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By Richard Miller

WORK was undertaken two years ago at the Hammond Laboratory for the purpose of determining the magnitude of the elastic range in single crystals of pure metals by means of creep tests, the assumption being made that if a true elastic range exists, the elastic limit represents the maximum stress for no creep. A sensitive extensometer was constructed, and creep tests were made on zinc single crystals at a variety of loads and temperatures1. It was soon discovered that there is tip measurable elastic limit in ductile zinc single crystals at, or above, room temperature. The inference that pure metallic single crystals may not possess a definite elastic range was not justified, however, since zinc had been tested in creep only above its recrystallization temperature, and several investiga-tors2,3,4 had already shown that above the recrystallization temperature polycrystalline metals will flow under very small stresses, while below that temperature stresses of a much larger magnitude are required. For that reason, it was decided to extend the study of the elastic limit to other metals having a higher recrystallization temperature than zinc. Aluminum and silver were selected, because of the ease of obtaining pure materials and of preparing large single crystals, and because the crystallo-graphic glide system of these metals is well known. Owing to the limited time available, the elastic range was investigated by slow tensile tests rather than by creep tests.

Jan 1, 1937

By Neil H. Cole

Cost and price inflation and financial gearing through loans are characteristic of modern resources projects. Conventional discounted cash flow and 1P.R analyses, in real terms, and without financing, have inadequacies which can yield misleading results. The degree of improvement in value for project equity owners is limited to the value of the additional tax benefit accorded through the financing instrument used. Debt financing may be low in price and value, but its priority means that the equity owners assume a higher risk, thereby increasing the cost, or price, of their capital. The cost of equity capital, or investment hurdle rate, is related to the Capital Asset Pricing Model. Distortions do occur, with inflation, due to depreciation effects, which can cause the adoption of misleading project rate of return or hurdle rate criteria. For investment decisions, the greatest accuracy possible in forecasting is essential, especially for inflation rates,

Jan 1, 1985

By John G. Bartram

The oil business has been relatively quiet in Wyoming during 1934. Only 34 producing wells were completed, 54 dry holes were drilled, and at the end of the year only 30 wells are listed as drilling. Wyoming still has a large reserve of production shut in, mostly in black oil or asphaltic base fields in the northwestern part of the state. The total oil production increased from 11,171,500 bbl. in 1933 to 12,539,470 in 1934, but light oil production continued to decline, and the increase was made by black oil fields. This is partly due to natural decline of light oil fields, especially Salt Creek, Big Muddy and Lost Soldier, but largely because of increased demands for road oil. The Rocky Mountain states spent much money to build and improve roads and a greater amount of road oil was used. The refining of black oil to manufacture road oil produced gasoline as a byproduct that slightly decreased the demand for light oil. The Oregon Basin and Frannie fields, in the Big Horn Basin, moved into second and third places in the list of producing fields in Wyoming because of their increased black oil production, and Big Muddy and Lost Soldier, light oil fields, dropped back. Wyoming stayed close to its allowed production, which was based on the needs of the refiners and purchasers. This activity in black oil resulted in a few more wells in the fields of the Big Horn Basin, but the greatest amount of drilling was in the shallow Osage field in eastern Wyoming. Osage supplies many little topping plants and at the close of 1934 there was not enough oil available there to supply all of them. In the Lost Soldier field and Salt Creek, one major company was rather active in a campaign to deepen, clean out and repair old wells to increase production, and the figures of that work are not included here. Of the light oil fields, Lance Creek promises to be most active during 1935, since the two wells in the recently discovered Sundance sand pool are producing and more wells will he drilled. With wildcatting almost at a standstill, two new oil fields were discovered in Wyoming in 1934. In Albany County, a 75-bbl. oil well was completed on Quealey dome in the Muddy sand (Upper Cretaceous)

Jan 1, 1935

By E. V. Manlapig, David J. Spottiswood

In recent years great advances in the automatic control of flotation plants have been made, mainly due to the development of reliable sensing instruments to monitor process performance and the development of an adequate understanding of system responses to process disturbances. Some of the control strategies used in flotation plants which apply computer control are presented here. These schemes, which involve the control of collector; depressant, frother, and air and pulp level, are analyzed with respect to their control objectives, control variables, and the instrumentation involved. The knowledge gained in understanding these strategies may be applied in the dew and implementation of control system in other concentrators.

Jan 1, 1981

By J. Federico Price, Joseph E. Aparicio

This paper describes the production of a specific iron oxide pellet that has given very good and consistent results as feedstock for HYC-Process Direct Reduction Plants. The sponge iron originated from these pellets has been used for the economic production of almost 15 Mt of low carbon steel via electric arc furnace meltshops. An overview of mining, beneficiation, pelletizing, direct reduction and steelmaking for this case is given with emphasis on the charactertitics of the self-fluxing oxide pellets.

Jan 1, 1982

By W. M. Brown

SEQUACHEE Valley includes portions of the counties of Marion, Sequachee, Bledsoe and Cumberland. It extends in a general direction parallel with the Great Valley of East Tennessee, some 75 miles northward from the Alabama state line. It is separated from the Valley of East Tennessee by a mountain arm about a dozen miles wide, known as Wallen's or Walden's Ridge. The genesis of the valley, geologically speaking, is simple. It is an erosion-valley along the axis of an anticlinal. The point of the wedge remains in a row of low "saw-tooth" hills, running up the center of the valley. These hills are of Lower Silurian age, and consist of Trenton limestone, covered and protected in some measure by chert. Walls of Carboniferous age form the inclosing mountains on either side; whilst a magnificent arch of Hudson River, Niagara, Hamilton and Subcarboniferous strata closes the valley at the

Jan 1, 1886

By James R. Evans

Forecasting demand is an art as well as a science, and much personal judgment is required. National forecasts made for sand and gravel, crushed stone, and/or aggregate may be misleading or unhelpful locally. This is because of significant variation in demand within different geographic and/or political areas in the US, and/or the use of an inadequate data base and forecasting methodology. The best forecasts may be made for local or regional market areas, irrespective of geographic or political boundaries, provided a proper data base is available.1 The Bureau of Mines compiles detailed statistics on commodities sold or used in the construction industries and, therefore, is in an advantageous position to make national aggregate demand forecasts.

Jan 1, 1979

By T. A. Rickard

We rejoice that the world-war is ended. We are proud of the part played by the English-speaking peoples-all doing equal honor to the traditions they share in common. One of the compensations for the calamity of the past four years is the fact that the Briton and the American, striving together in the cause of human liberty, have learned to understand and to respect each other. The mother country entered the fight resolutely at the beginning, while yet unready to meet the carefully prepared onslaught of the enemy; then the sons from the overseas dominions rallied to the old battle-cry eagerly and effectively; and last, but not least, the stepsons came from across the Atlantic, speaking the same speech, playing the same game, and fighting in the same clean way. It was a great foregathering of those that use the language of Shakespeare and idealize the principles of liberty for which the friends and associates of Shakespeare stood sponsor three centuries ago. At a time like this it is pleasant to dwell upon the fact that the liberal Englishmen who organized the Virginia company were the pioneers of self-government on the American continent. The Virginia Assembly, convoked in 1619, was the first example of a domestic parliament to regulate internal affairs on this side of the Atlantic.2 The Governor of Virginia, Sir Edwin Sandys, had been a pupil of Richard Hooker at Oxford and from that political teacher he and his friends had imbibed the idea of combining civil liberty with constitutional order. To this group of large-minded Englishmen, the American colonists owed their liberal charters and their successive triumphs over the royal prerogative. Let it be noted that the American colonists had to deal with James II and George III, the two smallest minds in the list of British kings. Another historical note more pleasant to record, is the connection between the two principal groups of American settlers. In 1608 when the Pilgrim fathers, William Brewster and John Robinson, led their Separatist congregation to Holland and there prepared the expedition to America, they were assisted by Sandys and the Virginia Council, who were willing to share their privileges with them. When the Pilgrims set sail in 1620 they had the promise, obtained by Sandys from King James, that they should have freedom of worship,

Jan 4, 1919

By J. M. W. Mackenzie, C. J. Wood

In attempting to describe the size classification performance of a hydrocyclone, most workers have elected to use either an equilibrium orbit theory or an non-equilibrium orbit theory. The equilibrium orbit theory has been used by the majority of workers including Lilge,' Bradley; and Yoshioka and Hotta. In applying this theory, it is argued that particles in the body of a hydrocyclone attain an equilibrium radial position where the drag force on the particle resulting from the inward radial fluid velocity is balanced by the outward centrifugal force caused by the tangential component of fluid flow. When considered over the full height of the hydrocy-clone, attainment of this radial equilibrium orbit results in the particle following a conical equilibrium envelope. It is then argued that if this envelope lies outside the envelope of "zero vertical velocity," the particle will report to the underflow, while if the equilibrium envelope lies inside the envelope of "zero vertical velocity," the particle will report to the overflow or vortex finder product. The d50-sized particle which reports in equal quantities to the underflow and overflow is assumed to correspond to particles whose equilibrium envelope is coincident with the envelope of "zero vertical velocity." In considering the equilibrium orbit theory, it is apparent that the horizontal position of the particles in the feed inlet pipe should have no effect on their ultimate destination on the hydrocyclone. Each particle should attain an equilibrium position which depends on the density, size, and shape of the particle; the density and viscosity of the fluid; and the flow patterns within the hydrocy-clone. The nonequilibrium orbit or unsteady state theory has been largely developed by Rietema4 and Mizrahi.6 Mizrahi has listed four main objections to the equilibrium orbit theory. These objections center on the short residence time in the hydrocyclone, the fact that the experimental classification curve is much less sharp than is theoretically predicted, and the absence of negative efficiency conditions in hydro cyclones operating on a feed material which is much finer in size than d50. Proponents of the nonequilibrium orbit theory argue that for a particle to discharge with the underflow it must have sufficient outward radial velocity to reach the downward-flowing region close to the hydrocyclone wall in which the flow lines are parallel to the wall and the ratio of vertical to radial velocity is constant. It is then postulated that a d50 particle entering the cyclone at the center of the feed inlet will just reach this downward-flowing region as it reaches the apex. Thus for uniform distribution of particles across the feed inlet, half the d50 particles—that is, those injected in the half of the inlet area nearest the cyclone wall —will report to the underflow while those injected in the other half will not reach the downward-flowing region and will be carried inward to the center of the cyclone and thus report in the overflow. The exact thickness of the down-ward-flowing region of fluid adjacent to the outer wall of the hydrocyclone is uncertain but Mizrahi considers it to be equal to the apex radius minus the air core radius. Particles larger than d50 have a greater outward centrifugal force acting on them than the d50 particles and may reach the wall even if injected at a distance from the wall greater than Di/2 (Di is inlet diameter). Conversely, particles smaller than d50 may not reach the wall even if injected at a distance less than Di/2 from the cyclone wall. Since the equations put forward by the proponents of both theories yield approximately the same values of d50, it is not possible to decide between these theories by measurement of d50. It should be possible however to examine the theories by injecting a small stream of solids into the feed inlet of a hydrocyclone running on clear water. If the efficiency or classification curve is measured for various horizontal injection positions, then the curves should be coincident if the equilibrium orbit theory holds. If, however, the unsteady state theory describes the cyclone operation, then the classification curves should show finer d50 sizes for particles injected close to the cyclone wall. Experimental A 6-in.-diam hydrocyclone with geometry as in Figs. 1 and 2 was used. Quartz particles were injected as a 50% by wt pulp via an 1/8-in. steel probe. For each in-

Jan 1, 1971

By T. V. Moore, H. D. Wilde

In many of the important problems of the petroleum engineer, it is necessary to know accurately the laws governing the flow of gas and liquid mixtures in vertical pipes. Although much work has been done along these lines, no satisfactory solution to the problem has been found. A good theoretical discussion of the energy balance in a gas-lift has been published by Versluys.1 One of the most important factors affecting the efficiency of the flow of oil and gas mixtures is slippage, and in most of the experimental work that has been done no provision has been made for the measurement of this quantity. As Versluys pointed out, since there is no method now known to estimate it from the data usually taken, slippage must be determined empirically. This paper presents the results of some work carried on to measure slippage in short experimental gas-lifts. As shown herein, slippage can be easily calculated in a vertical pipe carrying a mixture of oil and gas if the fractions of the pipe occupied by liquid and gas respectively are known. In this work, the fraction of the pipe occupied by the liquid was measured under a wide variety of conditions and the relationship between this fraction and other quantities, which are easily measured in ordinary work, was determined. It was hoped that the quantitative relationship obtained from this work could be used for making accurate calculations in flowing or gas-lift wells, but unfortunately it did not check satisfactorily when applied to actual wells. Apparently flow in long flow pipes is more efficient than in the short ones used for the experimental work. Nevertheless, it is felt that the data themselves arc of interest; that the method of attack may be of value in future work and that the relationship derived between slip and the relative velocities is a contribution toward the solution of the gas-lift problem.

Jan 1, 1931

By J. Charles Miller

NATURAL carbon dioxide has recently been exploited in the United States in consequence of oil and gas developments in the Western States and the growing demand by transcontinental and transoceanic shippers for solid carbon dioxide. The discovery by drilling of commercial deposits resulted in consideration of its geographic and geologic distribution and occurrence. Its wide distribution in nature is evidenced by its occurrence in the atmosphere, hydrosphere and lithosphere. The question of origin of carbon dioxide involves consideration of theories similar to those concerning natural hydrocarbons, although available evidence favors an inorganic rather than an organic source. Areas favorable to development of commercial production appear to be those in proximity to igneous rocks or in the vicinity of decadent volcanic activity, where, it has long been known, the gas is evolved either free or dissolved in the waters of fumaroles, geysers or mud pots. Structure contour maps are presented showing the Wagon Mound anticline in New Mexico and the Farnham anticline, Utah. A well drilled on the latter supplies gas to a 20-ton plant manufacturing solid carbon dioxide at Wellington, Utah, on the Denver and Rio Grande R.R., whence it is shipped to surrounding territory and to the West Coast. Before funds are invested in a plant for the manufacture of liquid or solid carbon dioxide, whether supplied by wells or springs, an effort to ascertain the volume of gas available is advisable. The use of present methods of estimation of gas reserves with modifications to account for the quantity absorbed by any water present in the producing formation is recommended, The Farnham anticline is used as an example and cornputationa are made of the probable volume of gas originally present in the structure. No attempt was made to compute reserves in the Niland area, California, for the reason that in such areas it is believed the volume is indeterminate. INTRODUCTION Carbon dioxide, in liquid and solid form, has found a wide variety of uses other than its primary application in carbonating beverages. It is now used in more than 40 different ways, ranging from cooling or freezing to use in gas or liquid form for mechanical purposes, chemical industry, explosive, fire extinction, and tire manufacturing. Undoubtedly the chief supply of carbon dioxide is obtained from industrial plants or artificial sources and until recently natural deposits of the gas have received little consideration. Few will question the utility and perhaps dependability of artificial sources, which possess the advantage over

Jan 1, 1937

By G. W. P. Rengstorff, R. B. Fischer

A study was made of the effect of impurities on the bend ductility of cast molybdenum. High purity molybdenum was repared by re-melting under high vacuum. The ductility of "transverse-grain" specimens indicated that intergranular brittleness decreased with an increase in purity of the metal. THE production of as-cast molybdenum with high ductility at room temperature would make working of the metal easier and increase the usefulness of the as-cast metal. Furthermore, a .knowledge of the factors that influence the ductility of as-cast molybdenum might be applied to the problem of making fusion weldments having satisfactory room-temperature ductility. Individual grains of commercial as-cast molybdenum are slightly ductile at room temperature. However, the presence of carbides at the grain boundaries may cause the metal to fracture in a brittle manner. This behavior has been discussed.' The amount and distribution of the impurities in as-cast molybdenum would be expected, from previous research on the metal, to have considerable influence on its ductility. Some effects of oxygen and carbon on the mechanical behavior of the metal were discussed by Parke and Ham,2 Woodside,3 and Zappfe. Landgraf, and Worden.4 Parke and Ham2 found that, if a sufficient number of molybdenum oxide particles were present at the grain boundaries, the intergranular cohesion was reduced to the extent that arc-melted molybdenum would rupture intergranularly during hot forging. They also found that if the oxygen content was less than 0.003 pct, the cast molybdenum was hot forgeable. It is suspected, however, that forgeable molybdenum may contain a small amount of oxide that could reduce the ductility of the as-cast metal at room temperature. Also, there is the possibility of the unfavorable distribution of other impurities having a detrimental effect on the ductility of cast molybdenum. The results of a study of the influence of purity on the room-temperature ductility of cast molybdenum are presented here. Vacuum Arc-Melting to Produce High Purity Mo One way of determining the effect of impurities on the ductility of molybdenum is to prepare and test metal as free of all impurities as possible. Accordingly, the present investigation was undertaken with this in view. Arc melting in high vacuum (less than 0.1 micron of mercury) was chosen as the method for reducing the impurities below the concentrations occurring in commercial molybdenum. Commercial arc melting of molybdenum is carried out at about 50 microns pressure. During the arc melting, carbon and oxygen in the metal react to form carbon monoxide. By virtue of the vacuum process, the partial pressure of carbon monoxide is maintained at such a low value that the reaction greatly lowers oxygen and carbon contents. An excess of at least 0.03 pct C is used in commercial arc melting to insure that the oxygen content will be below 0.003 pct. The excess carbon remaining after the deoxidation step forms carbides on freezing. Some of the carbides precipitate at the grain boundaries and, as will be shown, have an unfavorable effect on the room-temperature ductility. In the present work, only the small amount of carbon (0.003 pct) contained in the commercial powder-metallurgy molybdenum used for melting stock was present. Partial removal of oxygen from the melt probably occurred as the result of the volatilization of molybdenum oxides, or by distillation of oxygen at the high melting tem-

Jan 1, 1953

By J. O. Whitely

IT is difficult to give a refining outline that may be followed for any and all combinations of the platinum metals; different combinations require different methods of attack. This paper does not pretend to go into all of the reactions of the metals of the platinum group, but will outline the commercial refining of platinum scrap. TYPICAL PLATINUM SCRAP As a concrete case, let us take 100 oz. of miscellaneous scrap, made up of jewelry scrap, dental scrap and laboratory ware. This lot will contain some platinum, palladium, iridium, ruthenium, rhodium, gold, silver and copper. The first problem is to get all of the metals in solution. If the scrap is principally platinum, palladium and gold, a treatment with aqua regia is the course to pursue; but if the scrap contains alloys high in iridium or ruthenium, aqua regia will act too slowly. In the case in hand, we are going to presume that we have scrap high in iridium and ruthenium, and proceed accordingly.

Jan 1, 1928

By Morris Cohen

Within the past two years, a number of publications have called attention to the double peaks, or stages, that appear in the hardness and strength curves of certain aging alloys. The author has shown the existence of double hardness peaks during the aging of a high-purity silver-copper alloy;' and on the basis of electrical resistance, microscopic, dilation and lattice-parameter measurements, hc concluded that the initial hardness peak occurs prior to precipitation while the secondary hardening is due to precipitation. It was suggested that the general mechanism of age-hardening involves two consecutive processes, the first consisting of nucleus or knot2 formation, and the second consisting of actual precipitation and particle growth. It was further held that the two stages are interdependent, but because of nonuniform precipitation they may overlap each other to an extent that increases as the aging temperature is raised. At high aging temperatures, the effect of the first stage cannot be detected because of the rapid occurrernce of precipitation. The general theory of age-hardening recently presented by Dr. M. L. V. Gayler3 is in close agreement with the picture outlined above. With reference to work done on duralumin, copper-beryllium and copper-silver alloys, Dr. Gayler also concluded that age-hardening takes place in two consecutive steps: first, diffusion (in which the solute atoms migrate to certain crystallographic planes), and then precipitation. However, W. L. Fink and D. W. Smith4 have shown that the double aging peaks that appear in the strength curves of high-purity aluminum-copper alloys may be explained without recourse to pre-precipitation phenomena. By means of very careful metallographic technique, Fink and Smith demonstrated that during aging the precipitation takes place at an accelerated rate along the grain boundaries and slip planes as a result of the plastic deformation caused by the drastic quench from the solution heat-treatment temperature. The general precipitation occurs at a

Jan 1, 1939

By Morris Cohen

Within the past two years, a number of publications have called attention to the double peaks, or stages, that appear in the hardness and strength curves of certain aging alloys. The author has shown the existence of double hardness peaks during the aging of a high-purity silver-copper alloy;' and on the basis of electrical resistance, microscopic, dilation and lattice-parameter measurements, hc concluded that the initial hardness peak occurs prior to precipitation while the secondary hardening is due to precipitation. It was suggested that the general mechanism of age-hardening involves two consecutive processes, the first consisting of nucleus or knot2 formation, and the second consisting of actual precipitation and particle growth. It was further held that the two stages are interdependent, but because of nonuniform precipitation they may overlap each other to an extent that increases as the aging temperature is raised. At high aging temperatures, the effect of the first stage cannot be detected because of the rapid occurrernce of precipitation. The general theory of age-hardening recently presented by Dr. M. L. V. Gayler3 is in close agreement with the picture outlined above. With reference to work done on duralumin, copper-beryllium and copper-silver alloys, Dr. Gayler also concluded that age-hardening takes place in two consecutive steps: first, diffusion (in which the solute atoms migrate to certain crystallographic planes), and then precipitation. However, W. L. Fink and D. W. Smith4 have shown that the double aging peaks that appear in the strength curves of high-purity aluminum-copper alloys may be explained without recourse to pre-precipitation phenomena. By means of very careful metallographic technique, Fink and Smith demonstrated that during aging the precipitation takes place at an accelerated rate along the grain boundaries and slip planes as a result of the plastic deformation caused by the drastic quench from the solution heat-treatment temperature. The general precipitation occurs at a

Jan 1, 1939

By D. D. Porter, C. Fairhurst

Crack propagation in the region of a statically pressurized borehole is investigated to determine a role of the sustained borehole pressure following detonation in a blast. The case of a single-hole bench blast is reduced to a plate model, which is considered both theoretically and experimentally. Based on the principle of least work, it is hypothesized that the path of any crack in the plate will coincide with one of a family of maximum principal stress trajectories. These trajectories were computed, and critical experiments in glass, designed to test the effects of controlled crack origin and of changed trajectories from different loading configurations, confirm this hypothesis. It is concluded that under ideal conditions the crack path can be predicted and that cracks can be produced in the absence of either high-amplitude stresses or stress waves. Energy considerations for crack extension are discussed, and, based on the strain energy distribution, a relationship between hole burdens and spacings is revealed, a critical burden is demonstrated, and a maximum crater width is shown to exist.

Jan 1, 1971

By John Fulton

The Connellsville coal-field is a separate strip of the upper coal measures, flanking the Chestnut Ridge along its western side. It extends from a point a few miles south of Uniontown, in Fayette County, following a northeasterly course parallel to the trend of Chestnut Ridge, through Fayette and Westmoreland counties, with its terminal prongs resting 011 the southern portion of Indiana County, north of the town of Blairsville. This belt of coking coal will average about three miles in width and over sixty miles in length, affording nearly, if not quite, two hundred square miles of this large coal-bed.

Jan 1, 1885

By Richard P. Schoemaker

INTRODUCTION IN underground mining operations the effects of economic and mechanical factors on costs and profits can readily be appreciated and can perhaps be expressed in exact figures and percentages. Less apparent, but frequently more important, is the influence of physical stress. Stress causes failure of supports, collapse of openings, rockbursts, and other damage which directly affects the costs of maintenance, and also to a certain extent the accident rate. Stress can, however, if properly directed, be an aid to mining operations. The caving methods in metal mining and the long-wall method in coal mining are well-known examples. In large-scale mining operations it is almost impossible to neglect stress-control. A better understanding of the mechanism of rock pressure and the application of its principles to practical mining will inevitably lead to a reduction in operating costs. Many theories have been advanced to give the mining engineer a practical outline for stress-control but, although today most experts agree upon the principles of stress distribution around underground openings, there is still no generally accepted theory that explains all phenomena. The main reasons for this incomplete understanding of the problem are the lack of accurate knowledge of the physical properties of rocks under field conditions, and the great complexity of these conditions due to inhomogeneity of the rock, stratification, tectonic disturbances, and many other unknown factors. The research on the rock pressure problems has, however, yielded some valuable facts which, expressed in practical terms, and adapted to local conditions, may become a valuable aid for mining operations. The purpose of this paper is to give a review of the most important accomplishments of this research with respect to the stress phenomena around small underground openings, such as tunnels and shafts, so as to arrive at an outline of the problem as it stands today. Special emphasis is placed on a new theory by the German mining engineer, Rudolf Fenner, which has never before been published or discussed in English. THE PRESSURE DOME THEORY The formation of a dome-shaped space around underground openings is well known from field observations. When openings are made in rock under stress, the rock in the top of the openings will often fail, and caving will continue until the openings have assumed a dome-shaped form, after which equilibrium apparently is re-established. The oldest theory which attempted to explain the phenomenon is the "beam" theory, which postulates that the hanging wall consists of stratified measures that behave as independent beams with fixed ends and a uniformly distributed load. When failure of the beam occurs, inward shearing at the ends will cause the formation of a dome-shaped space. The pressure dome theory, which more or less evolved from the beam theory, merely

Jan 1, 1947

By B. K. Parekh, W. M. Goldberger

A novel process is proposed for continuous removal of ash and unreacted solids which become suspended in the oils obtained during coal liquefaction. The proposed method uses water in direct contact with the oil under conditions which cause the suspended residue solids to transfer from the oil to the water phase. Separation of the phases yields a product oil essentially free of suspended solids. The water is cooled, clarified or filtered by conventional low-cost systems, and recirculated. The paper describes experimental work leading to development of the novel concept and includes the result of batch experiments that establish the feasibility of the process.

Jan 1, 1980

By S. J. Kidder

Application of shrinkage stoping methods, without filling, in the mining of large silver-gold orebodies in the Mogollon district, where the ore is hard and wall rocks stand well without timbering and where veins make little water. Vertical and inclined shafts in use with both surface and underground hoisting stations. Storage pockets used on main hoisting levels, with electric signals and telephones for communication. Power is generated by De La Vergne engines having a total sea-level rating of 1540 hp. On account of the remote location of the camp, transportation is an important item of expense, amounting in 1922 to $0.641 per ton of ore milled or $0.265 per ton-mile on all freight hauled. THE Mogollon mining district is in the southwestern part of New Mexico near the southern end of the Mogollon range, from which the district takes its name. The town of Mogollon is but 37 1/2 mi. in an air line northeast of Clifton, Ariz. The air-line distance from Silver City is 52 1/2 mi. and from Tyrone, 57 mi. Supplies are transported by motor truck from Silver City. The distance by road is 75 mi., half of which is an improved highway of modern construction. Transportation has always - been a large item of expense in carrying on operations in the district. Valuable ore is said to have been discovered in the Mogollon Mountains as early as 1870 but the first regular prospecting was carried on in 1875, by James C. Cooney, a sergeant from Fort Bayard. His discovery of rich silver-copper ores in the region of Mineral Creek led to the establishment of the Camp of Cooney. Remote from any settlements where there was a semblance of law and order, and harassed by the Apaches, development was slow and nearly 10 years elapsed before the village of Mogollon was established on Silver Creek. Prospecting in this section of the district had disclosed the outcrops of several promising veins containing silver-gold ores. Among the early claims located were the Last Chance, Top and Confidence, on what has proved to be the most productive vein in the district.

Jan 3, 1924