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By J. E. Pavlick, W. W. Mullins, H. W. Paxton

The growth of nitrogen-austenite during nitriding of large-gvained ferrite between 650" and 800°C has been studied as a functimz oJ time and nitrogen potential of the atmosphere for a variety of alloying elements dissolved in the ferrite. Whereas no preferential grain boundary penetration by aistenite takes place in zone-refined iron, the addition of aboit I zot pct oj' V, Ti, Cr. Si, or A1 produces significant protrusion of austenite down former 0-0 boundaries. This group of elernents also produces ragged y-0 interfaces in the a grains which advance more slozuly than those in zone-refined iron. 1 zut pct of Ni, Co, Mn, or Mo dissolved in ferrite leads to essentially smooth 7-a interfaces, which advance at rates very sinzilar to those in zone-refined iron. The reasons for this effect are not clear. Two possible limiting hypotheses, not necessarily exclusive, are discussed. One involves p.referentia1 grain bozindary diffusion of nitrogen. the other the production of a zone of ferrite, stpersatcirated with respect to nitrogen, from which austenite precipitates helerogeneozisly on the a-a gyain boundaries. In many phase transformations which occur by nu-cleation and diffusion-controlled growth, information on the parameters which control the rates of nuclea-tion and of growth is frequently not quantititative. The present work describes a continuation of efforts to obtain quantitative data on growth rates in systems where thermodynamic and kinetic factors are known independently, and thus where comparison with models of the growth process is possible. The work has been conducted on iron-base systems for two reasons. Firstly, there are several interesting transformations in this system, many of which are of practical importance. Secondly, the information on phase diagrams, activities, and diffusion coefficients is more complete in this system than in any other. These data are still inadequate to check all the effects of alloying elements, but at worst it is possible to make estimates and thus examine order-of-magni-tude agreement with proposed models. It will be necessary to do this in the present work. The problem studied was the growth of nitrogen-austenite in from the surface of large-grained columnar crystals of alloyed ferrite exposed to an NHs/Hz atmosphere. Earlier work by Grozier et al.' had suggested that growth of austenite may occur preferentially along grain boundaries of alloyed ferrite, whereas zone-refined (ZR) iron shows no such effect, Fig. 1. Growth of nitrogen-austenite into single crystals of zone-refined ferrite is planar provided sufficient nu-cleation sites for austenite are present, and is controlled by volume diffusion of nitrogen through the

Jan 1, 1967

By F. S. McNicholas, M. S. Walker, V. C. Rogers

During the year of 1944 and the first half of 1945, the Climax Molybdenum Co. made a study of some of the problems in block and panel caving, with the use of a scale model. The experiments dealt essentially with the type of rock and conditions at Climax, but some experiments were carried out to simulate conditions found in other mines. Most of the previous experiments on the caving characteristics of rock have dealt with sedimentary or broken igneous material. The series of experiments described here was designed to show the caving action of unbroken igneous rock. Con- siderable difficulty was experienced in duplicating unbroken material in the model. The results obtained are believed to be relatively correct, but verification must necessarily come from future mine operation. Observations in the mine and glory hole, together with statistical data, were used as criteria for creating similar conditions in the model. In 1913, George R. Lehman' experimented with broken material in a model for the Inspiration Consolidated Copper Co. and, more recently, P. B. Bucky2 experimented with broken material with a capping of mill tailings. Mr. Lehman's model represented a maximum ore height of 70 ft. capped by 55 ft. of waste. He varied the draw-hole spacing from 6¼ ft. to 8? ft. and 12½ ft. The material used graduated from fines to 30-in. maximum size. Some of his conclusions were: "(I) The less the distance between chute centers, the greater the extraction (Fig. I); (2) the higher the ore column, the greater the extraction; (3) the less the amount drawn at a time from each chute, uniformly, the greater the extraction of clean ore before the capping appeared, but not the greater the total extraction to a I per cent copper final product." (Fig. 2.) Professor Bucky concluded, in part: "(I) Drawing of ore may take place at any time from any finger and in any amount without affecting materially: (a)

Jan 1, 1946

By John Chipman

The concentration of a solute in a dilute ),zetallic solution may be measured by any of several parame- ters including weight percent, atom fraction, atom ratio, and lattice ratio. The ratio of filled to unfilled interstitial sites is useful for interstitial solutes. A variable 2 proportional to this ratio is used as a measuve of concentration. For component 2 irz a bitzary solution z2 = n2/Ym - nz/b) where b is the numberber of interstitial sites per lattice atom. For a t~lul-ticortzporzent solution this becomes zz = n2/(nl + Cvjnj) in which Vj = - l/b for an interstial solute and +1 for a substitulional solute. In the infinitely dilute solution the activity of an interstitial solute 2 is proportional lo z2. At finile concentration the departure from this limiting law is expressed us an activity coefficient, his coefficient is a function of concentra1io)z expressed as tevactiolz coeffcient 8; is analogous to the jark~iliar e£ bul is found to be independent of concentvation in certain solutions for which data are available. It is found that the same equations may be used to express the activity of a nonmetallic solute, sulfur, in liquid solutions of iron containing other solutes, both metallic and nonmetallic. For a nonmetallic solute or for one which strongly increases the actiuity of sulfur, it is convenient to assign arbitvarily a value vj = — 1. When this is done the derivative is found to be constant in each of the ternary solutions studied. The activity coefficient of sulfur in a complex liquid iron solution may be expressed as where nk is a second-order cross product determined in the quaternary solution Fe-S-j-k. The equation is used to calculate tlze activity of sulfur i)z three sevetl- component solutions. IN thermodynamic calculations concerning dilute solutions it is unnecessary to invoke laws and relations which extend across the concentration range to include concentrated solutions. In most binary metallic systems, as arkeen&apos; has recently pointed out, there exist two terminal composition regions of relatively simple behavior, connected by a central region of much greater complexity. When the solute is a nonmetal there is only one such region and in many systems the concentration range is extremely limited. It is the purpose of this paper to suggest a method for the calculation of activities in such a terminal region in which one or more solutes are dissolved in a single solvent of predominantly high concentration. HENRY&apos;S LAW In the usual textbook statement of Henry&apos;s law, concentration is stated in mole fraction. This has the advantage that it makes Henry&apos;s law thermodynamically consistent with Raoult&apos;s law. Since all measures of concentration at infinite dilution are related by simple proportion it follows that mole fraction, molality, atom ratio, weight percent, or any other unit of concentration can be used with the appropriate constant. At finite concentrations, however, calculations based on the law depend upon the unit employed. Deviations from Henry&apos;s law at finite concentrations depend upon the composition variable employed. They are evaluated in terms of activity and interaction coefficients2 which have become familiar features of metallurgical thermodynamics. It is the purpose of this paper to propose a measure of concentration for metallic solutions containing interstitial or nonmetallic solutes by means of which the calculation of activities in complex solutions may be simplified. The discussion will be restricted to free-energy interaction coefficients3 typified by Wagner&apos;s c|a BINARY SOLUTIONS The several measures of concentration which are to be considered are shown in line a of Table I. The corresponding activity coefficients are in line b and the deviation coefficients, sometimes called self-interaction coefficients, are in line c. Henry&apos;s law simply states that the activity coefficient approaches a constant value at infinite dilution. By adoptihg the infinitely dilute solution as the reference state and defining the "Henrian" activity as equal to the concentration in this state, the activity coefficient is always unity at infinite dilution. This convention is far sim~ler and more useful in dilute solution than emploiment of the &apos;Raoultian" activities and it will be used in the following discussion. The several definitions and equations of Table I will be referred to by means of their coordinates in the table. Early observations of deviations from Henry&apos;s law in metallic solutions were shown graphically4 rather than analytically. For the case of sulfur in liquid iron5 the slope of a plot of logfs vs (%S) was constant in the range 0 to 4.8 pct S, indicating constancy of eh2&apos; in Ic. He was proposed by wagnerz and has been widely adopted. The a function of IIIc recently employed by ~arkenl was designed specifically for dilute solutions. Darken has shown that the value of a12 remains essentially constant for many binary solutions within a substantial range of compositions. The atom ratio is directly proportional to the molalitv.<, a conventional measure of concentration. IVb and C served as the basis for smith&apos;s6 classic studies of

Jan 1, 1968

By O. D. Gonzalez, R. A. Oriani

A thermo-osmosis technique has been used to measure the heat of transport, Q* , of hydrogen and of deuterium dissolved in a iron and in nickel, and of hydrogen in Feo.6Nio.4 in the tempevature range 400° to 600°C. For all these systems, Q* is negative and has a large temperature coefficient; an isotope effect can be established for the solutes only in nickel. The magnitude of Q* is considerably larger than the activation energy, E , for migration in the case of these isotopes in a iron, so that all variants of the Wirtz model must be rejected. The phenomenological definition of Q* is developed to show that Q* is related to the mechanisms by which the activation energy is dissipated back into the lattice, and that Q*/E is a function of the ratios of the mean free paths of electrons and of phonons to the distance of jump of the diffusing atom. A correlation is shown to exist between the sign of Q* in thermal diffusion and that of the effective charge in electro migration, and may be understood as due to the large ratio of the mean free path of electrons to that of phonons. THE study of nonisothermal diffusion in the solid state is of interest because certain aspects of the mechanism of diffusion are made manifest which remain concealed though still present in the isothermal case. The thermodynamics of irreversible processes characterizes nonisothermal diffusion, known as thermal diffusion or as the Ludwig-Soret effect, by a quantity, Q*, called the heat of transport, which essentially measures the sign and the magnitude of the steady-state concentration gradient produced by the imposed temperature gradient. The problem then is to understand the quantity Q* at the atomistic level. There does not exist a theory for the atomistic interpretation of the heat of transport. There are, however, two classes of simple models which seem to afford some physical insight into Q*. Wirtz&apos;s model1, z and its subsequent generalizations partition the activation energy, E, for the migration of the atom spatially about the region of the migrating atom, so that Q* is the difference between the portion of the activation energy centered about the original site of the jumping atom and that portion about the arrival site. Clearly, the magnitude of Q* cannot on this model be larger than the activation energy for migration. The model of Oriani3 also considers the spatial distribution of E not only before but also after the atomic jump, and Q* is related to the variation of the spatial distribution of E that is produced by the jump. The simplest kind of system with which to compare the consequences of these ideas is the interstitial solid solution, since one may easily choose a temperature at which only the interstitial component moves, the solvent lattice serving as a completely satisfactory frame of reference. Thus, one avoids complications arising when both species in a binary system move. In addition, one avoids the necessity of knowing the energy for the formation of a vacancy, something which is needed for the analysis of thermal-diffusion data on metals which diffuse by the vacancy-exchange mechanism. However, the number of well-measured interstitial systems is extremely small, and, in particular, there are almost no data in the published literature for the temperature dependence of the heat of transport. If one works with solutes which are gases in the pure state at ordinary temperatures, one may use the technique of thermo-osmosis4 which permits thermal diffusion to be measured over a small temperature difference so that the temperature dependence of Q* can be more easily determined. The choice of dissolved hydrogen in iron and nickel was based on these considerations as well as on the desire to look for an isotope effect associated with localized

Jan 1, 1965

By Rex B. McLellan

A simple model for dilute interslitial solid solutions is set up which enables a solubility equation for the equilibrium between the solid solution and the gaseous solute to be deduced. This solubility equation is used to estimate the partial thermody -namic functions of Ag-O and Fe-N dilute interstitial solid solutions from the measured equilibrium between these solutions and the gas phase. It is shown that the partial excess entropy of the solute atom in solution is a vibrational entropy which is due Principally to the oscillation of the interstitial atom and does not arise from electronic or elastic interaction between the solute atoms and solvent matrix. In this work measurements of the equilibrium between dilute solid interstitial solutions and a gaseous phase are used to deduce the important thermody-namic functions of the solid solution with the aid of a theoretical solubility equation formulated from a knowledge of the thermodynamic functions of the gas and a simple model for the solid solution. The quantity of principal interest which is deduced from the equilibrium data is the change in vibrational entropy occurring when a solute atom (u) is placed in an interstial site in the solvent (u) lattice. This paper forms part of a more general study in which the properties of condensed phases are deduced from measurements of the equilibrium between the condensed phase and a gas. Previous investigations have dealt with the equilibrium between krypton and liquid metals,&apos; a pure metal and its vapor,&apos; and dilute substitutional alloys and the vapor,3 and the subject has been popularly reviewed by McLellan.4 In the latter investigation3 the vapor pressures of very dilute Cu-Ag and Cu-Au alloys were measured with a Knudsen cell technique over a large range of temperatures and the analysis of the vapor-pressure data showed that the relative partial excess entropies were large and positive [ds= -Sudk = 30 for Au-Ag alloys and 150 for Cu-Au alloys; these values should be compared to unity, the value assumed for these exponentials in the quasi-chemical theory of solutions]. For many interstitial solutions experimental data is available for the equilibrium between the solution and a gaseous phase, and this can be used to deduce the vibrational entropies of the solute atoms in solution. The general method employed is to calculate the chemical potential of the solute atoms in the gas and equate this to pi, the chemical potential of solute atoms in the solid, which is deduced from a simple model set up for the dilute interstitial solution (in which the solute atoms act as bound oscillators in interstitial sites). This enables a theoretical solubility equation to be set up. In the case of Ag-O and Fe-N solid solutions the solubility c, is found to vary with temperature according to a relation of the type, where PU2 is the pressure of the O2 or Np molecules. Essentially, the theoretical solubility equation enables the parameter A(T), which gives the vibration entropy, and the parameter AH, which gives the energy of solution of a solute atom, to be estimated from the measured variation of solubility with temperature. The solutions treated are dilute enough to enable solute-solute interactions to be neglected so that the partial energy and excess entropy of solution E, and GS are not functions of composition and the configurational entropy is that of a random solution. Large positive values have been found for sxSu this quantity has not been given sufficient consideration in recent work on interstitial solutions and it is felt that the partial thermodynamic quantities of very dilute solutions should be understood before the thermodynamics of concentrated solutions can be fully appreciated. EXPERIMENTAL DATA 1) The Silver-Oxygen System. The measurements of Steacie and Johnson,= using silver foils, indicate that there is a pronounced minimum in the solubility vs temperature curve for O-Ag solutions. Eichenauer and Miiller6 have recently redetermined the solubility of oxygen in silver using a method developed in the investigation of metal-hydrogen systems.7 The solubility determinations were carried out on compact specimens of differing shapes and sizes and the results indicate a much lower solubility than was obtained by Steacie and Johnson with no minimum at 400°C. Subsidiary experiments showed that the erroneous results of Steacie and

Jan 1, 1964

By P. E. Hildebrand, S. W. Mao, C. N. Crain

Hydrologic and economic criteria figure in many obvious ways in water resources development, but they are rarely linked quantitatively, and most of the applications are pertinent only to the case in point. In the preparation of a regional plan for the massive program of groundwater development in the Punjab, situations have arisen where the choice among two or more alternatives was made by analyzing the economic implications of critical hydrologic parameters. Two of these situations which are of more or less general interest are described herein. The first involves basic development policy, i.e., the question of whether groundwater development should be based on the demand of the economy, or the conservation concept of safe yield. The analysis demonstrated that mining of groundwater is clearly indicated for areas where alternative supplies are unavailable. The second problem involves integrating hydrologic data into an economic model to determine optimum well design. From an analysis of all pertinent factors, a simple nomograph was derived for determining well specifications on site during construction. The nomograph can be modified for use in any alluvial terrain. In the Northern Zone of the Indus Plains —the region known as the Punjab- Pakistan is proceeding with integrated development of water and land resources on a scale never before contemplated. The heart of the development plan is a massive program of groundwater development to supplement canal irrigation supplies and to provide drainage relief to the irrigated lands. By the close of 1966 about 2500 high-capacity wells were in operation and furnishing the water supply and drainage requirements for nearly two million irrigated acres. The development plan calls for the construction of a total of nearly 30,000 wells with an aggregate capacity of 120,000 cfs by 1980. This is part of an integrated program eventually affecting over 20 million acres of irrigated lands. [This development program is administered by the West Pakistan Water and Power Development Authority (WAPDA) for which the firm of Tipton and Kalm-bach, Inc. serves as regional planning consultant for the Northern Zone. The material presented herein is derived from planning studies which have been made in connection with the preparation of a regional development plan for the Northern zone.] Pakistan is proceeding with this large-scale development of land and water resources at a time when she is at the threshold of an almost calamitous population growth. Furthermore, she is attempting this development at a time when most of her usable land is already occupied and her food demands exceed current production. Here in the Northern Zone is one of the largest continuous areas of irrigated land in the world, easily irrigated, with a warm, dry climate and ample potential supplies of surface water and groundwater. Except for an abundance of land and labor, other primary resources are lacking or in very limited supply. The agriculture sector so dominates the economy that only by means of an effective development of the agricultural resources can other sectors grow and contribute to a viable economy. Because of inadequate irrigation, farming here has not effectively participated in the twentieth century revolution in agriculture, and only by means of massive development of potential supplies can Pakistan catch up. Capital for any kind of mass development must come from the outside. But the overriding restraint to development of the land and labor resources is the availability of water. ECONOMICS OF DEVELOPMENT The decision-making process in planning regional development becomes increasingly complex as the various sectors of the economy become more highly developed. Where, as in this case, one sector dominates the economy and its development can be considered the key to development of other sectors, the decision-making process is simplified and it is easier to identify alternatives and to trace the prob-

Jan 1, 1970

MINING ENGINEERING presents the annual membership report of the Society of Mining Engineers; see page 147.

Jan 7, 1964

By R. Gibala

Internal-friction measurements on hydrogen-charged iron over the temperature range 4° to 300°K are reported. Two relaxation peaks, the hydrogen Snoek peak at 48 °K and the hydrogen cold-work peak in the range 145" to 2200K, are observed at 80 kc per sec. The effects of hydrogen-charging, aging, and deformation on the internal-friction results are determined and are used to show evidence of partitioning of hydrogen between solid solution and dislocations. The hydrogen-dislocation binding energy is estimated from the behaviors of the relaxation tiwzes and relaxation strengths of the Snoek peak and the cold-work peak. Its value is approxi,mately 6400 cal per mole. MANY investigators have demonstrated the usefulness of internal-friction measurements in determining the manner in which interstitial impurities interact with dislocations in bcc metals. Part of this success has resulted from the existence in bcc interstitial alloys of two anelastic relaxation peaks—the Snoek peak&apos; and the cold-work or Koster peak2 (designated hereafter by SP and CWP, respectively). The SP has its origin in the redistribution of interstitials in solid solution among sites made energetically nonequivalent by an applied stress. The rate at which the redistribution occurs, measured by the relaxation time for the process, is related in a simple way to the diffusion rate of the interstitial in the free solution. The relaxation strength is proportional to the concentration of interstitial in solid solution. The CWP appears to have its origin in the relaxation of an interstitial-dislocation complex for which the relaxation time at a given temperature is much longer than that for the SP. The relaxation strength depends strongly on the concentration of interstitial and the amount of deformation at relatively low concentrations and deformations.2-8 From the dependence of the relaxation strength on interstitial concentration, the SP and CWP may serve as measures of the concentrations of interstitials in free solution and bound at dislocations, respectively. Thus their behaviors have been used to investigate interstitial-dislocation interactions in Fe-C, Fe-N, and several refractory metal systems.&apos;-&apos; However, the Fe-H system has not been studied extensively,? even though disputes in recent years over the mechanism of hydrogen embrittlement in steels involve argument over the extent to which lattice hydrogen and hydrogen-dislocation interactions play an important role.?-&apos;&apos; Previous work on Fe-H indicates the internal-friction behavior to be qualitatively consistent with that for other systems. Apparently, both a SP and a CWP are observed in the temperature ranges 30" to 50°K and 100°to 140°K, respectively (at 1 cps). However, there is neither sufficient nor accurate enough information to identify convincingly these peaks with their supposed counterparts in other systems. Nor have there been any attempts to make quantitative use of these peaks to study hydrogen diffusion, aging, or interaction processes. In this paper, an attempt is made to obtain more complete information on internal friction of hydrogen in iron than presently available. Internal-friction measurements in the range 4° to 300°K on hydrogen-charged iron show that the two peaks discussed above are in fact the hydrogen SP and CWP. Several effects of hydrogen charging, aging, and deformation on these peaks are observed and are used to determine the partitioning of hydrogen between solid solution and dislocation sites in iron. EXPERIMENTAL Materials. The starting material for this investigation was a high-purity iron supplied by National Research Corp. as a 1-in.-diam rod. The following analysis was given (inwt pct): C, 0.004; N, 0.0003; 0, 0.007; P, 0.002; S, 0.005; Si, 0.006; Mn, 0.001; Cu, 0.002; Ni, 0.005; Cr, 0.001; Mo, 0.001. After an initial vacuum anneal (-5 XTorr) at 700°C, the rod was cold-

Jan 1, 1968

By Norman Weiss

THE need for more efficient utilization of labor in the metal-mining industry has been the subject of several recent editorials in the mining press, and one attractive possibility for such improvement lies in the designing of future milling plants particularly with economy of man-power in mind. We are accustomed to think of mill design as the selection and coordinated arrangement of process equipment, but if labor is to be efficiently utilized it must be given early consideration in planning the new mill. There are three good reasons for economizing in labor: (I) to reduce costs, not only in the form of wages but also in housing, hospital, welfare, and other obligations that a company accepts when a new man is added to the payroll; (2) to prepare for recurrent periods of manpower shortage, during which a well-designed plant can manage to get along with skeleton crews; (3) because a milling plant that must depend upon an inordinately large labor force for its operation and maintenance is certain to be inefficient in other respects, for many of the shortcomings in design that make necessary the excessive use of labor are generally not corrected merely by having too many men. A simple example of this is a poorly designed ore-feeding system: if this is inadequate to the extent that one man must be constantly unclogging feed chutes, it may help the situation to put two men or three at this task instead of one, but the feed rate will still be inconstant. First of the factors that affect labor saving is the location of the mill. This is often determined by transportation costs alone, and as a result the mill may be placed close to the mine regardless of the nature of the terrain. The designer must then adapt his layout to the conditions, favorable or not. This happens often at small properties, where capital investment may seem more important than operating expense. In most instances, however, a mill site carefully selected for the advantages it gives the designer in laying out the plant is the most economical in the long run, even if it involves a slight increase in cost of ore haulage. Given some freedom of choice, the design engineer may be able to find just the piece of ground that provides the proper gradient for the needs of the flowsheet, permits installation of essential yards and trackage, and perhaps supplies an excellent site for a tailing dam. Further justification for having placed the mill not too close to the mine sometimes emerges only years later as an opportunity to treat ores from other properties. When it is known from the beginning that the new mill will serve a number of scattered mines, a free choice of mill site is naturally stimulated. The most important single factor in limiting the labor requirements of a mill is its materials-handling system for bring-

Jan 1, 1946

By Dever C. Ashmead

Anthracite was first mined in the Wyoming Valley and sold as an article of commerce in 1808. As some preparation has always been necessary to make it ready to burn, the preparation of anthracite must date back over a hundred years. Two vital factors have determined to a large extent the degree and the method of anthracite preparation. These are, first, the character of the beds worked and the methods by which they are mined and, second, the equipment used and practices followed in the burning of the coal. It is not the intention here to go deeply into these phases of preparation as a paper of no mean length could be prepared on the history of either. Rather, the intention here is to point out the main considerations and to show the influence they have exerted on the preparation of anthracitc. Mining Methods and Their Relation to Preparation In the beginning of the nineteenth century, the coal beds were virgin with the possible exception of some outcroppings that had been worked, to a slight extent, by the Indians. It is known that the American aborigines had a, knowledge of the use of this fuel, because when the Wyoming Valley was purchased from them, in 1754, they mentioned the fact that, by selling the land, they would lose their coal. Real mining of anthracite began about 1808 when Judge Jesse Fell, of Wilkes-Barre, discovered that the "common stone coal of the valley" could be burned in an open grate. For some years thereafter mining was conducted near the surface. The working p1aces were driven narrow; only the best of the coal was selected and the remainder was left in the ground. Only the lumps could be used, as no market existed for other sizes. As time passed, however, it became necessary either to go farther into the ground or to widen the working places. When these places were widened, falls of roof were apt to occur, making it necessary

Jan 1, 1922

By R. L. Mauger, P. E. Damon

Potassium-argon dating of the late Mesozoic and Cenozoic intermediate to acidic plutons and volcanic rocks of Arizona and northern Sonora demonstrates the existence of two distinct magmatic episodes. The earlier episode begins in late Campanian time and dies out before the middle Eocene. Following a quiescent period in middle and late Eocene time, magmatism increases in Oligocene time, becomes most intense at the Oligocene-Miocene boundary and dies out as the Pliocene is approached. Pliocene magmatism is primarily confined to extrusion of post-orogenic basalts. The late Mesozoic-early Cenozoic magmatic pulse is essentially confined within the limits of the classical Laramide orogeny (Laramie through Wasatch time). The mid-Tertiary pulse is contemporaneous with the mid-Tertiary Basin and Range orogeny. The Laramide provides an excellent specific example of Umbgrove&apos;s concept of the pulse of the earth and in general his concept appears to be meaningful. Copper porphyry mineralization is time-congruent with Laramide magmatism and there seems to be no doubt as to the existence of a genetic relationship between the two phenomena. Two origins are tenable: direct accumulation of the copper sulfides in the copper porphyry liquid magmatic environment; or, introduction of the mineral constituents entirely from a larger source magma when the host rock is already crystalline. Transgression and regression of the epicontinental seas provide an excellent indicator of orogeny and epeirogeny. There was an overall transgression of the epicontinental seas from early Triassic time through the Turonian epoch in early late-Cretaceous time. Thereafter, there is a relatively continuous regression of the seas until the present time. Both the earlier transgressive episode and the later retreat are intermpted by temporary but distinct reversals. These interruptions can be correlated with classical orogenies. There are six distinct orogenies so indicated in the Mesozoic-Cenozoic eras. These occur at approximately 35 to 40 m.y. intervals. The regression of the epicontinental seas following the Turonian epoch was contemporaneous with the deepening of the Pacific ocean basin over the Darwin Rise. As the Darwin Rise was collapsing the East Pacific Rise was being elevated. The Western United States, situated on the eastern flank of the East Pacific Rise, was upwarped and tilted toward the east. Epeirogeny is the primary consequence of processes that operate on a global scale. Orogeny is an exothennic process that is limited in space and is treated here as a secondary consequence of epeirogenic-initiated warping. The off-campus buildings of the University of Arizona Geochronology Laboratories rest on the volcanic rocks of Tumamoc Hill. From this hill, the observer may obtain a beautiful view of typical Basin and Range topography. The city of Tucson lies below, contained within the broad Santa Cruz basin and surrounded on all sides by characteristic NW-SE trending ranges towering as much as 7000 ft above the valley floor. Since the senior author arrived in Tucson eight years ago, a great deal more has been learned about the geochronology of this and neighboring basins and ranges. For example, the volcanic rocks underlying the laboratory at Tumamoc Hill were shown on the state geologic map as Quaternary basalt. A student of the senior author has demonstrated that the so-called basalts are in fact alkali-andesites (Halva, 1961), and we now know that these alkali-andesites or doreites (Mielke, 1965) are of early Miocene age rather than Quaternary age (Bikerman and Damon, 1965). Is it any wonder then that geologists disagree on the nature and time of Basin and Range volcanism, plutonism and tec-tonism? The plain fact is that few definitive Cenozoic fossil sites were available upon which to base a chronology and geologists were forced to guess the ages of rocks in order to achieve the semblance of a time classification. We have now made considerable progress in developing a K-Ar chronology for the volcanic and plutonic rocks of the Basin and Range (Bikerman, 1965; Damon and Bikerman, 1965; Damon et al, 1964 and 1965; Mauger et al, 1965). It is the purpose of this paper to point out the main features of this chronology and to discuss the relationship of magma-tism to orogeny-epeirogeny during post-Turonian time. We will also discuss probable relationships during

Jan 1, 1967

By M. B. Ramachandra Roa

This paper records the results of the earth resistivity surveys made in the Godavari River in connection with the Ramapadasagar project. After describing the topographical and geological features of the area, the results of the investigation at the several sites have been mentioned. Further, a detailed account has been given of the resistivity methods adopted, the apparatus used and the interpretation of the curves. The resistivity measurements carried out over the water course have been specially outlined, and a review of the verification of the electrical indications by drilling in a number of cases, has also been presented. Introduction The Government of Madras has under consideration the Ramapadasagar project which is estimated to cost some Rs.660,-000,000 (about two hundred million dollars). The most essential feature of this project is the construction of a high dam across the Godavari near Polavaram for impounding the waters of this great river of South India, whose maximum discharge is 2 million cu secs in flood time. It is estimated that when the proposed reservoir is constructed, about one million tons of rice could be produced annually under irrigation. To those who have had any acquaintance at all with the recent distressing famine conditions which India has passed through and is still undergoing, the Lounteous effects which this project will bring about to the country in the future, are obvious. In the region of the proposed reservoir, the river flows for several miles through a hilly tract, hemmed in between flanks of hard, solid rock; but the river bed is mostly sandy. A few bore holes put down in this sandy bed touched rock at a depth of 180 to 200 ft. The river bed is about jo ft above the mean sea level (m.s.l.) and the bedrock was found at —125 to —160 ft m.s.l. The crest of the dam is proposed at +162 ft m.s.l. The proposed dam mould therefore be about 120 to 130 ft above the river bed, and the foundations would have to reach down nearly zoo ft below the bed at the deepest part. A number of alternative sites were proposed for investigation, and it became necessary to quickly ascertain the bedrock topography at these sites. Dr. M. S. Krishnan,* who was consulted in the matter, furnished a detailed account of the geological features of the region and suggested a geophysical investigation which the writer carried out from February to April 1944, employing solely the electrical resistivity methods. The total length of the survey lines for the electrical measurements amounted to 62,600 ft and the number of resistivity determinations was about 2500. Altogether nine alignments for the dam were inten-

Jan 1, 1949

By Davenport, Edmund S.

THE specific aim of this work has been to study certain forms of internal deterioration which occur in tungsten filaments when subjected to high temperatures under various conditions, and to determine the cause of such deterioration. This would naturally lead to a consideration of methods of control or means of prevention of the phenomena. The deterioration was first noticed as a peculiar condition in the grain boundaries of certain tungsten filaments which had been burned t for long periods in lamps. In these cases it was noted that the grain bound aries contained a number of minute black dots which were at first thought to be non-metallic inclusions. It was demonstrated later that these dots or pits, as they were designated, could be readily produced by burning filaments in an atmosphere of flowing hydrogen. This method was convenient and adequate for the purpose, and was adopted for most of the work discussed in this paper. The evidence accumulated to date indicates that these pits arc actually small voids between the grains. The purpose of this paper is to, present the information on this interesting subject gathered during a period of about 3 years. As applied to tungsten, the subject appears to be of considerable importance, experience having shown that this pitting is frequently associated with poor performance of filaments in lamps.

Jan 1, 1927

By John J. Dran

The elaborate analytical techniques for risk analysis used by the large mining companies in conjunction with the valuation of mineral reserve sites are totally inappropriate for the small miner. The small miner does not possess the financial and technical resources which are available to the large companies for such risk analysis. Even if these resources were available to him, the relatively small size of his investment would not justify a huge expenditure for risk analysis. What is required by the small miner is an improvement over the single point estimates provided by the valuation techniques that he currently uses. Such improvement should provide an indication of the extent to which the true value (known only after the fact) might differ from his estimated value of the mineral reserve site. In addition, a rough indication of the chance of occurrence of various differences between the true and estimated values would be helpful to him. These improvements must be obtained at low cost to be useful to the small miner. Such improvements would have to be based on a simple system requiring very few additional estimates by the miner. The small miner is not accustomed to dealing with sophisticated risk analysis techniques. Hence, any complex, time-consuming approach would be doomed to disuse or possible misuse. A simple, uncomplicated approach requiring a minimum of additional estimates by the miner can be based on a system devised by Frederick S. Hillier Although Hillier&apos;s method can be applied to various mineral reserve valuation methods used by the small miner, this note is specifically oriented to the discounted cash flow model. The basic discounted cash flow (DCF) approach provides a single point estimate of value and introduces the concept of risk (i.e. the possibility that the annual cash flows may differ from their estimated values and thus lead to an incorrect investment value) through the use of a risk-adjusted discount rate. This approach simply lowers the present value estimate with increases in the discount rate (i.e. increases in the risk assessment). The single point estimate still remains. Although the lower value estimate makes it less likely that the risky investment will be deemed profitable and undertaken, it provides no indication of risk that is suitable for examination and analysis. In addition to the "best guess" estimate of annual net cash flows required in the DCF model, application of the Hillier risk analysis model requires that the miner

Jan 1, 1976

By Donald W. Murphy, John Chipman

Recent developments in iron alloys containing nitrogen have indicated that this element may exert a considerable influence on the properties of the metal. This influence is not always in an undesirable direction and the indications are that nitrogen should be regarded as an alloying element, the amount of which should be subject to control, rather than as an inherently deleterious impurity. In controlling this element in liquid iron to the best advantage, it is necessary to have a reliable background of fundamental data pertaining to solubilities, rates of solution and chemical reactions of nitrogen in liquid iron. Obviously, the first step in such an investigation is the determination of the solubility of nitrogen in pure iron, and this has been the object of the experiments described in this paper. The solubility of nitrogen in solid iron has been measured by Jurich,&apos; Sieverts,2 Martin,3 and Iwasé4 and the agreement among the first three inspires confidence in their results. No accurate determinations of its solubility in liquid iron have been recorded though several investigators have obtained approximate results. Strauss6 was able to introduce 0.03 to 0.04 per cent nitrogen into steel by the action of either ammonia or nitrogen on the liquid metal. This was accomplished by Eilender and

Jan 1, 1935

By John Chipman, Donald W. Murphy

Recent developments in iron alloys containing nitrogen have indicated that this element may exert a considerable influence on the properties of the metal. This influence is not always in an undesirable direction and the indications are that nitrogen should be regarded as an alloying element, the amount of which should be subject to control, rather than as an inherently deleterious impurity. In controlling this element in liquid iron to the best advantage, it is necessary to have a reliable background of fundamental data pertaining to solubilities, rates of solution and chemical reactions of nitrogen in liquid iron. Obviously, the first step in such an investigation is the determination of the solubility of nitrogen in pure iron, and this has been the object of the experiments described in this paper. The solubility of nitrogen in solid iron has been measured by Jurich,&apos; Sieverts,2 Martin,3 and Iwasé4 and the agreement among the first three inspires confidence in their results. No accurate determinations of its solubility in liquid iron have been recorded though several investigators have obtained approximate results. Strauss6 was able to introduce 0.03 to 0.04 per cent nitrogen into steel by the action of either ammonia or nitrogen on the liquid metal. This was accomplished by Eilender and

Jan 1, 1935

By E. F. Raffo

THE design of the Chuquicamata concentrator offered an unusual combination of problems, all of which had, in one way or another, a definite effect upon the final arrangement of all the equipment and necessary facilities. First of all, a remotely located project of this magnitude required careful selection of equipment with an adequate supply of replacement parts and in some cases necessitated stand-by spare equipment ready for immediate use. Fortunately, in the course of determining the proper flowsheet, in itself a prime factor in the concentrator design, it was possible to conduct numerous grinding and flotation tests at the Anaconda and Andes concentrators. As a result of these tests made under actual operating conditions, most of the major equipment best suited for treating the Chuquicamata ore efficiently was decided upon while preliminary design layouts were still being made. The design has been based primarily on the treatment of sulphide ore crushed to about 3/4 or 1 in. However, until the new sulphide crushing plant is completed it will be necessary to handle ore crushed to 3/8 in. in the existing oxide crushing plants and to some extent a mixed ore which has had its oxide copper content removed by leaching. This mixed ore, known as leached residue, will contain a certain amount of sulphuric acid from the leaching process which necessarily requires special protective measures. Several factors influenced the final location of the Concentrator. The only established fact known during preliminary design layout was the elevation of the dumping floor over the fine ore bin. This was predetermined by the desired level railroad grade across part of the existing tailing and leached residue dumps from the oxide plant to the bin. Next it was necessary that a site be chosen that would not require an excessively long haul from either the present oxide plant or the mine and in addition provide a fairly constant natural ground slope sufficiently wide to accommodate the length of the ultimate concentrator. The site as finally chosen to meet the foregoing restrictions provided a natural ground slope of 6 to 7 pct. This was excellent, especially in a region subject to earthquakes, as it assured that foundations of heavy equipment and footings for building and crane columns would rest on cut or undisturbed ground. However, this shallow slope, although having some definite advantages in the overall consideration of plant layout, resulted in the need for extensive studies in the general arrangement of equipment. Wasteful and excessive vertical drops had to be eliminated in the

Jan 1, 1952

By Charles Shamel

I FEAR most of the Institute members are already weary of the perennial controversy about the apex law. I feel that way about it myself now, though I have been guilty of considerable contribution to the discussion in the past. The discussion does not seem to perceptibly influence previously held views and I would not again break into print on the subject but for the urgent invitation of the Chairman of our, Law Committee. This energetic and able member has firmly determined to secure a revision of the mining law and among other things to eliminate the so-called apex provision from the U. S. mining statutes. He is, however, fair about it and has invited me to make "the strongest possible argument in its favor." I am suspicious that he is acting on the psychological principle that it is usually easier to convince an audience against a cause vigorously but unsuccessfully defended than against one wholly mute. Nevertheless, I realize that personally he wishes me no harm, much as he hates the apex law, and so am willing that the Institute have whatever benefit may accrue from my taking up again the unpopular side of the discussion. I say this because the attitude of a large part of our "articulate" membership seems irreconcilably hostile; their minds are made up; favorable consideration is foreclosed; and they become impatient and even sarcastic at any attempt to elucidate a favorable view of the apex law. The exact question for discussion at the present time is not whether on abstract, or any other considerations, the apex law is the best possible rule, but the very different proposition whether, after nearly 50 years of statutory life and much longer as a practically universal miners&apos; custom, it is now just and expedient to repeal the apex law.

Jan 4, 1914

By Waldemar Lindgren

The following pages present data accepted by many geochemists and geologists regarding the succession of minerals and the temperatures of formation in ore deposits affiliated with igneous rocks. They also present the individual views of the author on the composition of the solutions that were active and on the mode of deposition. He does not regard these views as speculations or hypotheses but as forming a well motivated and consistent theory. It is not certain, however, that all investigators will subscribe to them. Introduction The mining engineer may not always be interested in the field of stability and temperature of origin in the mineralogy of ore deposits, but he certainly is interested in the succession of minerals because this has a definite bearing on the understanding of the ores and on the best processes of extraction. It is proposed, therefore, to summarize in plain language the principal features of succession as shown in metallic ores. Chemical analyses of ores are always important, but the real knowledge of succession—sometimes called paragenesis-—of ores has been gained only in the last 20 years, by the study of polished sections. The study of hand specimens threw much light on the subject—as shown, for instance, by Breithaupt, whose "Paragenesis," written a hundred years ago, is still useful—but the results have been modified by our slowly gained understanding of the processes of replacement. Indications of Temperature Melting Points.—In the first place, a distinction must be made as to whether the ore is a product of magmatic consolidation, of pegmatitiza-tion or of hydrothermal activity. Most of the ores fall in the latter class. In any case, the melting points, although of importance, are not definite indications. In a magma the oxides and sulfides are likely to be among the earliest crystalline products (magnetite, ilmenite, zircon, corundum,

Jan 1, 1937

By Howard C. Dunkle

Various factors can affect the quality of B1112 and B1113 steel as produced in a bessemer plant; among them: vessel-charging practice, blowing practice, ingot-pouring practice, ingot delivery-time practice, pit-heating practices, and ingot-rolling practice. Evaluation of the influence of ingot delivery time on quality has been chosen as the subject for this paper because this time is completely within the control of the operator, and on this particular factor there is a tremendous amount of information in the dusty archives of the average steel plant. In order to know how much improvement can be made and when attention should be directed to other factors that influence quality, in the continual struggle for improvement, the effect of ingot delivery time must be accurately evaluated. Once this is done, the importance of other variables can be accurately obtained, thus eliminating the necessity of resorting to opinions that are of doubtful value at best. In the study described herein, extensive use was made of the statistical card system as a method of determining the effect of ingot delivery time as a quality factor in bessemer screw-stock grades by simple direct correlation. The value of this statistical method as a means of accurately determining the influence of various factors has been amply demonstrated by Work1 for the bessemer process and by Hand and Gould2 and Fetters and Chipman3 for the open-hearth process. The quality records of 300,000 tons of bessemer screw-stock billets were used in this study of the effect of ingot delivery time on the rejections for breaks, pipe, check and seams. The reduction in the number of rejections for poor quality reduces the costs and increases the productivity per man-hour. The operator today, more than ever before, must know how to keep costs down, how to do it most quickly and in the best way, and how to obtain the highest quality in line with the ever increasing demands of the customer. It is necessary for him to know the individual relations and interrelations between various factors affecting the quality of the manufactured product if he is to produce material that will meet competitively the cost, performance, and quality demands of the trade. SIGNIFICANCE OF STEEL MANGANESE, MIXER SILICON AND STEEL SULPHUR AS QUALITY FACTORS In order to obtain the highest grade of material it is necessary to control many factors-not just one or two, as operators

Jan 1, 1945