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By John S. Johnson

THE purpose of this article is to describe several types of borehole lining in common use, and especially to offer a relatively new means of reducing the expense of maintaining boreholes where they are subjected to corrosive action of water flowing either inside or outside of their casing. In the Anthracite region of Pennsylvania, boreholes are used for many purposes, the principal ones being: openings between the surface and underground workings through which are passed steam, water and compressed-air lines, ropeways from surface hoists to underground rope haulages, conduits for electric power and signal lines, water-discharge lines from underground pumping stations, and inlets to mine workings for flushing material. LININGS FOR BOREHOLES The inadequacy of steel pipe for use in boreholes has long been recognized. Various substitute materials have been tried, including screw-joint cast-iron pipe (Fig. I). Cast-iron pipe, while very effective as a discharge line for acid water (mine water) being pumped to the surface, is not so effective when serving as a conduit for silt and crushed rock being flushed underground for filling mine voids. Terra cotta pipe (Fig. 2) has been used in boreholes, and lasts a long time if the glazed inner surface of the pipe remains intact. Its installation in a borehole is very difficult and is recommended only where it is certain that there will be no subsidence of the surrounding territory. Accessibility in order properly to join each section of the pipe is essential to a satisfactory job. In large water holes, where it is possible to lower a man into the hole for sealing the joints of the pipe, glazed terra cotta pipe has been used successfully for delivering mine water from pumps in the mines. For large holes used for flushing refuse into mine workings where the surface wash is shallow, standard paving brick have been used to form a tube through the wash to the bedrock. These brick are laid radially, backed by common brick and cobbles laid in cement. It is obvious that the shaft through the wash must be large enough to permit a man to work in it. The flushing material is carried through bare rock from the juncture at bedrock to the openings underground. This plan has been used, particularly where a cast-iron surface line is laid upon the surface to carry the flushing material from the breaker to the hole, and down the hole continuously, with no opening to the air at the top of the hole, thereby eliminating the necessity of an attendant at this point (Fig. 3). Another similar type of borehole lining is constructed of hexagonal pieces of vitrified brick (Fig. 4). This type requires a steel drive pipe through the surface wash large enough to provide a finished tube of the desired size surrounded by a brick wall about 4 in. thick. The special bricks are laid in cement, six to a circle, around a lubricated pipe used as a form, and lowered in sections inside the large drive pipe; the bottom section is seated in a socket drilled in the solid rock, having the same inside

Jan 1, 1941

By Frederick Prime

In this supplementary list no titles to which an * is prefixed have been seen by the compiler; and he will be most thankfu1 to have any omissions or inaccuracies in the list sent to him to be published as a second supplement in the next volume of the Transactions. The author is indebted to Messrs. Robert Clarke, of Cincinnati; Thomas Macfarland, of Towanda; Professor F. W. Simonds, of Chapel Hill; and Professor J. J. Stevenson, of New York, for valuable assistance. Cedar Point IRON Company, Baltimore, July 31st, 1880. Alabama. Geological Survey of Alabama. Report of Progress for 1877 and 1878; by Eugene A. Smith, State Geologist. Montgomery, 1879. 8vo., 139 pp., and 4 maps.

Jan 1, 1880

By Frederick Prime

IN this supplementary list no titles to which an * is prefixed have been seen by the compiler; and he will be most thankful to have any omissions or inaccuracies in the list sent to him to be published as a second supplement in the next volume of the Transactions. The author is indebted to Messrs. Robert Clarke, of Cincinnati ; Thomas Macfarland, of Towanda; Professor F. W. Simouds, of Chapel Hill; and Professor J. J. Stevenson, of New York, for valuable assistance. CEDAR POINT IRON COMPANY, BALTIMORE, July 31st, 1880. ALABAMA. Geological Survey of Alabama. Report of Progress for 1877 and 1878 ; by Eugene A. Smith, State Geologist. Montgomery, 1879. 8vo., 139 pp., and 4 maps.

Jan 1, 1880

By E. T. Turkdogan, P. Grieveson

Molten silver is equilibrated with silicon nitride at 1400°C in nitrogen + hydrogen gas mixtures, and from the solubility data the activity coefficient of silicon is found to be 1.76 at silicon concentrations below 1 pct. Using this value, and that available from the silicon cmbide solubility measurements, together with those derived from the phase equilibrium diagvam, the activities of silver and silicon are estimated for the entire composition range. The main feature of the activity data is that there is a pronounced positive deviation from ideality. The activity of silver in molten silver containing up to 5 pct Si was determined by Schadel, Derge, and Birchenall1 by measuring the vapor pressure of pure silver and of the alloy over a temperature range of 850º to 1050°C. They deduced from their results that there is a positive deviation from Raoult's law and that the activity coefficient of silver increases with decreasing temperature. However, as pointed out by Kubaschewski and Catterall,2 their activity coefficients are much too high, giving silver activities greater than unity. At a later date McCabe and Birchenal13 showed that the previous vapor pressure data on silver4 were high by a factor of about 1.3; presumably a similar error must have occurred with the vapor pressure measurements on the Ag-Si alloys. The activities of silicon and silver calculated by tager' from the phase diagram and by Gibbs-Duhem integration, respectively, show a positive deviation from Raoult's law for silicon activity and positive and negative deviations for the silver activity. According to these computations, at infinite dilution of silicon ygi = 1.12 at 1420°C. d'Entremont and chipman6 measured the solubility of silicon carbide in molten silver at unit carbon activity; the equilibrium silicon content is found to be Nsi = 0.017 ± 0.002 atom fraction for 1420°C. Using the data of Grieveson and Alcock7 for the free energy of formation of silicon carbide from pure silicon and graphite, the activity of silicon for unit activity of carbon and of silicon carbide is asi = 0.0308 at 1420°c; therefore for the above solubility data on silver, YSi = 1.81, which is somewhat higher than that given by Hager. Use is often made of silver alloys in the measurements of activities of solutes in metals where silver has a very low solubility; in fact, Ag-Si and Ag-A1 alloys have been used in the past for such purposes. In an attempt to gain more thermodynamic data on molten Ag-Si alloys, measurements have been made in the present study on the solubility of silicon nitride in molten silver; the results on these solubilities are given in this paper together with a detailed discussion of activities of silver and silicon. SOLUBILITY OF SILICON NITRIDE The standard free energy of formation of silicon nitride is known with a reasonably high degree of accuracy. According to the measurements made by Hincke and Brantle8 and by Pehlke and Elliott,' the following are the free energy data for the standard states of solid Si3N4, liquid silicon, and Nz at 1 atm pressure:

Jan 1, 1963

By Thomas P. Bispham

INTRODUCTION From the lender's point of view, the greatest period of risk in a project financing occurs during the construction phase. Therefore, most projects are supported during this phase by completion guarantees supplied by some credit-worthy entity; for example, the project sponsors in the case of a joint venture, such as that of W.R. Grace, Hanna Mining, and Liberty Capital; or by a strong contract with a utility or foreign importer/investor, such as the way North American Coal Corporation has structured many of its transactions. THE PROJECT LOAN REQUEST A project financing is a more complex form of term loan than one using an ongoing corporation's balance sheet as a credit base and, therefore, a potential lender will subject the loan request to a more rigorous analysis. To support this effort, the financial institution will require a more detailed information memorandum to evaluate the credit and technical risks of a project - especially since much of the necessary information is not otherwise available. (See also Gibbs and Sroka paper above in this Chapter) A well-prepared information memorandum will impress prospective lenders with the planning ability and general competence of management. Also, the process of preparing the memorandum will help management understand the true extent of the opportunities and limitations of its venture. Appendix A outlines the topics which comprise a complete information memorandum for a loan request. Of some interest to those seeking to sell a currently-operating mining venture, a similar information memorandum should be prepared i.e., covering the same topics discussed here, for the investment banker to use with potential purchasers. For that purpose, though, one might not want to prepare quite as much detail as for a lender. Appendix B outlines the elements of a reserve evaluation and feasibility study, often called the "Bankable Document." Usually, these studies are prepared by independent engineering consultants for use by potential borrowers and sellers. (Potential purchasers will often contract for a similar study for their use in evaluating an acquisition.) ELEMENTS OF A LOAN INFORMATION MEMORANDUM 1. Outline: The information memorandum should begin with a one-page outline covering such topics as: a. The borrower's name, address, and phone number. b. Principal contact at the borrower. c. Amount of the proposed financing. d. Desired pricing and structure of the proposed financing. This should include a description of the amount and source of equity in the proposed financing. e. Use of the proceeds and timing. 2. Summary: The most important information contained in the memorandum should be summarized in two pages. Note - If the borrower is a recently-formed single-purpose company, then elements 3, 4, and 5 will apply to the guarantors of completion and to the project sponsors. 3. The Borrower: This section is a brief biography of the borrower including such topics as date and state of incorporation, founder(s), lines of business, etc. 4. Capitalization: The borrower's current debt and equity position, including leases and trade debt, with amounts, terms, names, and addresses enumerated. Equity owners, and percentage ownership, should be identified. 5. Historical Financial Statements: If available, a minimum of five year's worth of complete historical financial statements

Jan 1, 1985

By Pierre I. Desré, Donald T. Hawkins, Ralph Hultgren

The torsion effusion method has been used to measure the vapor pressure of thallium over pure thallium in the temperature range 931" to 996'k The resulting 100 cal per g-atom is in excellent agreement with previous values. Vapor pressures of T1 above seven Ag-Tl alloys ranging from 33 to 90 at. pct T1 were measured at 979K. Calculated silver activities show a positive deviation from Raoult's law, approaching ideality near the liquidus. Measured thallium activities scatter less than previous measurements using the electromotive force technique. Values for the silver component were calculated by Gibbs-Duhem integration. This paper reports the results of a study of the liquid Ag-T1 system by the torsion effusion method. The method has been discussed in detail previously1 and will be only briefly summarized here. The sample is contained in a cell which is suspended on a torsion wire. Vapors effusing from orifices on opposite sides of the cell exert a torque on the wire. The torque is related to the vapor pressure by the following relation: where D is the torsion constant of the wire, 4 the angle of torque, fl and f2 the correction factors determined by Freeman and seamy2 to account for orifice length, a1 and a2 the areas of the orifices, and ql and q2 the distances of the orifices from the axis of rotation. By using the same cell for pure thallium and the alloy, it follows that: so that most systematic errors are eliminated in determining the activities. EXPERIMENTAL 99.999+ pct T1 was obtained from the American Smelting and Refining Co. and 99.999 pct Ag was obtained from Cominco American, Inc. Seven Ag-T1 alloys, ranging in composition from x^\ = 0.33 to 0.90, were prepared by melting together weighed amounts of the pure metals in sealed, evacuated Vycor tubes and quenching the melts in water. The apparatus and graphite cells were the same as those used by Hawkins and Hultgren3 in their study of the Pb-Sn system. RESULTS Ten measurements were made on pure thallium in the temperature range 931" to 996K, and the results are presented in Table I. Values of were calculated using tabulated Gibbs (free) energy functions.4 No dependence of on temperature or orifice size was found, indicating that equilibrium was attained. Data for the Ag-T1 alloys are shown in Table 11. Values were smoothed with respect to composition by a plot of where . DISCUSSION The value = 43,520 * 100 cal per g-atom for pure thallium (95 pct uncertainty limit) is in excellent agreement with previous investigations.4 In the Ag-T1 system, this study shows positive deviations from Raoult's law at all compositions. Fig. l gives the phase diagram according to Hansen, and Fig. 2 presents the activity values measured in this study as well as those from electromotive force measurements at 950°K by Terpilowski, Kundys, and slaby.'

Jan 1, 1969

By C. E. Birchenall, W. Batz, H. W. Mean

AT temperatures between 1095' and 1347ºC, 13 runs have been made on the diffusion of silicon in iron. In two of the runs the couple compositions were entirely within the loop of the Fe-Si system; the base alloys contained 0.0 and 1.0 wt pct Si. The other runs in which the couples consisted of a 2.3 wt pct Si alloy welded to a 3.7 pct Si alloy were a phase throughout. The alloys were made by melting electrolytic iron and commercially pure silicon. Trace impurities were not determined. The butt welded couples were diffused in an inert atmosphere of argon or hydrogen. After cooling, cuts of two mils or greater thickness were machined parallel to the weld interface. The chips were analyzed for silicon. When the concentration and distance data were examined on the conventional probability plot,' no marked variation of the diffusion coefficient with concentration was indicated over the narrow composition ranges employed. Therefore, a single diffusion coefficient is recorded for each run in Table I. The temperatures and atmospheres of the diffusion anneal are listed along with the compositions of the base alloys. For a iron the silicon diffusion coefficient is given by the equation: D = 0.44 e-48,000/RT where R is the gas Constant and T, the absolute temperature. However, since the scatter in the data is fairly large, the activation energy may be in error by as much as 6000 cal per g-atom. The two ? iron points do not permit estimation of the activation energy with any reasonable certainty. They do indicate that the coefficients reported by Smithells2 and Jost,3 based on the work of Fry,4 are much too high. Although very dilute solutions in iron of manganese,5 nickel,8 cobalt,7 and molybdenum8 give dif- fusion coefficients quite close to those obtained for self-diffusion in iron, the silicon values are considerably higher, though of the same order of magnitude. This seems to be consistent with the fact that the silicon atom is the only one of those listed here which is appreciably smaller than iron. The authors are grateful to the Office of Naval Research for their support of this work under Contract N6ori-47, Task order IV, Project NR 031-184, to J. K. Stanley and the Westinghouse Research Laboratories for the silicon alloys used, to several steel companies for the silicon analyses, and to C. Wells, of the Metals Research Laboratory, Carnegie Institute of Technology, for numerous suggestions during the course of the work. References 'C. Wells: Atom Movements (1951) Chapter 2. A.S.M. 2C. J. Smithells: Metals Reference Book (1949) p. 405. Interscience. Pub. Co. 3W. Jost: Diffusion (1952) p. 223. Academic Press. 4 A. Fry: Stahl und Eisen (1923) 43, p. 1039. T. Wells and R. F. Mehl: Trans. AIME (1941) 145, p. 315. "C. Wells and R. F. Mehl: Trans. AIME (1941) 145, p. 329. 7M. F. Hawkes and R. F. Mehl: Trans. AIME (1947) 172, p. 467; Metals Technology (August 1947). .J. L. Ham: Trans. A.S.M. (1945) 35, p. 331.

Jan 1, 1953

By W. A. McCurdy, Joseph W. Leonard, T. S. Spicer

INTRODUCTION by T. S. SPICER and J. W. LEONARD Utilization from the Point of View of the Preparation Engineer The primary interest of the coal preparation engineer is process design, operation and maintenance to produce an acceptable product which can be sold at the greatest possible profit. Because of these interests, attention to the unrealized potential value of coal is sometimes neglected. The intent of this chapter is to alert the preparation engineer to the utilization possibilities of both the product as well as the tributary coal flow moving through a modem coal preparation plant. Thus, coal types having similar physical and chemical properties tend to become increasingly concentrated according to size, specific gravity and/or surface chemistry. The basis for any unrealized potential derives directly from the coal seam itself. Most coal seams consist of coal bands and benches which are sandwiched together in layers and which visually differ from each other by physical structure and luster. Randomly selected physical and chemical ranges determined from layers of coal in a single seam can easily differ by as much as 30 Hardgrove grindability indices, 0.30 of a specific gravity point, 20 percentage points of ash, six percentage points of dry volatile matter and 10 percentage points of total sulfur.1 Similar wide variations exist for calorific value, seam moisture content and undoubtedly, for any other conceivable coal test parameter which might be used for comparative purposes. These observations all point to the long established fact that coal is not homogeneous as conventional analytical methods might tend to indicate, but is instead a highly heterogeneous substance. Since both coal and associated minerals entering a preparation plant are highly heterogeneous, a multi-product potential beginning with certain flotation cell concentrates and ending with plant refuse may exist. Such a potential can and to a limited extent is achieved at some operations by drawing off coal according to size, specific gravity and/or surface chemistry differences from individual coal cleaning processes. Such a sequenced draw-off of coal of increasing ash increments could yield, among other products, chemical coals, coking coals, coals for pulverized fuel boilers, cyclone boiler coals, coals for cement plants, limestone, shale and clay. Basis for Coal Evaluation and Selection Despite the known heterogeneity of coal, the final analysis of a given coal product is customarily reported as a single average since coal has always

Jan 1, 1968

By M. R. Geer

THE increase in the number of coal-cleaning plants employing dense-medium processes occurring since 1946 is especially interesting when viewed historically. Both sand and magnetite were introduced as material for heavy mediums at about the same time, sand in the Chance process in 1921 and magnetite in the Conklin process in 1922, but from that point on their records diverge. The Chance process enjoyed a steady growth from its inception, whereas no additional magnetite plants were built in the United States for over 20 years. Then, following the close of the World War 11, magnetite was again introduced, this time with marked success. During the following years some 47 plants employing magnetite medium were built.

Jan 7, 1953

By Leo J. Vogel, E. D. Hummer

INTRODUCTION by E. D. HUMMER An efficient refuse-disposal system is a necessary part of the modem cleaning plant. The large-scale refuse system and disposal area, engineered for the lifetime of the plant, has become more important due to the greater tonnages of refuse produced from increased quantities of mechanically mined and prepared coal. Laws and increased government regulations have affected the design and operation of disposal systems. THE EFFECT OF MINE AND PLANT OPERATION Refuse disposal starts at the mining face. The mining system, the type of roof support, the machinery used, and the degree of discipline at the face contributes to the amount and type of refuse that must be removed through the disposal system. Economies gained through modification of the mining system or mining machinery may be partially offset by increased dilution of the mined coal with impurities from associated rock formations. In some cases the change in the mining system and equipment has reduced the dilution. In all cases the ratio of impurities that must be removed from the raw-coal feed to the plant not only affects the maintenance and operating costs of the plant, but greatly affects the design of the refuse disposal system. The design of a mine and plant should include the location and the estimated capacity of the disposal areas for the life of the property or plant. Complete evaluation of the disposal system and an estimate of its annual cost of operation over the life of the property or plant should be incorporated in the plant and mine evaluation. Plant design should be as simple as possible, consistent with the efficient production of clean coal. Material transfer points, crushing, screening and pumping operations should be kept to a minimum to reduce degradation and the subsequent increased difficulty and cost of refuse removal. The maintenance of good process control by operating management will result in a minimum of misplaced material in both refuse and clean coal. Reduction of misplaced float material in the plant refuse is an important factor in preventing combustion in the refuse storage pile. THE REFUSE DISPOSAL AREA Combustion in refuse piles occurs when air enters the pile in sufficient quantity to support oxidation. At certain rates of air in-filtration, the heat produced by the oxidation process is not dissipated and temperature rises.

Jan 1, 1968

By John M. Cummings, Warren. Harry V.

THE Geology Department of the University of British Columbia has undertaken the task of examining the ores from as many as possible of the gold mines of British Columbia. The object of this work is two- fold. First, it is known that detailed mineralographic studies are useful in attacking ore-dressing problems, and these studies are intended to be helpful to mill operators. Second, it is hoped that mineralogical and mineralographical studies will prove useful adjuncts to those of lithology and structure in throwing more light on problems related to the origin of the deposits. The paper shows that gold, for all practical purposes, is not present in an ore mineral in solid solution nor as a eutectic with any mineral; if the latter were true the gold particles would be distributed equally throughout that mineral. The gold occurs either as native gold or as a gold-silver telluride and is not distributed regularly through any mineral or minerals. The relationship between the gold or gold-bearing telluride and the associated minerals affords a means of classification that is not only simple but also appears to be directly related to the geological nature of the deposit, which may be summarized as follows: 1. Disseminated Gold Type.-Precious minerals in extremely small grains, which are distributed without regard to grain size, fractures or grain boundaries: (1) Hedley variety-gold in native form; (2) Surf Point variety-gold predominantly as telluride. 2. Veining Gold Type.-Precious minerals in grains of various sizes, which occur mainly along fractures and grain boundaries: (1) Cariboo gold quartz-goldin native form. (2) Waneta variety-gold as telluride. Application Te Ore Dressing These mineralographic studies have proved to be of value to mill operators, and future studies of a similar nature should prove increasingly useful because every year provides a further opportunity to correlate

Jan 1, 1937

By David R. Mitchell, Ernest M. Spokes

MINING ENGINEERING, page 373, March 1958, vol. 211) S. C. Sun: This article by Spokes and Mitchell deserves high commendation. For many years mineral dressers have been at a loss to explain the variation in magnetic susceptibility of the same mineral species obtained from different localities. In fact, they do not even have a list of accurately measured data on the specific magnetic susceptibility of weakly magnetic minerals to consult. Experience as a university teacher has firmly convinced me that the average student has more difficulty in acquiring a satisfactory knowledge of magnetism than of any other branch of mineral dressing. This is almost entirely because the subject has been treated far too much from a strict practical standpoint and far too little from a fundamental one. It is no exaggeration to state that almost all the published theoretical discussions are based on the experimental results of manufactured chemicals and alloys, but not of naturally occurring minerals. In an attempt to remedy this state of affairs, the author of this article not only set up a new magnetic balance in the Department of Mineral Preparation of The Pennsylvania State University, but also performed work of fundamental value, thus pointing the way to further research. This is evidenced by the fact that an investigation of the magnetic susceptibilities of manganese minerals was recently completed by S. G. Watt under the direction of David R. Mitchell, now acting dean of the College of Mineral Industries of the Pennsylvania State University. D. J. Cook is studying the magnetic susceptibility of titanium minerals under my supervision. It is hoped that our research program can be continued for several years and that similar investigations will be initiated at other universities and research institutions. Ernest M. Spokes (author's reply): The discusser has touched the heart of a pedagogical problem in the field of minerals beneficiation—students do not understand magnetism and, as a result, neither do the graduate engineers. Only recently has the average course in engineering physics started teaching the fundamentals of magnetism, as they are understood in modern physics, in addition to the classical treatment of the mathematical aspects of magnetic phenomena. It is to be hoped that this increasing instruction in fundamentals will improve our understanding and inspire research to determine more of the basic magnetic data that are essential if we are to see improved methods of separation by magnetism.

Jan 1, 1959

It is not often that a mining district is discovered, opened up, exploited and developed into a rich producer within the space of three or four years. Not until the year 1903 was the existence of the rich cobalt-nickel arsenides and silver of Northern Ontario even suspected by the mining public. But it is worthy of record that Dr. W. G. Miller, the man who has done so much to develop sanely and honestly the mineral resources of Ontario, pointed out [ ] the possibilities of this region at least two years before the first discovery was made. . Dr. Miller, then Professor of Geology at the School of Mining, Kingston, Ont., referred in these words to the district: "It will be seen from what has been stated on preceding pages that the district examined contains as great a variety of rocks as probably any part of the Province of equal area . . . Although few discoveries of economic minerals have been made in this territory, it may reasonably be expected that deposits of value will be found when

Jan 1, 1907

By Sherwin F. Kelly

MANY baffling problems of crustal geology-of warping and folding, elevation, subsidence, and great dislocations of the earth's surface-may now be on the verge of yielding to the science of geophysics. Electric, magnetic, gravitational, geothermal, and seismic methods are being turned to the gathering of geological evidence buried by deep layers of rock, or lying beneath the waters of the oceans. In this hope, B. L. Miller expresses the opinion that these geophysical studies will sup- ply useful data bearing-on some of the more theoretical problems of North American geology. Among these for example, is the explanation of how Appalachia disappeared. This ancient land mass is supposed to have foundered beneath the Atlantic Ocean after the close of the Paleozoic era and the question arises, was it warped or faulted downward? The geophysical data, though meagre, indicate that the surface of the dense, basal rocks, the probable remnant of ancient Appalachia now underlying the Continental Shelf, slopes downwards to a depth of some two miles below sea level at a distance of 140 mi. from shore: thus suggesting that the subsidence was the result of warping downward rather than abrupt faulting.

Jan 1, 1938

By C. Scala, M. Gondouin

Published laboratory data have established that very significant streaming potentials can exist across mud cakes subjected to pressure differentials such as exist between a mud column and formation fluids. Since shale is similar in kind and in properties to a well-formed mud cake, it appeared possible that streaming potentials might also arise across shales. A practical consequence would be that the streaming potential contribution to the SP would be smaller than might otherwise be assumed since the SP is measured with respect to the "shale bare line". The resultant contribution would be the difference between the streaming potential across the shale and that across the mud cake. In order to investigate this possibility, a laboratory apparatus was devised for measuring streaming potentials under pressure conditions normally encountered in wells. Reported data on streaming potentids across mud cakes were verified. More important, appreciable streaming potentials were found across shale samples. As in the case of mud cakes, the shale potentials varied with the concentration and nature of the impregnating electrolyte. Dependence on pressure was In a different rela-tion than that for mud cakes, possibly because of the lower compressibility of shales. The differences in streaming potentials between the shales md mud cakes were generally small, although they might vary considerably in practice depending on the relative electro-kinetic properties of the particular shale-mud cuke combination. A "poorly eflective" shale with a "very eflec-tive mud cake" would produce the largest negative addition to the electrochemical component of the SP. Results of field experiments with pressurized wells were considered in the light of the laboratory results. INTRODUCTION Field experiments wherein the pressure of the mud column in a borehole was varied have often indicated the presence of a streaming potential, but its magnitude was not easily predictable and its sign sometimes changed from one formation to another in the same well.' In the interpretation of SP logs from standard surveys, nevertheless, the correct value of R,, is very frequently obtained, within the limits of field accuracy, using only the simple electrochemical expression of the SP provided that proper corrections are made for bed thickness, ion activity, etc.' Accordingly, it was apparent that the streaming potential component of the SP in a borehole was considerably more complex than commonly assumed and clarification was indeed necessary The close similarity in nature and constitution of a shale to a well-compacted mud cake suggested that a streaming potential might also exist across shales as pointed out by M. P. Tixier in 1953 and as recently emphasized by Wyllie." e practical consequence would be that the streaming potential across the mud cake would be canceled, at least in part, on electrical logs since the SP is recorded with respect to the shale potential as a base line. This appeared to be a plausible explanation for many of the effects observed but no supporting data were available. In 1955 preliminary experiments at low pressures were conducted in our laboratories which supported the hypothesis of the shale streaming potential and formed the basis for later studies at borehole pressures.* EARLY LOW PRESSURE EXPERIMENTS The early experiments were conducted primarily to determine the possibility of a streaming potential across shales. The shale used was a compact type designated as No. 7 from Reagan County, Tex. (Permian). Cut samples were saturated for over one month in .2 to 2.0-N NaCl solutions. In order to eliminate all electrode polarization effects, a dynamic method was used. A transient pressure of about 1 atm was applied across

By A. N. Holden

A DISLOCATION mechanism has been described by Cottrell' by which metals can yield locally, I. form Liiders bands, giving rise to a characteristic stress-strain curve with a sharp yield point and appreciable strain at constant or decreasing stress. It is undoubtedly the best mechanism that has been suggested to date." In its present development, however, the dislocation mechanism provides a more satisfying explanation for the sharp yield point than for the extensive localized flow occurring at the lower yield stress. The primary objective in this paper is to extend the dislocation mechanism to account for localized cataclysmic flow by a dislocation collision process and to give experimental evidence to support such a process. Only the yielding of iron containing carbon -will be discussed, although other metal-solute systems are known to behave similarly. Cottrell Mechanism In brief, Cottrell explains the yield point in the following way: The dislocations in iron which must propagate to produce slip usually lie at the center of local concentrations of carbon atoms, since segregation about these dislocatlons relieves some of the local stress resulting from them. A dislocation surrounded by a "cloud" of carbon atoms is thus anchored, and a higher stress is required to set it in motion than to move a free dislocation. Considering all available dislocatlons to be anchored in this fashion, the iron exhibits a yield point when the first dialocations break free and move through the lattice causing slip. This first breaking away of a dislocation enables other dislocations to break loose by "interaction" and the process becomes a cataclysm producing local deformation or Luders bands. The yield point in the stress-strain diagram for iron is absent in freshly deformed material, but returns gradually with time; the phenomenon is one aspect of what is called strain aging. The rate at which the yield point returns following straining depends on the temperature of aging. According to Cottrell the rate of return of the yield point in strained iron is limited by the rate of diffusion of carbon at the aging temperature, the mechanism is onr: of reforming the solute atmospheres around carbon-free dislocations that had stopped moving coincident with the removal of stress. If the specimen is retested immediately after straining and unloading, carbon will not have had time to diffuse to, and re-anchor, dislocations and the yield point will not occur. The carbon diffusion limitation for the rate of strain aging apparently applies if the criterion for strain aging is either the change in hardness" or the change in electrical resistance" of the strained speci- men with aging time. The possibility exists, however, that the yield point actually returns to strained iron at some rate other than that deduced from hardness or electrical resistance data. Therefore, as a preliminary experiment, the rate of yield point return in a rimmed sheet steel strained 6 pct in tension was measured at 27°, 77°, and 100°C. A plot of yield-point elongation for each of these temperatures against aging time appears in Fig. 1. The aging process is described by curves which rise to a plateau value of elongation that seems independent of temperature, but at a rate that depends on temperature. Very long times lead to a further rise in the yield-point elongation above the plateau value. However, if the later increase in yield-point elongation is ignored and the log of the time to reach half the plateau value of elongation is plotted against 1/T, a straight line results for which an activation energy of about 25 kcal pel- mol may be assigned. Within the accuracy of this sort of experiment this is approximately the activation energy for the diffusion of carbon in iron (20 kcal per mol), and the carbon diffusion limitation suggested for the yield-point return on strain aging is valid. The Cottrell mechanism thus explains in a qualitative manner the occurrence of a yield point in iron and its return with strain aging. It fails, however, to explain some of the other experimental observations that have been made of the yielding behavior of iron. For example, it is known that the yield point in iron becomes less pronounced with increasing grain size. Annealed single crystals of iron have very small yield-point elongations .if indeed they have any,' compared to a polycrystalline steel. If the only requirement for a yield point is that the dislocations in the lattice of the annealed. material be anchored by carbon atoms, the difference in the behavior of single crystals and polycrystals is not explained. That a dislocation mechanism may be entirely consistent with little or no yield point in an annealed single crystal will become apparent later when dislocation interaction is discussed. Strain aging produces a definite yield point even in single crystals. This accentuation of the yield-point phenomenon in single crystals after strain

Jan 1, 1953

By Francis Lucas

ANY metal which contains even a small percentage of aluminum possesses certain peculiarities of appearance and properties which are exhibited both when the metal is melted and after it solidifies. Pure aluminum, or an alloy containing a small proportion of aluminum, can be melted without flux-except for a layer of charcoal-because a film of aluminum oxide and metal forms at the surface of melted aluminum. Although very thin, this film is air-proof, and it prevents the metal underneath from oxidizing. This oxidized film does not move easily on account of its toughness and high surface tension. One very important point in connection with this process of still casting has not been strongly enough stressed, namely, that the same kind of surface film with the same peculiarities forms over the surface of all melted alloys that contain even a small proportion of aluminum. Experienced foundrymen know how desirable it is to cast aluminum under its "skin" or-under the surface of the film which tends to remain still. In the case of red copper, when in fusion, the surface shows pure copper only. This is due to the fact that liquid copper constantly absorbs the copper oxide which forms on the surface. By closely examining melting copper the oxide can be seen dissolving in the bath, and going into solution just as pulverized sugar dissolves in water. When copper is cast in the open, either in wire bars or cakes, the surface of metal exposed to the air is covered by a film of black, oxide that cannot be absorbed by the metal.

Jan 1, 1927

By B. Silliman

THESE ores occur in the Laurentian rocks in the town of Clifton, St. Lawrence County, New York. The Clifton Mining Company have opened these magnetites upon their estate of 23,000 acres, on the waters of the Grasse River, an affluent of the St. Lawrence, which flows for about nine miles across the estate, exposing a section of the formation, and affording ample water-power at numerous points. In approaching this district from De Kalb Junction, upon the Watertown and Ogdensburg Railway, the observer passes from the zone of the specular ores, which abound to a great extent in Jefferson County, across a belt of non-metal-liferous limestones, continuing for some miles intermingled with metamorphic rocks, and gradually giving place to heavy beds of granitic and porphyritic gneiss, the weathered surfaces of which present a gray and rough appearance, from the washing out of the feldspar; leaving the quartz very prominent, and completely disguising the real character of the rock, which, when freshly broken, has a lively reddish appearance from the predominance of flesh-colored and red feldspar. Beds of fine-grained quartzite appear also intercalated in the granitic gneiss. These are the dominating rocks of the magnetite region, but the magnetite is always found, so far as the speaker's observation extended, associated with beds of calcite, carrying hornblende, black and green, biotite, and brown garnet interspersed with yellow and magnetic pyrites. The strike of these rocks is about northeast, and their dip about 40° to 45° southeast.

Jan 1, 1873

By Joseph Kaye Wood

A metal is said to be overstrained when it is deformed beyond the elastic limit at a temperature well below the critical range, as in cold working. Quantitatively, overstrain might be considered as that part of the total elastic deformation of the piece of metal, left over after the external load is removed, that added to the permanent deformation due to plastic action will give the total permanent deformation. Ordinarily the effects of this phenomenon, which vary with the internal residual stress probably in accordance with Hooke's law, are more noticeable when the yield point of the metal is exceeded, but they probably also exist to a smaller degree when the load is just large enough to cause the least amount of permanent set. These effects, which we recognize as the result of overstrain, are as follows: 1. An apparent increase of the elastic limit in tension and a decrease of the elastic limit in compression, provided the external load is tensile. The reverse is true when the load is compressive. 2. An elastic after-effeet in which time and temperature are important factors. 3. A state of imperfect elasticity in which Hooke's straight line becomes slightly curved, giving rise to an hysteresis loop. 4. In addition to the apparent increase in the elastic limit, such properties as the hardness, ultimate strength, and resistance to fatigue failure are increased, provided the overstraining has not been carried far enough to make the metal brittle. 5. Correspondingly the ultimate elongation, reduction in area, magnetic quality, ratio of endurance limit (fatigue breaking stress) to elastic limit, and resistance to season cracking (in certain copper alloys) are decreased. The question naturally arises: how do these changes in the properties of a metal resulting from overstrain influence our method of design? The fact that most of the desirable qualities are increased makes overstraining a favorable process, from an engineering standpoint; but on the other hand, the loss of such qualities as perfect elasticity and complete

Jan 1, 1924

By Frederick L. Knouse

THE south border of Espirito Santo begins about 400 km. north of Rio de Janeiro and extends along the Atlantic Coast northward some 325 km. and inland 100 to 150 km. The area under consideration, where quartz crystal of strategic grades has been mined, extends from 19° to 21° and 30" south latitude; and from 40° to 41° and 30" west longitude. This includes the central part of Espirito Santo, chiefly south of the Rio Doce from the Atlantic ocean, and west across the border into Minas Gerais near the town of Aimores, in the municipalities of Aimores, Minas Gerais; Baixo Guandu, Santa Teresa, Santa Leopoldina, Colatina, Joao Neiva, Fundao and Domingo Martines, Espirito Santo (Fig. 1). During 1943 and the first half of 1944, this region accounted for approximately 3 to 5 per cent of the quartz crystal produced in Brazil. Shipments of crystal have been made chiefly by rail to Rio de Janeiro. This region is serviced by the E. F. Minas-Vitoria and E. F. Leopoldina to Rio de Janeiro through Vitoria; and by the E. F. Minas-Vitoria and E. F. Central do Brasil through Bello Horizonte, Minas Gerais to Rio de Janeiro. The major deposits are accessible from the railheads by dirt roads, some being 5 to 30 km. off the road, reached by trail. In 1943 and the first half of 1944, the bulk of the production was from inter mountain marshes and adjoining hillside alluvial placer deposits in the zone surrounding the town of Santa Teresa. Most of these deposits were formed from the erosion of pegmatites, quartz veins and pockets in the gneiss, with minor quantities produced from miarolitic cavity fillings in the granitic rock. EARLY OPERATIONS Mining of quartz crystal in this region began in 1928, and has been stimulated by the market demand for military uses. Before 1936 little attention was given to it, either in Espirito Santo or eastern Minas Gerais. From 1936 to 1941 the Japanese sent agents to various points of production or potential production to acquire quartz through purchase. They bought crystal as small as 10 grams. Since 1941 only the United States and Great Britain have received quartz from Brazil. The United States purchases crystals of loo grams and larger for strategic purposes. The first known discoveries were made either in the municipalities of Aimores, Minas Gerais, or in Baixo Guandu, or Domingos Martines, Espirito Santo. Marketable quartz crystal was first found either in the massive quartz replacement veins of the Victor Hugo mine in the municipality of Domingo Martines, or in the large cores of quartz in the pegmatites near Baixo Guandu, extending into Minas Gerais. PRODUCTION The production of quartz in Espirito Santo from 1936 through 1941 as recorded

Jan 1, 1946