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By A. S. Yue

The interface morphology of the Mg-32 wt pct A1 eutectic has been studied in terms of the freezing rate, the temperature gradient, and the impurity content. For the impure eutectic it has been found that for a given temperature gradient a fast freezing rate favors the formation of a cellular intwface with sub-grain strucfure. This cellular interface can be changed to a planar interface of the same substructure either by decreasing the freezing rate or by increasing the temperature gradient. For the eutectic of highest purity, as purified by zme-refining, no cellular interface was found for any growth condition and only a planar interface with subgrain structure was observed. Furthermore, a layer of liquid adhering to the interface during de-cantation freezes with shapes and sizes of the phase particles different from those in the main eutectic solid. WHEN a molten metal or a binary eutectic liquid with zero freezing range is solidified unidirec-tionally, a cellular interface is usually formed-3 This interface is schematically represented by Fig. 1. The profile of the solid-liquid interface has a corrugated shape, as shown in Fig. l(a), while the decanted interface consists of cells, as shown in Fig. l(b). The cell boundary in a frozen eutectic is distinguishable from the cell interior by changes in particle shapes, as shown in Fig. 4. The formation of a cellular interface, according to Weart and ack,' is attributed to a layer of constitutionally supercooled" liquid generated at the advancing interface by the simultaneous rejection of an impurity by the two phases of the eutectic mixture, which then permits freezing over an appreciable temperature range. This concept has been further elaborated by Tiller, who predicts that even in the absence of an impurity the rejection of solute ahead of each lamella of the eutectic may promote the formation of a cellular interface. More recently, Chilton and Winegard, and

Jan 1, 1963

By T. M. Berry

FOR the past several years it has been growing practice to install circular shafts at deep mining operations. Several factors have brought this about. Throughout eastern and midwestern coal fields circular shafts have been conventional for many years. Where large bodies of coal are mined, a production shaft may have a life of 20 to 30 years. Quantity production is essential; therefore the shaft must have a large cross-sectional area for larger skips and cages. Mechanical mining has become a necessity if a company is to stay in business today. Continuous mining machines and cutting, loading, and hauling equipment must be taken in and out of the mines. If the access shaft is not large enough there will be expensive dismantling and assembling. This has become a problem at many operations, particularly in the western sections where ore was originally mucked by hand into small cars and hoisted by a skip through a narrow rectangular shaft having small compartments. Mechanical loaders must be dismantled to wheelbarrow size to go into these mines.

Jan 7, 1957

By W. White, C. S. Barrett, R. M. Mueller

THIS communication reports film-recorded low-energy (-100 kev) proton blocking patterns'-3 for hcp and wurtzite crystals. In particular the sequence of relative line intensities* (corresponding to planar blocking) of common hcp metals is compared with those of the wurtzite semiconductors CdS and CdSe. The results show that the sequence is characteristic of structure. For closely similar structures such as those of CdS and CdSe, differences of line intensity attributable to the difference in atomic number, 2, of the scattering centers may also be seen. The apparatus and techniques used in this work were identical with those reported previously in a study of cubic systems.3 All metals were given standard metal-lographic etches, and the semiconductors cleaved, immediately prior to introduction to the vacuum system. Fig. 1 shows the unit cell of the wurtzite structure, and the geometry used to obtain the [1120] and [0001] patterns of Fig. 2. The axial ratio, c/a, for all ma- terials of Fig. 2 is close to 1.63. The patterns are then directly comparable in linear dimensions inasmuch as they have been reproduced at the same overall magnification of the patterns. (Overall magnification is proportional to the product of film-to-target distance and printing magnification. Thus the 1/6-in.-diam beam passage hole in the center of the film need not appear of uniform size in the prints.) The patterns for a given orientation, though similar

Jan 1, 1970

By William Y. Holland, Roger H. Cook

In view of the increasingly widespread deterioration of concrete structures as the result of the interaction of the alkalies sodium and potassium released by hydration of portland cement and susceptible rocks and minerals in aggregates, it is believed that a paper summarizing the geographic distribution of these aggregates will be of interest to producers and users of concrete, concrete products, and concrete-making materials.

Jan 10, 1953

By A. H. Daane, B. J. Beaudry

The Sc-Ti system was studied by thermal, metal-lographic, and X-ray methods. Scandium was found to transform at 1334 °C from a (hexagonal) to ß which was concluded to be bee since a continuous series of solid solutions is formed between ß scandium and ß titanium at elevated temperatures. There is a minimum in the solidus at 51 wt pet Ti and 1300°C, a monotectoid at 1050°C and 49 wt pet Ti, and a eutectoid at 875°C and 91.5 wt pet Ti. The maximum solubility of titanium in a scandium is 13.5 wt pet at the monotectoid temperature, while the maximum solubility of scandium in a titanium is 6.5 wt pet at 875°C. SCANDIUM, a member of Group 111 A of the periodic table, and now called a rare-earth metal,' has become of interest recently due to its low density (2.99 g per cc) and relatively high melting point (1539°C).Spedding,' et al. have described a method of preparation of pure scandium metal and have made a study of its basic properties. Since scandium is approximately 10 to 12 pet smaller in at. diam than the other rare earths while its electronegativity and valence are the same, a knowledge of its alloying behavior in contrast to these elements should be very helpful to fundamental alloy theory. Since scandium is quite scarce and difficult to prepare in pure form, its use as a structural material by itself seems quite unlikely. However, its use in special cases as an alloying addi- tive to other low-density materials is a possible application; the Sc-Ti system was chosen for this reason and for others of fundamental interest. Scandium was suspected of having a high temperature bee form as do some of the other rare-earth metals.3'4 Since titanium has a high-temperature bee form, a continuous series of solid solutions at elevated temperatures between ß scandium and ß titanium would prove the existence and structure of the high-temperature form of scandium. The existence of a continuous series of hexagonal solid solutions at room temperature was predicted by Burkhanov and Savitskiy,5 but Hias shown to be incorrect in early X-ray studies. EXPERIMENTAL METHODS Materials. The metals employed in this investigation were crystal bar titanium and distilled scandium prepared by the method described by Spedding,2 et al. The major impurities are listed in Table I in PPm. Alloy Preparation. All the alloys examined were initially formed in a nonconsumable electrode are-melting furnace under an atmosphere of purified helium or argon. A curve based on the observed weight loss of 0.6 pet* when titanium was melted

Jan 1, 1962

By Hermann Schmalzried, Carl Wagner

UPON heating a metal oxide or sulfide in H2, first only oxygen or sulfur is removed from the surface. Thus the metal/nonmetal ratio in the oxide or sulfide increases and the thermodynamic activity of the metal increases accordingly. For the formation of metallic nuclei, a certain super saturation is necessary, i.e., the activity of the metal must become greater than unity. Once nuclei of the metal have been formed, the supersaturation is supposed to decrease. Even under steady-state conditions of a reduction process, however, the activity of the metal inside an oxide or sulfide phase must be greater than unity in order to have a driving force for the individual steps of the reduction process. As an example, consider the reduction of Ag2S with a high mobility of cations and electrons. As shown schematically in Fig. 1, the reduction process involves the following steps:' 1) sulfur removal along the entire Ag2S surface in form of H2S, 2) migration of Ag' ions and electrons from the Ag2S surface to nuclei of metallic silver, 3) transfer of Ag+ ions and electrons from the Ag2S phase to the metal. For a finite rate of step 3, the activity of silver in Ag2S next to the Ag2S-Ag interface must be greater than unity. Moreover, for a finite rate of step 2, the activity of silver at the gas-Ag2S interface must be still somewhat greater. Theoretical considerations lead to the tentative conclusion that at least under steady-state conditions the supersaturation will be rather low.' To test this conclusion, the average activity aAg of silver in a Ag2S tablet about 2 mm thick with a diameter of 5 mm was followed as a function of time by measuring the electromotive force E of the cell Pt I Ag | Agl I Ag2S I Pt where AgI is used as a solid electrolyte in which only Ag+ ions are mobile. The activity aAg is calculated as aAg=exp(-EF/RT) Since the diffusion coefficient for transport of silver in Ag2S is very high (- 3 . l0-2 sq cm per sec),3 the average activity aAg is representative for both the bulk and the surface of the Ag2S tablet. Experiments were conducted at about 400°C. The cell was surrounded by an aluminum block in order to secure a uniform temperature and to eliminate thermoelectric effects. With the help of a potentiometer, first a potential of 0.16 v was applied to the above cell in argon in order to obtain a well defined initial state with a Ag/S ratio close to 2.000.~ Then the cell was disconnected from the potentiometer and a gentle stream of H2 was passed along the Ag2S surface. In view of the removal of sulfur in form of H2S, the electromotive force E decreased within 20 to 30 min to zero corresponding to a Ag/S ratio of 2.003 and became negative, indicating a value of aAg> 1. A representative plot electromotive force E vs time is shown in Fig. 2. The minimum of the electromotive force characteristic of the onset of

Jan 1, 1963

By R. S. Wagner, C. E. Miller, H. Brown

A dc field was applied to liquid BI-Sx or Au-Ge alloys of eutectic composition. The liquid alloys were kept at a temperature slightly above the eutectic. The concentration changes due to electrodijfusion are large enough to cause nuclcation and growth of the primary phases at the respective electrodes. Nearly complete separation of Bi-Sn eutectic was obtained as well as substantial separation of Au-Ge eutectic. The effect of an electric field on the solute distrihn-tion was itluestignted itt tlirectiortally solidified rods of a dilute Bi-Sn (0.5 al. pc,t Bi) alloy. Field-freezing was carried out in small-diameter cupillay tubes to avoid cotuectice mixing -of the liquid. The relative sollcte corzcentratioi, Cs/Co , was rneusred by n radioac1il.e tracer netlod. Cs/Co can be made both largev than unity or srialler than the equilibiuwz distvibrrlion c.oejyicienl, k, , oiler a substattiul portion of the soliclifi&apos;erl rocls. A direct current, passed through a liquid-metal solution, can cause substantial concentration changes by electrodiffusion. The magnitude of the change depends on the difference in ionic mobilities of the atomic species in solution. Electrodiffusion has been studied in many binary and ternary liquid alloys.&apos;y2 It was found that the rate of material transport decreases with time for a constant applied field, as a concentration gradient is established in the solution. A steady-state concentration profile is achieved when electro-diffusion is compensated by chemical diffusion. This may seem to limit the use of electrodif fusion for metallurgical application. However, a way of utilizing the effect of electrodiffusion is to combine it with crystallization or controlled freezing. rakin was first to propose this as a new method of separating metal alloys of eutectic composition at temperatures slightly above the eutectic temperature. It was possible by this method to separate Bi-Sn and Bi-Cd eutectics into their component phases. Angus et al discussed the possibility that the effective distribution coefficient, keff, could be varied by proper application of an electric field during solidification. The combination of electrodiffusion and solidification, called field-freezing, was discussed in detail by Pfann and aner. It was shown that field-freezing can be used as a crystal-growth process, an efficient method for eutectic separation, and a new means of changing the effective distribution coefficient. k,ff, beyond the usual range of ko < k,ff < 1. The liquid layer adjacent to the solid-liquid interface can be either increased or depleted in solute due to

Jan 1, 1967

By Hugh J. Leach, J. C. Van de Water

In open pit mining, as in other industries, it has I become necessary to improve operating efficiency in order to combat higher labor and supply costs. Moreover, orebodies are becoming leaner, pits are getting deeper, stripping ratios are increasing, and hauls are getting longer. There has been a steady increase in size, speed of operation, and reliability of the various machines involved in breaking, loading, and hauling ore. Changes have seldom been radical but are rather the result of steady improvement. Drilling: Notable advances have been made in the use of rotary drills and air powered percussion drills for blasthole drilling. Several hundred of these machines are now in use as replacements for churn drills in softer rocks such as limestone and shale. Their application to hard rocks such as iron ore and taconite is under current investigation, but in the Lake Superior iron mining district, open pit blast-hole drilling in ore has been accomplished almost exclusively by standard churn drilling. The only recent advance has been the use of larger machines drilling 9-in. holes. This has increased drilling speed somewhat and allowed wider hole spacing, with consequent cost reduction.

Feb 1, 1956

By Marc W. Bodine

Insoluble residues from three sequences of Paleozoic marine evaporates (Retsof salt bed in western New York, Salado Formation in southeastern New Mexico, and Paradox Member of the Hermosa Formation in southeastern Utah) are rich in trioctahedral clays. Chlorite (clinochlore), corrensite (mixed-layer chlorite-trioctahedral smectite), talc, and illite (the only dioctahedral clay) are the dominant clay minerals; serpentine, discrete trioctahedral smectite (saponite), and interstratified talc-trioctahedral smectite are sporadically abundant. These clay-mineral assemblages differ chemically and mineralogically from those observed in most continental and normal marine rocks, which commonly contain kaolinite, dioctahedral smectite (beidellite-montmorillonite), illite, mixed-layer illite-dioctahedral smectite, and, in most cases, no more than minor quantities of trioctahedral clay minerals. The distinctive clay mineralogy in these evaporate sequences suggests a largely authigenic origin. These clay minerals are thought to have formed during deposition and early diagenesis through interaction between argillaceous detritus and Mg-rich marine evaporate brines.

Jan 1, 1985

By B. A. Chomyn, P. Lapointe

Current work within the Magnetic Properties Task of the Canadian Nuclear Fuel Waste Management Program has indicated that a relation exists between the measured bulk magnetic susceptibility and fracture and lithological characteristics of granitic cores from the Lac du Bonnet batholith in Manitoba. Susceptibility minima correspond to fractured and associated altered rock; uniform background levels coincide with unaltered, non-fractured homogeneous rock; and susceptibility maxima denote the presence of xenoliths and intervals of core containing large and coarse-grained magnetic minerals. The observed variation in bulk susceptibility is largely controlled by the gram size and the relative abundance of iron-titanium oxide minerals of which magnetite is the most important. The magnetic minerals occur as monomineralic grains of magnetite and hematite, as aggregates of magnetite and ilmenite, hematite and ilmenite and as examples of either of these two categories but exhibiting evidence of oxidation and alteration. The degree of alteration of the oxides is commensurate with the alteration of the enclosing rocks. Susceptibility minima characteristic of fractured rock reflect decreases in oxide gram size and abundance, as a result of the oxidation of magnetite to hematite and the development of titanium-rich phases. Correlations between boreholes indicate the possibility of continuous fracture zones at 80 m and 150 m from the surface and another one at a greater depth.

Jan 1, 1984

Jan 1, 1879

By A. M. Sarem

For the performance prediction of multiphase oil recovery processes such as steam stimulation, there is an acute need for three-phase relative permeability data. No fast and simple experimental technique, such as the unsteady state method proposed by Welge for two-phase flow, is available for the three-phase flow. In this paper, an unsteady - state method is presented for obtaining three-phase relative permeability data; this method is as fast and easy as Welge&apos;s method for two - phase flow. Analytical expressions are derived by extension of the Buckley-Leverett theory to three-phase flow to express the saturation at the outflow face for all three phases in terms of the known parameters. It is assumed that the fractional flow and relative permeability of each phase are a function of the saturation of that phase. Other simplifying assumptions made include the neglect of capillary and gravity effects. The effect of saturation history upon relative permeability is acknowledged and attainment of similar saturation history in laboratory and field is recommended. The required experimental work and computations are simple to perform. The test core is presaturated with oil and water, then subjected to gas drive. During the test, required data are the rates of oil, water, and gas production, together with pressure drop and temperature. The ordinary gas-oil unsteady-state relative permeability apparatus can be readily modified to measure the required data. The proposed technique was applied to samples of a Berea and a reservoir core. The effect of saturation history upon relative permeability was studied on one Berea core. It was found that increase in initial water saturation has a similar effect upon three-pbase relative permeability as it does in two-phase flow. INTRODUCTION In the light of increasing demand for three-phase relative permeability data for predicting the performance of thermal and other multiphase-flow recovery processes, a simple and accurate method of experimental determination of such data is extremely desirable. Leverett and Lewis 1 described the simultaneous flow method of obtaining three-phase relative permeability data. However, Caudle et al.2 reported that this method is very time consuming and cumbersome. Corey3 proposed calculating the three-phase relative permeability from measured krg data. Corey&apos;s theory is based on simplified capillary pressure curves,4 assuming a straight line relationship between I/Pc2 and saturation. Also, Corey&apos;s method assumes a preferentially water-wet system. The simplest and quickest method of obtaining three-phase relative permeability data is the unsteady-state method where, for instance, oil and water are displaced by gas. However, in such a test the correlation of average saturation with relative permeability does not give a valid relationship because the rates of oil, water and gas flow in the sample change continuously from the upstream to downstream end. This difficulty in calculating valid relationships was solved by Welge for two-phase flow by deriving an expression for determining the outflow face saturation from Buckley and Leverett frontal advance equations.5,6 In this paper, relations are established to determine the outflow face saturation and relative permeability to all phases in a three-phase flow displacement experiment. PROPOSED METHOD The fundamentals established by Buckley and Leverett5 for two-phase flow were extended to three - phase flow and used as a basis for the derivation of saturation equations. This approach is comparable to Welge&apos;s6 use of Buckley and Leverett theory in arriving at expressions to determine the outflow face saturation of the displacing fluid in a two-phase flow system.

Jan 1, 1967

By P. W. Bridgman

During the war, the Navy undertook the construction, under my direction, of an experimental gun embodying features designed to lessen the cost and time of production. These experiments were initiated after representations as to their desirability had been offered by myself, by the Naval Consulting Board, and by the National Research Council. The first drawings were made in June, 1917, and the experiment was completed in November, 1918. For the sake of clearness it will pay to recapitulate briefly the fundamental idea of gun construction. It is well known that if a hollow cylinder is subjected to internal fluid pressure, the maximum stress occurs in the inside layers, the outer parts carrying much less than their due share of the stress. This inequality of stress is more pronounced the thicker the walls of the cylinder. If such a cylinder is pushed to the elastic limit, failure in elasticity will take place long before the outer lagers have reached the limit of their capacity. Economical use of the material would demand, however, that all parts of the cylinder reach the limits of their capacity simultaneously. This may be brought about, at least in cylinders of not too great thickness, by producing in the inner layers an initial compression, and in the outer layers an initial tension. The effect of internal pressure is at first to relieve the compression of the inside layers, while increasing the tension of the outside layers. If the initial stresses are properly distributed, all parts of the cylinder will reach their elastic limits simultaneously, thus giving a cylinder of maximum strength for its weight. In gun construction as hitherto practiced, this initial distribution of stress is produced either by winding the inner tube with wire, a common English practice, or by shrinking hoops over the inner tube, which has been the standard American practice. Either process is long and expensive, particularly with the larger guns, 12- or 14-in., which require

Jan 1, 1922

By W. M. Weigel

The rapid advance, during recent years, in the manufacture of articles that have been in common use for generations and the development of new materials entering into appliances and devices unheard of fifty years ago have created a demand for some of the more common non-metallic minerals. To supply this demand there has quietly developed a branch of the mining industry of which little is known by most mining engineers —the mineral-filler industry. In this paper, and generally in the trade, the term mineral filler is applied to a mineral used in its natural state after mechanical preparation only (such as grinding, milling and washing), without undergoing any chemical change and without exerting any chemical action on the substance with which it is incorporated. The consumption of mineral fillers is confined chiefly to large manufacturing centers in the Eastern and Northern Statcs. Where available, materials originating near the place of consumption are used, as most fillers bring a comparatively low price and, frequently, the freight may equal the cost of the finished filler at the mine. The Southern States have abundant deposits of non-metallic minerals suitable for fillers, which supply the manufacturing industries in adjacent states. Many of these deposits are equal to, or superior, in quality to those mined in the North, but they can not compete with them because of the freight rates. The mineral-filler industry has felt the present depression, but it has suffered less than most mining industries, for as a rule the mills are simple, the overhead expenses are low, and the labor is entirely local and can revert to farm work when the plant closes down. Many other deposits in the southern district will undoubtedly be developed when business revives and freight rates are adjusted. Most of the non-metallic mines are small and the tonnage handled is low in comparison with the tonnage involved in modern large-scale mining of coal, iron, copper, etc. On the other hand, at nearly all non-metallic

Jan 1, 1923

By Morris Muskat

ALTHOUGH the problem of well spacing is one of the most important involved in the production of oil, it must be considered at the present time as still subject to further development. The published literature on this question is so voluminous that we cannot enter here into a review of it, except to refer to the recent papers by L. L. Foley1 and E. A. Stephen-son,2 where other references are cited. However, a decisive and conclu-sive answer to the problem of well spacing in any general form does not seem to have been developed. And while we shall be unable to present the desired solution in the present paper, it is nevertheless felt that the material to be given here not only provides the physical ground work for the ultimate solution, but shows qualitatively the essential factors that enter the well-spacing problem. Field studies of the well-spacing problem, in which the ultimate recoveries from different fields with different well spacings have been compared, have generally suffered from the lack of knowledge as to the similarity of the inherent characteristics of the producing reservoirs being compared, such as the sand volumes, the sand porosities, the sand permeabilities, the original reservoir pressures, the presence or absence of gas caps, the presence or absence of effective water drives, and the economic limits of production rates at which the various fields were considered to have yielded their ultimate recoveries. Certainly no one who is evaluating originally the economic significance of any oil reservoir would deliberately ignore these phases of the problem. And it is equally certain that no one would reasonably expect the ultimate recoveries from two reservoirs, even with the same well spacing, to be identical regardless of these other factors. More reliable results might be expected from comparisons of the recoveries obtained from different leases with different well spacings, but producing from the same reservoir sand. Unfortunately, however, even conclusions for such studies may be subject to serious errors. The reason simply is that however much one may insist that an operator is entitled only to the oil immediately underneath his surface acreage he will nevertheless drain the surrounding properties as long as his reservoir

Jan 1, 1939

By W. M. Weigel

The rapid advance, during recent years, in the manufacture of articles that have been in common use for generations and the development of new materials entering into appliances and devices unheard of fifty years ago have created a demand for some of the more common non-metallic minerals. To supply this demand there has quietly developed a branch of the mining industry of which little is known by most mining engineers —the mineral-filler industry. In this paper, and generally in the trade, the term mineral filler is applied to a mineral used in its natural state after mechanical preparation only (such as grinding, milling and washing), without undergoing any chemical change and without exerting any chemical action on the substance with which it is incorporated. The consumption of mineral fillers is confined chiefly to large manufacturing centers in the Eastern and Northern Statcs. Where available, materials originating near the place of consumption are used, as most fillers bring a comparatively low price and, frequently, the freight may equal the cost of the finished filler at the mine. The Southern States have abundant deposits of non-metallic minerals suitable for fillers, which supply the manufacturing industries in adjacent states. Many of these deposits are equal to, or superior, in quality to those mined in the North, but they can not compete with them because of the freight rates. The mineral-filler industry has felt the present depression, but it has suffered less than most mining industries, for as a rule the mills are simple, the overhead expenses are low, and the labor is entirely local and can revert to farm work when the plant closes down. Many other deposits in the southern district will undoubtedly be developed when business revives and freight rates are adjusted. Most of the non-metallic mines are small and the tonnage handled is low in comparison with the tonnage involved in modern large-scale mining of coal, iron, copper, etc. On the other hand, at nearly all non-metallic

Jan 1, 1923

By P. W. Bridgman

During the war, the Navy undertook the construction, under my direction, of an experimental gun embodying features designed to lessen the cost and time of production. These experiments were initiated after representations as to their desirability had been offered by myself, by the Naval Consulting Board, and by the National Research Council. The first drawings were made in June, 1917, and the experiment was completed in November, 1918. For the sake of clearness it will pay to recapitulate briefly the fundamental idea of gun construction. It is well known that if a hollow cylinder is subjected to internal fluid pressure, the maximum stress occurs in the inside layers, the outer parts carrying much less than their due share of the stress. This inequality of stress is more pronounced the thicker the walls of the cylinder. If such a cylinder is pushed to the elastic limit, failure in elasticity will take place long before the outer lagers have reached the limit of their capacity. Economical use of the material would demand, however, that all parts of the cylinder reach the limits of their capacity simultaneously. This may be brought about, at least in cylinders of not too great thickness, by producing in the inner layers an initial compression, and in the outer layers an initial tension. The effect of internal pressure is at first to relieve the compression of the inside layers, while increasing the tension of the outside layers. If the initial stresses are properly distributed, all parts of the cylinder will reach their elastic limits simultaneously, thus giving a cylinder of maximum strength for its weight. In gun construction as hitherto practiced, this initial distribution of stress is produced either by winding the inner tube with wire, a common English practice, or by shrinking hoops over the inner tube, which has been the standard American practice. Either process is long and expensive, particularly with the larger guns, 12- or 14-in., which require

Jan 1, 1922

By J. B. Dilworth

The word ".development," as used in connection with mining, is a rather general term and in most instances must be qualified or explained before the exact thought in the mind of the user is made clear. For instance, by the development of a mining district is often meant its entire facilities of mineral production, such as railroads, towns, mine plants, etc. In speaking of the development of a property its prospecting by test pits or diamond drill borings may be referred to; or it may be the mines, strip pits or quarries from which the coal, ore or rock is won. Rut, as a rule, when the development of an individual mine is spoken of the idea in mind is the system of underground workings by means of which the mineral is recovered and transported to the surface. It is this character of development that is considered here. The discussion will be confined to the ordinary room-and-pillar system of mining practically horizontal coal seams that is used in most bituminous coal mines in this country, and to only two phases of this subject; viz., what is properly included under the head of "Development" as it appears on the books of a coal company or the inventories of an examining engineer, and how its " value " should be determined by the accountant or engineer. No absolute rule or definite agreement covers these points, yet these questions are far more than academic. Development is often an important part of a mining company&apos;s assets, affecting the amount of its invested capital (and hence its rate of taxation under present Federal income tax laws) as well as the value of its total assets and the amounts chargeable to cost of coal and to depreciation. Mine Development Account Perhaps the majority of mine accountants will agree that the mine development account is that capital account which shows the extraordinary expenditures incurred in opening and expanding the underground workings of a mine until it has reached its normal production, the expenditures being those made for shafts, slopes, rock tunnels, drift mouths and such relatively permanent work; also payments over and above ordinary mining costs made for driving entries, air courses and break-through; for

Jan 1, 1922

By Thomas L. Garwood, F. C. Menk

IT is generally accepted that no method of coal cleaning except froth flotation is effective in cleaning dust. In the majority of coals mined in the United States the dust sues contain a high percentage of impurities, hence the removal of the dust from the coarse sizes lowers the impurity content of these sizes. Dedusted coal is desired as a means of providing a better feed to cleaning plants because of increased efficiency in I both dry and wet plants. In dry-cleaning plants, a dedusted feed makes for a pervious and uniform bed. With a dusty feed the fines tend to segregate in the feed stream and pass en masse over the air separators, causing a lack of uniform aeration and fluidity of the bed necessary to efficient cleaning. In wet-cleaning plants dedusting of the feed often decreases the sludge problem to the point of eliminating the necessity of wasting wash water. It may be advantageous to eliminate sludge-settling equipment in favor of dedusting equipment, to provide the advantages of a dedusted feed to the wet-washing process. Dedusting advantages may include: (1) the removal of fusain, especially advantageous in plants washing coal intended for metallurgical coke; (2) prevention of the gradual build-up of solids in the wash water, with a consequent variation in the washing ability of the system; (3) prevention of the loss of dust to the sludge ponds, providing instead a fuel for local consumption or special markets. DEDUSTING The practice of dedusting, sometimes called aspirating, has presented a problem in disposing of the dust and intermediate small sizes recovered in the process. It has been found that no difficulty is experienced in disposing of the intermediate sizes, since they are free of fine dust and burn freely on grates built for small coal. They handle well, flowing freely from bins and hoppers and into conveyors, and pulverize easily. They have a low angle of repose. In tests made on this size as a feed to coke ovens, the results have been excellent, in that the natural breakdown of coal in handling and shooting in the mine gives this small-size coal good coking characteristics-producing a strong, fingery coke structure. Deduster dust from Illinois coal has been

Jan 1, 1950

By Cyril Stanley Smith

On the 6th of February 1684, Dr. Martin Lister mentioned at a meeting of the Royal Society1 that "brass is magnetical," and promised to give an account of that assertion at some other time. He repeated his promise but never fulfilled it, and it was left for William Arderon2 to show, in 1758, that brass could be made magnetic by hammering and that it would retain polarity after magnetizing. Twenty-seven years later Caval103,4 examined the matter in great detail. Working with cast calamine brass, he showed that it could be made magnetic by hammering and nonmagnetic by subsequent annealing at a red heat. He found that annealing at a very high temperature caused the samples to lose their magnetic quality permanently, even after subsequent cold-working, but that remelting and cold- working restored it. He encountered some samples of brass that could not be rendered - magnetic by any treatment. Experiments in which these were remelted with iron additions gave negative results, and Cavallo concluded that iron impurity was not the cause of the magnetism. He worked with 50-grain (3-gram) samples melted under the blowpipe, hence cooled very quickly. Bennet5 made whole crucible charges from copper and zinc, and found _ the resulting brass ingots to be magnetic only when iron had been added and then only after cold-working. All these observations applied to material in the cast condi- tion, in which coring would produce a continuous spectrum of composition and cooling would result in varying degrees of precipitation. This knowledge of the subject seems to have been forgotten in the nineteenth century. The older brass was made by the calamine process and frequently contained iron in amounts of 0.5 per cent or more, absorbed from the impure ore with which the copper and charcoal were heated in making the brass. When metallic zinc became available in commercial quantities, calamine brass gradually disappeared, and with it the knowledge of its curious magnetic properties. Only when sensitive apparatus replaced the compass needle of the earlier investigators could the effects be detected in relatively pure metal. The effect of cold-working in inducing ferromagnetism was rediscovered by Bitter8 in 1930 in a sample of impure copper, and this was confirmed by Lowance and Constant: Honda and Shimizu, l0,11 and others. In the same year, Tammann and Oelsen12 showed that copper-rich copper-iron alloys after certain heat-treatments could be rendered ferromagnetic or made more strongly ferromagnetic by cold-rolling. Kussman and Seeman13 showed that the change of susceptibility of relatively pure copper on cold-working was associated with the iron content, and concluded that actual precipitation of iron was caused by cold-working, which is a satisfactory theory until one considers the improbably high rate of diffusion that this would involve. When studying precipitation phenomena in

Jan 1, 1942