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By Paul D. Merica, H. Hanemann

The application of other than mechanical methods to the study of the mechanical-physical properties of metals has become in the last few years a topic of investigation of ever-increasing interest, both from the theoretical standpoint and from that of the engineer and constructor. Besides the investigations which have been made of the magnetic properties of ferromagnetic metals, in their relation to the mechanical properties of these metals, which will be discussed more in detail below, there have been made studies of other phenomena in the same relation, and methods for the mechanical testing 'of metals have even been suggested; for example, the microscopic method of Tammann,' and the thermo-electric method of Turnera for determining elastic limits. The application of all such methods, which are based upon the dependence of some physical, crystallographic, or possibly chemical property, upon the mechanical state of the metal, must be preceded by close and careful correlation of these various "test" properties with the known mechanical state of the different metals or materials. It is with this view that the present work, as well as that of many previous investigators of, what may be termed in the interests of brevity, the mechanical-magnetic properties of ferromagnetic materials of construction, has been done. Previous Investigations of Mechanical Magnetic Properties The effect of mechanical stresses and of deformation, elastic or otherwise, oil the magnetic qualities of iron, steel, and other metals, has been studied by a number of investigators from the time of Joule (1841) to the present. It will, however, for the present purpose be sufficient to give an account only of the principal results obtained in the course of these investigations. It was early noticed (Villari, 1865) that if an iron wire is placed in a

Jan 1, 1916

By C. M. Marquardt

Tramp iron and steel moving on a conveyor belt cause small currents to be generated in a coil situated in a strong magnetic field, which are converted to an alternating current and are amplified. The output voltage from the amplifier fires a thyratron with a relay in its anode circuit, which actuates a howler and simultaneously drops a spot of marker material on the belt. THE problem of tramp iron removal from moving ore belts is a long standing one. When heavy ore streams are carried on a belt, magnetic pulleys and strong surface magnets fail to remove tramp buried in the ore stream. Tramp iron buried in the ore stream cannot be pulled from the bed by surface magnets and is carried past the magnetic pulley by the falling ore stream. With the increased use of detachable bits the problem of the detection and removal of tramp has become more necessary and difficult. Several types of tramp detectors have been developed. It would serve no practical purpose here to review exhaustively the literature on the subject. Methods of tramp detection used are: (1) The magnetic method, wherein the small current generated by the magnetized tramp passing a Coil is used. (2) The unbalanced oscillator method wherein the tank circuit of a stable radio- or audio-frequency oscillator is unbalanced causing a change of frequency or a change in plate current due to changes in eddy currents, hysteresis, or dielectric because of the presence of tramp. (3) The bridge methods wherein the impedance of one leg of an alternating current inductive bridge is changed due to the presence of conducting tramp. Each of these methods of tramp detection has its field of usefulness. The second and third methods are excellent for oxide iron ores, coal, sand and gravel, grain, etc. However, these latter methods are not suitable for use on ores that contain rich conducting sulphides, since a large piece of pyrite or galena will cause the same detector response as a piece of tramp iron. At the Caselton, Nevada, plant of the Combined Metals Reduction Co., sulphide ores are treated; therefore, it was necessary that a tramp detector operating on only the magnetic properties of the tramp iron be used. Tramp iron detectors of this type operate on the principle that if a piece of tramp iron moves near a coil in a high intensity, steady magnetic field, the presence of the moving tramp iron causes the magnetic flux lines through the coil to change. This induces a mall current in the Coil. In series with the Coil is generally placed a relay sensitive to currents of 1 to 3 microamp. When the tramp iron passes near the coil the flux linkages change, causing this very sensitive relay to actuate. Since the contacts of such a relay are very small it must actuate a second relay capable of breaking a larger current

Jan 1, 1951

By E. Brunner, E. S. Mardock

A method of measuring oil saturations in cores or sand packs by neutron scattering is described. This method permits local SatUrations to be measured in a core enclosed in a steel pressure vessel without interrupting the flow. calibration data and a saturation distribution measurement obtained with the apparatus are included by way of illustration. Introduction In laboratory flow experiments designed to study the mechanism of oil production it is frequently necessary to measure the oil saturation in a core or sand pack containing Oil, gas, and perhaps brine. It is sometimes desirable that the saturation measurement refer to a relatively small portion of the core, so as to eliminate end effects; that it be made without interrupting the flow, and that it be applicable to a core enclosed in a steel Pressure vessel capable Of withstanding the Pressures encountered in petroleum reservoirs. None of the usual methods of measuring saturation meets all Of these requirements. To measure the gas saturation by observing the apparent compressibility of the gaseous Phase1 would require the interruption of the flow and would give an average saturation for the whole core. An electrical conductivity method is available for measuring brine saturations,2,3 but it is not applicable to oil. A radioactive tracer might be used if a suitable substance could be found that would dissolve in the oil, emit gamma radiation, and not be adsorbed on the sand, the steel core holder, or in an aqueous- phase. The large gamma-ray background from the mass of radioactive oil in other parts of the apparatus might, however, be undesirable. There remain for the saturation measurement methods involving the absorption or scattering of some penetrating radiation produced outside the apparatus. It might be possible to use X-rays or gamma rays; but these radiations would be so much less strongly absorbed and scattered by the oil than by the steel walls of the core holder and by the sand that it seems doubtful that much precision could be attained. In a beam of neutrons, however, there is a radiation that is very penetrating and, moreover, its scattering by substances containing hydrogen, such as oil, is qualitatively different from that occasioned by other materials. It would seem possible, and has proved to be quite practicable, to measure oil saturations accurately under the required conditions by means of neutron scattering. The first, to our knowledge, to suggest neutron scattering as a means of measuring oil saturation were F. Brans and ,. A. Bottema,4 of the Amsterdam laboratories of the Bataafache Petroleum Maatschappij, who made a few preliminary experiments to test the method while they were engaged in exploring the possibilities of neutrons for well-logging purposes. A comprehensive account of neutrons and their behavior will be found, together

Jan 1, 1946

By E. S. Mardock, E. Brunner

A method of measuring oil saturations in cores or sand packs by neutron scattering is described. This method permits local SatUrations to be measured in a core enclosed in a steel pressure vessel without interrupting the flow. calibration data and a saturation distribution measurement obtained with the apparatus are included by way of illustration. Introduction In laboratory flow experiments designed to study the mechanism of oil production it is frequently necessary to measure the oil saturation in a core or sand pack containing Oil, gas, and perhaps brine. It is sometimes desirable that the saturation measurement refer to a relatively small portion of the core, so as to eliminate end effects; that it be made without interrupting the flow, and that it be applicable to a core enclosed in a steel Pressure vessel capable Of withstanding the Pressures encountered in petroleum reservoirs. None of the usual methods of measuring saturation meets all Of these requirements. To measure the gas saturation by observing the apparent compressibility of the gaseous Phase1 would require the interruption of the flow and would give an average saturation for the whole core. An electrical conductivity method is available for measuring brine saturations,2,3 but it is not applicable to oil. A radioactive tracer might be used if a suitable substance could be found that would dissolve in the oil, emit gamma radiation, and not be adsorbed on the sand, the steel core holder, or in an aqueous- phase. The large gamma-ray background from the mass of radioactive oil in other parts of the apparatus might, however, be undesirable. There remain for the saturation measurement methods involving the absorption or scattering of some penetrating radiation produced outside the apparatus. It might be possible to use X-rays or gamma rays; but these radiations would be so much less strongly absorbed and scattered by the oil than by the steel walls of the core holder and by the sand that it seems doubtful that much precision could be attained. In a beam of neutrons, however, there is a radiation that is very penetrating and, moreover, its scattering by substances containing hydrogen, such as oil, is qualitatively different from that occasioned by other materials. It would seem possible, and has proved to be quite practicable, to measure oil saturations accurately under the required conditions by means of neutron scattering. The first, to our knowledge, to suggest neutron scattering as a means of measuring oil saturation were F. Brans and ,. A. Bottema,4 of the Amsterdam laboratories of the Bataafache Petroleum Maatschappij, who made a few preliminary experiments to test the method while they were engaged in exploring the possibilities of neutrons for well-logging purposes. A comprehensive account of neutrons and their behavior will be found, together

Jan 1, 1946

By C. M. Marquardt

Tramp iron and steel moving on a conveyor belt cause small currents to be generated in a coil situated in a strong magnetic field, which are converted to an alternating current and are amplified. The output voltage from the amplifier fires a thyratron with a relay in its anode circuit, which actuates a howler and simultaneously drops a spot of marker material on the belt. THE problem of tramp iron removal from moving ore belts is a long standing one. When heavy ore streams are carried on a belt, magnetic pulleys and strong surface magnets fail to remove tramp buried in the ore stream. Tramp iron buried in the ore stream cannot be pulled from the bed by surface magnets and is carried past the magnetic pulley by the falling ore stream. With the increased use of detachable bits the problem of the detection and removal of tramp has become more necessary and difficult. Several types of tramp detectors have been developed. It would serve no practical purpose here to review exhaustively the literature on the subject. Methods of tramp detection used are: (1) The magnetic method, wherein the small current generated by the magnetized tramp passing a Coil is used. (2) The unbalanced oscillator method wherein the tank circuit of a stable radio- or audio-frequency oscillator is unbalanced causing a change of frequency or a change in plate current due to changes in eddy currents, hysteresis, or dielectric because of the presence of tramp. (3) The bridge methods wherein the impedance of one leg of an alternating current inductive bridge is changed due to the presence of conducting tramp. Each of these methods of tramp detection has its field of usefulness. The second and third methods are excellent for oxide iron ores, coal, sand and gravel, grain, etc. However, these latter methods are not suitable for use on ores that contain rich conducting sulphides, since a large piece of pyrite or galena will cause the same detector response as a piece of tramp iron. At the Caselton, Nevada, plant of the Combined Metals Reduction Co., sulphide ores are treated; therefore, it was necessary that a tramp detector operating on only the magnetic properties of the tramp iron be used. Tramp iron detectors of this type operate on the principle that if a piece of tramp iron moves near a coil in a high intensity, steady magnetic field, the presence of the moving tramp iron causes the magnetic flux lines through the coil to change. This induces a mall current in the Coil. In series with the Coil is generally placed a relay sensitive to currents of 1 to 3 microamp. When the tramp iron passes near the coil the flux linkages change, causing this very sensitive relay to actuate. Since the contacts of such a relay are very small it must actuate a second relay capable of breaking a larger current

Jan 1, 1951

By George H. Ashley

The present critical state of the supply, distribution, and utilization of coal and the necessity for pooling and zoning coals calls renewed attention to the lack of any fully adequate classification of coal. In the past coals have been classified as anthracite, semianthracite, semibitumi-nous, bituminous, subbituminous coals, and lignite, and a few special types, such as splint coal and cannel coal. But under the term bituminous coal are included a great variety of coals differing markedly both physically and chemically. The term subbituminous coal covers as great a range of chemical differences. In order to distinguish these varieties of bituminous coals it has been customary to designate coal by names derived from the place where mined, or by the name of the bed from which it is mined. Thus, in the market reports, coals are quoted as Pocahontas coal, New River or Sewell coal, Moshannon coal, Ohio coal, Williamson County coal, Jellico coal, and so on indefinitely, no limit being set as to the boundaries of the area to which a given name is applied. Nor is there any scale by which the coal from one place may be compared with the coal from some other district or some other bed. On the one hand, coals from the same district may be quite distinct and sell at very different prices or coal from the same bed may differ greatly in different districts; on the other hand, coals from different states may be so similar physically and chemically that one could replace the other in practical use without any appreciable difference in service. The following classification, arrived at after a careful review of a large number of systems of classification and of all of the recognized characteristics of coal, brings together all coals that so nearly resemble each other physically, chemically, and in heating qualities that any coal of a given type could replace any other coal of the same type and grade in use. Thus, if coals A and B are classed as of the same type and grade they have, so far as known to the writer, approximately the same heating value when burned under the same conditions, and the same character, length of flame, and properties affecting transportation and stocking; and if of the same grade, approximately the same percentage of impurities.

Jan 1, 1920

By F. E. Brackett

THE simplicity of the propeller or disk fan, its small size and low cost, has, in recent years, led to an extended use of ventilators of this type at mines where only slight pressure is required. On this account the author of this paper has prepared for the new edition of Peele's Mining Engineers' Handbook a more accurate method of computing the required size, power, and so forth, than was possible for the first edition. The main object of this paper is to set forth the data collected in the course of that work, and to discuss the subject with more latitude than would have been advisable in a handbook, even if space had been available. Theory of Fans A great deal has been written about the theory of fans from Rankine's time down to the present. Nevertheless a rigid mathematical analysis of the propeller fan seems to be wanting. A general idea of the mechanics and difficulties in the way of analysis may be gathered from the following: The useful pressure and velocity effects of the oblique impact of the vanes on the axial current would evidently be nil if the blades were perpendicular to the plane of rotation, or if they were of such helicoidal form that the screw pitch multiplied by the speed represented an axial velocity agreeing with the actual velocity. Somewhere between these zero angles there is a pitch which, under given conditions of flow, would produce the maximum useful effect. A true helicoidal blade can be so arranged that it would offer no retarding effect on the air current at any part of the wheel, provided the axial velocity be assumed the same in all parts of the cross-section of the air course, but if plane surfaces are used, it is possible, under some conditions, that the air would be retarded at the middle parts of the wheel while it was accelerated at the circumference. Whatever be the form of vane, it seems evident that the tips are far more effective than the center of the wheel, because of their higher velocity. For this reason some investigators believe that a backward current forms through the middle of the wheel and that part of the air is circulated in a radial axial loop. Ignoring the possible existence of this eddy and the friction of the walls of the air course; and assuming the axial velocity of the air through all parts of the wheel, some rational analysis of the impact might be made according to the theory of deflecting surfaces, were it not

Jan 1, 1928

By C. O. Bundranl, Peter Dehlinger, W. H. Browne

Brief laboratory investigations are described which attempt to determine optimum .sand concentrations in gel-sand and oil-sand1 well-treatments. The investigations apply to the case where sand acts as a propping agent in formation fractures. Both analytically and experimentally it is demonstrated that optimum sand concentrations can be defined. It is difficult to translate laboratory results to field treatments, however, since the relative distribution of sand and fluid in fractures may not be the same as injected. This is because fluid may penetrate the furtherest narrow portions of fractures, which would not pass sand. Optimum concentration of a monolayer of Ottawa sand in fractures of 0.025-in. width at the usual range of pressures encountered in treatments appears to be about 95 to 2 lb/gal. of gel. An investigation of abrasion of rock-walls by sand in treatments, described in the Appendix, shows that such abrasion is not probable in significant amounts. INTRODUCTION Experience in the Spraberry formation of West Texas, as well as in other formations, has shown that. sand is a necessary and vital part of gel-sand and oil-sand treatments. Many observers of treatments have also concluded that there seems to be an optimum range of sand concentration for these injections. Brief laboratory investigations were made at Battelle Memorial Institute to study flow in fractures with different sand concen- trations. To investigate the existence and range of optimum concentrations in the laboratory, however, necessitates knowledge of the mechanism by which the sand aids in increasing subsequent production. The action of sand in fractures is usually thought to be either that of a propping agent, thus providing a greater effective formation permeability; that of an abrasive in eroding fill material in fractures; or that of an abrasive eroding rock-wall irregularities along fracture surfaces. Investigations described in the Appendix show that sand does not appear to erode rock-wall materials appreciably. In a subsequent paper it is reasoned, at least for the Spraberry formation of West Texas, that the primary action of sand is not in removing fill materials in fractures. In this formation, and probably others, too, the main effect of sand appears to be that of a propping agent. Both analytical and experimental investigations were made for the case of a monolayer of sand acting as a propper, in which sand concentrations were determined that would, after treatment, permit flow of the maximum quantities of oil from the formation into a well. If too few sand grains are injected into fractures in which the bottom hole pressure has decreased appreciably below the original formation pressure, the confining pressure in the formation may become relatively large, thus compress the rock-walls around the sand grains, essentially close fractures, and so decrease the subsequent flow of oil. Similarly, if too much sand is used, the flow of oil will he impeded by the volume of sand present. THEORY Although an analytical approach to determining optimum sand concentrations involves gross assumptions.

Jan 1, 1955

By C. A. Hope, H. B. Wishart

THE number and severity of surface imperfections on rolled slabs, assuming the reception of uniformly good quality heats from the open hearths, depend upon a number of conditions associated with heating and rolling of steel in the primary mills. While there are other elements that have an effect on surface quality, rather than make this paper too lengthy the discussion of mill processing variables will be limited to three factors in order to illustrate their effect on slab surface quality: 1—amount of reduction between ingot and slab, 2—slab finishing temperatures, and 3—influence of roll changes. Measurement of the percentage of surface removed by scarfing on the flat surfaces of the slabs was used for evaluating quality in this study. A study of this nature must be made on slabs that are inspected and conditioned under uniform conditions and standards. In order to be certain that steel of the best possible steelmaking quality was received at the rolling mills, a low carbon deep drawing grade of rimmed steel, made for sheet mill application and manufactured under carefully controlled open hearth practices, was selected. Use of this particular steel thereby reduced the steel quality factor as a possible source of variation. The measure of slab surface quality is the amount of surface removed by scarfing during yard conditioning and is expressed as percentage of surface removal. This percentage was estimated by experienced personnel to uniform standards and it should be noted that these percentage figures are representative only for the grade selected and under the rigid inspection standards to which the slabs were subjected. Surface removal is a matter of concern because the imperfections, if undetected, often are the cause of poor surface quality in the finished product and their removal, by conditioning, add to the total plant costs. The data was collected at various times over a period of six months and, with normal weekly fluctuation in the level of quality, it is to be expected that for any period of sampling there will be some variation in the plotted results. The type of defect that is responsible for most slab conditioning at Gary Steel Works is a light angular surface break. This defect is usually interconnected to form large defective areas and occurs mainly on the bottom half of the slab on both sides. This type of defect is illustrated in Fig. 1, showing a bottom portion of a slab; while a close-up of an area of the same slab where the surface breaks were found is given in Fig. 2. The large dark areas are heat patterns, results of hot stacking and cooling. Independent of these light breaks, but sometimes associated with them, are larger and deeper isolated breaks. However, most of the surface removal occurs from conditioning the large areas of small breaks. There are also occasional scabs of varying degrees of severity but these are relatively infrequent. The slabs are generally free of rolled-in scale. Ingot to Slab Reduction vs Quality Some ten years ago at Gary Steel Works, the minimum slab ingot thickness was 30 in. Subsequent operating and other quality features indicated the desirability of using an ingot of reduced thickness with the result that a series of molds that would produce a 22 in. thick ingot with various widths was adopted as standard. A minimum number of the thicker mold sets are still used. From the standpoint of quality difficulties from pipe and segregation, the smaller ingots are an improvement. From a quality surface viewpoint, the slab product from the thin molds requires approximately twice the surface removal as the slab product from the thick molds. This is shown in Fig. 3 where the percentage of surface removal is plotted against slab product rolled from

Jan 1, 1956

By Paul J. Bennett, James E. Castle

The kyanite minerals, including kyanite, silimanite, and andalusite, are anhydrous aluminum silicates with the formula Al2O3SiO2. lumortierite and topaz are also included in this group because they are closely allied in composition and thermal behavior. However, leither are mined commercially today. They ire typical metamorphic minerals which are found in metamorphic rocks on every continent. Kyanite minerals are prized chiefly for their refractoriness and are important components in a broad range of acid refractory products, especially in mortars and castables. World production of kyanite minerals is currently about 250,000 tpy and has been increasing at the rate of 3 to 8% a year for many {ears (Anon, 1972). While kyanite minerals lave widespread occurrence, the consumption of kyanite minerals is concentrated in the relatively few highly industrialized areas where refractories are manufactured, and which in turn are typically close to the major iron and steel producing regions of the world. Thus northern Europe, England, the United States, and Japan are the principal consumers of refractories and kyanite minerals. Of these countries only the U.S. is a significant producer. The largest use for domestic kyanite, both raw and calcined, is in the manufacture of refractory mortars, cements, castables, and plastic ramming mixes. In these applications kyanite constitutes from 10 to 40% of the mixture, the balance being refractory clays and coarser grog materials. A certain proportion of raw kyanite is used to offset the shrinking of the clay binder, whereas the calcined kyanite is used in the coarser sizes for body. Certain high grade refractory shapes and kiln furniture are composed chiefly of graded sizes of calcined kyanite bonded with a little ball clay. In most applications, however, kyanite is used only to fortify the mix or as a minor ingredient. Some manufacturers of mullite brick use domestic calcined kyanite for the fine-grained portion of the brick, but seldom in quantities exceeding 10% by weight. Kyanite is used by ceramic manufacturers of wall tile and sanitary ware to offset shrinkage and cracking after firing. Indian kyanite has traditionally been used to make the coarse grog sizes needed for the manufacture of mullite brick, and for the grog portions of mortar, cement, and castable mixes. It has been largely replaced, however, by synthetic mullite, high fired flint, and diaspore clay or calcined bauxite for other applications. Indian kyanite is available in lump as well as in granules and concentrates, as are sillimanite materials from India and South Africa. Andalusite is available as 8 mesh granules and as fines with chemical analyses not unlike those of domestic kyanites. From time to time and from place to place minor amounts of other aluminum silicate minerals such as dumortier- ite, topaz, and pyrophyllite have been made available at various prices and specifications, but have not been significant factors in the refractory industry. A mixture of kyanite and sillimanite of relatively fine grain-size and of low iron content was at one time offered to the molding sand industry by the Du Pont Co. as a byproduct from their deposits of heavy

Jan 1, 1975

By W. C. Krumbein

GEOLOGICAL problems are approached from a geometrical (space relations) viewpoint, a kinematical (time sequence) viewpoint, or a dynamical viewpoint. The first two require sound training in conventional geology and in field methods. The third approach requires a solid foundation of chemistry, physics, and mathematics. Modern training for geologists should include close integration of basic sciences with geological principles. INTRODUCTION Our knowledge of the earth has increased tremendously during the last half century. We know more about its surface configuration, the distribution of its natural resources, the procession of living forms that inhabited it in the past, the chemical composition of its oceans, the areal distribution of its surface rocks, the movements of its atmosphere, and so on. Not only do we know more facts about the earth, but we have a better understanding of the processes that take place on and within it, such as the nature of earthquakes, the thermodynamics of the atmosphere, the chemical equilibria involved in the formation of igneous rocks, the mechanics of stream flow, the dynamics of the earth's origin, and so on. Many sciences contributed to the sum total of this knowledge, including such established disciplines as geology, geography, physics, chemistry, astronomy, biology. Out of this accumulation of new knowledge grew also a group of new sciences, such as seismology, oceanography, meteorology, volcanology, hydrology. Collectively these latter are known as the geophysical and geochemical sciences, and to a large extent they began as branches of geology. Until the turn of the century, for example, the study of earthquakes (seismology) was a part of geology, although as early as 1846 Mallet, a physicist, had suggested that the subject could be investigated by elastic-wave theory. Comparatively little progress was made along these lines until the seismograph was developed near the turn of the century; since then, additional earthquake data have accumulated rapidly, but more important, the interpretation of these data essentially has kept pace with their accumulation. In similar fashion, meteorology, was generally considered a branch of geology as recently as one or two decades ago. Considerable progress had been made in such aspects as weather forecasting, but the science dates its recent rapid rise from the year 1911, when Bjerknes first applied the principles of dynamics to the analysis of air masses. The rapid development of such disciplines as oceanography, volcanology and hydrology was due in part to the application of principles of chemical equilibrium, of dynamics, and of thermodynamics to earth problems, by men who were essentially physicists or chemists by training. The last half century, therefore, and particularly the last two decades, saw the influx of numerous chemists and physicists into the realm of the earth sciences. In the meantime the main body of geology itself showed a marked growth, and

Jan 1, 1941

By R. W. D. Clarke, J. C. Folinsbee

INTRODUCTION This paper deals with a procedure for planning the mining of an orebody for which cross-sections, plans, grade of ore, and a geological estimate of the ore reserve have been prepared. The procedure begins with the preliminary selection of a mining method or methods on which an engineering evaluation will be carried out. The engineering evaluation is described in three parts: Conceptual Studies Engineering Studies Detailed Design An overall planning model is presented, plus an expanded model for the Engineering Study Throughout the discussion of the planning procedure, reference is made to three bulk mining methods, including block caving, sublevel caving, and longhole sublevel stoping, including a summary of the main characteristics of each of these mining methods. The planning model is designed for a longhole sublevel stoping method, but with modification, will apply to other methods. PRELIMINARY SELECTION OF A MINING METHOD To experienced mining engineers, identification of the nominal mining method for a given orebody normally involves a large measure of judgement. The geological data is reviewed to determine the configuration of the orebody, including size, shape, dip, grade, and metal distribution. Geotechnical data is considered, including the competence of the ore and host rock, faults, fracture patterns, groundwater, and the potential for in situ stresses. Geographical data, including the natural and societal conditions, are evaluated for their effect upon the mining method, and finally, economic data, basically defined as the value of the ore in the ground, but more specifically, including grade of mineable ore, distribution of ore grade throughout the orebody, and metallurgical recovery, will have a bearing on the nominal method selected. Preliminary evaluation of these factors will result in the elimination of the obviously inappropriate mining methods, leaving some method or methods for further, more detailed study. Since ore does not occur in simple geometric shapes, the method selected for more detailed study will require some variation to the standard. A few key factors will bear heavily on the selection and provide a basis for the most realistic choice. Geological Data The configuration of an orebody defined by the horizontal and vertical dimensions, the dip and strike, and the possibility of repetitive occurrences will have the major influence on the selection of the mining method. For bulk mining methods, the dip of the orebody should be steep, or the orebody must be thick so that gravity can be utilized to deliver fragmented ore to a central gathering area. Geotechnical Data The geotechnical data will be studied in greater detail when the nominal mining method has been selected and the engineering evaluation is undertaken. However, some basic initial information must be available. The structural strength of the ore and host rock, including the effect on it of faulting, fracturing, and insitu stresses, must be known. Data from exploration drilling and examination of drill core will assist in the preliminary assessment of these factors. Highly fractured ground may suggest a caving method of mining for certain orebody configurations, whereas highly competent or strong ore might indicate that for a similar configuration, longhole sublevel stoping will more likely succeed. Data obtained on groundwater from exploration drilling will be considered to determine if it can be controlled, or if it will represent a long term major expense or a hazard for which no control is possible.

Jan 1, 1981

By Randolph C. Specht

A two year study was made of the waste disposal of the pebble rock phosphate industry. Solid slimes are impounded in large settling areas and the process water is re-used. Clear effluent was not found to be toxic to fish or animal life in field tests or in controlled experiments. Survey: The pebble rock phosphate mining and washing operations in Florida (fig. 1) are along the river basins of the Alafia to the west and the Peace to the east. The elevation of the area varies between 40 and 170 ft above sea level. Effluents from the operations find their way into one of the two river systems (fig. 2), the Peace River which flows into Charlotte Harbor and the Alafia into Tampa Bay, both along the Gulf of Mexico. There are no major industries along these rivers below the phosphate operations. On the Peace River, the town of Arcadia, approximately 50 miles below the phosphate operations, obtains its water from the river. No other communities along the rivers use them as a source of water supply. Small communities, farms, and ranches are located along the rivers and both rivers drain vast swamp areas. Complaints had been received at the office of the Chief Sanitary Engineer, of the Florida State Board of Health,' that both rivers were turbid at various times and that fishing in the Alafia River was "not as good as it used to be." Tests made by another agency on the dissolved oxygen content of the Alafia River revealed that the oxygen content, at times, was comparatively low.= However, it was not shown that the phosphate wastes had any effect upon the oxygen content of the stream. The river waters are normally brown in color due to drainage from vast swamp areas and are very shallow, from 2 to 6 ft in depth. Turbid waters have been noted in streams coming from the present phosphate operations and also from streams along which there are no operations at the present time. It was learned from "old timers" that, when many more companies than at present were operating along both the Alafia and Peace Rivers forty or fifty years ago, no attention was paid to prohibiting the disposal of slimes along the river basins. During dry periods now in some of the river swamps where drainage ditches have been dug, it is indicated clearly that phosphate slimes were disposed of directly into the river swamps for many years past. Places have been observed where there were alternating strata of phosphate mud, leaf mold, and quartz sand. The former practice of indiscriminate disposal of wastes accounts for some turbidity, particularly after heavy rains and washouts and during clearing of land and digging of drainage ditches. During a six months' period in which a large tract of land was being cleared and drainage ditches dug, a small stream (Six Mile Creek), which previously had been clear, showed a turbidity of 600 ppm and remained turbid until the clearing was completed; after which the stream again flowed clear. An interview with the operator of the municipal water plant, which is about 50 miles below the phosphate operations on the Peace River and which used this river as a source of supply, revealed that there had been no taste in the water for the past ten years, other than that occasionally encountered from increased growth of algae. The operations of each of the cooperating com-

Jan 1, 1951

By Charles R. Holmes

MORE than 70 igneous pipes and dikes are known to occur in Cambrian sediments throughout an approximately circular area of about 75 sq miles in southwestern Ste. Genevieve County and southeastern St. Francois County, Mo., across the southern portion of the Farmington anticline, which is outlined in fig. 1. From evidence obtained from fossil fragments taken from some of the in-trusive~, and from the similarity in composition of the more basic intrusives to those of known age in surrounding states, these pipes and dikes are believed to be at least post-Devonian and probably Cretaceous in age. As first postulated by Rust,' these intrusives are believed to represent explosion tubes, or diatremes, punched through great thicknesses of solid rock by gaseous pressure. The particular intrusive studied is located about 1 mile north of the small town of Avon at an elevation of 880 ft in the EVz SEy4 NEY4 of see. 2, T. 35N, R. 7E. Outcrop is through the Bonneterre dolomite in two separated exposures. The larger outcrop extends east and west for about 50 ft along a tributary in a small ravine (fig. 2). The smaller exposure occurs as a few scattered patches over an area 20 ft square about 100 ft to the north. The area between the exposures is covered, but scattered patches of the Bonneterre dolomite outcrop throughout the area surrounding the diatreme. Where exposed, contact relations show the surrounding dolomite to be shattered and metamorphosed to a fine-grained rock for a distance of 15 to 20 ft from the intrusive. The igneous rock occurs as a dark greenish-gray porphyry near the center of the diatreme and as a fine-grained, greenish-gray material containing lapilli and metamorphosed fragments of dolomite near the contact with the country rock. The most abundant original mineral of the porphyritic rock is olivine now largely serpentinized as the result of extensive hydrothermal alteration at time of emplacement. The most common constituent of the fine-grained rock, which occurs near the border of the intrusive, is calcite. Mica is a common constituent of both types of rock, occurring as tufts or flakes. Magnetite makes up about 2 pct of the diatreme and occurs as small irregular grains or streaks of tiny grains. Singewald and Milton' have termed the rock of this body an "augite-free alnoite." Susceptibility measurements of pulverized specimens were made from selected samples taken from both the diatreme and the surrounding country rock. The susceptibility of the Bonneterre dolomite was found to be less than 40xlO-6 cgs (centimeter-gram-second) units and that of the metamorphosed contact dolomite less than 200x10-6 cgs. Measurements of individual samples of the igneous rock showed a wide variation in susceptibility between limits of 1000x10-6 cgs to 8000x10-6 cgs, with the maximum difference occuring in samples taken only a few feet apart. The maximum value was exhibited by a highly weathered sample taken from the northern outcrop, while minimum susceptibility was determined from a partially weathered sample taken only a few feet away. These extremes are believed to represent small local concentrations of stringers and grains of magnetite crystals in the igneous rock. A detailed magnetic survey of the horizontal and vertical components of the earth's magnetic field was made over the diatreme area. Stations were occupied at 20-ft intervals as shown by the grid on fig. 2. When greater detail was desired, intervening stations were also occupied. The field instruments were supplied by the Department of Geophysics, St. Louis University. The magnetometers are the Schmidt balance type constructed by the Ruska Instrument Co. These instruments are temperature compensated and have a standard sensitivity of 10 gamma. Calibration of the instruments

Jan 1, 1951

By Charles R. Holmes

MORE than 70 igneous pipes and dikes are known to occur in Cambrian sediments throughout an approximately circular area of about 75 sq miles in southwestern Ste. Genevieve County and southeastern St. Francois County, Mo., across the southern portion of the Farmington anticline, which is outlined in fig. 1. From evidence obtained from fossil fragments taken from some of the in-trusive~, and from the similarity in composition of the more basic intrusives to those of known age in surrounding states, these pipes and dikes are believed to be at least post-Devonian and probably Cretaceous in age. As first postulated by Rust,' these intrusives are believed to represent explosion tubes, or diatremes, punched through great thicknesses of solid rock by gaseous pressure. The particular intrusive studied is located about 1 mile north of the small town of Avon at an elevation of 880 ft in the EVz SEy4 NEY4 of see. 2, T. 35N, R. 7E. Outcrop is through the Bonneterre dolomite in two separated exposures. The larger outcrop extends east and west for about 50 ft along a tributary in a small ravine (fig. 2). The smaller exposure occurs as a few scattered patches over an area 20 ft square about 100 ft to the north. The area between the exposures is covered, but scattered patches of the Bonneterre dolomite outcrop throughout the area surrounding the diatreme. Where exposed, contact relations show the surrounding dolomite to be shattered and metamorphosed to a fine-grained rock for a distance of 15 to 20 ft from the intrusive. The igneous rock occurs as a dark greenish-gray porphyry near the center of the diatreme and as a fine-grained, greenish-gray material containing lapilli and metamorphosed fragments of dolomite near the contact with the country rock. The most abundant original mineral of the porphyritic rock is olivine now largely serpentinized as the result of extensive hydrothermal alteration at time of emplacement. The most common constituent of the fine-grained rock, which occurs near the border of the intrusive, is calcite. Mica is a common constituent of both types of rock, occurring as tufts or flakes. Magnetite makes up about 2 pct of the diatreme and occurs as small irregular grains or streaks of tiny grains. Singewald and Milton' have termed the rock of this body an "augite-free alnoite." Susceptibility measurements of pulverized specimens were made from selected samples taken from both the diatreme and the surrounding country rock. The susceptibility of the Bonneterre dolomite was found to be less than 40xlO-6 cgs (centimeter-gram-second) units and that of the metamorphosed contact dolomite less than 200x10-6 cgs. Measurements of individual samples of the igneous rock showed a wide variation in susceptibility between limits of 1000x10-6 cgs to 8000x10-6 cgs, with the maximum difference occuring in samples taken only a few feet apart. The maximum value was exhibited by a highly weathered sample taken from the northern outcrop, while minimum susceptibility was determined from a partially weathered sample taken only a few feet away. These extremes are believed to represent small local concentrations of stringers and grains of magnetite crystals in the igneous rock. A detailed magnetic survey of the horizontal and vertical components of the earth's magnetic field was made over the diatreme area. Stations were occupied at 20-ft intervals as shown by the grid on fig. 2. When greater detail was desired, intervening stations were also occupied. The field instruments were supplied by the Department of Geophysics, St. Louis University. The magnetometers are the Schmidt balance type constructed by the Ruska Instrument Co. These instruments are temperature compensated and have a standard sensitivity of 10 gamma. Calibration of the instruments

Jan 1, 1951

By J. Marin, H. A. B. Wiseman

This paper presents results of an experimental study dealing with the plastic stress-strain relations of aluminum alloy 14s-T6 subjected to combined biaxial tension and compression stresses. Plastic stress-strain relations for both constant and various types of variable stress ratios were determined and a comparison made with the simple flow theory of plasticity. THIS investigation was undertaken for two main purposes: 1—to obtain plastic stress-strain relations for Alcoa 14s-T6 when subjected to various combinations of biaxial stresses, and 2—to determine the validity of the flow theory in predicting plastic stress-strain relations for combined stresses. The biaxial stresses used were tension combined with compression. These stresses were produced by subjecting a thin-walled tube to axial tension and torsion. Various types of combined stress conditions were investigated. To provide control test data and information on the influence of biaxial stresses on the strength, the usual constant stress ratio type tests were made. These tests showed that the biaxial yield strength agrees approximately with the distortion energy theory. However, the Prager semi-empirical theory agrees best with the test results. For these constant stress ratio tests the plastic stress-strain relations were found to agree approximately with the flow theory. (For constant stress ratio the flow and deformation type theories are identical.) In view of the fact that the constant stress ratio tests cannot distinguish between the flow and deformation theories, a number of variable and special biaxial stress tests were made. These tests showed that the flow theory is inadequate, since large differences exist between the experimental and theoretical results. Special tests were also conducted to check the validity of the isotropic yielding assumption. This assumption is made in the linear-type flow theory. In these tests specimens were loaded in tension to predetermined values beyond the proportional limit stress. The tension load was removed from the specimen and the specimen was subsequently loaded in torsion to fracture. Other tests were applied with the order of torque and tension loading reversed. The nominal stress-strain curves for these two tests approximately coincide indicating that the assumption of isotropic yielding is valid. In addition, these tests verified the requirement by the slip theory of plasticity that prestraining below 140 pct of the proportioned limit stress in either torsion or tension did not influence the subsequent plastic stress-strain relations in tension or torsion. Another type of test was conducted to check the assumption that the axes of principal stress and strain coincide during plastic flow and variable stress conditions. These tests were conducted by applying combinations of axial tension, internal pressure, and torsional loads such that the axes of maximum principal stress could be rotated through 90" during the loading path. The results of those tests showed that the angle between the axes of principal stress and strain varied greatly and that the assumption of coincidence between axes of principal stress and strain is not valid. Introduction In various metal processes including forming of sheets, rolling of bars, and extrusion of rods, metals are subjected to stresses beyond the yield strength of the material. Often these stresses are not simple stresses acting in one direction, but are combined stresses acting in more than one direction. Structural and machine members are often subjected to combined stresses. To adequately determine the factors of safety for these members, it is necessary to know the plastic stress-strain relations of the material used for various combined stress conditions. Various theories have been proposed for predicting the plastic stress-strain relations for combined stress in terms of the simple tension plastic stress-strain relation for the material. To determine which theory might be adequate, test results must be obtained for various combined stress conditions, in order to compare the actual with the assumed theoretical behavior. Although there is considerable test data available for combined stress conditions in which the principal stress ratios are constant, relatively little test information is available for vari-

Jan 1, 1954

By Randolph C. Specht

A two year study was made of the waste disposal of the pebble rock phosphate industry. Solid slimes are impounded in large settling areas and the process water is re-used. Clear effluent was not found to be toxic to fish or animal life in field tests or in controlled experiments. Survey: The pebble rock phosphate mining and washing operations in Florida (fig. 1) are along the river basins of the Alafia to the west and the Peace to the east. The elevation of the area varies between 40 and 170 ft above sea level. Effluents from the operations find their way into one of the two river systems (fig. 2), the Peace River which flows into Charlotte Harbor and the Alafia into Tampa Bay, both along the Gulf of Mexico. There are no major industries along these rivers below the phosphate operations. On the Peace River, the town of Arcadia, approximately 50 miles below the phosphate operations, obtains its water from the river. No other communities along the rivers use them as a source of water supply. Small communities, farms, and ranches are located along the rivers and both rivers drain vast swamp areas. Complaints had been received at the office of the Chief Sanitary Engineer, of the Florida State Board of Health,' that both rivers were turbid at various times and that fishing in the Alafia River was "not as good as it used to be." Tests made by another agency on the dissolved oxygen content of the Alafia River revealed that the oxygen content, at times, was comparatively low.= However, it was not shown that the phosphate wastes had any effect upon the oxygen content of the stream. The river waters are normally brown in color due to drainage from vast swamp areas and are very shallow, from 2 to 6 ft in depth. Turbid waters have been noted in streams coming from the present phosphate operations and also from streams along which there are no operations at the present time. It was learned from "old timers" that, when many more companies than at present were operating along both the Alafia and Peace Rivers forty or fifty years ago, no attention was paid to prohibiting the disposal of slimes along the river basins. During dry periods now in some of the river swamps where drainage ditches have been dug, it is indicated clearly that phosphate slimes were disposed of directly into the river swamps for many years past. Places have been observed where there were alternating strata of phosphate mud, leaf mold, and quartz sand. The former practice of indiscriminate disposal of wastes accounts for some turbidity, particularly after heavy rains and washouts and during clearing of land and digging of drainage ditches. During a six months' period in which a large tract of land was being cleared and drainage ditches dug, a small stream (Six Mile Creek), which previously had been clear, showed a turbidity of 600 ppm and remained turbid until the clearing was completed; after which the stream again flowed clear. An interview with the operator of the municipal water plant, which is about 50 miles below the phosphate operations on the Peace River and which used this river as a source of supply, revealed that there had been no taste in the water for the past ten years, other than that occasionally encountered from increased growth of algae. The operations of each of the cooperating com-

Jan 1, 1951

By Elmer Weber, W. M. Baldwin

Solid lead obeys a single parabolic weight increase vs. time law. In contrast, liquid lead undergoes three successive parabolic weight increases vs. time laws, the first of which has a low constant relative to the latter two. The conversion times for the change from one parabola to the next decrease with increasing temperature. IN recent reports on the subject,1,2 it was noted that zirconium and titanium scale in air by a complex mechanism. The scale first forming on the metal is protective to the extent that it gives a low constant, K, for Tammann's, and Pilling and Bedworth's parabolic equation: w² = Kt [1] relating weight increase, w, due to chemical reaction of the metal with the air, and time, t. After hundreds of hours of apparent stability in some cases the first scale yields to another that offers little protection to the metal. This transition from one scale to another, from a slow parabolic oxidation reaction to a fast one, was not due to impurities in the atmosphere or incidental effects (changing environment, etc.) but was a specific behavior of the metal itself, the transition occurring at definite times (dependent on temperature) and showing other reproducible traits. In view of this behavior how can long-time service behavior be predicted from short-time laboratory tests, not only in the case of these metals, but in any case? Certainly a systematic study of the type of scaling behavior described above—wherever it is found—would help to answer this question. The present paper is a report on the behavior as it is found in lead—the only metal to the authors' knowledge for which the behavior has been described at all, if inadequately, for our present purpose.* At least four oxides of lead are known, of which one occurs in two allotropic forms. They are ß (red) tetragonal PbO stable up to 486°C;8 a (yellow) orthorhombic PbO stable from 486°C up to its dissociation temperature in air at about 2300°C;9 minium or Pb3O4 which from the dissociation pressure data given in Fig. 1 decomposes to PbO at 540°C in air; lead sesquioxide or Pb2O3,; and lead dioxide or PbO2 which, according to Fig. 1, decomposes in air at 400°C to minium. In view of the high dissociation temperature of PbO, lead will scale up to at least its boiling point. Further, it is known that oxygen is almost insoluble in liquid lead.'V his implies a fair probability that an oxide scale would not dissolve in the molten metal and would afford the same protection to lead in the liquid state as in the solid. All of the oxides of lead for which specific gravity data are available are more voluminous than an equivalent weight of metal or a lower oxide from which they might form, hence the scales will be in compression. Lead oxides are known to be ductile, so it would be anticipated that they would form coherent nonporous scales. It is not surprising to learn, then, that both solid and liquid lead scale according to the Tammann, and Pilling and Bed-worth law.14,15 (Gruhl states that at 600°C and above lead oxidizes linearly with time because of "spitting" of the scale.) The parabolic constants K reported by various investigators3,14-16 are badly scattered, however, as shown in Fig. 2. The oxides formed on solid lead were described as being reddish-brown but were not chemically identified by Pilling and Bedworth.15 Gruhl's descripdin³ of the appearance of the scales On his liquid samples indicates that a (yellow orthorhombic) PbO is formed initially on the specimens but gives Way eventually—at least at temperatures below 486 °C— to .ß (red tetraunal) PbO, and that below 540°C minium—Pb3O4 :is firmed at an even later time as an overlay on either the red or yellow PbO. Fig. 3 is a graphical interpretation of Gruhl's description. Gruhl does not indicate any change in the parabolic scaling rate as yellow PbO converts to red. He does indicate that minium reduces the scaling rate, al-

Jan 1, 1953

By Wm. R. Dotson

Forty years ago the atom was split and the Age of Fission dawned. Uranium was the element used in this earth-shaking accomplishment. Thitherto almost unknown to the man in the street, uranium soon became widely and persistently sought. And the quest for this unique material is not likely to diminish during this century. To find is one thing; to own is another. Who owns uranium in the ground? Where no mineral rights in the land have been severed by devise, grant, reservation or lease, the uranium belongs to the fee simple owner of the land. But where there has been a conveyance or reservation of all or part of the "minerals", determining WHAT a substance is has been the traditional way of determining WHO owns it. What, then, is this element called uranium? The 1907 edition of Watts Dictionary of Chemistry calls it "a lustrous, hard, silver-white metal". Of nature's three prime divisions it falls within the embrace of the mineral kingdom - substances neither animal nor vegetable. In its natural state uranium always is combined with other elements or substances in the form of an ore mineral. May we, then, put to rest any doubt or question as to the nature of uranium and classify it for all purposes, including that of ownership, as mineral? Not quite! That self-same logic would find oil and gas primly ensconced in the animal or vegetable kingdom. Technically, oil and gas are not minerals but legally they have been classified as such. Why? The Supreme Court of Tennessee sought the answer in 1897 in the case of Murray v. Allard, 43 S.W. 355. After citing authorities pro and con, and while admitting their origin to be "decomposition of marine or vegetable organises" that court firmly concluded that since they were obtained by a form of mining, oil and gas were minerals. From the above example two elementary truths emerge. First, for purposes of ownership, uranium is and will be whatever the courts say it is. Secondly, the courts historically and currently favor a practical rather than technical test to determine the "mineral" character of a substance. So now we turn to the jurisprudence for enlightenment and definition. EARLY CASES ALLOT URANIUM TO MINERAL OWNERS Two early cases involving the ownership of uranium followed what had been well-settled mineral within the meaning of the conveyances involved, confirming ownership in the mineral owners. In 1956 the U. S. District Court for New Mexico in the case of New Mexico and Arizona Land Company v. Elkins, 137 F. Supp. 767, appeal dism'd 239 F.2d 645 (10th Cir. 1956), found that a 1946 deed reservation of "all oil, gas and minerals underlying or appurtenant to said lands" included uranium and thorium. The court reasoned that uranium and thorium, being minerals within the scientific, geological and practical meaning of the term, would certainly constitute minerals within the purview of the reservation. While agreeing that uranium and thorium were "minerals", defendants argued that at the tine of execution of the conveyance it could not have been the intention of the parties to reserve them because they had no commercial value in the locality and were, in fact, not known to there exist until their later discovery in 1950. The court re¬jected, as a matter of law, this "lack of knowledge" theory citing the Supreme Court of Kentucky holding in Maynard v. McHenry, 113 S.W. 2d 13, that: "The mere fact that a particular mineral has not been discovered in the vicinity of the land conveyed or is unknown at the time the deed is executed rules of construction and held that uranium was a does not alter the rule . . ." that a grant or exception of "mineral" in a deed includes all mineral substances which can be taken from the land unless restrictive language is used indicating that the parties contemplated something less general than all substances legally cognizable as minerals. Further, argued the defendants, the only feasible mining procedure for such substances was open pit or strip mining, which would destroy the value of the land for grazing or agriculture. Finding that the language of the reservation was clear and unambiguous, the court would not permit the admission of extrinsic evidence as to mining procedures required. Elkins is the first uranium case construing the granting clause involved. In 1958 the Texas Court of Civil Appeals at San Antonio, in Cain v. Neuman, 316 S.W. 2d 915, no writ, held that a 1918 lease conveying "all of the oil, gas, coal and other minerals in and under" the land involved covered uranium. The lease provided a royalty of 1/10th on "other minerals." "We find no Texas precedent which discusses uranium," said the court, "but the usual arguments that uranium is not embraced within a lease are that the ejusden generis rule excludes uranium from the meaning of the lease

Jan 1, 1979

By E. A. Slover

THE usual reverberatory system of smelting cop--1- per concentrate or calcine has for its component parts a furnace and one or two waste heat boilers. These parts are operated on a basis of compromise, since the furnace can send gas to the boilers at too high a temperature and the boilers by plugging, due to dust or slag, can place a definite limit on the amount of fuel the furnace can burn. Over the years the copper concentrate smelting furnace has had few advances in design. The simple rules of design such as the flame should wipe the bath and the speed of the gases should be reasonably low for dust carrying purposes seem to cover the main features. In the construction of the individual furnaces some innovations are always being introduced. Among these are charging so that the work of smelting is a complete bath process, the use of suspended brick arches in place of sprung arches, the use of basic brick, not only in the crucible, but also in roof and sidewalls, the use of various means to feed the charge, the use of magnetite or other heavy material to construct the hearth, water cooling of bridgewall and slag skimming bay, the smelting of raw charge instead of calcine, the use of preheated air, and possibly the use of oxygen-enriched air for combustion. But the general outlines of the furnaces have not changed much except as to size. Furnaces at Hurley As shown on Fig. 1, the furnace at Hurley is 126 ft long between the longitudinal buckstays and 32 ft wide at the skewback plates. The foundation is a concrete retaining wall with piers at intervals that go deeper into the earth. Purposely the wall at the burner end of the furnace is not backed-up as tightly as the other parts of the foundation so that movement due to expansion may take place here rather than into the boiler foundations. Within these foundation retaining walls of concrete, the earth has been removed to allow the placement of the crucible brick base inside of which a silica hearth is laid 4 ft 6 in. in depth. No expansion is left in the brick base and crucible where they are in contact with the hearth. The hearth itself is of quartzite crushed to 1 in. size with fines left in the product. An 8 in. layer is laid and tamped with paving tampers to about 6 in. in thickness. Then a layer of silica flour is spread and vibrated into the hearth. This operation is repeated until a depth of 4 ft 6 in. is occupied by the silica mass onion-skinned in layers of approximately 6 in. Before firing the entire hearth is covered with broken slag to a depth of 4 in. so that a seal may be formed on the hearth. The crucible is completely faced with magnesite chemically bonded brick while the outside, against the foundation, is made of silica brick. The side-walls are carried up with silica brick in which expansion joints are left at intervals. Above the crucible the sidewall is corbelled to form a shelf on which the charge may build up along the side-walls, see Fig. 2. The arch of the furnace is sprung 20 in. silica brick, with the longitudinal centerline horizontal the length of the furnace, and some 9 ft in the center above the bath. Both straight and wedge brick are used in the construction and a thin silica mortar is troweled for joints. After the arch under heat has assumed its permanent shape, a silica slurry is spread over the arch to fill any cracks that have formed, thus giving bearing surface to the brick and preventing dust from entering the body of the arch to act as a future fluxing agent. The uptake of the furnace slopes up to the boiler entrance where a brick pilaster divides the gas stream for the two boilers. Over this flared uptake is a suspended flat arch of firebrick. The pilaster and sidewalls are constructed of firebrick but the bottom of the uptake is lined with silica brick and fettled through holes in the roof with siliceous fettling. Close to the entrance of each boiler is a brick covered slot through which water-cooled dampers may be lowered in event of boiler trouble. These water-cooled dampers are hung permanently in position ready to be lowered when needed. Flexible hoses to follow the dampers as they are lowered are connected at all times and individual chain blocks are used to lower the dampers. A pump supplying water is started before the dampers enter the heat. Charging of the furnace along the sidewalls for some 80 ft from the bridgewall is accomplished by electric vibrating conveyors fed by belt from charge storage bins above the furnace. These conveyors

Jan 1, 1954