows of 10,000,000 and 15,000,000 cu. ft., respectively, in the horizon where

Jan 1, 1930

By ROBERT. RICHARDS

I. INTRODUCTION The object of this paper is to enlarge the field of settling velocities treated by me in my former papers, Close Sizing Before Jigging, and Sorting Before Sizing.' There seemed need of work both on coarser and on finer sizes. Messrs. A. Sidney Warren and M. L. Nagel undertook the investigation for the coarser sizes, from 12.85 mm. down to 2.05 mm. diameter. Their work, because of the closer spacing and because of the increased number of observations and consequent stronger averages, called for a revision of the former work. Messrs. G., A. Barnaby and Ralph Hayden undertook this part of the work, from 2.49 mm. down to 0.28 mm., which is near the limit of sifting. Their work covers the ground much more minutely and comprehensively than the former papers. There remained to be covered the portion of the field too fine for investigation with the sieves. This part, covering the range of grains from 0.48 to 0.03 mm., was undertaken by Mr. E. S. Bardwell. For it he used the elutriation method. II. THE FIRST, OR COARSEST, SECTION OF THE FIELD. The first desideratum in this investigation was a series of sieves for sizing the sands preparatory to making the tests. It became necessary, therefore, to decide on a sieve-scale for this purpose. A sieve-scale is a series of sieves in which the dimensions of the holes of the successive members form a series increasing by a. definite ratio. There are three natural sieve-scales : 1, progressing by doubling the width of the hole for each suc-

May 1, 1907

By M. L. Fuller

DURING the last several years many papers have appeared dealing with the structure of highly polished metal surfaces. The awakening of interest in this subject is due to the applicability of the electron diffrac-tion technique to the study of surfaces. The original theory of Beilby1 considered the surface of polished metals as of the nature of a super-cooled liquid or a vitreous, amorphous solid. The electron diffraction effects from polished metals have been interpreted by many to be a direct experimental proof of the correctness of the Beilby theory. This inter-pretation has been strongly opposed by others, so that at the present time the subject is in an uncertain and controversial state. In the present paper new, and hitherto unpublished, electron diffrac-tion effects from polished zinc are described. These observations indicate that the polished surface of zinc is crystalline.

Jan 1, 1938

THE SOUTHWEST MINING SECTION of the National Safety. Council held a well attended two-day conference at Globe, Ariz., March 19 and 20; followed by two days of mine-rescue maneuvers at the Old Dominion mine in cooperation with the Globe-Miami District Mine Rescue and First Aid Association and the U. S. Bureau of Mines. C. L. Colburn of the Bureau had general charge of the arrangements and was chairman of the conference. All sessions were held in the Old Dominion Library. The program of papers was as follows: MINE FIRE PREVENTION AND FIGHTING What to do in Case of a Mine Fire. / Chas. A. Mitke, Consulting Mining Engineer, Bisbee, Ariz. Gunnite as a Fire Preventative. W. C. Browning, General Manager, Magma Copper Co., Superior, Ariz. Chemical Engineer's Part in Fire Fighting. Dr. L. H. Duschak, Consulting Chemical Engineer, San Francisco, Cal. Mine Fire Drills. A. C. Stoddard, Chief Mining Engineer, Inspiration Consolidated Copper Co., Inspiration, Ariz. Notes on the Installation of Fire Fighting Equipment in Mines. Benjamin F. Tillson, Assistant Superintendent, New Jersey Zinc Co., Franklin, N. J.

Jan 5, 1923

By R. M. Raymond

RECENTLY one of the Welsh coal companies, which has an excellent plant of up-to-date ma-chinery both on the surface and underground, operated under modern methods, sent one of its engi-neers to the United States to study actual operations in the mines. He visited several of the most important and best conducted collieries, went back, and reported that the greatest difference between operations in England and in the United States was. the closer con-tact between management and workmen. By manage-ment he meant management all the way through; close cooperation between office management, superintend-ents, foremen, shift-bosses, etc., and the workmen. A visit to some of the coal mines in that country by the writer made this fact rather impressive. The feel-ing on this side of the water that the methods in use in the coal mines in England are not up-to-date was found in many cases to be quite erroneous. Many mines, particularly those with very thin beds, in which profitable operations are doubtful under the best con-ditions, have necessarily had to adhere to old methods instead of making mechanical improvements. The Powell-Duffryn mines, in the center of the South Wales district, are certainly operating successfully, and have planned their business excellently. Sufficient areas of contiguous land have been leased for extended opera-tions. Mine plants are laid out in the valley, for work-ings on both sides, on a reasonable tonnage of 1500 to 3000 tons to each operation. The beds are from 30 to 48 in. thickness, and a 3-ft. seam is considered an ex-cellent thickness of coal; in fact, the miners prefer to work on the thinner beds rather than the thick ones, where they consider it more difficult to control the backs. This company is making use of its fine coal for produc-ing electric power, which is distributed to its own operations, and for use in the communities adjoining. For this purpose methods of cleaning the fine coal are being put into use. Compressed air is generated at the central power plant and is transmitted over long dis-tances to various mines in each valley. A byproduct coke plant uses more of the fine coal and gives further returns from non-commercial coal. The long-wall system applied in sections of limited size is popular in working the small seams, and me-chanical cutting is used, also handling either by shaking chutes or belt conveyors, or a combination of both. In some mines mechanical cutting is not necessary. The backs are so handled that in the softer or somewhat crushed seams hand cutting can be carried on effec-tively.

Jan 10, 1927

By M. J. Bradley, P. H. Dike

THE art of melting nonferrous metals, in smelting, casting, and in compounding of alloys, is highly dependent on a knowledge of the temperature of the metal. This knowledge may reside in the experience and judgment of the melter, or it may be based on measurement by suitable instruments. It-is our purpose to discuss briefly the instruments available for such measurements, and more at length the present, practice in molten metals, without recommendation. In the limits of time and space allotted, we can do little more than mention the available methods of measurement that are directly applicable in this field. In the 1939 edition of the Metals Handbook, issued by the American Society for Metals, pages 285-310, there is a more extensive discussion of pyrometry than can be attempted here, which should be referred to for details we must omit. For reasons that will appear, thermoelectric pyrometry will constitute the major portion of our discussion of the subject, only limited attention being given to radiation or optical pyrometry. METHODS OF MEASUREMENT THERMOELECTRIC PYROMETRY A thermocouple consists of two dissimilar wires, or a wire inside a tube of a dissimilar material, joined together at one end, which is placed in the region or medium where the temperature is to be measured, while the other ends are connected through suitable lead wires to a voltage-measuring device, which may be a millivoltmeter or a potentiometer. An electromotive force is generated in the circuit, which is proportional to the difference in temperature between the hot junction and the junctions of the lead wires to the measuring instrument. If this latter temperature is maintained constant, the e.m.f. measured varies only with the temperature of the hot junction. Every thermoelectric pyrometer is calibrated for a particular cold-junction temperature such as 0°F., 32°F. or 75°F., but usually it is more practical to compensate instrumentally over the probable range of cold-junction temperatures than to maintain the junction at the particular temperature for which the instrument was calibrated. Thermocouple Materials Only a very few pairs of metals are in frequent use for pyrometric measurements. The most generally used are iron-constantan for temperatures up to 1500°F. in oxidizing and up to 1800°F. in reducing atmospheres and chromel-alumel, which may be used in oxidizing atmospheres at temperatures up to 2400°F. for intermittent service. The accuracy of the latter deteriorates rapidly at temperatures above 2200°F. Platinum vs. platinum-rhodium thermocouples may be used up to a temperature of 3000°F , but they are easily contaminated by slow absorption of

Jan 1, 1946

By C. R. Hocott

THE viscosity of the oil in the reservoir is one of the properties that influence its movement through the sand to producing wells. Measurements of viscosity, therefore, are pertinent to problems associated with well behavior and with the estimation of recoveries, and afford an indirect means for partial evaluation of various methods of controlling reservoir behavior. The effect of dissolved gases on the viscosity of crude oil has been determined,1,2 but no data have been published on the viscosity of repre-sentative samples of reservoir oils. This paper describes a simple instrument that has been used to determine the viscosities of a number of subsurface oil samples at the temperatures and pressures existing in the reservoirs, and presents the results of the determinations for typical fields.

Jan 1, 1940

By William G. Kegel

Apart from a usable product and good mining conditions, the greatest asset for a profitable coal mining organization is an effective mine maintenance program. The first step in achieving this is to have good mechanics-or men who want to be mechanics and are interested in knowing, more about the design and control of the machines in their charge. A good mechanic's knowledge and ability result from ambition, curiosity, and determination. Starting with these qualities, the aspiring mechanic can launch his career by learning all he can about mechanics, electricity, and hydraulics. Though the path is rough, the end result is rewarding. Mining machinery probably receives as much, if not more, abuse as any other heavy equipment in use today. Considering the conditions under which much of the repair work must be done, it is essential that the mine operator has the best men and tools to perform the work. Mining machines, from their inception, have utilized the electric motor; and down through the years of mechanization, this power source has undergone many changes to better adapt it to the job. The first motors used were direct-current (d-c) motors since d-c power was the most economical power source for mining at the time of early mechanization. These motors were large open-type machines which are seldom used in modern mining. Because of the mine environment, the d-c motor has been reduced in size to better suit the application in mining machines and is now manufactured with dust-tight or explosion-proof enclosures. The d-c motor is constructed with either (or both) series and shunt fields located on the stationary part of the motor (stator) and an armature coil wound on the rotating part of the motor (rotor). Power is supplied to the armature by brushes which are held stationary and make sliding contact with the armature. The brushes requires regular and careful maintenance because worn or defective brushes will cause heat or arcing which can destroy the motor. D-c motors can be used as d-c generators when mechanical power is supplied to them by the rotating

Jan 1, 1981

By Chung Yu Wang

During the time I was in charge of this mine, from 1914 to 1915, I had occasion to read the interesting papers by T. T. Read and C. M. Weld about these deposits, to find how far their observations corroborated mine. To quote from the paper on "The Mineral Production and Resources of China" by T. T. Read:' "The iron ores at Tayeh * * * * lie along the contact between a marble and an intrusive body of a dark gray syenitic rock. * * * * At one place it is slightly magnetic, apparently having been partly reduced to the magnetic oxide by the action of reducing solutions, which have deposited small amounts of copper and iron sulphides along the foot wall." To quote from the paper on "The Tayeh Iron Ore Deposits"2 by C. M. Weld: "I find the orebodies described as occurring along an approximately E-W contact between hornblende-granite and limestone. * * * * The granite is a granitoid rock consisting essentially of quartz, potash-feldspar and hornblende."' These quotations show the differences of opinion entertained by two observers. My own study of these interesting deposits has been intermittent amid the manifold duties devolving upon a superintendent. General DescriptLon of the Deposits The deposits are situated to the west of the Yangtse River, being connected with the river by a standard-gage railroad of 66 li (18.16 miles, 26 km.) in length, as shown in Fig. 1. The general topography of the region is of mature age, showing broad valleys with sluggishly meandering streams. These deposits are worked as two mines, named the Tieh Shan Mining Department and the Teh Tao Wan Mining Department; the former consisting of three orebodies more or less connected, named Tieh Man Kan, Sha Mau Tze and Lung Tung, and the latter consisting of Chang Pei Shan, Sze Tze Shan, Ta Shih Men, Yeh Chih Ping and Tsin Shan, also more or less connected, as shown in Fig. 2.

Jan 1, 1918