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By Roswell H. Johnson

What becomes of the water which must have filled the oil and gas sands at the time of deposition, has long puzzled students of oil and gas and has found expression in Munn's well-known article on the hydraulic theory. Both Munn and Clapp have pointed out that in the Appalachian field the deeper sands carry increasingly less proportionate amounts of water. It seems to me probable that the principal source of oil and gas has been in the shales in proximity to the sands which now contain these products. The sand spits which mark off the lagoons from the sea comply particularly with the requirements of a limited sand imbedded in shales rich in organic matter. Cunningham Craig has objected to this view that the rich organic muds of lagoons are found only at the surface. That such muds do extend to considerable depth 1 am assured by Prof. Douglas W. Johnson, who has made an extensive study of the Atlantic Coast marshes. As any particular sand body becomes weighted by a heavier and heavier overburden, the result of increasing deposition, a part of the very large percentage of water in the uncompacted sand and mud is forced out. The water percentage of freshly settled mud is vastly higher than that of the resultant shales, or even of a very porous sand. If beds of less compressible material meet or underlie the shales in question, there will frequently be a lateral motion along such beds to some point where the upward movement will be resumed. We find in our laboratory work here that oil, gas, and water have extremely slight capacity for gravitational sorting while in a state of rest, but when moving the gravitational sorting is readily accomplished. As the oil, gas, and water pass a body of larger pores, the gas, owing to its lack of capillary attraction, is retained in the large pores. This has been predicted by Washburne, Blatehley and others on the ground that the water has a higher capillarity and grips the finer pores in such a way that there will be a greater proportion of oil and gas in the large

Jan 1, 1915

By I. Fatt

This paper proposes the network of tubes as a model more closely representing real porous media than does the bundle of tubes. Capillary pressure curves are derived from network models and pore size distributions are calculated from these curves. In this way is shown the difference between the true and calculated pore size distributions when the capillary pressure curve is used to obtain pore size distribution for porous media. INTRODUCTION Despite the technological importance of the laws governing flow through porous media, many of these laws have not yet been clearly formulated. This is especially true of the laws governing multiphase flow. The static properties, such as the capillary pressure curve, are also not at present interpretable correctly in terms of the pore size distribution and other structural properties of porous media. In the absence of any well founded theoretical description of fluid flow through porous media, many empirical descriptions have been proposed. In addition to the strictly empirical flow equa- tions, some equations have been developed rigorously from simple geometrical models of the pore spaces. These equations are only as valid as is the model used in their development. The two models used in the past, the sphere pack and the bundle of tubes, have been too simple, and as a result, the equations derived from them have failed to predict the observed properties. Agreement between theory and observation has been achieved for these models by inserting parameters of doubtful physical significance. The work to be reported here was undertaken in the belief that the study of a model more closely resembling most real porous media than does the sphere pack or bundle of tubes would yield useful information concerning the structure of real porous media and the relation between structure and flow properties. There was no intention of developing any calculational procedures, as for example calculating relative permeability from capillary pressure data. The objective of the study was instead to develop a better qualitative understanding of the relation between the various measurable properties of porous media. The model chosen for study is the network of tubes in which each tube represents a pore space in the porous medium. Microscopic observations leave no doubt that sandstones and clastic carbonates are three-dimensional irregular networks of irregularly shaped pores. The irregularity of these structures makes any accurate theoretical study of their properties impossible. Results from an oversimplified model such as the bundle of tubes are worthless when applied to real systerns. The sphere pack model, on the other hand, not

Jan 1, 1957

By Enid C. Plante

This paper deals with the flotation of the mineral fluorite (calcium fluoride) and of two associated gangue minerals, calcite and quartz. The aim of the investigation was to produce "acid-grade" fluorite, which must contain less than one per cent of silica. Several reagents are used successfully in practice for floating fluorite from its ores. Oleic acid is the most widely used collector, usually at temperatures above 60°C, with sodium silicate as a dispersant for quartz and quebracho or tannin to depress calcite. Sulphides (e.g., galena) are often removed first by xanthate flotation. Many investigators23 report results in which more than 80 pct of the fluorite is recovered in a concentrate assaying 96 pct or more of fluorite and less than I pct of silica. This investigation was undertaken with the intention of floating the gangue, which is the minor constituent of the ore, from the fluorite. Hence emphasis was first placed on the cationic compounds that float quartz. No satisfactory separations were obtained in this way, and other reagents were investigated to discover whether these were more effective than oleic acid in floating fluorite from quartz in the usual way. The first part of the paper describes experiments with several long-chain collectors available commercially. Most of this work has been by captive-bubble and cylinder flotation tests, with some batch tests in a flotation machine. The second part describes the use of sodium cetyl sulphate as a collector for fluorite and includes laboratory tests and extension of the work to batch tests in the flotation machine. A method for determining the adsorption of sodium cetyl sulphate on fluorite has been developed and is described. Theory of Collection by Paraffin-chain Salts It may be assumed that these compounds are adsorbed at the mineral surface in one or more of three ways outlined by Kolthoff:12 1. Exchange adsorption between lattice ions in the mineral surface and collector ions in solution. Closely related is adsorption by the collecting mechanism postulated by Taggart,17 in which there is metathesis between the collector and the mineral cation or anion. 2. Exchange .adsorption between adsorbed gegen ions (p. 67, ref. 19) and collector ions in solution. 3. Adsorption of nonelectrolytes (polar-nonpolar) without displacement of adsorbed ions. With cationic collectors, inorganic cations in the solution (e.g., hydrogen ion) compete with the collector ions and therefore act as depressants, while inorganic anions have the same effect with anionic collectors. From this follows the general conclusion that ions of the same charge as

Jan 1, 1949

By E. R. Atkins, G. H. Smith

Results of laboratory tests are presented to show that lire value of "m", in the Archie expression dernlined by the shapes of the particles in the system. Tile value of m "the shape factor", is constant for a system of particles of a given shape for a range of F - + values. Applying this concept, one can predict F - + relationships for mixtures of particles with different shapes, and these predicted relationships are useful in electric log interpretation. It is suggested that an equation of the form 1/F -10mcan be used to describe the properties of natural formations containing varying amounts of sand and clay. From this work and values of "a" and "m" reported in the literature, it appears that in many cases rocks in the same geological horizon have a common primary porosity but contain varying amounts of a particular clay. It is concluded that the equation can be applied to a rock-water system only when values of "a" and "m" have been established for the particular system. INTRODUCTION The petroleum literature contains many reports of the results obtained by determining formation resistivity factor F and porosity + of rock samples from oil fields all over the world. The usual practice is to use data from a large number of samples from a number of fields to find an average relationship between F and +. Several such average relationships have been advanced. In the absence of data on a particular formation or field, it has been the practice to use the average relationships to give a rough approximation of the F - + relationship. The purpose of this paper is to report on basic relationships that exist between F and + for naturally occurring particles in water solutions. Other workers' have found the same relationships apply to the diffusion of hydrogen through packed beds of dry particles. In the work discussed here, relationships for application to unconsolidated sands or shales containing mix- tures of particle shapes are derived. These relationships, developed for unconsolidated formations, may apply to consolidated formations. EXPERIMENTAL To evaluate F- relationships for unconsolidated rocks, the results of laboratory measurements on simple slurries of clay or sand will be used. Such laboratory studies are concerned with the electrical behavior of water-containing rocks. The wet rock constituents are electrically similar in slurries and in rocks. Archie2 defined formation resistivity factor as All resistance measurements were made using a 1,000-cycle impedance bridge with an oscilloscope as the null detector." The accuracy of this bridge was better than * 0.15 per cent. For the particular apparatus employed, no additional reactance was required to achieve balance for samples with resistances between

By S. H. Williston

IT IS not often that bore hole surveys can be checked by actual civil engineering methods. A recent Arizona survey was checked by normal surveying methods and the comparison of the results should be of value to both oil and mining men. During the summer of 1948 the Phelps-Dodge Corporation, at its Copper Queen property near Bisbee, Ariz., drilled a 1245 ft, 8 in. diam, churn drill-hole in a mineralized area and cased part of it, intending to use it to transfer mill tailings for stope fill. The hole, as frequently occurs, was not straight, and, in endeavoring to locate the bottom in the underground workings, they found no evidence of the hole at the underground coordinates directly below the surface location.

Jan 10, 1950

ERNST PROCHASKA, Bonne Terre, Mo. (written discussion*).-The special importance of this paper is the fact that it calls special attention to the existence of organic sulfur in coal. Many writers have denied the existence of a chemical compound of carbon with sulfur in coal, .but later investigations, and especially the paper by Fraser and Yancey, prove undeniably its existence. As we become more fully convinced of its existence and as the present methods of washing, either in a jig or on tables, are unable to separate the organic sulfur, it remains for an inven-tive genius to perfect a chemical washing process whereby the sulfur will be, dissolved out of the coal, or we must abandon entirely the washing of such coal.

Jan 11, 1919

By N. F. Neumann, A. W. Schlechten

Metal chlorides were formed by reacting metal oxides and calcium chloride; the effect of additions to the reaction mixture was studied. It was found that by use of proper additions, metal chlorides could be prepared from mixtures that were not reactive under ordinary conditions. ManY recent metallurgical developments involve the use of chlorine or chlorides as primary reagents; good examples are found in the production of ductile zirconium and titanium by reduction of their chlorides with magnesium. Various methods of preparing metal chlorides are used and many others have been proposed. Some chlorides are formed by the direct combination of a metal or alloy with chlorine. Other processes react chlorine and metallic oxides; carbon or other reducing agents are usually employed to reduce the metal oxides and so promote chlorination. Metallic chlorides have also been produced by the exchange of chlorine between metal oxides and a chloride, such as sodium chloride. This type of reaction was the basis for the old process of chloride roasting in which metal ores were roasted in the presence of salt. Soluble chlorides thus formed

Jan 1, 1959

By H. De Cizancourt

France.—Pechelbronn remains about the only producing field, 41 per cent of the 1937 output of 496,525 bbl. being mined by shaft and 59 per cent produced from pumping wells. At present Gabian has only a very small production. During 1937 there was no private undertaking for petroleum research. Only the Office National des Combustibles Liquides has done any drilling, unsuccessfully, at Pezenas and Frangy-Chilly. Algeria.—No new research has been made and Tliouanet, a small acreage pool that has been declining for several years, gave only 2193 bbl. in 1937. Morocco.—The SociCt6 Chhrifienne des Petroles continues active work. First tests of production made on the Jurassic structures of the Tselfat and Bou Draa must be mentioned for 1937. In connection with these tests, which have yielded 16,495 bbl., 14 new wells have been located

Jan 1, 1938

By Donald L. Katz, Michael J. Rzasa

With greater effort being devoted to the discovery of new oil and gas reserves and a consequent increase in bottom hole pressures due to greater drilling depths, the phase relationships of hydrocarbon fluids at pressures above 10,000 lb psi are becoming increasingly important. The present paper discusses the results of research with a windowed cell on a methane-Kensol 16 system to pressures of 25,000 Ib psi and temperatures to 260°F. Kensol 16 is a commercial high narrow-boiling-range oil. It is shown that for the temperature range of 60 °F to 260 °F, this particular system exists in two phases to pressures of approximately 14,000 lb psi, and data are presented giving the relative amounts of liquid and vapor phase? coexisting under these conditions. Partial phase diagrams are shown for six different mixtures of methane and Kensol 16, three of which include the critical region. In contrast to mixtures composed of substances of fairly close volatility. critical opalescence was noted for as much as 200°F of the critical temperature. The critical locus of the methane-Kensol 16 system was estimated and the conventional pressure-composition and temperature-composition diagrams were prepared. From these, the equilibrium vaporization factors for methane and Kensol 16 were estimated for temperatures from 60 °F to 700 °F and to pressures above 12,000 lb psi. The relations of this study to petroleum production problems and other phase equilibria research are discussed. INTRODUCTION A knowledge of the physical behavior of naturally-occurring hydrocarbon mixtures is fundamental to a thorough treatment of nearly all operations involved in the recovery, refining, and transportation of petroleum. The operations may involve the applications of phase relationships, and the relative

Jan 1, 1950

By R. B. Porter, R. P. Porter, R. A. Lothrop

Changes became necessary in dredging methods employed in Idaho through passage of the Dredge Mining Protective Act (1954). Among other provisions, the law requires dredge operators to construct settling ponds of sufficient capacity and character to reasonably clarify the water used in the mining process before such water is discharged into the stream. Porter Bros. Corp., a placer mining company with many years operating experience in Oregon and Montana, became interested in strategic mineral placers in Idaho in 1950 when it was learned that prospectors had discovered a radioactive mineral deposit in Bear Valley Creek, 95 miles northeast of Boise. The company acquired mining leases and proceeded with exploration and development work on the property. After extensive research had resulted in the determination of successful separation processes, contracts were negotiated with the federal government and deliveries of columbium-tantalum and uranium concentrates commenced in 1956. The mining operations are located in a primitive area of Idaho among salmon spawning grounds and crystal-clear mountain trout streams. To avoid involvement in a very controversial issue, it appeared advisable for the company to develop water treatment procedures exceeding those requirements stated in the Idaho Dredge Mining Protective Act. Operation: The company operates one 6 cu ft continuous bucketline dredge and one 4 1/4 cu ft continuous bucketline dredge on the property. The dredges are jig-equipped, with feed being screened to 3 in. by trommels. The screening and gravity concentration methods satisfactorily separate the heavy minerals from companion clays, sand, and gravel. However, this separation of the heavy minerals requires water from the dredge pond with a minimum content of silt and colloids; therefore, water for dilution is added continuously to the dredge pond to suppress solids buildup. Discharge of this highly turbid water to maintain the proper pond level would ultimately result in an excessive silt load in Bear Valley Creek. To prohibit the turbid pond water from flowing directly into Bear Valley Creek, it was necessary to isolate the dredging area. Main by-pass canals were constructed along each side of the dredge pond and numerous secondary canals were dug for diverting seepage and snow runoff. One by-pass canal, extending more than two miles along the west side of the valley, diverts the main stream as well as tributaries entering from the west; a canal east of the dredge area diverts streams entering from that direction. At the beginning of operations in 1956, the dredge pond effluent was filtered through tailings and settled by use of coagulents in a series of lagoons. The filtrate was then discharged directly into the stream. Although this procedure gave satisfactory results in conformance with the state law, ice buildup and lagoon freezing hindered the efficiency of the process during periods of low temperature. For this reason, testing began in 1956 on a water treatment process that would operate efficiently under the extreme weather conditions encountered in Bear Valley. Development of Water Treatment System: Porter Bros. Corp. established the following requirements for effective continuous treatment of dredge pond effluent to the stream which, at low flow conditions, effluent to the stream which, at low flow conditions, would not result in a turbidity exceeding 25 ppm in the stream, 2) produce a sludge sufficiently dense to minimize disposal area requirements, 3) be semi-portable to follow dredge movements, 4) be capable of operating at low temperatures, and 5) be capable of handling a variety of capacities and turbidities.

Jan 1, 1961

By I. W. Alcorn

The cost of drilling in the past few years of proration and ever decreasing allowables has received increasing thought and study. It seems to parallel the strides made with respect to pumping problems in 1932 and 1933. Low profit margins stimulate the search for economies. Any discussion of slim-hole drilling involves a multitude of abstract values, and the problem can be attacked only by a study of records and rational thinking. In a measure, traditional methods must be studied with a questioning attitude. The words "slim hole" may be somewhat misleading, as the term is entirely relative. For that reason I wish to define it as used in this discussion. On the Gulf Coast, I would define a normal hole as one in which 10 3/4-in. surface casing has been set and below which a 9 7/8-in. hole is dug. With this as a datum, holes of larger diameter below surface would be called "large holes," with 121/4 in. as the "extra large" class and holes of smaller diameter classed in the slim-hole range, 6 1/4 in. representing about the minimum size. The optimum size has not been definitely determined, but the preference is for a program that would call for setting 8 5/8 -in. surface casing and digging a 7 3/4 - in. hole. Different sections of the country might very properly deviate from this practice because of differences in depth, formations, regulations, or other factors. This paper will be confined to a discussion of the drilling of exploratory wells, as the drilling of this class of wells is quite a different problem from that of drilling a proven field, although many of the same considerations apply in both cases, as will be apparent. Although for many years shallow slim-hole and core-test holes of small diameter had been dug, it was not, I believe, until the fall of 1937 that serious consideration was given to its application in drilling wells 7000 ft., 8000 ft. and 9000 ft. deep on the Gulf Coast. This does not mean that nearly all such wells drilled on the Gulf Coast now are of the slim-hole variety, but only that efforts have been aimed in that direction with very encouraging results and there has been a very definite trend to reduce the size of holes, a trend that probably will continue. As to exploration policy, there appear to be two distinct and opposite views. The one usually followed in the past was more or less designed to "shoot the works" on one well. Generally on the Gulf Coast, the depth at which production might be obtained is limited by the drilling equipment and economics. With this thought in mind, wildcat wells are often planned with the idea of carrying the depth to 10,000 It., or even 15,000 ft. All of the possible hazards are anticipated and the general drilling and casing programs are so predicated. Such wells contemplate the drilling of large-diameter holes; the setting of at least one protective string of casing and an extensive coring policy, all of which finally adds up to an expensive well. AS opposed to this general policy is the slim hole. This, on the Gulf Coast, recognizes that new discoveries represent gam-

Jan 1, 1941

By I. W. Alcorn

The cost of drilling in the past few years of proration and ever decreasing allowables has received increasing thought and study. It seems to parallel the strides made with respect to pumping problems in 1932 and 1933. Low profit margins stimulate the search for economies. Any discussion of slim-hole drilling involves a multitude of abstract values, and the problem can be attacked only by a study of records and rational thinking. In a measure, traditional methods must be studied with a questioning attitude. The words "slim hole" may be somewhat misleading, as the term is entirely relative. For that reason I wish to define it as used in this discussion. On the Gulf Coast, I would define a normal hole as one in which 10 3/4-in. surface casing has been set and below which a 9 7/8-in. hole is dug. With this as a datum, holes of larger diameter below surface would be called "large holes," with 121/4 in. as the "extra large" class and holes of smaller diameter classed in the slim-hole range, 6 1/4 in. representing about the minimum size. The optimum size has not been definitely determined, but the preference is for a program that would call for setting 8 5/8 -in. surface casing and digging a 7 3/4 - in. hole. Different sections of the country might very properly deviate from this practice because of differences in depth, formations, regulations, or other factors. This paper will be confined to a discussion of the drilling of exploratory wells, as the drilling of this class of wells is quite a different problem from that of drilling a proven field, although many of the same considerations apply in both cases, as will be apparent. Although for many years shallow slim-hole and core-test holes of small diameter had been dug, it was not, I believe, until the fall of 1937 that serious consideration was given to its application in drilling wells 7000 ft., 8000 ft. and 9000 ft. deep on the Gulf Coast. This does not mean that nearly all such wells drilled on the Gulf Coast now are of the slim-hole variety, but only that efforts have been aimed in that direction with very encouraging results and there has been a very definite trend to reduce the size of holes, a trend that probably will continue. As to exploration policy, there appear to be two distinct and opposite views. The one usually followed in the past was more or less designed to "shoot the works" on one well. Generally on the Gulf Coast, the depth at which production might be obtained is limited by the drilling equipment and economics. With this thought in mind, wildcat wells are often planned with the idea of carrying the depth to 10,000 It., or even 15,000 ft. All of the possible hazards are anticipated and the general drilling and casing programs are so predicated. Such wells contemplate the drilling of large-diameter holes; the setting of at least one protective string of casing and an extensive coring policy, all of which finally adds up to an expensive well. AS opposed to this general policy is the slim hole. This, on the Gulf Coast, recognizes that new discoveries represent gam-

Jan 1, 1941

By Thomas J. Almy

The Ontario croppings were struck July 19th, 1872, by Herman Budden, who, together with his partners, at once began to prospect their claim. Within five weeks their development work enabled them to sell it for $30,000 to R. C. Chambers, who represented the

Jan 1, 1888

By D. R. Parrish, K. W. Beaver, H. W. Wood, R. W. Rausch

A pilot test of forward combustion in the Shannon pool, Salt Creek field, Wyo., is described. The Shannon sand, 950-ft deep, contains a heavy (25" API), viscous (76 cp) oil. Natural reservoir energy is limited. Primary production, intermittent since 1889, recovered only about 2 per cent of the oil in place. The field is operated by Pan American Petroleum Corp. for the Midwest Oil Corp., the owner. The original pilot was a 1.32-acre five-spot. The expanded pilot has eight producing wells surrounding a roughly triangular area of about five acres with the injection well near the center. A control or comparison well was also recompleted in another part of the field. Operation of the pilot has been little different front an ordinary gas drive. Little special equipment was found to be absolutely necessary. Except for some use of a temperature-resistant cement, all wells were conventionally completed. In spite of poor oxygen consumption, the over-all performance of the pilot has been good. Total oil recovery to June 1, 1961, was 73,971 bbl. The wells of the original pilot alone had produced about 24,000 bbl, equivalent to 50 per cent of the oil in place, when fire breakthrough at the first well occurred. These wells have now produced oil equivalent to more than 74 per cent of the oil in place in the original pilot area and production is continuing. It appears that ultimate recovery will approach theoretical maximums before the wells must be abandoned. Performance of the pilot has been encouraging, and expansion to a fieldwide combustion operation is being investigated. INTRODUCTION The results of both laboratory investigations and field tests of underground combustion have been reported previously.' However, most of the field tests were primarily experimental. More information and experience are needed before forward-combustion operations can be engineered with confidence. The purpose of this paper is to present the results of a successful pilot test of forward combustion. These re- sults should increase confidence in forward combustion as a practical method for commercial oil recovery. HISTORY OF THE SHANNON POOL The Shannon pool is located on the north end of the Salt Creek field in Natrona County, Wyo. It is approximately 50-miles north of the city of Casper. The Shannon pool's3 discovery well was completed in 1889, making this one of the oldest oil fields in the Rocky Mountain region. Three more wells were drilled in 1890. First production was hauled in wooden barrels by horse and wagon to the railroad in Casper. In 1894 a small refinery, the first in Wyoming, was built in Casper to process the Shannon crude. In the following years the field changed hands several times. It appears that each new owner did some development drilling as several wells were completed in each of the years 1895, 1902, 1905 and 1912, with negligible development in the intervening years. Forty-eight wells were drilled in this period, but many were later abandoned. Discovery of the more prolific Salt Creek field proper ultimately forced suspension of operations at the Shannon pool. After 1915 there was only sporadic production, mostly to supply cheap boiler fuel to drilling rigs in the Salt Creek field. But even this was discontinued in 1931. Since then the pool had been dormant until the recent operations, which are the subject of this paper. The Shannon pool is now owned by the Midwest Oil Corp. Field operations are conducted for Midwest by Pan American Petroleum Corp. THE RESERVOIR Fig. 1 is a map showing subsurface contours of the Shannon pool. The reservoir is on a nose of the Salt Creek anticline dipping to the north at about 500 ft/mile. The trap is provided by a shallow fault on the updip side of the productive area. The downdip limits are bounded by water, but this water has not provided an effective source of reservoir energy. The Shannon sand outcrops at many places in the immediate vicinity, providing good surface indications of the Salt Creek anticline. At the Shannon pool the sand has been lowered by faulting and is overlain by about 900 ft of shale and other sands. The Shannon sand consists of two members. The upper, a water sand, is about 40-ft thick and is separated from the lower member by several feet of sandy shale. The oil pay occurs in the lower mem-

By D. Brion, J. J. Prédali, J. Hayer

The need to grind volcanic-sedimentary ores very finely (d80 < 20 µm) so as to liberate Pb, Zn, and Cu sulfides from their pyritic gangue causes difficulties in selective flotation. The pyrite, which accounts for 70-80% of the mineral content, is insufficiently depressed by the usual pH and NaCN techniques. To determine better depressing methods, the surface evolution of pyrite during flotation was followed by ESCA spectroscopy to compare the stability range in the Eh-pH diagram. Surface iron hydroxide was formed, which is the main pyrite-depressing factor. NaCN appears to play a more restrictive part, since no ferricyanides were detected, except for very small amounts at pH 7.

Jan 1, 1980

By John C. Osmond

One of the least known geologic regions in the U.S. is the area now called the Basin and Range Province. It is paradoxical that so little geologic information has been compiled for a province that has yielded billions of dollars worth of metals and is currently producing a small amount of oil. Regional stratigraphic studies of parts of this large territory have been published only recently, and regional structural interpretations of even parts of the province are rare in the literature. This, of course, does great injustice to the earliest workers: Gilbert, Russell, Le Conte, Spur, Louderback, and others, who recognized the area as distinctively different from the rest of North America. Their simplified picture of the structure of the ranges and the province as a whole is the groundwork for present understanding and has never been superseded. Since their early works, however, geologic data from the province has consisted largely of detailed reports of widely scattered mining districts. Each district has been described as though it were an island in an unknown sea.

Jan 3, 1960

By O. A. E. Jackson

Pebble milling has been practiced in the reduction works of South Africa gold mines for well over 50 years. Originally flint pebbles were imported from Denmark to grind stamp-mill amalgamation- process tailing, which contained a good deal of extractable gold, but local operators soon found that large pieces of ore could be used for the same purpose. The ore is a hard, tough conglomerate in which quartz pebbles are cemented together by a matrix of redeposited silica interspersed with pyrite crystals. The gold, rarely visible, occurs as fine particles mostly segregated at the interface of the pebble and matrix, although a small fraction occurs within the pyrite crystals. There is seldom any gold in the pebbles themselves.

Jan 11, 1959

By C. Ernest Birchenall

TWO recent papers1,2 cite measurements of surface contour changes on copper which, when attributed to surface self-diffusion, can be interpreted to yield activation energies for surface self-diffusion that approach1 or exceed2 those reported for volume self-diffusion in the same metal.3 It is acknowledged2 that AS must be assigned much too large a value to be physically reasonable in order to make the theoretical Do&apos;s agree with the experimental values, if the jump distance is of the order of the interatomic distance. However, long jumps would probably lead to marked anisotropy on planes that consist of ridges and valleys (like (110) in fcc) whereas only mild

Jan 1, 1963

By C. H. Li, R. J. Stokes, T. S. Liu

Poly crystalline silver chloride specimens having different micro structures were prepared by extruding monocrystals or precompressed powder at varying temperatures. Extrusion at high temperature (370°C) produced a Fully recrystallized equi-axed material which was brittle and fractured by simple cleavage below its transition temperature (60°C for notched specimens). Extrusion at low temperatures (down to -196°C) produced an extremely tough cold-worked material with grains elongated in the extrusion direction. This material fractured below its transition temperature (which varied from —20" to —200°C) by an intergranular mode. It is concluded that cold work increases the resistance to transgranular cleavage. Fracture is then de-flected to propagate intergranularly ouer surfaces making an angle with the tensile axis with a corresponding improvement in notch toughness. This deflection is greater for extruded powder than for extruded monocrystals because of the extremely elongated grain shape. PREVIOUS work1,&apos; on the fracture properties of fully recrystallized silver chloride under notch impact conditions has indicated that the fracture behavior is rather invariant. Thus polycrystalline materials originating from a number of sources ranging from relatively pure Harshaw single crystals to commercial-purity powder and prepared by hot extrusion at 370°C all fracture by simple cleavage with a ductile-brittle transition at 60°C, see Fig. 1. This behavior is also typical for fully annealed single crystals and appears to be fundamental to silver chloride for the particular loading conditions and notch configuration adopted. One way in which this characteristic fracture behavior can be modified is by the dispersion of alumina particles in the silver chloride matrix.&apos; Then, particularly when the alumina particles are in the shape of spheres, the duc tile-brittle transition is much less sharply defined and occurs over a range of temperature, the transition temperature is lowered considerably and the fracture mode changes from simple cleavage to a fibrous or shear mode. The reason for this change is believed to be partly due to the nucleation of cavities in the region of the dispersed alumina particles which influences the state of stress locally and the distribution of plastic constraint at the root of the notch. It is emphasized however that this is not the sole factor responsible for the increase in toughness. In extruded materials it is reasonable to expect that the resultant grain size, texture, and the residual cold work will be influenced by the presence of a dispersed phase. The present experiments were initially designed to determine the extent to which cold work influenced the fundamental ductile-brittle transition temperature and fracture mode of silver chloride. They were stimulated by the discovery that silver chloride could be extruded at temperatures as low as -25°C when commercial-purity powder was used and as low as -196°C when single crystals were used. This working temperature was far below that previously used (370°C) and it was found that such extruded material was exceedingly tough. The reasons for the enhanced toughness and its relation to the previous work on silver chloride-alumina compacts will be discussed. EXPERIMENTAL PROCEDURE Materials Used. Two forms of silver chloride were used in this study: i) silver chloride powder

Jan 1, 1964

By George A. Packard

The shaft of the Raven mine, at Butte, Mont., is an incline 1,700 ft. in length and dipping at various angles. At the top the dip is 70" from the horizontal, but this is gradually flattened until at the 300-ft. level the inclination is only 47. This angle continues to the 1,100-ft. level, below which it curves with a 125-ft. radius to 78". In addition to these variations in dip, the shaft does not lie in the same vertical plane, with the result that the hoisting rope not only rubs at intervals on both the hanging and foot walls, but presses strongly against the west dividers near the collar, while 300 ft. below it runs close to the east end plates. The early operators used no idlers, aid wall plates cut 6 in. deep by the rope resulted. Later operators first attempted to overcome the excessive friction, and the wear of rope and wall plates, by introducing solid cast-iron idlers, 3 in. in diameter. To allow for the travel of the rope from side to side some of these had to be 3 ft. long and were very heavy. Judging from the appearance of the old idlers of this type found at the mine, they often failed to turn in the bearings, which is not surprising when it is considered that they would have to make 1,000 rev. a minute under ordinary hoisting conditions. The next rolls were made of wood, 6 in. in diameter, with an iron band about each end, and a pintle of 1-in. round steel driven in at the ends to serve as a shaft. These wore rapidly, and were soon replaced by rolls made from water pipe, 5 or 6 in. in diameter, cut to the desired length and fitted with a wooden cylinder into which the pintle was driven. Where the idlers were used on the hanging wall of the shaft the original bearing was simply a piece of + by 1 3/2 in. strap iron, 10 in. long, turned up at the end in a circle 11/8 in. in diameter to receive the shaft. A small hole served for oiling, and common black oil was generally used, although filtered oil from engine bearings and compressor bearings was also used. When the rolls were to be placed on the foot wall the bearings were made from two pieces of 1 by 3 in. steel, 6 in. long. A half circle was cut on the flat side of each piece and the two half circles together formed a bearing. Oil holes were provided, and in some cases holes were bored through the two pieces so that they could be screwed or spiked to the wall plates.

Jan 1, 1915