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By M. G. Corson

INFORMATION regarding the use of manganese alloys has hitherto been incomplete and available only from widely scattered sources. This paper attempts a systematic description of properties and uses of alloys other than manganese bronze, manganin and duralumin, which are probably the only non-ferrous alloys associated with manganese in the minds of most metallurgists.1 PROPERTIES OF MANGANESE Manganese can react either acid or basic; it is hard to obtain in the pure state; it has two different crystalline lattice structures, both of the cubic system, one stable above 850° C. and the other below 650° C., both coexisting in the intermediate range. Although the commercial product is hard and brittle, the pure metal seems to be ductile. In fact Zhemchuzhny, in Russia, was able to obtain ductile manganese and draw it to fine wires by the simple expedient of adding about 3 per cent. copper to the alumino-thermic product. Copper most probably brings the sili-cides, aluminides, nitrides and carbides present in the commercial product into a much less harmful form of distribution. One industrial use that can be foreseen for wrought manganese articles is as anodes for electrolytic processes in sulfate and nitrate solutions, particularly with high voltages. A practically insoluble skin of manganese peroxide is likely to form in such cases and an insoluble and strong anode material will be available.

Jan 5, 1927

By Howard Martens, Pol Duwez

XPERIMENTS were performed on a Cr-Fc alloy Econtaining 44.7 pet Cr in order to determine the heat evolved during the transformation of the a solid solution into the s phase, and the change in volume accompanying the transformation. Since previous measurements on the rate of formation of a from s indicated that the reaction was quite fast as soon as the equilibrium temperature of 820°C was exceeded by some 50°, standard thermal analysis experiments were performed on heating specimens of s at the rate of approximately 40°C per sec. A definite thermal arrest was observed at 870"C, Fig. 1. This result indicates that the reverse seaction of into a is exothermic. From the heating curve of Fig. 1, taking 15°C per sec as the heating rate in the neighborhood of the transformation, 2.4 sec as the time for transformation, and assuming that the specific heat of the alloy at 850°C is an average between iron and chromium, namely 9.5 cal per mol per "C, the latent heat of transformation is approximately 342 cal per mol. The order of magnitude of this latent heat was also obtained by comparing the heating curve of Fig. 1 with a similar curve obtained with pure iron under identical experimental conditions. It was found that the length of the thermal arrest for s was about 1.8 times as long as that for iron. Since the latent heat of the a to 7 iron transformation is 203 cal per mol1, 2 the latent heat of it to a would be 365 cal per mol, which is in relatively good agreement with the value determined from the heating curve. For the determination of volume change, thermal expansion curves were recorded using a specimen containing 44.7 pet Cr and completely transformed to cr by previous treatment. The curves were recorded at a rate of heating of about 4°C per min and at approximately 840°C a sharr, increase in length of about 0.08 pet took place. Fig. 2. It is therefore established that the specific volume of a near the transformation temperature is about 0.24 pet smaller than that of a, and consequently, when the s phase forms in an a matrix, it would tend to shrink away from the matrix. Since the s phase is known to be extremely brittle, these results offer an explanation for the microscopic cracks often observed in the a phase under the microscope. The results of this study are in qualitative agreement with previously published data on stainless steel 19-9DLa and on a Cr-Fe alloy containing 45 pet Cr.' The increase in density due to the transformation from n to s given in ref. 4 is 0.90 pet. These measurements, however, were made at room temperature. whereas the presently reported 0.24 pet is the change at the temperature at which the transformation takes place during heating. In the graph of Fig. 2, the percentage change in length that would be observed at room temperature is given by the length X, which is about 0.27 pet. This would correspond to 0.81 pet in volume change. Acknowledgment This work was done at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. DA-04-495-ORD-18 with the Army Ordnance Corps, Washington, D. C. The authors wish to thank this agency for permission to publish the results of this investigation. References I H. Klinkhardt: Measurements of True Specific Heats at High Temperatures. Annalen der Physik (1927) 84, pp. 167-200. - H. Esser and W. Runghardt: Influence of the Method, of Dctcrmination on the Measured Heat Content of Iron. Archtvo ffur Dct Eisenhiittenwesen 11934) 8, pp. 37-38. J. J. Gilman, P. K. Koh, and 0. Zmeskal. Delta Ferrite Formation and its influence on the Formation of Sigma in a Wrought Heat Resisting Steel. Trans. ASM 1 1949) 11, pp. 1371-1388. 1 J. M. Thomas: Discussion of ref. 3. Trans. ASM (1949) 41, pp. 3 390-1392.

Jan 1, 1957

By T. Lane Carter

BEFORE describing the experience with the Chinese on the Rand and the work they have accomplished, it will be necessary, sary, first, to give a brief account of labor-conditions in the Transvaal since the war, and then to show how the necessity of importation of labor arose. As is well known, the Transvaal mines are run on the dual system of labor-that is, the rough work is done by colored laborers under the superintendence of white men. From the start of mining operations in South Africa there has been the cry of shortness of native labor, due in great measure to the failure of Kaffirs to work continuously in the mines. While he works, the Kaffir is a satisfactory laborer, but his period of service is short, averaging about nine months. People unacquainted with the Kaffir have maintained that, by offering a higher wage and better accommodation, better results would be obtained from the native workers, but an increased wage simply aggravates the trouble. The Kaffir's wants are few. While at work he spends little of his money, and before long has sufficient capital with which to buy wives and become a gentleman of leisure. Doubling the wage of the Kaffir means that he acquires a competency in half the time, so that his period of service is correspondingly reduced. In 1899, before the war, there was always a cry about the scarcity of Kaffir labor. The highest number of natives at work was in July and August, 1899, when nearly 100,000 were employed. At the outbreak of hostilities the Kaffirs were scattered far and near, many doing well during the war by working for the military authorities. On the, resumption of mining operations on the Rand a serious mistake was made. Based on past experience, it was argued that if the whole industry decided to start anew with

Sep 1, 1908

By J. Moore Samuel

THE prospective change in ore receipts at the Copper Queen reduction works necessitated a careful study of conditions to determine the most economical method of smelting. The first step, calculating the known, probable, and possible results, showed the economy of a unimetallurgical flow sheet f which the three pyrometallurgical stages would be roasting, reverberatory smelting, and converting. The past and future ore receipts (not including converter flux) are as follows: AVERAGE MONTHLY FUTURE MONTHLY RECEIPTS, 1918 RECEIPTS TONS PER PER CENT. OF TONS PER PER CENT. OF MONTH TOTAL RECEIPTS MONTH TOTAL RECEIPTS Ore 84,553 82.3 43,000 44.0 Gravity concentrates 16,375 15.9 25,500 26.0 Flotation concentrates 1,883 1.8 29,400 30.0 Total 102,811 100.0 97,900 100.0 Of the 102,811 tons per month received in 1918, only 28,945, or 28 per cent., was treated in the roasters and an average f 14.1 roasters out of 20 were in operation; the remaining ore was treated in the blast furnaces. The change to "all reverb." practice, therefore, called for considerable additional roaster capacity, which could be obtained either by building additional units, or by remodelling the present units so as to give increased unit capacity. In view of the progress in roasting practice since the construction of the Copper Queen roaster plant and the heavy investment in that roaster plant, the second plan seemed to be the more desirable. The Copper Queen roaster plant consisted of twenty six-hearth, McDougall roasters, 18 ft. in diameter, equipped with cast-iron arms that originally were water cooled but now are air cooled. They have no top dry hearth and the feed is discharged through the top arch, near its periphery, by plunger feeders from two bins at opposite sides of the roaster.

Jan 7, 1921

By Oliver Bowles

GLASS razor blades, glass chairs, and marble window panes attest that creative genius was still active in 1935. Many less striking, though doubtless more important, developments are to be recorded for the nonmetallic mineral industries, and not the least of them is the establishment of an Industrial Minerals Division in the A.I.M.E. under the able leadership of Samuel H. Dolbear, Chairman. Thus the nonmetallics are rightly granted equal dignity with metals and fuels in the category of mineral industries. The brief review of progress that follows merely touches the fringe of important developments in this broad field.

Jan 1, 1936

By Wheeler North

THE United Eastern Mining Co.'s property is located in the Oatman, Gold Roads mining district of Mohave County, Ariz. The mine and mill are some 26 mi. (41.8 km.) southwest of Kingman, the nearest railway connection. The ore consists of a mixture of calcite and quartz with some andesite. The values, which are mainly gold, alloyed with approximately 34 per cent., by weight, of silver, are extremely fine so that fine grinding is a most important factor in extraction. The milling process, briefly, consists of single-stage, coarse-crushing, two-stage ball milling in cyanide solution, followed by combined mechanical and air agitation, and by straight counter-current decantation. The Merrill zinc-dust precipitation method is used to recover the values, and is preceded by the Crowe vacuum treatment of the solution. The most notable features of the plant are the absence of filters, and the use of short peb mills loaded with steel balls, for fine grinding. As originally designed, the capacity of the mill was to be 200 tons per day, although the grinding end was to be capable of handling double that amount. By adding extra agitators and thickeners and by some alterations to the grinding end, the daily capacity has been raised to 285 tons. This, it is hoped, may be increased to 300 tons during the warm months of the present year. TONNAGE MILLED PER DAY 1917 average 234 Maximum month 272 Minimum month 146 1918 average 253 Maximum month 276 Minimum month 217 As this article primarily deals with plant operations, those interested in the mechanical description are referred to the article by Mr. Otto Wartenweiler,1 the designing engineer, which gives the details and costs of design and construction. The following changes have been made since that article was published:

Jan 8, 1919

The Library of the above-named Societies is open from 9 A.M. to 10 P.M., except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 7, 1917

By T. L. Joseph

The extent to which hot metal from the blast furnace affects open-hearth practice and the quality of steel produced has been discussed widely. Open-hearth operators have attributed difficulties experienced in making satisfactory steel to characteristics of the pig iron not disclosed by ordinary analysis. The commonest criticism of the iron has been that it is "physically cold" or "dirty." Often when the blast furnaces are working irregularly the quality of the iron is questioned. A cold hearth, slipping and hanging, the use in the past of unsintered flue dust, and the use of ores difficult to smelt have been associated with the production of iron of poor quality. The difficulty of the situation is that we have no proven yardstick for quality aside from ordinary analysis. Uniformity in analysis is recognized as being important, but the difficulty of changing the open-hearth practice when the iron analysis varies widely may not always be fully appreciated. Although the problem of correlating the characteristics of steel with those of pig iron is admittedly obscure, the effort of producers of quality steel to investigate all factors that may have a bearing on the final product is justified. This report contains data on the oxides in several hundred casts of basic iron produced in a furnace during the course of normal operation on Lake ores. Incidental to the study of the oxides in the iron, it was desirable to follow closely the temperature of the iron. The effect of temperature of the iron upon the silicon and sulphur present is discussed. A general relation between the basicity of the slag and the sulphur in the metal was developed. The amount and composition of oxides in the hot metal and in the steel bath during various intervals between melt-down and tap are discussed. Heats of rimmed steel, killed steel, and semikilled steel were investigated. The hot metal on individual heats was either all taken from a mixer or consisted partly of direct metal and partly of metal from the mixer. Samples of the iron for oxide determinations were

Jan 1, 1937

By George Burrell

INTRODUCTION THE senior author of this paper, while in Colorado on other official business, made a trip to the Cripple Creek gold-mining district to get more data than are at present available regarding the composition of the gas that issues from the rock into the mines of the district. This was done at the suggestion of George S. Rice, Chief Mining Engineer of the Bureau of Mines. There are many questions of interest and importance in connection with the ventilation of the mines in the Cripple Creek district, such as the menace to life and mining of a suffocating gas entering the mines from the rock, the danger due to powder smoke (from blasting operations), and danger of continued inhalation of rock dust by the miners. This report confines itself to the first problem, the gas from the rock, and principally to one phase of this question, the composition of the gas and its effects on men and lights. A more thorough study of this and other ventilation problems is planned. That the, rock gas is a real menace is shown by the fact that miners (variously estimated from 25 to 50 by different persons interviewed) have been killed by it in the 25 years that mining has been vigorously carried on at Cripple Creek. Many men have had narrow escapes from death, some of them having been incapacitated for days. In addition, much loss of time results because at certain periods of the year or on certain days it is impossible to enter some workings. At a few mines fans force air into the workings, thus supplementing the natural ventila-

Jan 5, 1916

By G. G. Marino, J. W. Mahar

This paper provides an understanding of the behavior and potential damage of homes resulting from sag-type mine subsidence. This is done with extensive research of numerous case histories in Illinois collected by the authors. The house response to subsidence-induced ground displacements are summarized and evaluated. A damage level criteria, specifically developed for residential structures, is presented based primarily on repair costs. Damage levels and the associated subsidence profile characteristics for each case history are compared.

Jan 1, 1986

By Stanley Reichert

The manganese deposits of the Embree Iron Co., Embreeville, Tenn., are thought to be fairly typical and representative of the East Tennessee type of deposit, and so to warrent rather detailed description. The methods used by the Embree Iron Co. for prospecting and mining, and to a lesser extent for milling; should therefore be applicable to other East Tennessee manganese deposits, as yet' undeveloped. Early History and Discovery of Manganese Brown iron ore (limonite) was mined by the Embree Iron Co. at various times from 1890 to 1910. The early method was simply pick-and-shovel mining in open pits. Later hydraulic giants were used and sluice lines carried the ore down the mountain slopes to log washers.. During this phase of mining, manganese ore was discovered under the iron ore in some of the pits. In other areas oxidized zinc ore was found under the iron. It thus happened that the valuable zinc deposits were discovered in 1914. During the World War period, from 1914 to 1918, there was sporadic prospecting for manganese ore among the abandoned iron workings, but the main activity then centered around the recently discovered lead and zinc deposits. It was not until 1934 that manganese mining began in earnest, under the supervision of R. D. Pritchett, Mine Superintendent. Geology of the Manganese Deposits United States Geological Survey Folios 151 (Roan Mountain) and 118 (Greeneville show that Bumpass Cove is a synclinal structure thrust faulted along the southeast flank, but with normal sequence of strata along the northwest flank. Fig, l. shows the areal geology of Bumpass Cove as taken from the folios superposed on the U.S.G.S. -T.V.A. 1/24,000 topographic maps of the Erwin and Telford 7 ½ minute sheets. The manganese mines occur near the contact of the unfaulted Shady dolomite and the Erwin quartzite. This contact zone is deeply weathered, with overburden averaging 40 to 60 ft. thick. The material overlying' the bedrock along this normal contact is a very tough, plastic clay, termed "buckfat" or "ocher" by the miners. It is not a true ocher, however, in the sense of having commercial value. The manganese deposits occur along this "ocher" band. Fig. 1 also shows how the manganese deposits occur along the broad topographic terrace between the 2100 and 2200-ft. contour lines. This terrace lies at the foot the Erwin quartz ridge. Apparently it is the topographic is expression of the deeply weathered zone along the Shady-Erwin contact.

Jan 1, 1941

By D. O. Hobson, J. O. Stiegler, C. J. McHargue

The effects of alloy composition, deformation temperature, heal treatment, ad inlerstilial contamination on the occurrence of deformation twins were studied. The twinning transition temperature varied with composition and was a maximuni of 140°C for the 40 pcl V composition. Tire remperature range of the transition was very narrow. Alloys of 20 to 70 pet V could he cold-rolled and exhibited profuse twinning. The alloys which did not twin at room temperature (10, 80, and 90 pel V) could plot be cold-rolled. Oxygen additions systematically lowered the transition temperatures for all vanadium contents. The transition temperature for a 30 pet V alloy increased with annealing temperature, apparently due to changes in dislocation density and configuration. Twinning did not nucleate fracture in any specimen in the 20 to 60 pet V composition range. THERE is great current interest in the refractory metals and alloys as structural materials. An important factor in considering the ductile-brittle behavior of such materials is the role of mechanical twinning as a deformation mechanism. Mechanical twins have been observed after deformation at low temperatures or at high loading rates in the pure metals iron,1 vanadium,2,3 columbium,4,5 tantalum,6 Chromium,7 molybdenum,8 and tungsten.9 Binary alloys in which mechanical twins have been observed include: iron with silicon,10 phosphorous," or aluminum;12 and chromium, molybdenum, or tungsten with rhenium.13-17 The increase in low-temperature ductility obtained by alloying the Group VI-A elements with rhenium is very important with regard to fabricability, and there has been considerable effort to understand the so-called '(rhenium effect". Factors suggested to explain this effect include:'' 1) increase in solubility of interstitial impurities with alloying (electronic effect): 2) changes in the nature of grain boundary phases; 3) changes in interfacial energies of grain boundaries and stacking faults: and 4) promotion of twinning. Although an outstanding characteristic of these alloys is the profuse twinning that accompanies low-temperature deformation, most studies of the rhenium effect have been concerned with the other factors. During recent studies of refractory-metal alloys, it was noted that solid solutions of columbium and vanadium exhibited high hardness and strength at room temperature and elevated temperature and, surprisingly, also showed considerable ductility at room temperature and below. These alloys deformed by twinning at room temperature when subjected to slow loading rates. It appeared that the low-temperature ductility resulted at least in part from the relaxation of stresses by twinning in a system where slip is difficult. The reason for enhanced twinning behavior in some bee solid-solution alloys is unknown. There have been suggestions18,19 that, as in fee alloys, the

Jan 1, 1965

By AIME AIME

HOLDING the annual dinner-dance of the Institute at the Waldorf-Astoria had become such a tradition that there was widespread regret when it became known that the demolition of the building to make way for a huge office structure would perforce bring to an end the long and enjoyable series of gatherings our Institute had held there. This year the . Commodore was the place at which it was held and the commuters on the New York Central and the New Haven railroad systems, at least, found it a more convenient place for them. Except for the famous "Hoover" dinner, which will probably set a mark for all time, it was the largest dinner the Institute held, 1000 being present, and it taxed the facilities of the hotel to the utmost.

Jan 1, 1930

By D. Turnbull, J. C. Fisher

ACCORDING to the "reaction-path" modell,2 of martensite nucleation, the shear angle of the embryonic martensite plate must be treated as a variable, and included in any calculation of nucleus critical size. Also, as can be deduced from this model, the interfacial free energy between austenite and martensite does not reach its final value until the shear is completed. It is zero for zero shear angle. However, in order to account for the kinetics of the martensite transformation, some sort of interfacial energy barrier appears to be necessary even with the reaction-path model, for otherwise the volume and the energy of formation of the critical size nucleus both collapse to zero.3 Cohen independently suggested that surface energy could be incorporated into the reaction-path model, with the overall free energy of a martensite embryo being a function of its volume and shear angle.' It is possible to estimate the energy associated with the formation of a critical-size martensite nucleus starting with the reaction-path model and including a surface free-energy barrier. As the dependence of interfacial free energy upon shear angle is unknown, a simple type of dependence will be assumed, with the belief that the true dependence would not lead to appreciably different results. Consider the work required to form a lenticular martensite plate with radius r, thickness t, and shear angle 8. There are three contributions; one being the interfacial free energy, one being the free energy change in the martensite plate, and one being the free energy increase in the surrounding austenite. The interfacial free energy u is assumed to depend upon the shear angle 0 according to the relationship s=s0(?/?0)n [1] where 8, is the equilibrium shear angle and n is an exponent that may lie in the range 0 n 2. The work required to form the interfaces of a martensite plate then is W. = 2pr² s0(?/?0)n [2] The free energy change per unit volume of martensite is composed of two parts, one the ordinary volume free energy ?f1. which is negative, and the other the elastic strain energy G?m²/2, where G is the shear modulus and 7, the shear strain relative to the martensite structure. This expression for the strain energy is valid only when the shear strain ym, is sufficiently small that the martensite is within its linear elastic range. There is no doubt that ym, lies beyond the linear elastic range for embryos that are considerably subcritical. However, for critical nuclei it will be shown that ym, is 1.5 pct or less, within the linear elastic range of martensite. For embryos of nearly critical size, then, the strain energy of the martensite is correctly given by G?m²/2. The shear strain in the martensite is ym, = 8, — 8, and the work required to form the strained martensite is Wm --= (pr²t/2) [?fv + G(?O - ?)²/2] [3] The free energy change in the austenite is entirely that due to elastic distortion. The elastic strain is not uniformly distributed in the austenite, being large near the martensite plate and small elsewhere. Approximately, however, the energy corresponds to a uniform shear strain ya= (?t/2)/r [4] throughout the volume 4pr³/3 surrounding the plate. The work required to strain the surrounding austenite then is Wa = (4pr³/3) (G?a²/2) = (G?²/6) prt² [51 For simplicity, the same shear modulus G is assumed for each structure. The total free energy for forming a plate then is W = W3 + Wm + Wa. = 2pr² s0 (?/p?0)n + (pr²t/2) [?fr+G(?0-?)²/2] + (G?²6) prt2 [6] This expression is correct for nuclei and for embryos of nearly critical size, where, as will be shown, the strain energy in the martensite is correctly given by the expression G (? — ?)². Having W as a function of r, t, and 8, as in Eq. 6, there is a saddle-point where W has a stationary value, W subsequently decreasing indefinitely as the nucleus volume increases along the reaction path. The stationary value of W is the energy of the critical nucleus. The critical nucleus has radius, thickness, and shear angle such that ?W/?r - awlat: = ?W/?p? = 0. Performing these differentiations and calculating the critical nucleus energy, W* = [8192p(G?/6)²;s/27 ?fv4] [7] where a= (?/?0)3n+1[l +G(8"-8)'/2af.]' [7a] and where 8 is to be determined from the equation (1 + 3n/4) + G8(6O - (9)/[Af. +G(6>o-6>)72] = 0 [8] For ?f, near —200 cal per mol or —10" ergs per cc, and 8, near 1/6, as for iron-base alloys, Eq. 8 gives ?0 - ? ~ - (4 + 3n) ?f1./4G0O [9] as the difference between the equilibrium shear angle and the actual shear angle for a critical nu-

Jan 1, 1954

By James Hance

INTRODUCTION SEVERAL years ago the writer was connected with the Mint and Assay Service of the Federal Government as Assistant Assayer at the-Salt Lake Assay Office. At that time cyanide bars formed approximately half of the bullion purchased by that office. Disagreement in valuation between the producer and the office was not infrequent and to a lesser extent between the Assay Office and the Mint, this latter issue being soon obviated, however, by adopting uniform methods of sampling the bars. A nice problem seemed to offer itself for research and the writer began a series of experiments which were soon terminated, however, by his going into other work, and which he regrets have not since been completed. The results attained may suggest lines of approach to this problem and are, therefore, offered in this article. Frederick P. Dewey, Assayer of the Mint Service, U. S. Treasury, has had abundant opportunity to study this phase of metallurgy, and has published several articles relative thereto.1 In the last article cited Dewey quotes analyses of cyanide bullion similar in content to that with which the writer worked, and which show some of the variations met with. In the discussion of these papers,2 comparison has been made in terms of copper bullion, but to the writer this seems of questionable value. Copper bullion may resemble silver bullion, but its similarity to, gold bullion with little or no silver content is another thing. The freezing-point diagram of Roozeboom, reproduced on page 881 of the discussion cited, is for the gold-silver series as stated. The original problem under discussion, however, is not this alloy but gold with base metals other than copper. As for the statement that the corners are the worst places or

Jan 2, 1916

Discussion of the paper of PAUL BILLINGSLEY, presented at the New York meeting February, 1915, and printed in Bulletin No. 97, January, 1915, pp. 31 to 47. JAMES F. KEMP, New York, N. Y.-Mr. Billingsley has spoken so concisely that we may not realize the many important topics which he has passed in review and upon which lie has thrown much illumination. The exact determination of the age of the granite, itself, is one. If we were to look over a geological map containing the region of Butte and 25 years old, we would find this coarsely crystalline mass assigned, as were others of its kind, to the pre-Cambrian, or as we used to say, to the Archean. In the course of time it was found to be later. The Butte Special Folio, 1907, described it as post-Carboniferous and possibly post-Laramie. Mr. Weed in Professional Paper No. 74 of the U. S. Geological Survey (1912) placed it as probably Niocene because of its relations with the andesite, which was believed to be Eocene. Mr. Billingsley now by a very neat demonstration circumscribes it more definitely and we recognize that it must be latest Cretaceous or earliest Eocene. We see, however, that extensive field observations, ably correlated, were necessary to establish the conclusion. For some years all familiar with Butte have known that there was a central area the veins of which carried copper ores in a quartz gangue; and that outside this area there were veins carrying silver ores in a gangue of manganese minerals. Mr. Sales's able and detailed paper, read at the Montana meeting, August, 1913, not only corroborated these relations, but emphasized the transitional character of the intermediate or passage zone. Mr. Billingsley is now able to show from observations at increasing depths, the tendency of the copper ores to appear deep down in the veins

Jan 5, 1915

By R. P. Smith

IN 1937 the employees of the Hollinger Consolidated Gold Mines Ltd., at Timmins, Ont., Canada, approached organized medicine for a plan to provide themselves and their families with a complete medical service including hospitalization. This approach was made because of two conditions: (1) the necessity for some organization whereby contributions could be made in instalments to offset the sudden and large expense connected with illness for which the average employee is not prepared, and (2) the need for a more cohesive quality of service to replace a contract practice then in vogue, which did not take care of the employee's family or dependents. In different parts of the United States and Canada similar plans were in force, not only for employed groups but for numbers of people in circumscribed areas. In Europe different countries had adopted various forms of health insurance plans. It then was no surprise that these employees as a group should ask for some similar plan. With the cooperation of the management, a plan was instituted. The plan has one object only-the provision of medical services, including the accessory services such as hospitalization, X-rays, nursing, and necessary drugs and medicines. It is not concerned with cash benefits, sickness and accident payments, or any form of monetary return as the result of illness, but is simply an organization to provide medical services and pay for them from a central fund. It is a nonprofit organization and the only shareholders are the employees and their families who contribute and who in turn receive services. The Hollinger plan is limited to the employees of the Hollinger mine, who live in Timmins and the immediate vicinity. At first, the membership was voluntary. In the third year, it was made a condition of employment, with the proviso that at the end of any Association financial year an employee may withdraw if he wishes to do so. After withdrawal, he cannot again become a member until the end of the next Association year, and then only by the payment of the back dues. This step was taken to ensure continuity, and to prevent employees from withdrawing when well and reentering when faced with impending illness or operations. The employee himself is subject to medical examination on application for employment, and if accepted is subject to further examination by a specialist in chest diseases under the Workmen's Compensation Board of Ontario. Thus it is possible to exclude those who have heart disease, tuberculosis, or other disabling conditions when first employed. Wives and families of employees are not subject to medical examination but other dependents of an employee-mother, father, or other relative-who are declared by the employee to be wholly dependent upon him must be examined. The employee

Jan 1, 1944

By H. H. Johnson, Eric W. Johnson

A newly developed ac technique was used to measure the electrical-resistivity changes associated with both cyclic stressing and subsequent annealing of high-purity and OFHC copper. The early stage of push-pull fatigue was explored at 293° and 4.2°K, with stresses chosen for an expected fatigue life of 2 to 8 X 105 cycles. For high-purity copper, fatigue at 293°K was accompanied by an initial increase in resistivity. After about 5000 stress cycles, no further increase was observed. Annealing studies showed that the resisticity increment could be accounted for solely in terms of an increased dislocation density, to about 2 x 1010 disl pev sq cm. Fov 42°K fatigue, however, the resistivity increased continually, with no evidence of saturation, as approximately (No. of stress cycles)1/4. This is intevpreted to result from both dislocation multiplication and vacancy production; estimated vacancy concentrations are 10-4 to 10-9. The continuous resistivity increase was inhibited by interspersed annealing treatments at 293°K, which also raised the level of the stress-strain curve. These effects are attributed to annealing of vacancies into dislocation loops. In contrast, OFHC copper fatigued at 4.2°K showed saturation of electrical vesistivity after only a few hundred cycles, and it appeared that vacancies annealed out completely between 77° and 293°K. MaNY observations suggest that both dislocation multiplication and point-defect production are important aspects of fatigue deformation. An increase in dislocation density with number of stress cycles has been demonstrated or implied by several experimental techniques, including optical metallography with lithium fluoride,' electron microscopy with copper,2 thermal conductivity of Cu-Zn alloys,3 and peak-stress measurements during cycling at constant plastic strain amplitude.4,5 At low amplitudes and/or stresses saturation of fatigue hardening and dislocation density occurs early in the expected fatigue life,4-6 frequently by a few hundred cycles. The evidence for point-defect production is somewhat less extensive, but it is nonetheless persuasive. Rosenberg7 reported briefly that, for equal stresses, copper fatigued at liquid-hydrogen temperature displays an increase in electrical resistance some ten times that which accompanies unidirectional stressing. Further, the extra resistance saturates after a few hundred stress cycles, and does not anneal significantly until a temperature of about 170°K is attained.' Point-defect production during fatigue is also suggested by 1) the softening during cyclic stressing of initially strain-hardened polycrystal-line copper9, 2) the strong temperature dependence of the yield strength of fatigue-hardened mono- and polycrystalline copper,579"0 and 3) the influence of intermediate annealing upon slip-band formation in copper fatigued at 90°K.8 It is evident that characterization of the fatigued state requires a knowledge of both point-defect and dislocation densities. For this purpose electrical-resistivity measurements are useful, but they are difficult to perform because of geometric limitations. Push-pull fatigue is necessary to obtain a macroscopic ally uniform deformation over the specimen cross section; however, the specimen must then have a low slenderness ratio to avoid plastic buckling, while the standard dc resistivity technique requires a very slender specimen for

Jan 1, 1965

By Joseph Daniels

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

Jan 1, 1926

By D. W. Brunton

Discussion of the paper of D. W. Brunton, presented at the Spokane meeting, September, 1909, and published in Bulletin No. 33, September, 1909, pp. 837 to 855. WILLIAM' KENT, New York, N. Y.:-The Institute may congratulate itself on the opportunity of reading the splendid address of President Brunton. It is au admirable summary of the progress that has been made in the mining and metallurgical arts in recent years. The paper rightly give's the chief credit for this progress to the aid which has been rendered to these arts by the advances in mechanics, chemistry, and electricity. It is notable that most of the headings in Mr. Brunton's address refer to the work of the mechanical engineer, the electrical engineer, and the chemist, rather than to that of the specialist in mining-operations. It seems that. the most successful mining engineer of the present day is the one who makes the most intelligent application of the inventions and designs of engineers and others who are not directly engaged in mining. A tabulation' of the headings of the address, grouped as below, shows this most clearly. Work of the Mechanical Engineer-Rock-drills, hoisting-machinery, tramming, pumping, ventilation, dredging, sampling, concentration, briquetting, fume-recovery. Work of the Electrical Engineer-Electric machinery for hoisting, pumping, tramming, lighting and signaling, electric . transmission, electric smelting. Work of the Chemist and Metallurgist-Explosives, chlorination, cyanidation, roasting, lead-smelting, and copper-smelting. Work of the Geologist-Economic geology. Work of the Mining Engineer-Mine-mapping, surface-mining, timbering, tunneling; and planning and supervision of the work in general. The mining engineer of the present day, who is in responsible charge of a large plant, finds his chief work not in doing

Jan 1, 1910