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By E. H. Lee, F. J. Fayers

Problems in reservoir analysis can usually he cupressed in terms of a system of nonlinear partial difjerential equations. A rnethod for .setting physically reasonable boundary conditions for these systerrls by ayplication of the theory of characteristics is discussed. A short description i.c. given of the technique for finding chnmcteristics of general first order and second orrler equations. Specific examples are quoted jrorn eqrrations occurring in theoretical reservoir studies. The princip1e. ossocicred wit11 the use of chnracteristic to set physically realistic boundary conditions me developed, and thr method is discussed in terms of boundary condition for the noncupillary, compressible, two-phase flow problen: jor the cupillary, ir~cowlpressible, two-phase flow problems for the tlrtergent flooding prohlenl; as for the compressible. noncapillary, two-phase flow pro11letn. INTRODUCTION In most problcms in reservoir analysis the physical situation is described by a system of nonlinear partial differential equations. The general solution to the set of equations usually comprises a wide range of functions ancl a particular solution is normally selectetl by applying suitable boundary conditions to the problem. In some cases it is clear from the physical situation what form the boundary conditions should take, but it is usually desirable to have an independent mathematical check of the suitability of the chosen conditions. From the mathematical standpoint, a system of partial differential equations with boundary conditions is said to be properly set if the combination determines a unique solution which is continuously dependent on the equation and the boundary conditions. Such a solution is sometimes termed "reasonable". In investigating the properties of the mathematical representation, it is useful to determine the structure of the system by the application of the theory of characteristics. This theory determines in the space of the independent variables, lines or surfaces which play a special role in thc system's behavior. The characteristics determine the possibility and nature of the propagation of discontinuities in the derivatives of the dependent variables. Along the characteristics certain differential relations hold which for some problems allow a so- lution to be obtained analytically. In the case of hyperbolic equations the characteristics can bc used as 3 basis for a numerical solution. If a complicated nonlinear system is to be solved, a study of behavior of the characteristics will indicate what boundary conditions should be chosen. By using the method of characteristics, several advances have rccently been made in solving reservoir engineering problems. Sheldon, Zondek and Cardwell' have discussed how the the method may be used grap-phically to solve the incompressible two-phase displaccmerit problem when the gravity term is included in the equations. Fayers and Perrine' have applied the method to study the equations representing detergent flooding. When compressibility and solution-gas effects are introduced into the two-phase flow problem, the equations and their characteristics become more complicated. It will be seen that in this problem the characteristics are useful for indicating a reasonable set of boundary conditions but cannot readily be used to compute a numerical solution. This problem has been solved on the IBM 701 using normal finite difference methods hy West, Garvin and Sheldon." The material to be prcscntcd in this report is divided into three sections. The first discusses the determination of the characteristics of first and second order partial differential equations; the second describes the selection of suitable boundary conditions by the application of the principle that the future cannot affect the past; the third discusses the use of characteristics for setting the boundary conditions of the two-phase solution-gas flow problem. A useful introduction to the method of characteristics has been given by Hildebrand.' A summary of the method will be given in this section of the paper. The First Order Equation The quasi-linear equation of first order is It is linear in the partial derivations of z. The properly linear equation has the form The characteristics of are curves along which the

By J. Szekely, V. Stanek

Steady state heat transfer and fluid flow rates are predicted for the counter-current contacting of gas and solid streams. For a .fixed pressure drop across the bed the convective heat transfer rate is affected by the gas flow rate, which in turn is affected by the temperature distribution in the system. Variations in bed voidage and in particle size were found to change the predicted temperature profiles quite markedly, in particular when the thermal capacities of the gas and solid streams were equal. IN Part I we examined the effect of step and pulse changes in the inlet gas temperature on transients in the flow of gases through fixed packed beds. Here we shall discuss heat flow and fluid flow interactions in the counter-current heat exchange between packed solids and a gas stream. Counter-current heat exchange in packed beds has been extensively studied. In his now classical paper, Furnas' assumed constant property values and developed a simple analytical. expression for the temperature profiles in the gas and in the solid stream. A highly sophisticated analysis of counterflow systems, allowing for transients and interparticle conduction was developed by Amundsen. In preparing a very readable review of this topic Elliott' also presented a number of elegant solutions, including the case involving heat generation. A great deal of work has been done on the application of these concepts to the modelling of the blast furnace. However, in all this previous work the mass flow of the gas was regarded as a quantity independent of the gas-solid heat exchange process. In the following we shall consider counter-current heat exchange between a gas stream and a packed bed of solids, under conditions where the pressure drop across the bed is specified, rather than the mass flow of the gas. FORMULATION Consider a packed bed, extending from y' = 0 to y' = L, in which moving solids and a moving gas are contacted in a counterflow arrangement. Let cold solids, with an initial temperature Tsi and mass flow GA, enter at y' = L, and hot gas with an initial temperature of Tgi and mass flow Gg enter at y' = 0. In contrast to the problems considered in Part I this system has a nontrivial steady state and we shall restrict our attention to the study of the pressure drop flow relationships and the resultant temperature distributions for steady state conditions. Under these conditions the formulation of the problem requires the statement of the following: 1) heat balance on the gas 2) heat balance on the solids 3) the mechanical energy balance equation and in addition the knowledge of the equation of state, and a functional relationship between viscosity and temperature and an expression for the heat transfer coefficient in terms of the other parameters. On neglecting temperature gradients within the solids and for a constant mass flow of the gas, the solution to this problem is well known.'" The expressions for the temperature profiles of the gas and solid streams may be put in the following form: where Tg and T, denote the dimensionless gas and solid temperatures respectively, y is a dimensionless distance, and R is the ratio of the thermal masses. These quantities are defined as follows: For the particular case of equal thermal mass capacities by the gas and the solid, that is R = 1, the Eqs. [1]and[2] simplify to Eqs. (71 and[8], respectively: i.e., the resultant profiles are linear. As for most practical cases , solutions given by Eqs. [7] and [8] will contain only the inlet temperatures as parameters. For a fixed, predetermined value of C;b the above

Jan 1, 1970

By M. J. Marcinkowski, K. S. Sree Harsha

A detailed numerical analysis has been made of the equilibrium configuration of partial dislocations in a blocked deformation twin under an externally applied stress. Twins made up of both pure screw and pure edge partials have been considered. The components of stress in the vicinity of the twin tip associated with each of these configurations have been plotted. It has been found that at some critical degree of oblateness the shear stress fields of the blocked screw or edge twin can both sPontaneously nucleate slip, whereas only the component of stress oxx about the edge twin can nucleate and propagate cracks. TWINNING becomes a predominant mode of plastic deformation at low temperatures and/or high strain rates. Fig. l(a) shows what must be the first step in the formation of a deformation twin, namely the formation of a loop of imperfect dislocation bounding a stacking fault. In an fcc crystal the partial dislocations have Burgers vectors of the type 1/6 a,(112) and the fault is of the intrinsic type while in the bcc crystal the partials have Burgers vectors of the type ao(lll). The stacking sequence of (111) planes in a perfect fcc crystal is given by ABC ABC, and so forth, and in one which contains a twin by ABCABACBA, and so forth. It is apparent that the stacking fault and twin give rise to no mistakes associated with adjacent close-packed planes; however, with respect to second-neighbor close-packed planes the faulted crystal has twice as many mistakes as the twin. The energy of the twin boundary may thus be taken to be one-half that of the intrinsic fault boundary. In the case of the bcc crystal the stacking sequence of (112) planes is given by ABCDEFABCD, and so forth, in a perfect crystal, by ABCDCDEFA, and so forth, in a crystal which contains a fault, and by ABCDCBAF, and so forth, in one which contains a twin. An analysis similar to that applied in the fcc crystal shows that both the fault as well as the twin involve no neighbor violations across adjacent planes. However, there are twice as many violations across second-neighbor (112) planes associated with the fault as compared to that of the twin. Thus once again the energy of the twin boundary may be taken as one-half that of the fault. It is important to note that, unlike the fcc, the faults in the bcc crystal involve first nearest-neighbor violations and are thus expected to be of much higher energy than those in fcc crystals. A more detailed analysis of the material discussed above can be found in Ref. 1. To a good approximation then, the lenticular twin shown in Fig. l(b) can be generated by adding partial dislocation loops on successive (111) planes for fcc crystals or (112) planes for bcc crystals in the manner shown, with no additional expenditure of chemical energy other than that required for the fault shown in Fig. l(a). In practice, deformation twins are much more extended than that shown in Fig. l(b) and more closely resemble one shown schematically in Fig. l(c). It is readily apparent that the free energy of the twin and matrix are identical. In those cases where the partials lead to a structural change, the free energy of the material contained within the dislocation array is lower than that of the matrix and we have the so-called martensite transformation. The present investigation is the first in a series of five major theoretical-experimental efforts which will deal with the static and dynamic behavior of twin nucleation and growth. There has been a recent surge in activity pertaining to the equilibrium shapes of twin lamellae2'3 and

Jan 1, 1969

By F. J. Tuck

THE Hayden mill of the Ray Mines Division, Kennecott Copper Corporation, is now equipped with two 9 by 12-ft. rod mills having a daily capacity of 6000 tons of coarse-crushing plant product from the mine. These two mills crush a 3/4-in. product to approximately 19 per cent on 14 mesh, with only one pass through the mills. Each rod mill has taken the place of four sets of 42-in. Garfield rolls with their attendant screens, and is making a product for the fine-grinding department comparable to that formerly made by rolls in closed circuit with screens. The rod mills are lined with wave-type liners of white iron, varying in thickness from 2 to 3 in. The shell and end liners last approximately 600 to 700 clays. Manganese-steel lifter bars, 3 5/8 in. thick, are used, spaced about 11 in. apart, and they give a life of 350 to 450 clays. Fig. 1 shows the general design and thickness of the wave-type liners and lifter bars; 1 1/2 -in. liner bolts are used to fasten the lifter bars to the shell. The shell liners are held in place by the tapered lifter bars. A ¾-in. wood hacking is used between the shell and the liners. The rod-mill scoop has removable manganese-steel lips, which last 250 to 300 days. The scoop proper has shown some wear in spots; and these spots have been protected by rubber bolted over them. Water and milk of lime are added to the elevator feeding the mill, but not enough water to cause a pounding of the rods against the shell. Roughly, the water added amounts to 2.5 to 33 per cent of the ore. Addi-tional water is added to the mill discharge to facilitate distribution to the classifier bowls in the fine-grinding department.

Jan 1, 1938

By Martin Weinstein

A technique is described for preparing finegrained lead telluride by ultrasonic agitation of a solidifying melt. Material prepared by this technique is dense and chemically homogeneous. N-type PbTe, containing 0.03 mole pct PbIz, has been made and its thermoelecCric Properties have been measured as a function of temperature. For comparison, the properties of similarly doped PbTe made by cold pressing and sintering, and by extrusion, have also been measured. The ultrasonically prepared material compares favorably with the others in its thermoelectric-efficiency factor. Comparison of compressive-flow curves for the three kinds of PbTe show that the ulhasonically prepared material has much superior ductility. The cleavage strength of the ultrasonic material is related to the grain size, D, by the Petch relation:Extrapolation to infinite grain diameter yields a fracture strength of 5000 psi for single-crystal PbTe. WHEN metals and semiconductors solidify in a mold they normally assume one of three cast structures illustrated in Fig. 1.' Solidification in a casting starts at the mold walls where a large number of fine crystals of random orientation can be nucleated to form the chill zone. Because of the anisot-ropy of the growth rate, those crystals whose direction of maximum linear growth is parallel to that of the heat flow grow faster and crowd out the crystals of less favorable orientation. A second zone, having a preferred orientation, called the columnar zone, thus forms adjacent to the chill zone. The speed of growth of the columnar grains will depend, in the case of limited undercooling of the melt, on the rate at which heat can be abstracted. The columnar zone can extend to the center of the casting, Fig. l(a), but it is frequently followed, in solid-solution alloys, by another zone of equiaxed randomly oriented grains in the central portion of the casting, Fig. l(b). The equiaxed structure in Fig. l(c) represents the completely grain-refined case where the equiaxed grain size is small. The third type of structure is the most desirable because it imparts a somewhat higher strength for all except high-temperature applications, it reduces segregation of the doping constituent, and it reduces the possibility of hot tearing (the separation of grains due to the melting of a low-melting point constituent in the grain boundaries). In order to obtain fine-grained castings, the nu-cleation frequency must be increased and grain growth must be restricted. Various techniques have been employed for obtaining this end, namely: rapid cooling, vibration, and inoculation of the melt. The success of these techniques depends upon the characteristics of the metal species and on factors controlled by heat transfer through the crucible walls. Recent studies2" have shown that the application of ultrasonic energy to the solidifying ingot is an extremely powerful tool in the improvement of the crystalline structure of metallic castings. Both the mechanical properties and homogeneity of the ingots are improved. Ultrasonic oscillations may affect the crystallization process by 1) permitting subcritical nuclei to agglomerate and thus form nuclei of sufficient size to cause crystallization, 2) changing the state of surface adsorption of various catalysts found in the liquid melt, 3) breaking pieces of solid from the solidified surface near the supercooled region thereby increasing the number of possible nuclei, 4) causing temperature fluctuations to occur in certain parts of the melt thereby increasing the supercooling at specific points in the liquid, and 5) decreasing the critical nucleus size by increasing the pressure at specific points in the melt.' Various investigators have concluded that the effectiveness of the ultrasonic oscillations results from cavitation which disrupts the growing solid-liquid interface The present paper describes the application of ultrasonic oscillations to the crystallization of the semiconductor N-type PbTe. The purpose of this study is to prepare crystalline

Jan 1, 1964

By Robert A. Haney, Stephen J. Gigliotti, James L. Banfield

A series of investigations were made by the Mine Safety and Health Administration to evaluate the performance of various face ventilation systems as part of a program to reduce frictional ignitions of methane and to develop face ventilation systems that could be used with the line brattice more than 10 feet from the face. Tests were conducted in a full-scale laboratory model of a face area. Systems tested included unassisted blowing and exhaust line brattice, diffuser fan and spray fan systems. Systems were evaluated at air quantities ranging from 1.4 to 7.0 m3/s (3,000 to 15,000 cfm), and brattice-to-face distances from 1.5 to 9 meters (5 to 30 feet.). Tests were designed so that systems could be evaluated for the location of the high-point methane concentration in the face area, methane dilution capacity, and face ventilation index. The methane dilution capacity is the total amount of methane a system can dilute to 1.0 volume-percent. The face ventilation index is the efficiency at which the available face air volume is being used.

Jan 1, 1982

By E. D. McMurry

INTRODUCTION Before discussing the use of the free piston; it may be well to explain briefly the type of gas lift valves with which the loo] is designed to function. The gas lift valve ii nothing more or less than a small back pressure regulator. It; construction consists of an outer hous ing covering a seamless metallic bellows in such a way as in form a sealed pressure vessel or pressure dome. To the bellow* in attached a stem and to this stem is attached a .rating member. When the valve is run into the hole, a pre-delermined pressure charge is placed in the pressure dome. As shown in Fig. 1. the valve is furnished in four different major assem-blies. to accomplish good results in different types of wells. The valve is mounted on a pup joint (Fig. 2a) : the eoin-plele assembly is entered into the tubing siring at the desired location. Each valve is furnished with a revere flow check valve (Fig. 2-b) to eliminate any back wash through the mechanism. Valve action is as follows: At any time the casing pressure is allowed to exceed the pressure forces within the pressure dome of the valve, the valve simply opens and passes gas from the rasing annulus into the tubing. When the casing pressure forces arc allowed to bleed to a force less than the pressure force within the dome, of the valve. the valve closes. With this type of construction. it is possible to open and close the valve or valves at will from the surface, the medium of the gas pressure in the rasing annnlus. The cycle of operation is governed by a tine cycle motor valve, commonly referred to as a gas lift interutitter or gas life surfacr controller (Fig. 3). In actual practice. after the well is unloaded only one valve is in operation . . . all other valve.: remain in the closed position. On pre-determined time cycles, it is possible to open and close this operating valve at will, and to pass the desired amount of gas through this valve wheneler needed. This method of gas lift is widelv used and has been found In be very efficient. However, it has long been known that even greater efficiency would be obtained if it were possible to place Piston between the injected gas and the fluid head. The free piston which will be discussed here was designed to accomplish this end and has been found to do so with very satisfactory results. DESIGN AND OPERATION OF THE FREE PISTON Basically. the free piston consist- of a telescoping assembly in which are incorporated the various control and operating parts (Fig. A set of sleeve valves which are opened and closed by movement of the telescoping section is contained in the. tool. A cross section of the free piston is shown in Fig. 4-11, 'rile main body cotain- a seamless monel bellows of the same type as that generally used in pressure charged gas lift valves (Fig. 4-c), and a valve core to permit placing a pressure charge in the bellows before the free piston is placed in service. The bellows is the main control unit of the free piston and performs two function: 1. It governs the opening and closing of the sleeve valves. a.: dictated by the producing activities of the well in which the piston is operating. 2. In its normal position, it holds a rubber packer in an elongated position to permit passage of fluid between the packer and the tubing walls. The lower section of the free piston contains a hydraulic shock absorber which cushions the return of the tool to its

Jan 1, 1953

By Herbert H. Kellogg

Graphs representing the standard free-energy of formation as a function of temperature for 21 fluorides are presented, along with estimated values for the standard free-energy of formation of 20 atedadditional fluorides. A few of the many possible uses of these data in metallurgical calculations are discussed, including the fluorination of oxides, sulphides, metallurgicaland chlorides, and the reduction of metal fluorides. RECENT papers which have presented free-energy data for oxides, sulphides, chlorides, carbonates, sulphates, and silicates in the form of free energy vs. temperature plots,1-5 have found important uses in teaching and metallurgical development work. This method of presentation of thermo-dynamic data serves to make available in readily usable form thermodynamic constants which are scattered throughout the literature, and to show by graphical means the stability relations which exist between the compounds of a given type. It is certainly desirable to have these free-energy-temperature diagrams for as many types of compounds as are of present or potential use in metallurgical processes. Thus, even though there are but few uses of metallic fluorides in extractive metallurgy today, the potential uses of fluorine processes are of great importance and serve as the principal justification of this paper. Recent developments in the production of fluoro-carbons have resulted in vastly improved methods for the production and handling of fluorine and corrosive fluorides, with consequent reduction in costs.".' The extractive metallurgist should no longer overlook possible fluorine processes when development of a new process for a relatively high unit-price metal is being considered. In a previous paperv he author outlined in some detail the importance and use of free-energy data in metallurgical calculations and also discussed the properties of a standard free-energy vs. temperature diagram. The same method of presentation is adopted in this paper, and the reader is referred to the earlier work for explanations of the use of free-energy data. Thermodynamic Data This paper presents standard free-energy vs. temperature diagrams, Figs. 1 and 2, for those fluorides for which the major thermodynamic constants are known. In the calculations of the standard free-energy of formation (AGO), values of the enthalpy of formation at 298°K (?Ho,) were taken from "Selected Values of Thermodynamic Constants"8 most of the values of standard entropy at 298°K (S°298) were taken from "Selected Values"," but in a few cases the values given by Kelley9 ere preferred; data for the Phase changes came from "selected Values" and several of Kellley's publics- tions;0-12 and most of the specific-heat data were taken from Kelley.l0 The appendix gives a detailed list of the sources of the data. As explained in an earlier paper,6 he accuracy of some of the standard free-energy relationships is not high. An error of +1 kcal at 1000°C is expected in most of the curves of Figs. 1 and 2. The error may be as high as +3 kcal in some of the curves. Rather than attempt to estimate the reliability of each curve, the source of the data used is reported in the appendix, and the reader may compare these data with newer values as they become available. Figs. 1 and 2 fail to show values for the fluorides of many important metals. In most cases this is because the entropy of the metallic fluoride is unknown. For preliminary calculations it is often useful to have available the best estimate of an unknown datum, rather than no information at all. With this in mind, Table I lists estimated standard free-energy values for a number of important metallic fluorides not included in Figs. 1 and 2. The values reported in Table I were, calculated by Brewer et al.13 and are based on estimated entropy values. The estimated uncertainty of the values for each fluoride were calculated from the uncertainty values given by Brewer1' for ?H°, and the entropy function.

Jan 1, 1952

By H. W. Mead, C. E. Birchenall

SELF-DIFFUSION in pure gold has been studied by Sagrubsky,1 McKay,2 Gatos and coworkers,3,4 and Okkerse.5 Sagrubsky used a sectioning technique but reported results far lower than any of the others. The work seems to be carefully done, and it appears that a factor of 60 must have been omitted in his calculations or the units misstated by an equivalent amount. McKay used a surface activity method, and Gatos and Kurtz, following Gatos and Azzam, applied autoradiography to the measurement of activity on an oblique section through the diffusion zone. These two investigations agree well with each other but give results below those reported here. Okkerse employed a very careful sectioning technique. Chemical interdiffusion in Au-Ag alloys has been measured under several concentration conditions. Average values of the diffusion coefficient for the range of 0 to 18 atomic pct Au were obtained by Braune.6 since the diffusion coefficient probably varies markedly over this range, the values may not be too useful. Also, a plot of these data suggests that grain boundary contributions may have been appreciable at the lowest temperature employed. Ebert and Trommsdorf7 give average values for 0 to 9 atomic pct Ag, and Johnson8 reports average values for 45 to 55 atomic pct Au. Johnson also measured silver and gold self-diffusion coefficients in 49.2 atomic pct Au alloys, and self-diffusion in pure silver. The self-diffusion of gold in pure silver has been determined by Jaumot and Sawatsky.10 Other measurements which do not cover a range of temperature or are of low precision are not mentioned in this account since a review by Kubaschewski is available." This contribution reports diffusion coefficients for self-diffusion in gold, self-diffusion of gold in Au-Ag alloys, and chemical diffusion in Au-Ag alloys. Although it had been intended to obtain silver self-diffusion data in the alloys it now appears unlikely that these measurements can be done soon, so a table has been worked out for a self-consistent scheme of diffusion coefficients which should not be too far from the true values. Experimental Details Experiments on pure metals were conducted using fine gold of 99.99+ pct Au and silver of the same purity. Alloys were prepared by melting the two metals together in a graphite crucible in vacuo and allowing the slug to solidify in the crucible. After machining to a cylinder about 0.85 in. diam each slug formed one half of a diffusion couple. Compositions were determined later by analyzing chips taken from the extremities of the diffusion zones. The gold used in the preparation of alloys was sometimes pure gold but was normally either in the form of clean pickled alloy from previous experiments or gold recovered by oxalic acid precipitation from warm aqueous solution. Chips from the various stages of experimentation were dissolved in aqua regia and the solution taken to low bulk, diluted with water, and again taken to low bulk before diluting for the precipitation. This precipitated gold contained a small amount of silver as the only impurity detectable by spectrographic analysis. Disks for use in diffusion couples had opposite plane faces abraded on emery paper as far as zero grit, were annealed for 12 hr at 900°C in argon, and had one face of each disk polished to 000 emery paper. Radioactive gold was plated at about 2 ma per sq cm from a small volume of cyanide solution containing 1 mg of inactive gold as a carrier. Specimens , were freshly abraded on 4/0 emery paper immediately prior to plating. In the case of the active couples disks of a similarly prepared but unplated alloy or pure metal were placed on top and welded to the active disk. With the concentration couples disks of different compositions were welded. Welding was performed after a pressure of 5,000 lb had been applied at

Jan 1, 1958

By R. S. Wagner, H. Brown

Criteria for nucleation with the aid of twin planes during crystal growth from the melt are discussed. It is shown experimentally that bismuth crystals can grow from a subercooled melt in a twinned bismdtic form. A mechanism of growth based on the presence of at least me twin plane is proposed. It is well known that faceted growth can be observed in crystals grown from the vapor phase, dilute solutions, or from the melt. Faceted growth, in which the crystal is bounded by its slowest growing faces, will occur if the growth rate is strongly orientation dependent. The addition of atom layers on a facet plane can only occur by two-dimensional surface nucleation or with the aid of an imperfection. Nucleation with the aid of dislocations was proposed by rank' and observed to be of particular importance in crystal growth from the vapor phase. Nucleation with the aid of two-dimensional imperfections, notably twin planes, was suggested by stranski2,3 and Frank.4 A twin plane, terminating at the growth interface, can form a reentrant step at which nucleation can occur at a much smaller super-saturation (or supercooling) than required for two-dimensional surface nucleation. Nucleation by a twin plane usually results in a fast growth rate along a crystallographic direction parallel to the twin plane. Such a nucleation mechanism, based on the presence of a twin plane, has been used by Dawson5 to explain the growth and morphology of sheet-like crystals of paraffin n-hectane. In recent years more evidence was found that nucleation by twin planes occurs frequently in crystal growth from the vapor phase and from dilute solutions, for example, in cadmium,' barium titanate,7 silver,8 silicon9 and gallium arsenide.10 In crystal growth from a supercooled melt, however, nucleation by twin planes has so far only been observed in materials with the diamond or zinc blende structure. Bennett and Longini11 were the first to recognize the important role a single twin plane plays in the growth of germanium dendrites. Subsequently, it was found that a prerequisite for continued propagation of germanium dendrites is the presence of two parallel twin planes which form a self-perpetuating system of nucleation sites.12 Sili- con and some III-V compounds such as InSb also grow dendritically by twin plane nucleation. It appears that the following criteria must be satisfied in order that nucleation with the aid of twin planes can occur: A) The growth form of the material must be faceted." B) The formation of twin boundaries, by a fault in layer sequence during growth, by plastic deformation, or by an accidental meeting of properly oriented crystals, must be possible. C) Twinning must form a reentrant step where the twin boundary terminates at the faceted growth interface. D) These three conditions are necessary, but in certain cases not sufficient for continued crystal growth with the aid of a twin plane. Depending on interface morphology, a combination of more twin planes is sometimes required to form a self-perpetuating system of nucleation sites. This investigation was carried out with the idea in mind that nucleation with the aid of twin planes is a more general phenomenon and should occur in those materials, grown from a supercooled melt, which satisfy the criteria outlined above. It has been found that crystals of high-purity bismuth grown from a supercooled melt can grow by the aid of a twin plane. In the first two sections the faceted growth form and the twinning elements of bismuth are discussed. In the last section prismatic crystals of bismuth, which appear to grow with the aid of a deformation twin are discussed.

Jan 1, 1962

By C. C. Templeton, S. S. Rushing

Methods previously developed for the study of air-liquid displacements in microscopic capillaries (inner diameters of 3 to 40 microns) have been used to investigate oil-water displacements in capillaries initially filled with water. Displacement calculations assuming perfect displacement and no capillary pressure hysteresis yielded oil effective viscosities smaller than the macroscopic viscosities. For a given liquid pair, the oil effective viscosity decreased both with decreasing capillary size and with increasing oil-water viscosity ratio. This behavior can be explained by the existence of an annular water film (20 A to 260 A thick) on the capillary wall. When the capillary was first filled with oil, the ratio of the oil effective viscosity to the normal oil vircosity was highest for the first water displacement and decreased with subsequent displacements. Sometimes the oil effective viscosity ratio during the initial water displacement was greater than unity. INTRODUCTION In a previous paper1 a technique was described for studying air-liquid and liquid-liquid displacements in very small capillaries of uniform diameter, in the hope that such microscopic data would further the understanding of the nature of multiphase fluid flow through porous media. That paper contained comprehensive data for air-liquid displacements in Pyrex capillaries, with a few data for oil-water displacements in capillaries initially filled with water. The purpose of this paper is to present more complete results for oil-water displacements in capillaries initially filled with water, and to describe for the first time such observations in capillaries initially filled with oil. In this way the effect of the wetting history of the system upon the displacement process may be studied. METHODS The basic techniques employed were described in the previous paper.1 The measuring procedure and the working equations will be briefly summarized here and a few modilications will be pointed out. For the present study, temperature control within 0.l °C was obtained by placing the microscope and its immediate accessories in a thermostated air bath made of a steel frame covered with plexiglas. The water and oils used in this work were the same as in the previous paper,1 with the addition of "Medium Mineral Oil, U.S.P. supplied by the Harshaw Scientific Co. When the first liquid was introduced into the horizontal capillary, the air-liquid static capillary pressure Poc was measured along the observable length of the capillary. From the relation Poc = 4y cos 0/d, the capillary diameter d could be calculated from Poc if the "microscopic" air-liquid boundary tension, To = y cos On, was taken as equal to its known "macroscopic" value. This calculation involves assuming that cos 6 = 1 and that capillary size or the resulting high interfa-cial curvature has no effect on surface tension, or y cos 6, as was verified by our work, and also by that of Cohan and Meyers on air-liquid-solid systems. For several capillaries these calculated diameter values were compared with values measured visually with a filar micrometer eyepiece. For a given capillary the average values for the two methods agreed within 1 or 2 per cent, but the visual values were less reproducible than the calculated values. Further the calculated values were much less subject to personal bias and took into account any slight ellipticity that might be present. Hence diameters calculated from air-liquid Poc data were used throughout this paper. The second liquid was introduced in such a way that a single spherical interface separated the two liquids. Displacements were always made with a constant pressure, Pt, between the ends of the capillary. The times (t) at which the interface passed certain

Jan 1, 1957

By S. E. Hasko

It is the purpose of this note to report the crystal-lographic data for nine new B5A compounds* having the Cu5Ca structure, with A a rare earth and B a transition element, Co, Ni or Cu. In previous papers, some magnetic data1 and preparation and crystallo-graphic data2 for other B5A compounds having the same structure have been reported. Crystallographic data for these compounds are shown in Tables I and 11. These results are in agreement with others of this series reported previously by Wernick and ~eller.' The abnormally large atomic volume of Yb metal3 is not manifested in Ni,Yb, when one compares it with the compounds reported here and the data of reference 2. This is not true for the compound YbAl,, having the cubic Laves structure (MgCuz), to be discussed in other papers.4'5 Thus, it appears that Yb has a valence of 3; i.e., the 2 s and Id electrons are lost to the conduction band.4'5 Lattice constants for four of these compounds prepared by levitation melting have been reported by Nassau, Cherry, and wallace.' The lattice constants

Jan 1, 1961

By B. R. Berger

The Getchell area in the northern Osgood Range, Humboldt County, Nevada, was first prospected in the late 1800s for silver, copper, and gold; the first recorded mention of mining activity concerned a silver discovery. The September 17, 1874 edition of the Winnemucca Silver State notes that the Crystal Mining District was newly organized in the Fremont Range (as the Osgood Range was then called) to include discoveries of silver, lead, and antimony made on the Louisa claim. The name Crystal was derived from the plentiful quartz crystals found in-cavities near the prospects. This same area, occurring on the northwestern margin of the Osgood granodiorite stock, was later mined as the Richmond tungsten property, and crystals may still be found there in cavities in a massive garnet tactite. By 1878, how-ever, the name Crystal had been abandoned in favor of Potosi. The next flurry of activity in the Osgood Range was reported in 1899 when a copper strike on Granite Creek in the southern portion of the range received attention. The copper occukences were in a granite contact zone on the southeastern edge of the Osgood stock and, in 1916, the first tungsten in the district was discovered in the same deposit. During the last part of the nineteenth century, cattle and sheep were brought into the Kelly Creek Valley east of the Osgood Mountains by various ranchers. Alphonso and Adrian Bernard were among these ranchers, and in the first decade of the twentieth century, one of them recognized the altered rock where the Getchell Center it is now located. A 3-m (10-ft) deep prospect pit was dug on the outcrop, but the highest assay ran about $11/t ($10 per st). No further work was done on the gold-bearing rock. In 1934, Emmet Chase of Battle Mountain and Ed Knight of Golconda prospected in the area of the Bernard prospect pit and located several lode claims. At this time, Noble H. Getchell, a state senator, was looking for new mining opportunities to develop. He held interests in the Gold Circle Consolidated at Midas, which was becoming a losing venture. Chase and Knight brought their discovery to his attention, and he grubstaked them to prospect further in the area. In need of financial backing, Getchell solicited the help of George Wingfield, Sr., who held a minor interest in the Gold Circle. Wingfield was a successful banker and mine operator during the heyday of Tonopah and Goldfield, and he had become good friends with Henry C. Frick and Bernard Baruch. Wingfield let Baruch in on several very successful mining ventures in Goldfield, and Baruch returned the favor by underwriting the financing of the Getchell mine. Eleanor Roosevelt and Jack Dempsey were early stockholders in the Getchell operation. George Wingfield brought his brother-in-law, Roy A. Hardy, a consulting engineer who had constructed the American Flat mill near Virginia City, to look at the property. Upon inspecting the Chase-Knight claims, Hardy declared the whole area to be mineralized. A crosscut was driven to check the extent of the ore, and the results were better than anticipated. The locators were reportedly given $50,000 for the claims. The Getchell Mine, Inc., was organized on November 5, 1936. A small railroad that ran from Battle Mountain to Austin was purchased, and the ties and rails were moved to Getchell to be used in underground exploration. Enough reserves were found in the Center and South pit areas to construct a 40 t/d (44 stpd) mill. The financial and engineering help for the mill was provided by the Newmont Mining Co. for a 17 1/2% interest in the corporation. Newmont set about trying to solve the metallurgical problems with the sulfide ore, and also directed the early development work. Newmont wanted to grind the sulfide ore underground and oxidize it in the atmosphere by spreading salt on it. Detrital Flat in Arizona was purchased to provide salt for

Jan 1, 1985

By R. M. Rose, D. P. Ferriss, J. Wulff

Single crystals of tantalum, tungsten, and the binary alloys thereof were grown by electron-beam zone melting and tested in tension between 77° and 373°K. The ductile-to-brittle transition temperature increased sharply with solute concentration, for both tungsten-rich and tantalum-rich alloys; apparently, the maximum transition temperature exists near the 50 pet concentration. Twinning was observed to be a consequence of cleavage-crack propagation. Cleavage occurred on(100)planes, and extensive tearing and "river markings" were present. The onset of brittleness could not be associated with any change in deformation mode, the yield point phenomenon, or the large rise in yield stress with decreasing temperature. Cleavage was observed to initiate at either the specimen surface, or subgrain boundaries. The observation was made that the grain boundaries of Polycrystalline materials are probably even better as nucleation sites for fracture, and are responsible for brittleness at high temperatures and lower solute concentrations than those of the corresponding single crystals. TUNGSTEN and tantalum, the two high-melting neighbors in the third transition period of the periodic table, present striking contrasts. Although both are bee, tungsten has far higher elastic moduli, and the highest ductile-to-brittle transition (DBT) of all the pure metals.' Tantalum, however, is ductile at liquid helium temperatures. Large strain aging and yield point phenomena are observed in tantalum,2,3 but only to a lesser extent in tungsten.4 Tungsten work-hardens at a high rate,5 whereas this effect is negligible in tantalum.' Since the mutual solid solubility of these two metals is complete,7 and no ordering has yet been reported in the binary system, the possibility of depressing tungsten's DBT by tantalum additions was considered. Also, tungsten additions to tantalum could produce hard, high-melting alloys which might be ductile at room temperature. Such alloys offered excellent bases for complex alloy development, particularly with regard to the effect of rhenium on Group VI metals.8"10 In addition, there was the opportunity to examine flow and fracture modes in the vicinity of the DBT, with particular emphasis on the correlation between brittleness and fundamental deformation mechanisms. Myers11 has reported that recrystallized alloys with up to 10 pet W in tantalum are ductile at room temperature, but alloys with 20 pct W could not be swaged at temperatures as high as 500°C. The whole spectrum of Ta-W alloys has been surveyed by Braun, Sedlatschek, and Kiefferl2 using sintered powder compacts. In addition to some physical properties they reported a maximum hardness at about 50 at. pet W, dropping to much lower hardness levels for the pure components. They were able to cold work tantalum-base alloys with as much as 30 pet W and to warm work tungsten-base alloys with up to 20 pet Ta by procedures similar to those used for pure tungsten. EXPERIMENTAL In order to study deformation modes and to keep the impurity concentrations at a minimum, electron-beam zone melting was used to prepare single crystals of high purity. The electron-beam zone melting apparatus is similar to that described by Calverley, Davis, and ever" and incorporates a grid control rectifier to maintain control of emission current. Pure metals were refined by making three zone passes at 4 mm per min up the rod. Alloys were prepared by melting together wire of one constituent on a previously melted rod of the major constituent. Subsequently, two zone passes were made in opposite directions to level the composition after the manner suggested by pfann.14 Purification of the starting materials was accomplished by evaporation of the several impurities, and the degree to which this was accomplished is indicated in the chemical analyses of Table I. The uniformity of composition along a zone levelled rod was within the i 1 pet accuracy of the fluorescent X-ray technique used to determine composition. Crystallographic orientation of the

Jan 1, 1962

By Kenneth K. Humphreys, J. W. Leonard, T. S. Spicer

INTRODUCTION Reasons for Thermal Drying The continuing increase in the percentage of - '/4 in. ( -6.3 mm) coal produced as a result of the increased use of mechanical mining methods has, over the years, tended to shift considerable portions of the work of producing salable coal to the fine coal cleaning section of the preparation

Jan 1, 1979

By John S. Brock

INTRODUCTION The Oxford Dictionary says that the word "promoter" has usually been used in an opprobrious sense since at least 1876. This popular image of mining promoters is of cigar-chomping shysters and Brooklyn-Bridge vendors, improving their standard of living with the aid of funds raised through the sale of stock to little old ladies. It is unfortunate that mining promoters are considered crooks until they can prove their integrity and honesty by finding a mine. A common rule of thumb states that for every 1,000 prospects, 100 come to be drilled, and one becomes a mine. However, it is also a statistic that there have been mining promotions, where money raised has gone elsewhere than into the ground; Junior exploration companies can be handy vehicles for unscrupulous financial activity. One must remember though that every stock exchange has had its share of sound mining promotions that, because of the one in 1,000 odds, have failed for legitimate reasons. The promoter must be able to rationalize the worth of a mineral discovery which, on an industry- average basis, probably cost more to find than the discounted value of its net return, which return is not an assured percentage of invested capital, and furthermore, is ultimately from a wasting asset. So, it is easy to understand why the promoter must constantly justify the credibility of his operation to his grubstakers during the course of the "five phases of exploration," those being (1) euphoria, (2) disillusionment, (3) search for the guilty, (4) punishment for the innocent, and (5) distinction for the uninvolved. The promoter with the exploration organization that does not have the benefit of positive cash flow, by definition for the sake of this article, works for a promotional outfit, a Junior Company, that must raise its exploration budget from a variety of sources. Promotion, as discussed here, will not entirely refer to the formation and operation of a joint- stock company but rather to the overall methods of raising risk capital for mineral exploration ventures from outside sources. THE NECESSITY OF PROMOTION In Canada, the publicly financed Junior Company has had an enviable record of mine-finding success. In the Province of British Columbia alone, the discovery of fifteen out of twenty-four mines has been as a result of the activity of the Junior Company (B. C. & Yukon Chamber of Mines, 1977). In the Province of Ontario, one research study indicated that between 1951 and 1974 the 'Juniors' spent only 28 percent of the total exploration funds but were responsible for 62 percent of all economic discoveries (Freyman, 1978). The reasons for the success of the Juniors are tied to a variety of factors, the main one being personal initiative based on incentive. In other words, the principals, or their employees have 'a piece of the action.' The smaller companies can operate faster and more efficiently than their larger counterparts. The Junior Company is also destined to take some bigger risks, the 'long shots,' many of which efforts by virtue of the Junior's perseverance coupled with a touch of 'ore is where you find it' philosophy, result in major discoveries. The individuals, syndicates, private and publicly financed Junior Companies, because of high costs of exploration and development, cannot hope to finance most mineral prospects all the way to production. Exceptions do exist, those being the lower capital cost, small, high-grade deposits. Private investors and publicly financed Junior companies, therefore, can usually afford to finance most exploration through the initial drill-testing stage. The major resource company will enter a mining deal with a Junior Company usually by way of option or joint venture agreement, and will finance to production to earn an equity in the prospect or the Junior Company or both. The conventional lending institutions, banks and government agencies, will usually only participate through loaning a portion of capital

Jan 1, 1985

By H. Doi, Y. Fujiwara, K. Miyake

In order to throw light on the mechanism of plastic deformation of WC-Co alloys, compressive tests of WC-(7 to 43) vol pct Co alloys have been carried out at room temperature, and stress-micro strain relation has been investigated in detail. The analysis of the factors affecting the yield stresses reveals that the yield stresses can be predicted by modified Oro-wan's theory if one properly estimates the planar in-terfiarticle spacings. Conzpressive straining of some of the alloys by 0.066 to 0.17pct increases the decrements by a factor of as much as 3.4 to 14, whereas the corresponding increase in the electrical resistivities is less than 10 pct. The analysis of the decrement data in terms of -Gramto and Lücke theory shows that the marked increase is attributed to increased dislocation darnping itt the binder (cobalt) phase. By cornbilling the decrement data and the conzjwession duta, one obtains the relation between flow stress in shear (?t) and increase in dislocation density (p): At = const . v6 . This is interHeted to mean that the mechanism of strain hardening of CirC-Co alloys is essentially sarne as the one for dispersion strengthened alloys. The possible effect of bridge formations between the carbide particles has also been examined. OWING to the combination of hardness, strength, and other physical and chemical properties, WC-Co alloys have opened the way for unique fields of applications, the recent ones being, for instance, anvils for super-high-pressure generation apparatuses. In such applications, the alloys are frequently subjected to very high compressive stresses: these stresses may cause the alloys to deform plastically and eventually to fail. However, much remains obscure regarding the nature of the plasticity of the alloys. Evidently, the alloys owe their high strength to the hard carbide particles which frequently occupy as much as 80 to 90 pct in volume fraction, whereas the ductility required for practical applications is provided by the small amount of the binder phase between the carbide particles. When the volume fraction of the carbide phase is not very large, deformation behavior of the alloys may be described by some of the current dispersion strengthening theories. However, greatly increasing the carbide phase is thought to lead to some carbide skeleton structure or bridge formations owing to the increased chances for direct contacts between the carbide particles;1,2 this may appreciably affect the plasticity of the alloys. Regarding the effect of formation of the carbide skeleton structure, it is interesting to note the work by Ivensen et al.3 on compression tests of the alloys containing somewhat large carbide particles; they observe extensive generation of slip bands in the carbide particles after application of some preliminary compressive stresses. They interpret the results in terms of plastic deformatiot: of the carbide particles which are supposed to have formed a skeleton structure; the binder phase plays only a passive role, at least in the early stages of the deformation. That carbide crystals exhibit microplasticity at room temperature is apparent from the work of Takahashi and Freise4 and French and Thomas5 on indentation of WC single crystals. On the other hand, Dawihl and coworkers6-10 maintain that even when volume fraction of the carbide phase is very large (for instance, more than 90 pet), a very thin binder layer generally exists between the carbide particles. They interpret the results of the extensive mechanical tests in terms of the plasticity of such a layer. Gurland and Bardzil11 point out that decrease in ductility of the alloys with increase in the carbide phase is caused by the effect of plastic constraint exerted by the dispersed carbide particles. Drucker12 further develops this concept from a continuum-mechanics approach on an assumption that a continuous thin binder layer separates the carbide particles. A common feature of the studies reported so far on the plasticity of the alloys is that the information deduced is invariably qualitative in nature. Thus, very few systematic experiments for obtaining reliable and sufficiently detailed stress-strain curves of the alloys varying widely in the microstructural features have been carried out. In particular, it may be of special interest to investigate in detail the early stages of the plastic deformation of the alloys in order to shed light on the strengthening mechanism. However, such work appears to be extremely rare. Doi et al.13 recently reported a first brief account of the results of some quantitative analysis of the plasticity of the alloys in terms of dislocation theory. Their experiment was rather limited in the composition range covered (volume fraction occupied by the carbide phase: 79 to 83 pct), and thus they could not necessarily elucidate the controlling mechanism of plastic deformation of the alloys of a more general composition range. Consequently, in the present investigation, deformation behavior and some other physical properties of the alloys were investigated and discussed in more detail over a much wider composition range. SPECIMEN PREPARATION WC-Co alloys used in this experiment were prepared in cylindrical or rectangular form by sintering in vacuo compressed mixtures of tungsten carbide and cobalt

Jan 1, 1970

By Y. C. Liu, G. A. Alers

measurements of the anisotropy in Young's modulus produced in copper by rolling 95 pct reduction in thickness below room temperature have been carried out in order to study the dependence of the texture on rolling temperature. The results clearly show the transition from a copper-type texture to a brass-type texture as the temperature of rolling is lowered. The intermediate textures observed can be described very well as a simple mixture of the two terminal textures. These results cormbined with other texture measurements make possible afresh review of the experimental facts velating to rolling textures in fee metals and, as a consequence, a critical examination of the current theories is presented. PREVIOUS experiments have shown that the transition from the copper- to the brass-type rolling texture is clearly displayed and can be quantitatively analyzed by measurements of the anisotropy of Young's modulus.' Application of this method to the Cu-Zn alloy system showed that the description of the texture transition as a gradual rotation of the grains from the orientation characteristic of the copper texture to the {110}(112) texture of brass2 was inconsistent with the data. Instead, the data suggested that the texture within the transition region could be described as a simple mixture of the two terminal textures.5 Unfortunately, it was difficult to establish this point conclusively because of the inadequacy of corrections for the composition dependence of the single-crystal elastic constants. Since a rigorous establishment of the nature of this texture transition is essential to our understanding of the formation of rolling textures in fee metals, it is clearly important to undertake an investigation in which the composition dependence of the elastic constants would not enter. A suitable composition-independent texture transition is provided by the well-established variation in the rolling texture of copper with rolling temperature. This temperature-dependent texture transformation has been studied by smallman' in several fee alloys and by Müller5 and others"' in copper. They observed that the texture characteristic of copper rolled at room temperature changed to a brass-type texture when the rolling temperature was lowered to 77°K. Although it is not possible to decide unequivocally from the published pole figures whether or not the 77°K rolling texture of copper is entirely of the brass type,' this complication does not affect the main purpose of the present investigation. In addition to establishing the nature of the texture within the transition region, the modulus data should also provide a determination of the temperature at which the transition occurs as well as the temperature range over which the transition extends. This information when combined with the modulus data on Cu-Zn alloys would then provide a considerable body of new information on textures in fee metals. Since these modulus results and the data obtained from pole-figure studies must be internally consistent, it is appropriate to compile a brief summary of the experimental observations based on all available methods rather than on the pole-figure data alone as has been done in the past. The primary purpose of such a summary would be to yield a more precise definition of the experimental facts on the rolling textures of fee metals, and thus greatly facilitate our evaluation of various proposed theories in this field. The final section of this paper is devoted to this compilation of consistent, experimental facts and their application to the various theories. EXPERIMENTAL PROCEDURE Two 18-lb ingots of cathode copper of 99.99 pct purity were induction-melted under a nitrogen atmosphere in a graphite crucible and chill-cast into a steel mold. The ingots were repeatedly cold-rolled and annealed (I hr at 500°C) into slabs about 1 1/8 in. thick. Blocks 3 1/4 in. wide, 2 1/4 in. long, and 1.000 in. thick were machined from each slab. The rolling schedule used was the same as in the previous investigation1 and the final thickness of the sheet was 0.050 in. with a rolling reduction of thickness of 95 pct instead of 97.5 pct as in the previous work.' The compositions and temperatures of the cold baths used for the low-temperature rolling were as shown in Table I. After each pass the rolled strip was immediately immersed in the cold bath for about 1 min or until the bubbling of the bath had subsided. The modulus data were taken within 2 hr after the rolled strip was warmed to room temperature for the first time, so that effects due to recrystallization were minimized. The modulus specimens were in the shape of flat bars, 3 in. long, 4 in. wide, and 0.050 in. thick, cut with their long dimensions oriented at 15-deg intervals between the rolling direction and the transverse direction. The values of Young's modulus were deduced from measurements of the frequency at which these long narrow bars were set into longitudinal, resonant vibration as previously described.9 To excite the mechanical vibrations in the specimen, an electromagnetic drive similar to that employed by Thompson and lass" was used. The maximum in the amplitude of

Jan 1, 1968

By Allan D. Taylor

INTRODUCTION From the designer's view, the installation starts with the first definition of the orebody, and progresses through a long and complex development. The design is affected not only by the characteristics of the ore, but by all of the personalities and events of the project during its development. The following discussion attempts to touch on the most important aspects which define the context in which the designer must work in apply the do's and don'ts. That context is the basis of the viewpoint. WHAT CAN GO WRONG The Project Is Going Over Budget This is a common and serious concern to the plant designer. The Project Falls Behind Schedule Another common and disturbing condition with which the plant designer must cope. Some Equipment Fails to Perform This can be due to either faulty equipment or operating deficiencies. It can be the result of a wide variety of causes, but the designer will be an interested party in the search for the cause and the cure. The Plant Isn't Flexible Enough Sometimes a plant will handle some or even most of the ore satisfactorily but is unable to treat another type properly. This can be a significant problem. An example might be a case where low capacity of a cyclone feed pump makes it impossible to accompany an increase in grinding mill throughput with a corresponding increase in dilution water. This could lead to an increase in cyclone feed density, and a loss in product grade or a limit on the plant capacity. Spillage And Cleanup Are Excessive This is one of the most common and annoying defects in metallurgical plants, and one for which the designer can rarely delegate blame. Maintenance Is Excessive Another common complaint in new plants, and also one for which the dedesigner must accept most of the responsibility.

Jan 1, 1982

Organisation Place Date 1918 American Society of Mechanical Engineers New York, N. Y. Dec. 3-6 Society for Promotion of Engineering Education, with British Educational Mission Cambridge, Mass. Dec. 6-7 Geological Society of America Boston, Mass. Dec. 28-31 American Association for the Advancement of Science Boston, Mass. Dec. 27- Jan. 2.

Jan 12, 1918