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By T. V. Philip, Paul A. Beck

IN a previous note1 it was pointed out that the available information suggests a distinct correlation between the occurrence of the CsCl-type ordered structures formed in equi-atomic binary alloys of transition elements and the location of the components in the periodic table. A definite increase in the bond strength between unlike atoms, as compared with that between like atoms, is indicated when, in binary alloys of iron group elements, the other component is changed from chromium to vanadium or tantalum, to titanium. Laves and Wallbaum,2 eported a CsCl-type ordered structure for the stable intermediate phase at the equi-atomic composition in the Ti-Fe system (and also in the Ti-Ru and Ti-Os systems). On the other hand, Tagaya, Nenno, and Nishiyama8 found no ordering of this kind in the body-centered-cubic solid solutions in the Cr-Fe system. It was concluded' that the occurrence of a CsC1-type ordered phase of intermediate stability may be expected in the V-Fe system. Preliminary results were described: suggesting that at least some degree of order does exist in the equi-atomic alloy VFe, annealed at 1200° C and quenched in cold water. Using CrK radiation, at least one weak superlattice line was found in the X-ray diffraction pattern which could be indexed as (100). and which disappeared, as expected, when FeK radiation was used. It was found more recently that the impurity phase (presumably VN), previously giving rise to additional X-ray diffraction lines and thus preventing definite indentification of the (111) superlattice line,' can be eliminated by preparing the alloy by arc melting in a helium atmosphere. The alloy specimen melted in this manner had clean surfaces and showed very littte, if any, nitride phase in the microstructure after annealing in vacuum at 1250°C and quenching. The relative intensity of the (100). superlattice line with CrK radiation was greatly increased and, in addition, a fairly strong (Ill) , superlattice line and even a detectable (210) , super- lattice line was obtained, when the powder produced by filing from the 1250°C annealed and quenched specimen was reannealed in vacuum at 625°C for 1 hr. By using a cellulose acetate film as a filter in front of the photographic film in order to absorb the soft radiation resulting from air fluorescence, the background intensity could be reduced considerably in relation to the intensity of the diffraction lines. All three superlattice lines, (100),, (111)., and (210)a, disappeared, as expected, when a radiation other than CrK, was used.1 For the powder reannealed at 625ºC, the strongest lines of the s pattern also appeared weakly, indicating that during an: nealing at 625°C a small amount of transformation took place from the body-centered-cubic to the u phase. However, since all superlattice lines to be expected in the 0 angle range used were actually very clearly present, it was evident that the high temperature body-centered-cubic phase had transformed into a CsCl-type ordered structure before much s phase could form. Reannealing filings for 1 hr at 700°C resulted in complete transformation into the u phase. After 1 hr at 650°C the transformation into IT was not quite complete, the strongest body-centered-cubic diffraction lines were still present, although fairly weak, and only the (100), super-lattice line was detectable (extremely weak). These findings not only confirm the previous conclusionsL as to the existence of a CsCl-type ordered structure in the Fe-V system, but they also indicate that this metastable ordered structure forms at about 600°C preceding the formation of the stable s phase, while at 1250°C the disordered body-centered-cubic phase is stable. The faint (loo) , super-lattice line previously observed in specimens quenched from 1200°C was probably due to the fact that the quenching of the powder in an evacuated fuse:! quartz capsule was not fast enough to prevent completely the ordering reaction on cooling. The present results conform with the suggestion that the A-B bond, in relation to the A-A and B-B bonds, increases in strength from CrFe to VFe to TiFc. It is, therefore, of interest to compare the measured values of the average atomic diameter for these three alloys with the corresponding average atomic diameters calculated from the atomic radii of the elements concerned. ASSUming A-B contacts

Jan 1, 1958

By B. A. Wilcox, A. H. Clauer

DURING the course of an investigation on the high-temperature creep behavior of TD Nickel* (Ni + 2) vol pct ThO2), it was observed that the creep fractures were similar in appearance to low-temperature ductile fibrous fractures and creep ruptures by cavitation. Microfractographs of fibrous ruptures are typically characterized by a dimpled appearance, with second-phase particles frequently found near the bottom of the dimples.'-4 These somewhat resemble creep ruptures by cavitation, in that fracture occurs by void formation, with the subsequent growth and final merging of the voids to form a complete fracture.' It is the purpose of this communication to describe the creep fracture of TD nickel and suggest a mechanism for the rupturing process. The discussion is relevant to material crept to fracture in vacuo at a constant stress of 18,000 psi, over the temperature range 900" to ll00°C. The material used in this investigation was 1/2-in.-diam bar stock supplied by Du Pont, contain- ing 2.3 vol pct Tho2. The final fabrication treatment consisted of -95 pct reduction by swaging followed by a 1-hr anneal at 1000°C. Transmission and replica electron microscopy revealed that the material had a fibered structure with a transverse grain size of -1 µ and a longitudinal grain size of 10 to 15 µ. Selected-area diffraction indicated that the fiber axis was parallel to (00l), in agreement with the results of Inman et a1.6 The thoria particle size varied from 80 to 1000Å, with an average size of 400Å, and the mean particle spacing was about 1200Å. The remarkable structural stability7 was confirmed by annealing for 6 hr at 1300°C (about ' 0.9 the absolute melting point). Transmission electron microscopy revealed that the only structural change was a slight decrease in dislocation density. Furthermore, recrystallization or grain growth during creep has not been observed. All specimens were annealed in vacuo at 1300°C for 3 hr prior to creep testing. The following times to rupture were obtained for vacuum creep tests at a constant stress of 18,000 psi: 900°C, 854 hr; 930°C,

Jan 1, 1965

By J. Lyndon Rosenblad

This chapter describes the development of a rocklike model material for use in tests with a rock-blocks model to investigate the failure mechanism of a discontinuum. In order to provide reliable results, the model material must be characteristic of natural rock and obey the laws of similitude. Initially, the development of such a material does not appear to be a difficult problem. Only when one undertakes such a task does he realize how little is actually known, and that there is considerable work yet to be done. A material that simulates rock in all of its physical properties probably will never be developed. There is now and probably always will be room for improvement. Improvement is needed not only in the component materials but also in the technique of preparation. The material developed and subsequently described in this chapter simulates rock in general and a schistose gneiss rock in particular. The material possesses many rocklike physical properties not found in previously used model materials. One of the most significant improvements of this material is that there is an increase of Young's modulus with an increase in confining pressure as determined by triaxial compression tests. A change in the usual procedure of material preparation was used to develop this material and is also described. MODEL MATERIALS USED IN THE PAST Intact Materials Numerous materials have been used by investigators in models in the past to simulate a wide range of prototype materials. Some of the materials used include cork, plastic, concrete, plaster of Paris, portland

Jan 1, 1972

By Stanley W. Ivosevic

The South-Central Osa Peninsula produced around 30,000 kg (100,000 troy oz) of gold since prehistoric times. Gold freed by erosion from quartz lodes in the Mesozoic Nicoya ophiolite complex was reconcentrated through three generations of Quaternary sedimentary deposits. Resultant gold placers grade upward from 1 g/m3 (0.03 troy oz/m3) and are of moderate size.

Jan 1, 1980

By Norman C. Stines

Russia's mineral potential is a secret that has been effectively kept by the Iron Curtain. There is no conclusive data and because of its extreme importance to the Free World, the subject is greatly discussed. Opinions range from those presented by Paul Tyler in his article "Russia's Mineral Potential," June issue of MINING ENGINEERING to those of Norman C. Stines, presented herewith. Mr. Stines is a consulting mining engineer of Los Gatos, Calif. He was in Russia, China, and Manchuria from 1909 to 1918 as a mining executive. From 1917 to 1919 he served as assistant military attache Intelligence Branch U. S. Army in Petrograd, Russia.

Jan 11, 1951

By William P. Lohden

INTRODUCTION It is recognized that, for a variety of reasons, some companies in the mineral industry today are by no means cash-rich and, in fact, are reporting a growing proportion of long-term debt in their capital structures. A review of recent balance sheets of small, medium-size, and some larger companies, indicates that a fair number still have substantial positions in cash equivalents such as U.S. government issues and other short-term money market instruments. In part, this paper concerns itself with companies which have sufficient cash and equivalents and/or cash generation to internally finance mining projects or expansions but which, for some reason, choose to borrow funds. Misconceptions which appear to frequently underlie so-called "leveraging" decisions are explored in this paper. Also considered are those circumstances under which any company, including one that is cash-rich, should consider borrowing for a project in an amount beyond what would otherwise be necessary based upon its internal financing ability. I do not 'attempt to cover the raising of equity capital in public markets in this paper. OVERALL RETURN ON TOTAL POOL OF INVESTABLE CASH SHOULD INFLUENCE FINANCING DECISIONS If you approach an individual with an investment which can be financed from his savings, or by borrowing at a rate higher than he is earning on his savings, he will quickly tell you that to pay interest at a rate higher than he is earning would reduce his overall income. Assuming he is not currently considering any additional investment

Jan 1, 1977

Dubbed "Freeport's Mission Impossible" by the trade press, the company's Ertsberg mine in West Irian nevertheless shipped its first concentrates in December 1972, ahead of schedule. This is a new and great chapter in the history of Freeport Minerals Co. and its contractors. Exploration and construction were only possible by moving equipment and supplies by helicopters. This work was carried out by Petroleum Helicopters, Inc., of Lafayette, La. At the peak of operations six machines were in service manned by 11 pilots and supported by 10 mechanics. During the month of August, with work in full swing 1,604 tons were moved, including 3 DC-6 tractors requiring 18 trips each; flying hours for the month were 636.

Jan 1, 1973

By Kendall Y. Keuhey

The Mercur Mine, developed and operated by Getty Mining Company, is designed to process 3,000 tons/day of gold ore from the historic Mercur Hill mining district. The mill process involves crushing, grinding, and cyanide carbon-in-leach for recovery of gold from ores ranging from 0.08 to 0.10 oz/ton. During the mining of normal grade ore, a substantial tonnage of material containing 0.02 to 0.05 oz/ton is mined and would be available for heap leaching. Also, Getty Mining is developing methods to test and prepare lower grade material for heap leaching by rejecting a coarse rock fraction from the grinding SAG mill circuit. This lower grade fraction is suitable for heap leaching, and its removal will upgrade the regular mill feed. Other test methods are directed toward leaching techniques on some 4.0 million tons of tailings that resulted from roasting and/or cyanide leaching Mercur ores in the early 1900's. The natural carbons associated with the Mercur deposits require special treatment to reduce their gold adsorption effects when leached with cyanide.

Jan 1, 1984

By G. Gabra

The kinetics of acidified thiourea leaching of pyrite concentrate was investigated at temperature ranging form 20 °C to a 60 °C. The effect of various parameters on the dissolution rates are discussed. The gold extraction was found to be zero and first orders with respect to Fe (111) and thiourea concentration, respectively. The order of the reaction with respect to sulfuric acid was found to be zero. The activation energy was determined from the Arrhenius plot as 2,039 kcal mole -1 (for a freshly prepared acidic solution containing Fe (111) as the oxidant and at 800 rpm stirring speed. This relatively low activation energy value suggests that the gold extraction is controlled by a-physical phenomenon. Under optimum conditions, more than 90% of gold has been dissolved in about 30 min. and 95% in 60 min. Attempt to recover gold from thiourea solution using active carbon is also discussed.

Jan 1, 1984

By Joseph Daniels

IN connection with a study of the feasibility of establishing a blast-furnace industry in the Puget Sound region of Washington, possible sources of ore supplies along the Pacific rim were investigated. Many of the South American countries are known to contain important resources of iron, particularly Brazil and Chile. This latter country, because of its position on the west coast and the easy accessibility of its de- posits, appeared to be a logical place to consider as a potential supply for the Pacific Northwest. Accordingly, a brief field study was made of the deposits in September, 1924. Attention was confined to a limited number of properties on the west coast in the provinces of Antofagasta, Atacama, and Coquimbo. Passing consideration was given to the question of coal resources, and a short visit was made to a blast-funace plant at Corral in southern Chile which had been operated for a limited period as a producer of pig iron. In the following paper, a brief outline is given of the general observations made and of the salient facts rioted in the time available for the general study.

Jan 1, 1926

By K. E. Brown, J. P. Brill, A. R. Hagedorn, T. C. Doerr

A recent correlation for multiphase vertical flow by Hagedorn and Brown1,7 has been used to examine the effect of numerous variables such as pipe size, gas-liquid ratio, liquid flow rate, liquid viscosity, liquid surface tension, oil API gravity, water cut, etc., on flowing pressure gradients. Most previous correlations were derived by using a form of the general energy equation which assumed negligible changes in kinetic energy. Under certain flow conditions this can lead to serious errors in predicting pressure traverses. Examples of traverses calculated both with and without the kinetic energy term are included here. The Chew and Connully correlation for calculating changes in viscosity with changing pressure and temperature has been extended so that the effect of a changing viscosity with depth on pressure gradients can also be predicted. Examples illustrating the effect of tubing size show the importance of this correlation in determining pipe sizes for initial well completions. Limitations on production rates in small pipe sizes from excessive friction losses can be predicted with greater accuracy. The combined use of a vertical-flow correlation with a horizontal-flow correlation provides a method for determining the maximum flow rate possible from both flowing and gas-lift wells. Examples are included to illustrate application of the combined use of vertical and horizontal-flow correlations in optimizing production rates and minimizing excessive costs from over injection of gas in gas-lift wells. INTRODUCTION The problems of multiphase vertical and horizontal flow are immediately encountered in any producing well. Fig. 1' shows three stages of production: flow in porous medium, vertical flow and horizontal flow. All three stages affect the production rate from a well. If we are confronted with a particular well and consider only the variables involved in the vertical and horizontal stages of Fig. 1, we should be capable of calculating the flowing bottom-hole pressure necessary to produce a particular flow rate. A change in any of the variables results in a new solution to the problem. Recent approaches in developing horizontal and vertical-flow correlations have improved to the extent that the solution can now be obtained with more confidence than previously. VERTICAL AND HORIZONTAL FLOW CORRELATIONS Since Poettmann and Carpenter's' original work in multiphase vertical flow, there have been many additional vertical-flow correlations developed which have greatly improved the accuracy of pressure-loss calculations. These

Jan 1, 1967

By Carl L. Renzoni

INTRODUCTION This paper defines equity as the issuance of a permanent interest in the business on a broadly distributed basis. As such, it excludes the issuance of equity to either a merchant bank or to another corporation. Nearly twenty years ago the equity markets were very simple: The instruments used were primarily common shares, convertible debentures or convertible preferred shares. Another equity-type option often used, especially by junior companies, was the sale of joint venture interests. Issue sizes were generally in the order of $25 - $100 million and issues were syndicated primarily in North America and Europe by one or two investment dealers. Mining corporations today benefit from a market with much more depth. Issues are syndicated by dealers on a truly international basis, and issue sizes now often range up to $300 million. Moreover, dealers are now willing to take significant risk in buying the issues for redistribution. This discussion of trends in equity markets will encompass: 1) common shares 2) warrants to buy common shares 3) convertible debentures 4) commodity backed instruments A review follows of events that affect the mining industry and investment dealers as they have a bearing on the equity markets for the metal producers. FACTORS AFFECTING THE MINING INDUSTRY The current business cycle, up to October 1987, had been characterised by a buoyant stock market and depressed base metal prices. Mining companies entered this period with weak balance sheets and little prospect of cash flows meeting capital needs. The issuance of equity and the sale of assets were used extensively to reduce debt to manageable levels. During this period, the relative high price for gold, and more important, the very high earnings and cash flow multiples afforded to gold producers, caused companies to target gold as the only game in town. The need for capital to acquire and develop gold properties prompted an unprecedented volume of equity issues. (Burns Fry led or co-managed over $1 billion of mining equity issues per year during this period). This high demand for equity capital by the industry prompted an increase in the use of equity instruments, such as commodity backed instruments. In addition, government tax incentive programs in Canada, such as flow-through shares, allowed smaller companies to raise significantly more equity than would otherwise have been possible. Over $1 billion in flow-through equity was raised in 1987 alone. The abundance of flow-through capital in Canada made it easy to form a new company. One flow-through share fund developed a system of providing the working capital required for a company to be eligible to receive flow-through share capital so that an entrepreneur required only a mining property to get started. Many new companies were formed and several flourished in a buoyant stock market environment to the point that market capitalizations grew to $100 million or more. The current period is in stark contrast to that before October 1987. The equity markets are generally available to the resource industry only on a window basis and only for senior companies and for special situations. The industry is benefitting from buoyant metal prices, and bankers are anxious to provide debt capital. Investment dealers previously processing several equity issues

Jan 1, 1990

By T. A. El-Bassyouni, Paul Gordon

Grain-gvowth data in zone-refined aluminum and in dilute alloys of copper with this aluminum have been obtained. The amounts of copper added were from 4 to 400 at. ppm. It was found that in both the unalloyed aluminum and the alloys grain growth was characterized by a high value of n in the isothermal growth equation 6n = Kt The inadvertent presence of 1 at. ppm Fe in the alloys was found to he more potent in slowing growth than the purposely added copper. Possible rationalizations of these observations and their general relevance to the theoretical use of gvain-grozvth data have been discussed. Grain growth data of Winegard and his co-workers' on zone-refined tin and dilute tin alloys were analyzed with some success2 in terms of approximate theoretical equations for boundary migration.2-4 In view of this success, experiments were carried out in an effort to obtain similar data on zone-refined aluminum and on dilute copper-in-aluminum alloys. The results obtained were anomalous in several respects and could not be used to test theory. A discussion of these anomalies is presented here; they have been attributed to impurity effects and serve to emphasize the sensitivity of grain growth in general—and the particularly high sensitivity in aluminum—to impurities. The resulting difficulties in the theoretical use of grain-growth data are also discussed. EXPERIMENTAL DETAILS An aluminum bar was zone-refined and leveled by methods similar to those described previously.' The degree of purity obtained is indicated in Table The data in Table I were determined by mass-spectrographic methods through the courtesy of Mr. Thomas A. Johnson of AIAG Metals, Inc.* Three dilute copper alloys with this aluminum were prepared also by methods described previously.' The alloys contained nominally 4, 40, and 400 at. ppm of Cu, respectively (0.001, 0.01, and 0.1 wt pct). Each material was fabricated by swaging and rolling into a round bar about 1/4 in. in diameter with an annealed penultimate grain size of approximately 0.003 to 0.007 cm. In order to minimize preferred orientation the fabrication was carried out in several steps, each consisting of a reduction of about 40 pct followed by a recrystallization anneal. Annealing temperatures for the grain-growth studies were attained by the use of boiling liquids up to 213°C and molten metal baths at higher temperatures. Temperatures were controlled to within 1°C. Samples for measurements were cylinders about 3/4 in. long and 1/4 in. in diameter cut from the fabricated rods. In the interests of sample economy a single sample was used for the grain-growth measurements at each temperature. Each sample was, thus, annealed for several successive periods of time, the grain size being measured at each annealing period on a transverse surface exposed by

Jan 1, 1965

William H. Blauvelt, Syracuse, N. Y.:—Is the coal itself from which the briquettes are made of good quality for steam-ing-purposes? Mr. Parker :—It is an anthracite coal mined near Bank-head arid used on the Canadian Pacific railroad. It contains about 83 of carbon, 8 of ash, and 8 per cent. of volatile material. With regard to briquetting of a mixture of fine coal and coke-dust, I understand that a plant has been installed near Detroit in which coke is mixed with anthracite; also the plant of the United Gas Improvement Co. near Philadelphia is briquetting a mixture of anthracite coal, the resultant briquettes being used in the gas-retorts. Mr. Blauvelt:—The purpose of the Detroit briquette-plant of the Solvay Process Co. has been partly to use up the coke-breeze from the by-product ovens and partly to utilize the pitch. There is no necessity for mixing anthracite with the coke-breeze, but the supply of breeze is limited, and anthracite

Jan 1, 1909

By Simon D. Handelsman, Reg M. M. Rowe

The mechanism of using gold as the basis for a loan was suggested to the treasurer of a mining company operating two gold heap leach mines at a time of high interest rates. Due to the seasonal nature of cash flows from operations, and the relatively low cost of funds this scheme was attractive. The paper describes the agreement with the bank, gives an example of the transactions, and describes other types of gold loans.

Jan 1, 1985

By John V. Beall

Let's start at the beginning, Mr. Turner. Where and when were you born? In Lansing, Mich., on July 31, 1880. And what was your education? I went to the University of Michigan, where I got an A.B. degree in 1902; then to the Michigan College of Mines at Houghton, graduating from there in 1904 with a B.S. and an E.M. What was your first job in the mining industry, Mr. Turner, and what were you paid? In the summer of 1902, 1 was a field assistant for the U. S. Geological Survey in southwestern Idaho and southeastern Oregon, working under Israel C. Russell, professor of geology at the University of Michigan, who incidentally, had just returned from an expedition to study the effects of the eruption of Mt. Pelee, on Martinique. I was paid $60 a month and found; in addition to doing geologic and hydrographic work, I cooked many of the meals for a party of four, and wrangled four horses. I slept for four months under the stars, without a tent.

Jan 1, 1949

By A. S. Michaels, R. S. Timmins

A study of the effect upon oil recovery from an un-consolidated porous medium of chromatographic transport of selected reverse-wetting additives during water displacement is described. Flow tests were performed on hydrocarbon oil-saturated sand columns (containing connate water) into which small volumes of short-chain aliphatic amine solutions were introduced during water flooding. Concurrently, meusurements of oil-silica contact angles, oil-water interfacial tensions and oil-water distribution coefficients were measured us a function of additive concentration. Certain treatments were found to cause a slight reduction in oil recovery, while others produced a significant increase (up to 50 per cent of the normtzl irreducible rninimum oil saturation). Recovery eficiency was correlated most satisfactorily with the maximum degree of reverse wetting produced during additive transport; conditions which resulted in only mild oil wettability of the sand reduced recovery, while those favoring strong oil wetting increased recovery. A mechanism of reverse-wetting additive action during chromatographic transport is developed which ascribes the results to transient changes in oil-solid contact angle during flow, with consequent release of oil trapped by capillary forces. Implications of these observations with regard to improved waterflood efficiencies are discussed. INTRODUCTION The need for finding improved methods of oil production is amply illustrated by the large volume of oil considered economically unrecoverable by existing production practice. Water flooding has long been an excellent method of secondary recovery. However, even in those areas of a formation which are well swept by a water flood, 20 per cent or more of the oil remains trapped within the formation and is not recovered. This trapping of oil within the pores of the rock structure results primarily from interfacial forces. If these interfacial forces were altered, it is possible that the trapped oil could be released and recovered. The addition of surface-active agents to a water flood to alter the interfacial properties of the oil-water-solid system has received considerable attention as a method of increasing oil recovery. Studies of surfactant treatment have yielded varied and, in some cases, apparently conflicting results. Increased oil recovery using surface-active agents has been reported by a number of investigators. Others have found that use of surfactants in a water flood either has no effect upon oil recovery or decreases it. Since surface-active agents tend to alter the formation wettability and oil-water interfacial tension simultaneously, several investigators have tried to determine the role these two factors play in oil recovery. Data have been presented which indicate that the most desirable condition for the solid surface is strongly water-wet. Other results indicate that, although breakthrough recovery may be less, the greatest ultimate recovery is obtained when neutral wettability prevails.", " The desirability of low interfacial tension seems to depend upon the wettability of the formation. Reports of higher recoveries, when the interfacial tension is high in a water-wet system and low in an oil-wet system, are at odds with reports of increased recovery in water-wet systems when surfactants which decrease the interfacial tension are added to the water flood. A review of previous work studying the effects of using surface-active agents in a water flood shows that these agents produce widely different effects and that opinions as to the role of the various interfacial properties are diverse. The consensus, however, is that the interfacial properties are quite important in the displacement of oil from a porous medium by water. Even in those investigations where appreciable increases in oil recovery resulted from treatment with a surface-active agent, economic considerations generally made practical application of the treatment unattractive because surfactants tend to be adsorbed within the formation. This adsorption would necessitate using large quantities of surfactant if all of the flood water were treated to contain a given surfactant concentration, even if this concentration were quite low. Preston and Calhoun suggested that the principles of chromatography could be applied to the use of surface-active agents as a means of increasing oil recovery. A small volume of surface-active material is injec-

By R. J. Charles

PREVIOUS study' of simple impact systems indicated that energy required for fracture and size reduction of brittle materials is greatly dependent on the type of loading that is employed. In this regard it was postulated that fracture and size reduction of a brittle specimen might be accomplished by a high velocity impact at an energy level at which a low velocity impact would leave the specimen relatively undamaged. The finite time required to propagate energy away from the point of loading of an impacted object to other parts of the object and to its supports may permit a concentration of energy at the point of impact if the rate of loading is high. Localizing of energy at the point of impact could quickly initiate fractures that would propagate through the impacted material along with the traveling stress waves. As the cracks form, the initially absorbed strain energy would be released and portions of it travel ahead of the wack tips as stress waves. These secondary stress waves, combined with the initial stress waves derived from the impact, would produce high localized strain conditions in front of the fracture zone. The fracture zone would propagate and the specimen shatter. High rates of loading are brought about by short impact times, in turn obtained by employing high velocity projectiles that are of small mass compared to the impacted object. In the case of a low velocity impact, at an energy level equal to that of a high velocity impact that causes fracture, loading rate would be relatively

Jan 1, 1957

By D. B. RUSHhIORE

I. INTRODUCTION. OF primary importance in mine-installations is the hoist, which has a very direct bearing on the successful operation of a mine. Conditions vary greatly with different mines, and especially in different localities. Such factors as depth, incline, the number of levels, permissible or desirable speeds, conditions of ore, etc., are always more or less special in each case. Veins of ore are never exactly duplicated, and the nature of the ground through which shafts are sunk may considerably modify permissible values. As mining-laws are made by the different States, they necessarily vary somewhat, and, even when not fully observed, they introduce factors which qualify the conditions of hoisting men and ore. The amount of timbering required is often of importance as relating to hoisting-conditions. Methods of loading ore affect the time required, as also does the question of the use of cars or skips. Safety-precautions must be very carefully considered, and the number of men in each mine, the number of compartments, and often the method of removing water from the mine, must. have careful consideration. While a general discussion of the subject. of hoisting is possible, most cases are entirely special, and can be considered only in connection with the peculiar conditions pertaining to that particular installation. The cost of installation of the hoisting-plant may be an appreciable amount, while the cost of raising the ore may be but a small part of the total operating-charge. In many cases, however, the output of the mine is limited by the capacity of the hoist, and the latter thus becomes of the first importance. * Presented also, by mutual agreement, at the meeting of the American Institute of Electrical Engineers, New York, N. Y., Mar. 11, 1910.

May 1, 1910

By James A. Barr

Prospecting methods used in Tennessee have gradually improved with the years, as required by depletion of the easily accessible and shallow deposits and the universal trend toward mechanization, and as necessitated by exploring deeper beds, often occurring under limestone and flinty overburden. In the early days it was a very simple matter to dig pits by hand, using a plentiful supply of local farm labor to expose relatively shallow deposits of "brown rock" under shallow clayey overburden that would stand up without timbering. Visual inspection of the exposed phosphate and expert judgment of the "grade" analysis, aided by a "biting" test to reveal presence of unwanted silica, furnished most of the information required. All this might be helped by a few samples sent to the local chemist† who supplemented his income by judicious trading or tanning a few bear skins. The extra curricula activities did not affect the accuracy of the analysis which hold up even under present day standards. Some shot and core drilling was done in Hickman County, mostly for the limestone-like blue Phosphate deposits. The next step was the use of a 4-in. posthole auger, hand operated as described by Guenther, followed by a completely mechanized rig, as described by Pickard. Both these methods are practically adapted to the prospecting of the relatively soft brown rock deposits at moderate depths of clay overburden. For prospecting in areas of deeper overburden, such as are often found in Hickman County, up to 150 or even 200-ft depths, a modified core-drilling method is described by Guenther. Johnston describes a special diamond-drilling technique, developed by TVA, to penetrate flint horizons, which was adopted by the International Minerals in chemical corporation to prospect in Hickman County where deposits had previously been prospected at considerable expense and with difficulty, by small, temporary, hand-dug shafts.

Jan 1, 1948