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By Hans Lundberg

In order to comprehend the help and information that may be expected from electrical prospecting, it is necessary to have at least a general knowledge of the methods and principles involved in preparing and interpreting results obtained in the field. Electrical prospecting is rather complicated, both in theory and practice, and in order to make a brief description clear to the practical mining man it has been necessary to idealize and generalize the problems, at the risk of having such simplification criticized by the theoretical man. This simplification must not be misinterpreted as showing a lack of theoretical knowledge. For its operation, electrical prospecting mainly depends on the fact that most metallic ores conduct an electric current much more readily than barren rocks. If an electric current flows through a block of ground within which a body of chalcopyrite is enclosed in country rock of schist, the current will find less resistance to its passage through the chalcopyrite than through the schist, even though the passage through the latter be much shorter. This is because the longer path through the chalcopyrite offers less resistance, owing to the superior electrical conductivity of the chalcopyrite (Fig. 1). The good conductor, chalcopyrite, in the poor conductor, schist, thus attracts the current and deflects the normal flow far outside the conduct-

Jan 1, 1929

By John V. Beall

Copper production in the. United States in 1972 amounted to 1,658,000 tons according to the USBM. This figure is up over 1971 but falls below 1970 production of 1,719,101 tons. This report is essentially about the status of copper mining operations in the U.S. and is an update and expansion of the report "Southwest Copper-A Position Survey" published in [A=], October 1965. At that time, the trend was toward using larger equipment to mine lower grade ore and toward the expansion of dump leaching practice. That trend continues today but, it is overlain by intensive activity to comply with existing environ¬mental legislation and uncertainty over proposed revisions of venerable laws governing mining. In the U.S. today there is, practically speaking, no excess smelting capacity so that expansion of copper production through the startup of new mines is inhibited. Owners of a large undeveloped orebody would have to decide before going into production whether to sell the concentrates offshore, which has many problems, whether to try one of several unproved chemical processes for producing refined metal from concentrates or embarking on the construction of a traditional pyrometallurgical plant in the face of considerable uncertainty over the pollution standards that eventually must be met. The situation is such that not only is the present rate of U.S. copper production threatened but the ability to meet projected increased demand in the years ahead may have been severely retarded.

Jan 4, 1973

By Hjalmer Sjögren

AMONG the feldspar-rocks there are certain types which occur constantly in different areas-viz., the aruphibolitic plagioclase- rocks and the granulitic rocks Composed of quartz and alkaline feldspars. Among the latter soda: granulites as well as potash are met with; also the corresponding gneisses occur. GROUP I.-THE ORES OF THE ARCHEAN CRYSTALLINE SCHISTS. The Rocks. The ore-bearing rocks of the ore-province of central Sweden are chemically and petrographically unlike the more monotonous gneiss- and granite-areas which surround them. On the whole, they constitute a quartz-feldspar formation in which purer quartzitic rocks, limestones, " skarn " rocks, and ore-bodies are very subordinate members. (Skarn is the Swedish name for rocks of varying composition, mostly consisting of lime, magnesia, iron, and alumina, silicates of the pyroxene, amphibole, and garnet groups; as secondary minerals, epidote, chlorite, biotite, and talc occur. The skarn is scarcely an independent rock but is connected with the ore-deposits. It is formed through an interchange between the silica of the quartz-feldspar rocks and the basic constituents of the ore-formation.) [A BRIDGED SUMMARY.-The amphibolites must be considered as stretched and dynamo-metamorphosed dioritic rocks. The granulites are divided into two groups, one showing predominant plagioclase, the other equal or predominant orthoclase. Evidently, the iron-ore deposits are connected in some way with the

Jan 1, 1913

By Charles G. Maier

It has long been supposed that when crystalline materials are comminuted the energy used in the production of increasingly smaller grain sizes is not entirely dissipated as heat but that a certain portion is "stored" as a part of the internal energy of the material. This portion usually has been called the "surface energy" of the particles. The practical interest of the Bureau of Mines in this subject in connection with the energy requirements of crushing processes has led to the author's attempt to measure the "stored" energy in finely divided calcite by heat-of-solution methods1.t The experiments on calcite showed that "storage" of energy could not be proved for this material, because fine grinding caused a lack of chemical homogeneity evidenced by loss of carbon dioxide and subsequent adsorption of water on the surfaces of the calcite particles. When thermochemical correction was made for composition changes the corrected heat of solution was less for fine material than for coarse. Continuation of the experimental work into the problem of comparing work and heat in the deformation of metallic crystals, where the calorimetric difficulties were less, showed, however, that in the case of copper and aluminum a real discrepancy between work and heat could be shown. Similar results had previously been obtained by Farren and Taylor2 and Hort3 and more or less simultaneously with the author's work by Rosenhain and Stott4 and by Taylor and Quinney9 The results obtained by the different investigators were not satisfactorily consistent, but the experiments of Taylor and Quinney constitute by far the best figures obtained to date. The previous paper1 presented evidence to show that if energy is stored in the surfaces of crystals the densities of fine crystals should differ

Jan 1, 1936

By J. A. Scott, F. R. Hensel

The paper deals with the investigation of two types of coreless induction furnaces, one of 60 cycles, the other of 5000 cycles. Nickel was used as test material and the absorption of oxygen by molten nickel was chosen for determining the influence of the frequency on the metallurgical characteristics of the furnaces. Dr. Herty's aluminum method, slightly modified, was found suitable for determining the nickel oxide content in nickel. Also an electrolytic method for determining alumina in nickel was worked out. The solubility-temperature relations for nickel oxide in molten nickel were determined approximately. It was found that the solubility of nickel oxide increases with the temperature. Comparative tests on the rate of oxygen absorption made in a 60 and a 5000-cycle furnace showed that the absorption of nickel oxide in nickel is an increasing function of turbulence, time and temperature. The rate of oxygen pickup in the 60-cycle furnace is about three times as great as in the 5000-cycle furnace. In the 60-cycle furnace the maximum oxygen content of the melt comes close to the saturation limit. Melting under an oxygen-free atmosphere prevents oxidation in both types of furnaces. DISCUSSION (Iloward Scott presiding) H. Scott, East Pittsburgh, Pa.—When Professor Desch was in Pittsburgh recently he mentioned that the induction furnace has practically replaced the crucible furnace in Sheffield except for the carbon tool steels. Dr. Hensel is to be congratulated on the development of analytical methods for determining inclusions and for getting two different methods to agree. F. R. Hesnsel—Recently the purification of molten metals with hydrogen or other suitable gases has become an important issue and a number of patents have been taken out covering gaseous treatments of molten metals. In this connection I wish to call

Jan 1, 1933

By Robert S. Dalzell, Ernest A. Curth

Following the introduction of shields to the U.S. longwall mining scene and the steady increase in the number of shield faces during recent years, the occurrence of longwall -ground-control -associated accidents has shown a welcome downward trend. But even though the accident experience is favorable, problems exist. New mining systems, however efficient, have run afoul of roof control. Shield faces have suffered extended stoppages because of roof cavities. Therefore, the Bureau of Mines has reviewed foreign remedial techniques to evaluate their potential for domestic application. Such technology includes cribbing, strain absorbent modules (SAM'S), inflatables, wire meshing, chemical rock stabilization, synthetic foams, and monolithic fills.

Jan 1, 1984

By John Birkinbine

" Whether an iron-ore should be roasted is a question which very seldom arises ; at least, this question seldom ought to arise. With the exception of the red impalpable oxide, the whole series of ironores require roasting—even the specular iron-ore, if it is very compact—but the best oxide, if too compact, works badly in the furnace. All other ores should be subjected to calcination. Some ironmasters are in the habit of using the hydrates raw, but this should riot be done where clay-ores are smelted or where the hydrates contain either chlorides or phosphates. But in the latter case, the pig metal will be cold-short if there is too much phosphorus. Under all circumstances, however, it is best to roast the ores if we expect good metal and well-regulated furnace operations. " The object of roasting ores is to produce higher oxidation and to expel injurious admixtures. In both cases liberal access of atmospheric air is required ; we should, therefore, so arrange our roasting operations as to fulfil these conditions, from which it will appear that different ores require different treatment."* The above may be considered an extreme, and perhaps erroneous view; but there is no question as to the absence of a general appreciation concerning the value of preparing ores of iron for smelting in the blast-furnace.

Jan 1, 1884

By C. A. Stickels

The preferred crystallographic orientations developed during recrystallization of polycrystalline electrolytic iron sheet, cold-rolled 90 pct, were ivestigated. Recrystallization at 500° or 565° C for relatively short limes produces a texture which is similar to the rolling texture. A duplex partial fiber texture, significantly different from the rolling texture, is found when the annealing time is increased. Recrystallization at 700°C also produces a sequence of textures with increasing annealing time. In order of their appearance, these textures are: 1) the duplex partial fiber texture found at lower temperatures, 2) a four-component texture "near {322}(296)", 3) a {112)(110) +(111)(110) texture, and 4) a two-component "near {554)(225)" texture. Secondary recrystallization, or discontinuous grain growth, accompanies the development of the latter texture. However, the "near {554} (225)" texture was nol observed when secondary recrystallization occurred under other conditions. All of the ideal orientations found in recrystallization textures can be accounted for by the growth of minor components of the deformation texture. IN recent years there has been increased interest in improving the drawability of metals by controlling the preferred crystallographic orientation of the sheet.1-l3 Since more low-carbon steel is drawn than any other material, considerable attention has been focused on the properties of sheet steel. Efforts to improve drawability through texture control have been hampered by the lack of any published systematic study of the recrystallization textures developed in iron annealed below Acl. The purpose of the present work was to supply some of this missing information, specifically, the recrystallization textures obtained by isothermal anneals of polycrystalline iron, cold-rolled 90 pct. LITERATURE REVIEW—DEFORMATION TEXTURES Barrett14 reviewed and summarized the investigations of rolling textures in iron and low-carbon steel prior to 1952. The texture of heavily deformed iron (rolled 90 pct or more) is described as consisting of two partial fiber textures. The dominant fiber texture (designated here as fiber texture A) has a (110) fiber axis in the rolling direction and includes the orientations (001)[110], {112}( 110), and {111}(110). The secondary texture (designated here as fiber texture B) is described as having a (111) fiber axis in the sheet normal direction, and includes the orientations {111)( 110) and (111)(112). Since the publication of Barrett's book, there have been two detailed studies of the deformation texture in polycrystalline iron. In both instances, the more sensitive diffractometer methods of pole-figure determination were used. Bennewitz15 studied the cold-rolling textures developed in polycrystalline low-carbon steel and a 3 pct Si steel. He determined (110), (2OO), and (222) pole figures for specimens reduced 30, 50, 60, and 90 pct and analyzed his results in terms of partial fiber textures. He distinguished three stages in the development of the final deformation texture. 1) Grains rotate to form two incomplete fiber textures, with (110) fiber axes inclined 30 deg to the sheet normal toward the rolling direction (fiber texture B). After 50 pct reduction, the highest density of poles is near an ideal orientation {554}(225), the two components of which are members of this duplex fiber texture. 2) With increasing amounts of reduction, grains rotate about the former fiber axes toward ideal orientations of the type {112)( 110) (common to fiber textures A and B). 3) Finally, grains rotate about their ( 110) axis in the rolling direction, clockwise and counterclockwise from the orientations {112}(110). This produces the range of orientations from (111)(110) to (001)(110) commonly found in the rolling texture of heavily deformed iron (fiber texture A). No significant difference was found between the deformation textures of low-carbon and silicon steels. A few years earlier, Haessner and weik16 had determined (110) pole figures for carbonyl iron rolled to 30, 60, 80, and 90 pct reduction in thickness. heir data agree quite well with the more complete data of Bennewitz, but a somewhat different description of the evolution of the deformation texture was given. The appearance of (110) poles in the transverse direction is ascribed to a (100)[011] component rather than "near {554}( 225) " components, and the (110) fiber axes of fiber texture B are described as located 35 deg rather than 30 deg from the sheet normal. Both of these studies agree that the secondary texture present in heavily rolled iron, the duplex fiber texture B, has (110) fiber axes and not a single ( 111) fiber axis normal to the sheet, as

Jan 1, 1965

By J. L. Huiatt, G. M. Potter, R. B. Tippin

The US Bureau of Mines and Great Salt Lake Minerals and Chemical Corp. have developed a froth flotation process for concentrating potassium salts from Great Salt Lake solar evaporites containing about 6% K2O. The crude evaporites, which were predominately halite (NaCl) with smaller amounts of kainite (KCl.MgS0, 2.7Hp0) and schoenite KeS0,MgS04.6H,0), were conditioned in a saturated brine solution., thus converting nonfloatable kainite to the floatable mineral schoenite. Schoenite was then selectively floated with a medium-molecular-weight fatty acid. Continuous small-scale pilot-plant testing indicated that 80% of the potassium could be recovered from the crude evaporites in flotation concentrates assaying about 13% K2O.

Jan 1, 1976

By T. Yoshioka, Paul A. Beck

SILICON, germanium, and tin occur with both the white tine-type structure and the diamond cubic structure. In the latter form these elements are semiconductors; in the former they are metallic. The metallic form of germanium and silicon is obtained only under high pressure.' For all three elements the transition from the semiconductor to the metallic state is accompanied by a decrease in the atomic volume of somewhat more than 20 pctily2 Table I. At such a large compression the widening of the s and p bands is sufficient to make the energy gap of 1.1 ev, or less, of the semiconductor disappear, giving rise to the metallic state.*

Jan 1, 1965

By George A. Koenig

This new departure in assaying is the outcome of a long-felt desire to shorten the time required in muffle-assaying, as well as to do both crucible- and scarifi cation-work in one furnace. The first object in view was the gold-assay, which must always be a combination of the crucible- and muffle-work. The large lead buttons consume much time in their reduction by scorifying and cupelling. The Hoskins gasoline furnaces have been a great convenience, for years past, in that class of practice, where only one assay was required at a time. But even with them I found myself hampered, since the crucible-furnace only takes one crucible at a time, and my practice implies always duplicate assays. Another difficulty was to get the muffle up to the necessary heat and to maintain it at that heat. Whecever I had pumped myself into perspiration and out of breath, the question presented itself, " Is the muffle necessary to do this work properly ?" Hartmann and Plattner and all their blow-piping disciples have shown that very good results are obtainable by playing a direct flame upon the work-lead. Could this be done on the regular muffle-assay scale ? I placed a cupel upon a fire-brick, surrounded it with charcoal, and then played upon it with a Bunsen gas blow-pipe. The result was encouraging. With some care a 2.75-inch scorifier charged with 0.1 A. T. of a 100-ounce ore could be melted down and scorified without any apparent loss. I thought then of constructing a furnace with four blow-pipes in a row; but the combination of gas and charcoal seemed unpractical. Instead, I placed an F crucible, bottom up, in a Hoskins crucible-furnace. Upon this support I placed a charged scorifier. The rapidity with which a very refractory charge melted and scorified was simply amazing to me. Then a cupel was put in the place of the scorifier, the lid was moved sideways, and a blow-pipe was

Jan 1, 1899

By James A. Crookston, William D. Fitzpatrick

Committee C-8 of the American Society for Testing and Materials defines refractories as "material, usually nonmetallic, used to withstand high temperature," and it defines the term refractoriness thus, "in refractories, the capability of maintaining the desired degree of chemical and physical identity at high temperatures and in the environment and conditions of use.” The ability to withstand high temperatures is critical to classifying a material as a refractory. However, as the foregoing definition of "refractoriness" implies, the refractory material may be subjected to and is expected to resist not only high temperatures but a variety of other destructive forces incidental to its use. These include abrasion, impact, thermal shock, chemical attack, and high level loads at high temperatures. The various industrial applications of refractories represent an infinite variety of combinations and degrees of severity of these destructive forces, including high temperatures. Naturally, such a variety of application conditions leads to a need for a wide variety of refractory products to satisfy those conditions. The number of refractory products available is great enough that some form of classification is necessary to a discussion of refractories. Refractories may be classified in several ways, but the most suitable one is based on their general compositions and to lesser degrees on their physical condition and distinctive properties. The primary types of brick include aluminosilicate brick (fire clay and alumina), basic brick (magnesia and chrome ore, alone and in various combinations), silica brick, insulating brick, and special refractories (carbon, SiC, ZrO2, zircon, borides, and nitrides). Brick is, of course, preformed and usually is heat treated at high temperatures before use, but in some instances is unburned and/or chemically bonded, including the relatively new class of tar-bonded magnesia and/or dolomite brick. In addition to preformed refractories, another broad category includes the so-called specialty refractories, which are usually made in the same types as itemized for brick-bonding mortars and high temperature cements, hydraulic setting castables or refractory concrete, plastic firebrick, and ramming mixes. Refractory grains, such as fire clay and high alumina calcines, dead-burned magnesite and periclase, and dead-burned dolomite are also considered refractory products. Bricks are also classified on the basis of physical dimensions, as standard sizes and special shapes. The standard sizes are those which are of definite shape and design and are designated as 228.6 x 114.3 x 63.5 mm (9 x 4 ½ x 2 ½ in.) and 228.6 x 114.3 x 76.2 mm (9 x 4 ½ x 3 in.) straights and series. Bricks of nonstandard sizes are referred to as special shapes. These come about as a result of a particular need for a given furnace or for a particular application. Types and Classes of Refractories Fire Clay Refractories Classification: Fire clay refractories, as the name implies, are composed essentially of fire clay and/or calcined fire clay in varying proportions. The ASTM Standard Classification of Fireclay and High Alumina Refractory Brick, C27-70 (reapproved 1976), gives five classes of fire clay brick designated as super-

Jan 1, 1983

By C. H. Hitchcock

The puiblication by the Institute of a small geological map of the United States calls for an explanation of its peculiarities. The title intimates that it is intended "to illustrate the schemes of coloration and nomenclature recommended by the International Geological Congress." By way of further explanation it is said to be "based, by permission of the Director of the United States Geological Survey, upon the map published in his Fifth Annual Report, the portions not colored in that map being here supplied from other sources." The map referred to was prepared by W. J. McGee, and in the text of the report containing it he has given a list of the authorities employed in the compilation. The scheme of coloration used for the map was the one proposed by the Director, in the Seeond Annual Report, for the publications of the United States Geological Survey, which differed materially from those employed by the older American geologists. Because of the increasing diversity in the particular colors employed to represent rocks by geologists in different countries, and of the existence of very dissimilar schemes of nomenclature, it seemed best to the American Association for the Advancement of Science, at its Buffalo meeting in 1876, to appoint an international committee of geologists, who should consult together, and, if feasible, to call an International Congress to discuss these subjects. The proposition met with favor, and the meeting was called. The first session was held at Paris, in 1878, when geologists were present from twenty different countries. Once organized, the Congress has perpetuated itself, enacting regulations for its conduct, choosing the French language for its medium of communication, and arranging for the compilation of a geological map of Europe upon which the perfected schemes of coloration and nomenclature will be delineated. The American Association maintains a standing committee to represent it at the international sessions, and to report their proceedings. Sixteen countries were represented at the second Congress, at Bologna;

Jan 1, 1887

By W. L. Freyberger, R. B. Booth

Froth flotation is a chemically induced method for beneficiating or up- grading an ore, which utilizes a layer or column of froth as a separating medium to segregate and remove the valuable minerals from the worthless gangue components of a finely ground ore suspended in water. The object of this chapter is to discuss the theoretical aspects of froth formation, the various frothing agents employed in flotation, and the effect of chemical structure on froth formation, and to correlate these factors with flotation technology. The flotation method of separation is conducted in three main steps: 1) selective chemical modification of the surface of specific mineral particles to effect floatability or nonfloatability; 2) contact between air bubbles and mineral particles, the selective adherence of floatable minerals to these bubbles, and the rejection of nonfloatable minerals; and 3) separation of the floatable minerals from the nonfloatable minerals. As indicated above, these three operations are achieved by the use of chemicals. Frothers play their most important role in the second and third steps by influencing particle- bubble contact and by affecting the degree of separation obtained in the froth column. Frothers, as defined by flotation operators, are compounds that are used specifically for the purpose of creating a froth in a flotation separation. How- ever, some collectors produce froths that are adequate for some flotation operations. Although this chapter is chiefly concerned with the specific frothers used in flotation, some discussion of frothing collectors is included. Otherwise, collectors (or promoters) and modifiersare not discussed at length; for information on these types of flotation chemicals, the reader is referred to other sections of this book or to other sources.l HISTORICAL DEVELOPMENT OF FROTHING AGENTS Historically, there are two distinct phases in the development of frothing agents and other flotation chemicals: 1) 1860 to 1920-oil flotation, and 1921 to date-chemical flotati0n.2~3 Early in the first period, large quantities of fatty and oily materials, up to 10 to 20% of the weight of the ore, were used as a means of separating the sulfide and oxide components from the gangue minerals in ore pulps. Later, various gases replaced these large quantities of oil as a buoyant and separating medium, decreasing oil requirements to less than 1% of the weight of the ore. With this reduction in oil

Jan 1, 1962

By C. H. Mathewson

THIS paper was prepared upon request as a contribution to a symposium covering the manufacture, properties, and uses of the important non-ferrous metals. In approaching a subject as broad as this, there is a natural desire to build up a comprehensive and finished production which shall constitute a dependable source of information on all questions properly belonging to this branch of metal technology. There are, however, a number of circumstances, apart from the mere routine of labor and thought involved, which operate rather effectively against the possibility of completing such an ambitious program at the present time. First of all, as far as any public record of results is concerned, the commercial rolling, drawing, and forming of zinc with relation to changes of structure and properties-and this we consider to constitute the elements of metal technology-might as well be an unpractised art. We have never seen a published photomicrograph showing the structural characteristics of either hard or soft sheet or strip, although the structure of castings has been frequently described, and other coarse-grained structures resulting from hard-hammering and annealing have been reproduced. Thus, an author in this field must proceed to his task without much assistance from the literature, and the outcome can represent only a personal estimate of principles, facts, or findings, and not a summary

Jan 9, 1919

By E. S. Lenker, H. J. Van Hook

A complete swies of solid solutions has been found between the compounds InAs and GaAs Below the solidus. The melting relations determined by differential thermal and static quenching technzques, indicate that the liquidus and solidus are of the simple ascendant type. No evidence of unmixing of the homogeneous solid solutions was observed at sub-solidus temperatures. A quenching method for locnting the solidus, using X-ray diffraction techniques, is described in some detail. THE semi-conducting properties of compounds formed by various combinations of the less familiar intermetallic elements have created an increasing interest in the phase relations in systems involving these elements. The complete phase diagram of such a system, containing a compound of special interest, will often provide information as to the most favorable conditions for preparing large crystals from a melt, as well as specifying the temperature stability of the crystalline phase or phases produced. In view of the current importance of gallium arsenide in semiconductor research and of the structural similarities of indium arsenide, it was thought that the complete phase relations of the system InAs-GaAs should be investigated. Previous work on the system Ga-As by Koster and homa' and on In-As by Liu and peretti2 has shown that GaAs and InAs are the only compounds formed, having melting points of 1238° and 942°C, respectively. In a survey of various systems of elements from groups IIIb and Vb, spengler3 also re- Mines Ltd., for his continuing encouragement and for permission to publish the results of this work. ports complete miscibility of gallium, indium, and arsenic in the liquid state. In a partial investigation of the InAs-GaAs system, Woolley and smith4 found extensive solid solution throughout the alloy range. Their subsolidus work, however, was inconclusive at temperatures below 900" and they did not determine the liquidus relationships of the system. PRESENT INVESTIGATION The starting materials used were high-purity gallium, indium, and arsenic. The method of preparation of the compounds follows that devised by M. Shafer and is described in detail in a paper by Shafer and eiser.' The end-member compounds, GaAs and InAs, were first prepared by reaction of the elements in the desired proportions in evacuated silica glass vials. The vials were rotated in a furnace as the temperature was slowly raised to insure rapid and complete reaction at low temperatures. Thereafter the starting materials, GaAs and InAs, were melted by heating the sealed vials to 1300" and 1000°C, respectively; the vials in this case were filled as completely as possible to keep the vapor space small and thereby minimize the loss of arsenic to the vapor phase. Ten binary mixtures of these compounds were then prepared by reaction of the powdered material in the solid state just below solidus temperatures. At 900C preparations containing 3, 5, 8, 10, 25, 35, 50, and 75 mol pct GaAs were found to be single homogeneous phases, indicating a complete series of solid solutions between GaAs and InAs. Moreover, it was discovered that the homogeneity of any crystalline binary preparation could be very accurately checked by X-ray diffraction because of the large differences in unit cell dimensions of the end membe5s. The cubic lattice constant ofor GaAs is a = 5.652A and that of InAs is a = 6.061A

Jan 1, 1963

By Mary Barrett, Walter Rose

INTRODUCTION The conventional way to program reservoir problems* for solution on the electric analyzer1 is one which concentrates the block units towards the inner radius of the prototype system being represented by the analog model. This is achieved by the device of considering block units of equal value radial resistance, leading to the consequences: (1) the ratio of the external to the internal radius of each block unit is a constant (i.e. r1/ri-l = constant a); (2) the external radius of the nth block unit is equal to the innermost radius of the system times the constant a raised to the nth power: (3) the capacitance of the block units increase by a factor of a2 going out radially from the innermost to the outermost boundaries of the system; (4) given n block units in the radial direction, the capacitance ratio of the outermost to the innermost block unit is a (2n-2); and (5) the vertical resistance of the block units decrease by a factor of a going out radially from the innermost to the outermost boundaries of the system, such that the ratio of the maximum to minimum vertical resistance is also given by the factor a(2n-2) PRESENT PROGRAMMING METHOD While this conventional way of programming problems is quite adequate for routine uses of the electric analyzer, it leads to difficulties in those cases where the inner radius of the prototype system (e.g., the well-bore) is small compared to the external radius (e.g.. the external reservoir boundary). To handle such a case by the conventional method would require either that a large value be selected for the constant a or that a large number n, of radial block units be chosen. In consequence, the capacitance and vertical resistance ratios become impossibly large, as will be evident from the relations given above. In any event, the size of the smallest and largest capacitors will always be limited by the size of commercially available components, and the analyzer itself will determine how many mesh points are available for radial block units. For example, it can be shown that if the maximum capacitance ratio which can be electrically handled is a factor of l04, the maximum external radius of the system which can be considered (assuming an internal wellbore radius of 0.25 ft is: It is thus seen that in direct consequence of having the inner wellbore radius small compared to the external radius, models extending beyond 30 to 40 ft are not possible when the capacitance ratio is limited to l04. (NB. A value of 10-9 farads can perhaps be taken as the minimum electrical capacitance possible if corrections for the capacitance of the lead wires are to be avoided. Values greater than 10-5 farads would require the use of unstable and inaccurate electrolytic capacitors). On the other hand, models extending out to 500 to 5,000 ft may be desired in single-well problems, and hence the need for a revised method of problem programming. * REVISED PROGRAMMING METHOD The revised method of programming is one which attempts to retain the desirable features of the conventional method (viz. concentration of block units towards the inner boundary, simplicity in computation, etc.) without having as a consequence that impossible capacitance and vertical resistance ratios will be required. Other advantages will also be achieved by the revised

Jan 1, 1957

Edward Payson Mathewson EDWARD PAYSON MATHEWSON, President of the American Institute of Mining and Metallurgi-cal Engineers, was born in Montreal, Canada, Oct. 16, 1864, of Scotch-Irish ancestors. After preparation in private and public schools, he graduated from McGill University with the degree of Bachelor of Applied Science, in 1885, having specialized in mining engineer-ing and metallurgy. He spent the succeeding summer as a surveyor with the Canadian Geological Survey, being employed in the lake region of Ontario. The following spring he left Canada for Colorado, where he immediately obtained a position as assayer with the Pueblo Smelting & Refining Co. Within three years he became superintendent of the plant, and his success in this position brought him to the attention of the Guggenheim family, whose employ he entered in 1897. He was first in charge of their Pueblo plant, but was soon transferred to their refinery at Perth Amboy, N. J. During the succeeding five years he was in charge of important smelting operations conducted by the firm in Mexico and South America. In June, 1902, Mr. Mathewson accepted a position at the Washoe reduction works at Anaconda, soon thereafter becoming manager of the property. It is unnecessary to recount the improvements and enlarge-ments instituted at that plant under his management, until it became the Mecca of all metallurgists visiting the United States. The esteem in which Mr. Mathew-son was held, not only by the men directly under him, but by all his fellow citizens, was expressed in a send-off such as probably no other plant manager has ever received, when he left Anaconda in October, 1916, to accept the general managership of the British America Nickel Corporation, at Nickelton, Ont., Canada. Soon thereafter Mr. Mathewson accepted an appoint-ment as director of the American Smelting and Refining Co., acting as consulting metallurgist for the company and its subsidiaries. In November, 1919, he resigned this position and opened an office in New York City as a consulting metallurgist.

Jan 3, 1923

By H. Rush Spedden, A. M. Gaudin

Although the number of minerals that are ferromagnetic‡ or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various non-sulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing Laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. The separator (Fig. I) consists of: 1. A powerful magnet, the strength of which can be adjusted by, means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators." Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike thai obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943

By H. Rush Spedden, A. M. Gaudin

Although the number of minerals that are ferromagnetic‡ or highly paramagnetic is strictly limited, it has been known for some time that many minerals have slight but supposedly characteristic magnetic susceptibilities. With the exception of pyrrhotite, however, sulphides have been thought nonmagnetic. A new magnetic separator has been made available recently in limited quantity to research laboratories. This device, the Frantz Isodynamic Separator, has been used for the separation of various non-sulphides from each other. Its application to the separation of sulphides, however, does not seem to have been reported. In the Richards Mineral Dressing Laboratories, the success achieved through the use of this device in separating associated sulphides has been so startling as to lead us to believe that it constitutes a magnificent adjunct to heavy-liquid separation and to quantitative mineragraphy as a tool for the mineral investigator. The separator (Fig. I) consists of: 1. A powerful magnet, the strength of which can be adjusted by, means of a rheostat; 2. A vibrating chute of nonmagnetic metal on which the mineral to be separated is made to flow (Fig. 2); 3. A feed bin and adjustable feeder; 4. Receptacles for the collection of products; 5. Means for changing, setting, and accurately reading the two slopes of the chute; viz., the cross slope and longitudinal slope. The separator is made operative by the special shape of its pole pieces, which ensures a strongly converging field. It is said by the makers of the machine that the pole pieces apply a constant mechanical force to a particle of given susceptibility, regardless of its position in the operating space of the separators." Susceptible particles, therefore, behave as though of lower specific gravity than under ordinary circumstances. This effect, combined with the slopes of the chute and the action of the vibrator, causes a stratification not unlike thai obtainable on a shaking table. The chute is of rectangular cross section, and shallow; it is broadened toward the discharge end and divided longitudinally by a partition into two compartments that lead to the collecting receptacles. Although the separator probably can be used to make separations at fairly coarse

Jan 1, 1943