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By R. A., Pallanch

THOUGH the flotation of gold ores has come into the lime- light largely in recent years, it is not a product of recent economic conditions but rather as old as flotation itself. It could hardly be other- wise, since gold, when in the right state of comminution and surface condition, is one of the more readily floated of minerals. In early practice it was not generally recognized that gold was floated as well; it was - thought that the gold was bound up with sulphide minerals that floated, but now we know that free gold must have been floated as well.

Jan 1, 1935

By Frank Foote

IN recent years the constitution of the high-silver aluminum-silver alloys has been extensively investigated. Hansen1 has re-viewed the literature to 1935. More re-ently, Obinata and Hagiya,2 Hofmann and Volk,3 Taziri4 and Tishchenko5 have con-firmed the general features of the phase diagram in the region around 25 atomic per cent aluminum. In this paper we present the results of high-precision measurements of lattice con-stants of the silver-rich alpha solid solution in the homogeneous range and the neigh-boring two-phase regions. These results are used to establish the nature of the solid solution, the identity of directly measured densities with those calculated from lattice constants and the homogeneity limits of the alpha solid solution with respect to three different neighboring phases. A study of the earlier investigations indicated that the last two subjects in particular required new and accurate data.

Jan 1, 1940

By FREDERICK W. BRADLEY

MINING methods are evolved rather than devised; and the process is slow. The advance in no particular year is phenomenal, but progress is un- questionably being made constantly in several directions: (a) better adaptation to given conditions of various "systems" of mining; (b) better utilization of mechanical equipment ; (c) improvement in working conditions so as to promote the health, safety and efficiency of the workers. During the year 1930 operations were commenced at a number of important new mines. Methods adopted are not new, except in minor detail, but the fitting of methods to conditions is interesting, because, as the engineers presumably started from scratch, they have selected the methods that experience under similar conditions has indicated as being the best.

Jan 1, 1931

By AIME AIME

IT is unlikely that any oil field has ever threatened the future course of the oil industry as does Kettleman today. It seems that nature has striven to outdo herself in combining in this field every possible factor conducive to a tremendous production of the petroleum product in greatest demand-gasoline. This field already has 13,700 acres of proved land and an oil zone of known thickness of 1400 ft. It has wells yielding several thousand barrels of oil of virtually motor fuel grade, together with millions of cubic feet of gas at almost unheard of pressures. The field would have been the. answer to an oil man's prayer in times of under-supply, but now it is the oil man's nightmare, for drilled in -the manner of most other fields and without regard to available markets for oil and gas, the greatest physical and economic losses in the his¬tory of the oil industry will result.

Jan 1, 1930

By Å. Sterten, R. Tunold, J. Brun, K. Dalatun

c axis compression behavior of beryllium single crystals at three purity levels under hydrostatic pressures up to 27 kbars was determined. Extensive non-basal slip, observed by two-surface trace analysis and transmission electron microscopy, occurred under a hydrostatic pressure of about 12 kbars (175 ksi) for the high-purity (twelve-zone pass) material and at about 19 kbar (275 ksi) for the lower-purity (zone-leveled) material. Prismatic loops with a (c + a) Burgers vector were observed in association with second-phase parti- A principal factor limiting the use of beryllium is its brittle behavior when tested at the usual strain rates (E = 10-4 sec- 1) at temperatures below about 200°C and under impact conditions at temperatures in excess of 200°C. It has been proposed' that the brittle-ness of beryllium is associated with the lack of a sufficient number of independent slip modes and the absence of a slip mode with a Burgers vector out of the basal plane [presumably (c + a) pyramidal slip mode] and to the ease with which beryllium cleaves on the basal and second-order prism planes. The absence of pyramidal slip has been attributed to a high Peierls-Nabarro stress associated with the motion of dislocations with a (c + a) vector and the ease with which cleavage occurs on the basal and second-order prism planes. The experimental evidence in support of the proposed explanation for the brittleness of beryllium is far from complete; for example, that the ductile-to-brittle transition in polycrystalline beryllium is associated with the operation of profuse (C + a) slip has not been unequivocally established. The occurrence of (c + a) slip ({1122}(1123)) has been experimentally established2-5 under conditions where basal and prism cleavage are restricted in a c axis compression test. In these investigations (C +a) slip was found in high-purity beryllium single crystals tested in c axis compression* at 200°C and in Be-4.4 pct Cu and Be-5.2 pct cles in the lower-purity materials tested. The loops were related to surface "extrusions" observed on many of these same specimens. Nonbasal dislocations operating on (1122) planes with a (c + a) Burgers vector were observed. The presence of c and a dislocations together with (c + a) dislocations suggests that the (c + a) dislocations dissociate presumably on unloading or after failure of the test crystals to c and a dislocations. terial, (c + a) slip has only been observed near the the fracture4 surface in room-temperature c axis compression tests. Fracture in these tests occurs without measurable plastic flow, as determined with a strain sensitivity of 10"6. Since it has been shown for many metals that the application of hydrostatic pressure suppresses fracture,?-' it was felt that studying the behavior of unalloyed beryllium single crystals stressed in c axis compression under a hydrostatic pressure would reveal whether (c + a) can occur if fracture was prevented, and that it might elucidate the role of (c + a) slip in the ductile to brittle transition. Evidence that (C + a) slip is associated with increased ductility in a high-pressure environment has been found in stress-strain tests on poly crystalline beryllium.10 The present paper describes a study on the influence of a hydrostatic pressure environment on the occurrence of (c + a) slip in beryllium single crystals. Material of two purity levels was tested in c axis compression over the pressure range ambient to about 27.5 kbars.* 1) MATERIAL PREPARATION AND CHARACTERIZATION Two lots of low-purity single-crystal beryllium were used. The first lot was "ingot secondary refined grade" and designated lot A. The second lot (lot B) was produced by a two floating zone pass zone-leveling operation in an argon-filled sealed quartz apparatus on a 1-in.-diam by 12-in.-long bar of Pechiney secondary refined-grade vacuum-cast and hot-extruded material. The high-purity material (lot C) was made by traversing twelve floating zone passes through a similar bar of Pechiney secondary refined-grade vacuum-cast and hot-extruded material. In a series of spark cutting and lapping procedures,11 single-. crystal specimens some 0.12 in. sq by 0.30 in. high were made with the sides Parallel to the first- and second-order prism planes and the basal plane within 3' of arc of the top and bottom surfaces of the specimen. Such an accurate orientation is necessary because of the large difference in resolved shear stress

Jan 1, 1970

By George A. Moore

A recent survey of existing analytical results, and an attempt to correlate them with each other and with the known history and behavior of the samples, indicated that none of the commonly applied methods could be considered established as intrinsically reliable. It was. therefore, desired to attempt to establish the reliahility of some one method by external evidence. If this were to be accomplished, other methods could then be evaluated in terms of the method establibhed. The correct method was accordingly to be chosen without regard for cost, speed, or convenience; with the requirements for routine application to be reserved for 1ater consideration. The method of total combustion was chosen and submitted to a limited number of tests against primary standard samples. Considerable experimental difficulty was encountered, indicating that additional work on the experimental arrangements is desirable. While the work to (late by no means represents a completed investigation, it is helieved that the combustion method is basically sound and that its development should be continued. Choice of Method Of the several available methods, mechanical disintegration. electrochemical methods'2'3 modifications of the Sieverts experiment,% and vacuum fusion, were all judged to contain one or more factors of un- certainty not at present completely cvaluated or suhject to complete control. These methods, therefore, were considered currently unsuitable for referee purposes. Solid evolution was considered to be of doubtful significance when conducted in the alpha range. A reasonable chance for a true analysis was found for evolution in the gamma range. Preliminary tests have indicated a very slow rate for evolutioll from gamma iron. indicating a running time of possibly 100 hr. for a one-centimeter sample. Difliculty in distinguishing such slow. evolution from blank gas was anticipated, hence the method was not consitlerctl the most suitable for the present purpose. The combustion method was evaluated as being most sound on fundamental principles. The only important unknown would be to determine that the iron oxide formed did not occlude water at the tcmperaturv of the combustion.with the odvious precautions of using a sound and clean specimen, providing a system sufficiently tight to give acceptable blanks in longtime runs, and providing a suficicntly sensitive measuring system, reasonable, precise, and truthful analytical results could be logically expected. Apparatus The equipment as originally operated is shown in Fig. I, and the glassw-are in its latest modification in Fig. 2. The sulphuric acid drier and small safety tube in the upper right of Fig. I were replaced by a KOH drier and combined manometer safety tube, to permit operation at reduced

Jan 1, 1945

By G. Derge, M. Bourgon, G. M. Pound

A STUDY of electrical conductance in molten Cu-Fe sulfide mattes' has shown that pure molten Cu,S behaves like a semi-conductor in that it is an electronic conductor and its specific conductance, of the order of 100 ohm-' cm-', increases with increase in temperature. On the other hand, pure molten FeS, another electronic conductor, behaves like a metallic conductor in that its specific conductance, about 1500 ohm-' cm-', decreases with increase in temperature. Molten solutions of Cu,S and FeS follow a roughly additive rule of mixtures with respect to both specific conductance and temperature coefficient. The behavior of molten Cu,S may be understood, by analogy to the situation in solids, in terms of semiconductor theory.' It is thought that, although the melt consists of cuprous and sulfide ions, the bond between these atoms has a certain degree of cova-lency. According to the simplest concept the electrons in the partially covalent bonds are thermally promoted to a conduction band. In another concept, small amounts of impurities (undetermined) provide donor or acceptor levels in the forbidden zone between the valence and conduction bands and thus facilitate semi-conduction in the usual way. However, the metallic behavior of molten FeS is difficult to explain, because one might expect from similar reasoning that it too should act like a semi-conductor. It was suggested that the apparent metallic behavior of molten FeS might be explained by a large negative temperature coefficient of density. Thus if molar conductance instead of specific conductance were plotted versus temperature, the slope might prove to be positive, indicating semi-conduction instead of apparent metallic conduction. Accordingly, density measurements were made in order to answer this question in regard to molten FeS and also to provide data for conversion of specific conductance to molar conductance for molten Cu,S and a molten 50-50 wt pct Cu-Fe sulfide matte. Experimental Diagrams of the apparatus are given in Figs. 1 and 2. A 3 x 8-cm dense alundum crucible containing the prefused specimen is positioned in the uniform temperature zone of an induction furnace tube and melted under a helium atmosphere. Then the cell assembly, consisting of two 3-mm spectro-graphite rods, one of which is in a 1-cm ID open

Jan 1, 1959

NEW, MEMBERS The following list comprises the names of those persons who became members during the period July 10, 1916; to July 31, 1916: BOYD, ROBERT RUSSELL Supt:,-Arizona -Commercial Min Co., Globe, .Ariz. BRADLEY, HENRY FRANKLIN, Chem, American Smelt & Ref. Co. Murray,:Utah: BROWN, THOMAS ELLIS, JR..:'. L .:.::..55 Hill, St;; Morristown, N. J. CARY, WEBSTER P., Expert Operator,-General Engineering. Co:, Salt Lake City, Utah. CLARK, ALONZO WEBSTER 3223_ Scottwood Ave., Toledo, Ohio. CORP, CLIFFORD Old Dominion Copper Min. & Smelt. 60., Globe, Ariz. CROMBIE, W. RANSOM, Min. Engr Detroit Copper Min. Co., Morenci, Ariz. DELANEY, EUGENE A., Chief Engr., Berwind-White. Coal Mining -Co., Windber, Pa ELBELT, WILLIAM HENRY, Dept. Foreman., Chino Copper Co., Hurley, N. Mex. FOSTER, L. JULIO, Mgr., Minas i Fundicion ; ?La Junta," San Bernardo, Chile, South America. GASKILL, JAMES PHILLIPS, Genl. Mgr.,.Ajo Cons. Copper Co., Ajo, Ariz., via Gila, Ariz. .

Jan 9, 1916

By Samuel M. Dunaway

INTRODUCTION ASARCO Incorporated purchased the East Tennessee Zinc Mines of the American Zinc Company and commenced operating on November 29, 1971. Presently, three mines are operating producing 6620 t/d (7300 stpd). The ore mined is sphalerite which occurs In lower Ordovician carbonates of the upper Knox Group and occurs in open space and fracture filling. Orebodies range from 3 to 46 m (10 to 150 ft) thick with dips from flat to 20º. The mining method is random room and pillar modified by shrinkage and bench stoping. Like other mining departments, the mining group at the Tennessee Mines Division is constantly looking for methods to improve productivity and safety and to reduce mining costs. This involves testing new equipment, trying new ore extraction ideas and making mining plant alterations to meet changes in operating conditions. The areas of change that will be described in this paper are longhole raising, jumbos and LHD loading, shaft sinking, conveyor transport of ore and sublevel haulage developments. LONGHOLED RAISES Raise driving has always been a hazardous occupation for miners and today it is becoming more difficult to get competent people for this kind of work. This problem has led us to seek an easier, safer way in which to excavate raises. The first longhole raises were excavated in the early 1970's using a Gardner-Denver air trac equipped with a PR-123 rock drill. The machine used 38 mm x 244 cm (1 ½ in x 8 ft) round rods with rope

Jan 1, 1977

By G. L. Hassler, E. Bruner

An apparatus and method is described whereby the relation between saturation and capillary pressure under decreasing saturation can be quickly determined for small core samples. The initially saturated core is cen-trifuged at increasing rates and the average saturation is measured at each rate with the aid of a stroboscope device. A theory and calculation procedure is given whereby the accelerations and saturation values can be converted into a true curve of capillary pressure versus saturation. The present work differs from previously described use of the centrifuge to obtain capillary-pressure curves of core samples3 in that the core is centrifuged alone, so that the whole range of saturations required by the properties of the sample and the radially varying centrifugal force occurs within the sample. The calculation procedure nevertheless secures correct results from simply obtained values of the average saturation. The apparatus described was developed in connection with studies of capillary pressure and wetting of oil-field rocks, and the paper provides the apparatus background for a previous publication' dealing more fully with the uses and implications of the data in petroleum engineering. The method is applicable, however, to general combinations of immiscible fluids and porous or comminuted solids, and may be useful in other fields. Introduction The importance of capillary phenomena in determining the behavior of liquids in porous media has long been recognized. The concept of capillary Pressure was early formulated, and in recent Years discussions of the application of the laws of capillarity to oil field problems have appeared.l-3 One reason why progress in the application of capillary phenomena to the solution of problems of reservoir mechanics has not been more rapid has been the lack of a, satisfactory technique for measuring the capillary pressures in reservoir rocks. It is the principal purpose of this paper to describe a method by which the relation between capillary pressure and saturation can be determined for small consolidated core samples which have been extracted and resaturated, Capillary Diaphragm Perhaps the most direct way to measure the capillary pressure in a rock is to make piezometric contact with the wetting liquid through a diaphragm of porous material with high displacement pressure saturated with the liquid in question.3-6 The liquid in the diaphragm assumes the pressure of the liquid in the core, which can then be measured with a manometer, while the atmospheric air is prevented by capillarity from entering the diaphragm and affecting the pressure measurements as long as the displacement pressure of the diaphragm is not exceeded. With an apparatus of the type illustrated schematically in Fig. I, the relation between capillary pressure and saturation can be measured for a small core sample by starting with the core saturated 100 per cent, applyillg successively greater suctions

Jan 1, 1945

By I. E. Rosenzweig

THE problem considered in this paper is as follows: An arbitrary horizontally stratified area is given. The electrical properties of this area are characterized by a function p(z) (Fig. 1), which shows the relationship between resistivity p of thes oil and the depth z. For such general case the apparent resistivity p* will be computed, by FIG. 1.-GRAPH OF FUNCTION p(z) FIG. 2.-GRAPH OF p(Z) FOR n HOMO-GENEOUS LAYERS. earth-resistivity measurements carried out by any given configuration of electrodes. General solutions of this problem appear to be very important for interpretation of field results of resistivity measurements, concerning structural investigations. Such solutions have been given by many authors for the special case of a finite number of homogeneous layers (Fig. 2)1-4 as well as for the more general case of continuously rang-ing resistivities. 5-8

Jan 1, 1939

By J. J. Brown

The ore-hearth was the earliest type of furnace used in smelting Mississippi Valley lead-ores, which are very pure, and low in silver-content. The first smelters made no attempts to recover lead from the smoke; and since about 15 per cent. of the lead in the charge escaped in this manner, early practice with the hearth was decidedly wasteful. At most of the large smelting-plants blast-furnaces with auxiliary roasters were substituted for the hearths long ago. But, upon the introduction of the Lewis and Bartlett bag-process for collecting fume, the ore-hearth was used by companies engaged in the manufacture of pigments, simply on account of the large percentage of fume made by it. In fact, the extraction of lead mas kept down by the use of hot blast and other devices. During recent years, however, several smelting companies have realized that the preliminary roasting of galena for the blast-furnace is not economical, and have, therefore, replaced the roasting-furnace with a modification of the old Scotch hearth, in which a large percentage of the lead in a charge is

Jan 1, 1912

By Avnulf Muan, Egil Aukrust

Activity-composition curves jor cobalt oxide and manganese oxide in solid solutions with spinel-type structure have been determined by studying the equilibrium between the spinel phase and a coexisting solid-solution phase in the tewzperature range 1100" to 1400"C. Within limits of experimental error, the system displays the behavior of a regular solution. The excess integral free energy of mixing is represented by the equation . The standard free energy of formation of cobalt manganite, CoMn,O,, from the oxide components COO mzd Mn2OS at 1200°C is calculated to be -8.6 kcal. AMONG the technologically and theoretically most important oxide phases are those which crystallize with the same structure type as the mineral MgO . A120,. Although the name spinel originally was used only for this mineral, the term is generally used today to designate the whole group of oxide phases with this same structure type. It is in this wider meaning that the term is being used in the present paper. The previous literature on spinels is very extensive. There are two aspects of spinels which have attracted particular attention: the structure, including the nature and distribution of the cations present, and the physical properties (electric, magnetic). The status of knowledge in these fields has been well-summarized in recent review articles.1'2 By contrast, thermodynamic properties of spinels are virtually unknown. Delineation of the activity-composition curve over the whole composition range of a solid-solution series with spinel-type structure is the objective of the present work. The system at elevated temperatures (>1000"C) constitutes such a series. The activity-composition curves for this system can be calculated from a study of the equilibrium between the above spinel solid solution and a solid solution (Co,Mn)O with sodium chloride-type structure. Data for the latter solid solution have become available recently.3 The system, in contact with metallic CO at 1200°C, obeys Raoult's law. The determination of the activity-composition curve for the spinel phase is based on the following relations. Consider the reduction-oxidation equilibrium for cobalt ions according to the equation: Because it is impossible in practice to measure single activities of electrically charged constituents, we will treat the equilibria in terms of electrically neutral components. Eq. [I] can then formally be written as follows: where and the activities of cobalt oxide in the (Co,Mn)O and the spinel solid-solution phases, respectively, K is a constant at constant temperature, and Pa is the oxygen pressure of the gas phase. The numerical value of K can be determined from a determination of the oxygen pressure P& for the equilibrium coexistence of Cos04 and COO in the binary system Co-0. Under these circumstances be set equal to 1, and hence K = [Po Eq. [3] can therefore be written

Jan 1, 1964

By D. P. Morton

Since 1923, which closed the speculative era in the bituminous coal fields of the United States, there have been wide annual fluctuations in the national production of bituminous coal. These changes in annual output have been variously attributed to: (1) increased competition from petroleum products, natural gas and hydroelectric power; (2) lower unit consumption of coal; and (3) fluctuations in the general business level. The purpose of this paper is to measure, from a practical standpoint, the net effect upon the annual trend of bituminous coal production, and to give those who are interested a basis for estimating in advance the probable output of bituminous coal. It can readily be shown that changes in the level of general business affect the national production of bituminous coal more than does any other factor. Therefore it is necessary to use some standard measure of the relative business level for purposes of comparison. The Federal Reserve Board Index of Industrial Production offers the basis for such a measure.l This Index, a weighted composite of 81 different series, rests upon the averages of the years 1935 to 1939 as 100, and is presented graphically in Fig. I. Even a cursory examination of the chart will indicate a definite uptrend for industrial production over a period of years. This uptrend is due to at least two factors: (I) an actual increase in national population, and (2) a probable increase in the per capita consumption of goods. This means that there is no such thing as a fixed Normal, rather Normal is a variable, tending to increase from year to year. In order to measure the amount of annual increase in normal, the Index of Industrial Production must be studied in relation to its major components, Durable Goods and Nondurable Goods, Durable Goods are those made from the lasting materials such as iron, steel, other metals, lumber, stone, cement, clay, glass. Nondurable Goods are those for early consumption, such as foods, textiles, tobacco, chemicals, paper, gasoline, and goods made of leather and rubber. The purchase of Durable Goods may be postponed, but Nondurable Goods must be purchased currently unless the standard of living is lowered. The Federal Reserve Indexes of durable and nondurable goods are shown graphically, 1920 to 1939, on Fig. a (pp. 764-765 of ref. I). It is apparent that fluctuations in the production of nondurable goods are not nearly so wide as in the production of durable goods, and that the curve of Industrial Production (Fig. I) would fall between the two curves on Fig. 2. It would, however, seem logical that both curves should follow the same long-term trend, or that over a period of two to three decades the relative proportion of durable and nondurable goods, in periods of normal production, should be the same. It is neces-

Jan 1, 1942

By D. P. Morton

Since 1923, which closed the speculative era in the bituminous coal fields of the United States, there have been wide annual fluctuations in the national production of bituminous coal. These changes in annual output have been variously attributed to: (1) increased competition from petroleum products, natural gas and hydroelectric power; (2) lower unit consumption of coal; and (3) fluctuations in the general business level. The purpose of this paper is to measure, from a practical standpoint, the net effect upon the annual trend of bituminous coal production, and to give those who are interested a basis for estimating in advance the probable output of bituminous coal. It can readily be shown that changes in the level of general business affect the national production of bituminous coal more than does any other factor. Therefore it is necessary to use some standard measure of the relative business level for purposes of comparison. The Federal Reserve Board Index of Industrial Production offers the basis for such a measure.l This Index, a weighted composite of 81 different series, rests upon the averages of the years 1935 to 1939 as 100, and is presented graphically in Fig. I. Even a cursory examination of the chart will indicate a definite uptrend for industrial production over a period of years. This uptrend is due to at least two factors: (I) an actual increase in national population, and (2) a probable increase in the per capita consumption of goods. This means that there is no such thing as a fixed Normal, rather Normal is a variable, tending to increase from year to year. In order to measure the amount of annual increase in normal, the Index of Industrial Production must be studied in relation to its major components, Durable Goods and Nondurable Goods, Durable Goods are those made from the lasting materials such as iron, steel, other metals, lumber, stone, cement, clay, glass. Nondurable Goods are those for early consumption, such as foods, textiles, tobacco, chemicals, paper, gasoline, and goods made of leather and rubber. The purchase of Durable Goods may be postponed, but Nondurable Goods must be purchased currently unless the standard of living is lowered. The Federal Reserve Indexes of durable and nondurable goods are shown graphically, 1920 to 1939, on Fig. a (pp. 764-765 of ref. I). It is apparent that fluctuations in the production of nondurable goods are not nearly so wide as in the production of durable goods, and that the curve of Industrial Production (Fig. I) would fall between the two curves on Fig. 2. It would, however, seem logical that both curves should follow the same long-term trend, or that over a period of two to three decades the relative proportion of durable and nondurable goods, in periods of normal production, should be the same. It is neces-

Jan 1, 1942

Long range expansion plans begun in 1966 by The International Nickel Co. of Canada, producer of over 50% of the free world supply of the white metal, are so mammoth as to give rise to the speculation that something might have to burst at the seams. From an annual level of capital expenditure of $35 to $70 million, the company jumped in 1967 to $145 million in new capital investment and will come close to $200 million in 1968. Inco expects to spend $700 million in the next five years, beginning in 1968, for new mines and surface facilities in Canada. The program involves the opening of nine new mines within the next 3 1/2 years, expansion of producing mines, and construction of new plants and modernization and expansion of established ones to process the increased ore production. Beyond this, the company is committed deeply in developing new sources of nickel abroad. Any one of these new projects, if proven economic, would necessitate expenditures of about $100 million or more. For Inco, the economic strain was relieved without a rupture this spring when Henry S. Wingate, company chairman, reported' at the stockholders annual meeting that $150 million had been raised by the sale of bonds. This marked the first time in 32 years that the company had gone into debt.

Jan 10, 1968

By Francis L. Sperry

Up to within a few years, the consumption of nickel has been more directly dependent upon the available supply than that of any of the other useful metals. The Gap mine, in Lancaster county, Pennsylvania,* has been, for the last quarter of a century, the only property in this country furnishing nickel in paying quantities. Its yearly output was about 300,000 pounds of metallic nickel, or nearly half the amount used annually in the United States. Foreign nickel from mines on the New Caledonia islands, in the South Pacific, found entrance into our markets as the production of the Gap mine fell off. The price of nickel was constantly maintained, and no special effort was made to extend its use. Over-production was cautiously guarded against, and all surplus metal was held by the banking-houses of the Rothschilds, who assumed the bonded indebtedness of the Sociètè le Nickel. The opening of the Ontario nickel-mines has, however, brought about a radical change; and nickel from the Sudbury district can be delivered in New York within four days, and in European markets within two weeks, as against two months consumed in transporting South Pacific ores. Former prices have been irretrievably smashed, and European trade-journals comment favorably on the influence which Canadian nickel has had in making lower prices, and breaking the backbone of the " nickel trust." Production and Costs. The quantity of nickel produced and the prices which it commanded may be briefly summarized as follows: The total production of the world from 1840 to 1860 was about 100 to 250 tons yearly of metallic nickel; from 1860 to

Jan 1, 1896

By José G. Aguilera

With the imperfect knowledge that me have of the geology .of the country in general, and of the numerous mining districts in particular, it is impossible to present an accurate idea of the geographical and geological distribution of the mineral deposits of the Mexican Republic. But, notwithstanding this, it is elear that the deposits are concentrated in limited regions of the country, and that certain deposits are so closely associated as to indicate, beyond doubt, a genetic relationship. The mineral deposits are numerous, and the most of them are found in the western part of the country in a zone following a SE.-NW. direction from Oaxaca to Sonora. In the eastern

Jan 1, 1902

By George Lehman

THE Inspiration Consolidated Copper Co. had an orebody at Miami, Ariz., of close to 100,000,000 tons of low-grade copper ore, and the method of mining this ore most profitably was of great importance. The selection of a method was practically limited to a "top-slicing," a "shrinkage-stope" or a "caving" method. The "top-slicing" method would give a high extraction of the developed ore, at a high mining cost, and the ?shrinkage-stope" or "caving" methods ) a lower extraction of, the developed ore, at a lower mining cost. ORE-DRAWING TESTS To decide on the method to be used it was necessary to know about what extraction of the ore could be obtained by the "shrinkage-stope" or "caving" methods. As no definite information regarding the question was available at the time, C. E. Mills, the general manager, thought that some information could be obtained by experimenting in drawing ore, covered with capping, from an experimental box. Some work had already been done along these lines by W. C. Browning for the Inspiration Copper Co. and by myself for the Live Oak Development Co. The idea was to represent as nearly as possible, in the experimental box, the conditions within an area of caved stopes of caved ore all ready for drawing. That is, the area was supposed to represent a semibroken mass with the capping above it in the same condition and ready to follow the ore downward as it was drawn out of the chutes under the ore. To represent the above condition, in the experimental box, crushed ore from the mine was placed in it to a given height, and red barren capping from the mine was placed on top of the ore.

Jan 9, 1916

By G. F. Tagg

Earth-resistivity measurements are often of service in obtaining information regarding geological formations, particularly when applied to structural problems. In such problems the masses of the various bodies are large, and have a corresponding effect on the average resistivity of the soil. Much work has been done using such measurements, but in general the method of interpretation employed is empirical. Since certain simple cases can be investigated mathematically, it appears to be quite sound to endeavor to apply the mathematical solutions to the practical results, in order to deduce from the latter such unknown quantities as depth. This paper deals with such a method of interpretation for the simple case of a single horizontal stratum. In the method described by Wennerl for measuring earth resistivity, four stake electrodes are driven into the earth in a straight line as shown in Fig. 1. A current I amperes is passed between the two outer stakes and the potential difference V volts between the two inner stakes is measured. Then if a is the electrode separation, the specific resistance of the soil, which is assumed to be homogeneous, is given by the formula P = 2?v/1 [1] v or if v/1 is called a resistance R ohms, p = 2?aR [2] If a is in inches, p will be in ohms per inch cube, or ohm-inches, and if a is in centimeters, p will be in ohms per centimeter cube or ohm-centimeters. As stated above, this formula is true only if the earth is homogeneous, and when this is not the case an application of one of these formulas

Jan 1, 1934