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By E. T. Turkdogan, P. Grieveson

STAFF: Editor, Gerhard Derge Acting Editor, Paul G. Shewmon Carnegie lnstitute of Technology Sc hen ley Park Pittsburgh 13, Pa. Editorial Assistant, M. A. Redmerski Production Editor, Otto T. Johnson THE METALLURGICAL SOCIETY: Karl L. Fetters, President; J.S. Smart, Jr., Past-President; R. C. Cole, Vice President; R. L. Hennebach, Treasurer; R. W. Shearman, Secretary. PUBLICATIONS COMMITTEE OF THE METALLURGICAL SOCIETY: W. 0. Phil-brook, Chairman; H. L. Bishop, R. C. Cole, J. N. Hobstetter, W. A. Krivsky, E. R. Morgan, F. C. Langenberg, R. E. Lund, Paul Queneau, L. L. Seigle, R. L. Smith, and T. '4. Wainwright. Review and selection of manuscripts is under the supervision of the following Publications Committes: Extractive Metallurgy Division: R. E. Lund, Chatrmon; M. E. Wodsworth, Vice Chairman; D. H. Baker, Jr., G. M. Bell, R. E. Groce, W. A. Krivsky, R. A. Lewls, Charles O'Neill, A. W. Schlechten, R. E. Shinkoskey, and W. W. Stephens. Iron and Steel Division: T. V. Wainright, Choirman; H. L. Bishop, R. E. Boni, T. E. Dancy, C. W. Murphy, Johonnes M. Uys, J. B. Wagstaff, and R. G. Ward. lnstitute of Metols Division: J. N. Hobstetter, Chairman; P. A. Beck, J. J. Becker, G. F. Bolling, J. O. Brittain, J. 8. Clark, R. S. Davis, A. E. Dwight, R. W. Fountain, L. R. Girifalco, J. C. Gurland, H. S. Kclish, E. L. Harmon, J. J. Heger, A. A. Hendrickson, L. Himmel, J. P. Hirth, H. H. Johnson, Jr., R. R. Nosh, T. N. Rhodin, R. H. Richman, H. C. Rogers, W. Rostoker, C. Sherby, C. W. Spencer, L. Slifkin, J. K. Stanley, R. Steinitz, H. C. Stumpf, and R. Swolin. Published bimonthly by the American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc., 345 East 47th Street, New York 17. N. Y. Telephone PLaza 2-6800. Subscription $30 per year for non-AIME members in United States and North, South, and Central America; $32, foreign; $7.50 for AlME members. Single copies, $6.00, single copies foreign, $6.50. The AlME is not responsible for any statement made or opinion expressed in its publications ... Copyright 1962 by the American lnstitute of Mining, Metollurgical. and Petroleum Engineers. Inc. . . . Registered cable address, AlME New York . . . Indexed in Engineering Index, lndustriol Arts Index, and Chemical Abstracts . . . Second class postage paid at New York, N. Y., and Ann Arbor, Mich. Volume 224, Number 6.

Jan 1, 1962

By Alexander Bowie

Of the following problems, some have been suggested by recent articles in technical journals, which have led me to believe that the mathematical discussion here submitted may be of use to mining engineers. Problem I. To Find the Grade or Angle of Inclination upon which the Power Required to Move a Loaded Car Down-hill Will Haul an Empty One Up-hill. Let a be the desired angle of inclination; C, the coefficient of' friction; W and w, the weight in pounds of the loaded and of the empty car, respectively.

Jan 1, 1902

By Meredith Johnson

THE year 1924 saw little change in the production of oil and gas it either Pennsylvania or New York. In the early months of the year the price of Pennsylvania crude oil, $4.00 to $4.50 a barrel, was sufficiently high to cause operators to lay plans for rather extensive drilling opera-tions. But when, in August, the price dropped to $2.85 a barrel, there was no inducement for new work and drilling was curtailed. In spite of the curtailment, however, the combined production of the two states for the year showed a slight increase over 1923, the production being 8;859,000 bbl. in 1923, and 8,901,000 bbl.1 in 1924. The increased production was due entirely to. the continued development of flooding operations in the Bradford field, all other oilfields showing a decline for the year. TABLE 1. Production of Crude Oil in Pennsylvania and New York for the Last Ten Years a Production, Barrels Production, Barrels Year Year Pennsylvania I New York Pennsylvania I New York 1915 7,838,000 888,000 1920- 7,438,000 906,000 1916 7,593,000 874,000 1921 7,418,000 988,000 1917 7,733,000 880,000 1922 7,425,000 1;000,000 1918 7,408,000 809,000 1923 7,609,000 1,250,000 1919 8,137,000 851,000 1924 7,535,0006 1;366,0006 a U. S. Geological Survey figures. b Estimated. Much of the drilling in the southwestern part of Pennsylvania was done in search of gas. Natural gas in Pennsylvania is fast being recognized at its true worth and the increased prices allowed 'the gas companies for their product induced quite a bit of new work. The relative importance of natural gas compared with manufactured gas is shown in Table 2.2

Jan 3, 1925

RACAL COMMITTEE OF ARRANGEMENTS Henry McCormick, Chairman; David Watts, Secretary; H. H. Campbell, A S. McCreath, S H. Chauvenet, C. E. Stafford, George S. Comstock, Jones Wister, E. C. Felton, F. W. Wood, Harvey Fisher. CITIZENS' RECEPTION COMMITTEE Governor H. M. Hoyt, Hon John C. Herman, Hon Simon Cameron, Hon. J. D. Cameron, W T. Hildrup, Charles L. Bailey, W. W. Jennings, Lane S. Hart, H. U. Carter, Gilliard Dock, T. T Wierman, Jr, James Boyd, D. L. Jauss, Dr. T J. Dunott, S. C. Gilbert. William J Rose, James Lynah, Dr. H. B Buehler, William N Lamberton, John Wister, G. M. McCauley, David Fleming, John Q. Donney, M. E. Olmsted, H. S Gross, Henry Gilbert. John B. McPherson, Lyman D. Gilbert, F. W. Forman, L. S. Bent, A. J. Dull, F. R. Leib, Dr. G. W. Belly, James McCormick. The opening session of the meeting was held in the hall. of the Young Men's Christian Association, on Tuesday evening, October 25th. Mr. Jones Wister, of the Local Committee of Arrangements, introduced the Hon. John C. Herman, mayor, who, in a brief address, extended to the members present a welcome to the city, of Harrisburg ; Lieutenant Governor Stone made an address of welcome on behalf of Governor Hoyt and the Commonwealth of Pennsylvania. President Metcalf responded, on behalf of the Institute, to the cordial addresses of the mayor and lieutenant-governor. The following persons proposed for members and associates of the Institute, and recommended by the Council, were unanimously elected :* MEMBERS. William F. Aldrich, - Montevallo, Shelby Co., Ala. George H Blake, - Steelton, Dauphin Co., Pa. L. Bertram Cady, - Salisbury, N. C. John B. Church, - Pottsville, Pa. Walter S. Church, - Pottsville, Pa, Frank L Clark, - Pittsburgh, Pa. * In the following list are included those elected at a subsequent session of this meeting.

Jan 1, 1882

Jan 1, 1944

Jan 1, 1944

By J. D. Bateman

At Giant Yellowknife, where high grade gold-bearing orebodies are highly irregular in shape, geology has been applied extensively to the mining of ore. The classical functions of the mine geologist in the fields of exploration and mine development have been extended to guide ore extraction, ensuring "clean" mining and effectively reducing waste dilution.

Jan 12, 1951

By H. H. Pentz

This paper gives the derivation of a practical formula for the calculation of slopes in seismic reflection prospecting. The derived formula is an approximation and can be used where the slope of the reflecting horizon is less than 250 ft. per 1000 and the depth to the reflecting horizon is greater than 2500 ft. The slope of sediments in oil regions is generally considerably less than 250 ft. per 1000. This is particularly true of the Gulf Coast, with the exception of the salt domes, which usually have the sediments at a greater slope than 260 ft. per 1000. Derivation In Fig. 1, o represents the image of the shot point a. Then the length of the path acb is equal to ob and ae'd is equal to od. In the triangle aob, p is equal to ob, x is equal to , and c is equal to ao. The angle u is the apparent dip of the reflecting horizon. Angle oab is equal to (90" - u). The quantity m is the slope of a line tangent to the curve, defined by equation 1, at the point (p, x). The quantity m' is the slope of the line tangent to the curve at the point (p', 2').

Jan 1, 1940

By H. H. Pentz

This paper gives the derivation of a practical formula for the calculation of slopes in seismic reflection prospecting. The derived formula is an approximation and can be used where the slope of the reflecting horizon is less than 250 ft. per 1000 and the depth to the reflecting horizon is greater than 2500 ft. The slope of sediments in oil regions is generally considerably less than 250 ft. per 1000. This is particularly true of the Gulf Coast, with the exception of the salt domes, which usually have the sediments at a greater slope than 260 ft. per 1000. Derivation In Fig. 1, o represents the image of the shot point a. Then the length of the path acb is equal to ob and ae'd is equal to od. In the triangle aob, p is equal to ob, x is equal to , and c is equal to ao. The angle u is the apparent dip of the reflecting horizon. Angle oab is equal to (90" - u). The quantity m is the slope of a line tangent to the curve, defined by equation 1, at the point (p, x). The quantity m' is the slope of the line tangent to the curve at the point (p', 2').

Jan 1, 1940

By P. G. Shewmon

THIS paper is concerned with the redistribution of a second phase when a 2-phase solid alloy is annealed in a temperature gradient. An examplewhich is discussed in detail is the redistribution of carbides in a low-carbon steel annealed in a temperature gradient below the A, temperature. As a result of such a treatment, the carbides at the cooler side disappear, while those at the hotter side grow in size. In a 2-phase zirconium-hydrogen alloy, the amount of hydride will tend to be increased at the cold end and decreased at the hot end. That such an effect can occur in solid metals is not generally appreciated. However, with the trend toward higher operating temperatures in several fields, this phenomenon will become more important in the future. Actually, such effects should be rather common in the core of nuclear power reactors where the op- erating temperatures are high and temperature gradients are an order of magnitude higher than in previous high-temperature applications of alloys. The purpose of this paper is to point out the existence of such an effect, to discuss the manner in which one predicts whether a redistribution of the second phase will occur in a given system, whether the second phase will go to the hot or cold face, and how rapidly the redistribution will occur. One aspect of this problem has been discussed by pfam and Wernick2who considered the migration of a small liquid region through a solid. In their case, the diffusivity in the liquid is much larger than in the solid and they have interpreted their results successfully by using Fick's first law as the flux equation in the liquid, and taking the concentration gradient from the phase diagram. For all the cases they have studied, this type of analysis predicts that the liquid region migrates from the cold end to the hot end, and this is what was found ex-

Jan 1, 1959

One Hundred Sixteenth Meeting of the Institute, Monday, Feb. 18, to Thursday, Feb. 21, inclusive, 1918 A preliminary program, for the New York Meeting was printed in the January Bulletin, and a more detailed program was mailed to all members early in January. The following schedule is the outcome, of sundry committee meetings up to the middle of January. Committee on Arrangements J.` E. JOHNSON, JR., Chairman BRADLEY STOUGHTON, Vice-Chairman RALPH W. DEACON MRS. S. J. JENNINGS E. M. SHIPP J. V. N. DOER A. R. LEDOUX G. D. VAN ARSDALE L. `V. FRANCIS . . F. T. RUBIDGE ARTHUR L. WALKER Summarized Program MONDAY, FEBRUARY 18 9 a. m. to 5. p. m. Registration at Institute Headquarters. 10 a. m. Sessions on Coal and Non-Ferrous Metallurgy. 12.30 p. m. Luncheon at Engineering Societies'. Building. 2 p. m. Visit to Subway Workings.

Jan 2, 1918

By Roger L. Winter, Borje O. Saxberg

Some form of wage incentives has been used traditionally in the mining industry to determine miners' pay. However, very little is actually known about the administration of such wage incentive plans in mining. As far as the authors know this is the first time a general examination of wage incentive systems as applied to underground mining has been undertaken.* This article reports the results of an investigation pertaining to the administration of wage incentive programs for miners who drill, blast, and load- mainly in underground metallic mining operations. This investigation was conducted to obtain management's views and attitudes towards wage incentives; therefore, the results do not necessarily represent accurately the thoughts of the miners themselves nor those of any organized union of miners.

Jan 10, 1960

By Myers, J. F.

The purpose of the mill tests reported herein, was to determine the relative power efficiency of fast and slow rod mill speeds on the ores of the Tennessee Copper Co. The tests were carried out at the lsabella Mill of the Tennessee Copper Co. under normal operating conditions. Every effort was made to keep the ore supply and other conditions constant, but it will be noted that some slight variation did occur. The open circuit 6 by 9 rod mill, and ore, used in these tests have been previously described.' Four motor drive pinions were available and the tests were performed in the following manner: each pinion was used to drive the mill for a period of one week. Constant sampling prevailed during the test run, and a composite sample for each speed test was made. Realizing that some slight liner wear took place during the four-week test-run, and that some slight variation of the ore may have taken place, a second and then a third series of four-week test- runs were made with the four different pinions. The screen analysis of each of the thee-week run samples at the various speeds were composited and the results are shown in Table 1. The authors feel that the 12 weeks of operation consumed during these test-runs would represent fairly the effect of each mill speed. The data of line 37 show that within the error of sampling and plant operation, the tons of minus 65-mesh material generated per horsepower hour was the same at all four speeds.

Jan 1, 1949

By S.H. Ash, P.S. Miller

Extensive and diversified resources justify large populations and great industries. To carry on the business of commerce and meet the demands of large populations, the utilization of tunnels in some form for transportation purposes constitutes an important link in modern civilization. The driving of tunnels has been appropriated by the tunneling branch of the heavy-construction industry, and the progressive steps taken by modern tunnel builders were not even dreamed of 50 years ago. Great strides have been made toward more rapid progress in tunneling in the United States during the past I0 years. Tunneling consists of a definite cycle of operations developed from ideas that are crystallized and translated into action programs through various engineering phases that begin with the first preliminary survey and do not end until the job is completed. Once the line of the bore is established and a time set for the completion of the work, the face must advance according to estimates prepared before the work commences. This schedule must be followed in regular sequence from the moment the drills start against a new face of rock until they are ready again to drill the Succdeding face, constituting a round. Mining is largely tunneling carried on under conditions often more inherently hazardous than actual tunnel construction, but for various reasons" tunne1ing is more hazardous than mining in any branch of the mineral industry. On the other hand, obstacles are sometimes encountered in heavy-construction tunneling projects that when met in mining enterprises do not offer comparable tasks to avoid or overcome them. One is the existence of water under high pressures. In mining enterprises, various alternatives offer a solution in driving a tunnel, even to the extent of its discontinuance or the abandonment of the mine, but a "construction" tunnel usually must go forward because some important project depends largely if not entirely upon it. This paper describes an unusual method of driving a water-supply tunnel through rock carrying water under pressures and conditions that did not permit the use of ordinary tunneling methods. The Delaware Aqueduct The new Delaware aqueduct is a Manhattan project of some magnitude; when regular it will contain what probably will be, for some time to come, the longest tunnel in the world. Various features in its construction are currently described in the trade journals of the construction industry, and informative engineering details are given in the Delaware Water Supply News, published twice a month by the Board of Water Supply of the City of New York. Work was begun on this project on March 24, 1937. The tunnel will convey water from reservoirs at the headwaters of the Delaware River to the City of New York.

Jan 1, 1943

By P. S. Miller, S. H. Ash

Extensive and diversified resources justify large populations and great industries. To carry on the business of commerce and meet the demands of large populations, the utilization of tunnels in some form for transportation purposes constitutes an important link in modern civilization. The driving of tunnels has been appropriated by the tunneling branch of the heavy-construction industry, and the progressive steps taken by modern tunnel builders were not even dreamed of 50 years ago. Great strides have been made toward more rapid progress in tunneling in the United States during the past I0 years. Tunneling consists of a definite cycle of operations developed from ideas that are crystallized and translated into action programs through various engineering phases that begin with the first preliminary survey and do not end until the job is completed. Once the line of the bore is established and a time set for the completion of the work, the face must advance according to estimates prepared before the work commences. This schedule must be followed in regular sequence from the moment the drills start against a new face of rock until they are ready again to drill the Succdeding face, constituting a round. Mining is largely tunneling carried on under conditions often more inherently hazardous than actual tunnel construction, but for various reasons" tunne1ing is more hazardous than mining in any branch of the mineral industry. On the other hand, obstacles are sometimes encountered in heavy-construction tunneling projects that when met in mining enterprises do not offer comparable tasks to avoid or overcome them. One is the existence of water under high pressures. In mining enterprises, various alternatives offer a solution in driving a tunnel, even to the extent of its discontinuance or the abandonment of the mine, but a "construction" tunnel usually must go forward because some important project depends largely if not entirely upon it. This paper describes an unusual method of driving a water-supply tunnel through rock carrying water under pressures and conditions that did not permit the use of ordinary tunneling methods. The Delaware Aqueduct The new Delaware aqueduct is a Manhattan project of some magnitude; when regular it will contain what probably will be, for some time to come, the longest tunnel in the world. Various features in its construction are currently described in the trade journals of the construction industry, and informative engineering details are given in the Delaware Water Supply News, published twice a month by the Board of Water Supply of the City of New York. Work was begun on this project on March 24, 1937. The tunnel will convey water from reservoirs at the headwaters of the Delaware River to the City of New York.

Jan 1, 1943

By James G. Crawford

Correlation Of water with its reservoir zone or formation has been one of the applications of oil-field water analysis of greatest direct value to the petroleum engineer. The water in each producing zone tends to have diagnostic characteristics by which it can be distinguished from every other water above or below that zone in that immediate vicinity. Representative analyses of oil-field waters from producing oil and gas fields in the Rocky Mountain region are included, and the diagnostic characteristics are discussed briefly. It is concluded that the generally dilute nature of Rocky Mountain oilfield waters is a result of dilution by meteoric waters, and that there is no relationship between presence or absence of commercial oil and the character of water in a structure. Introduction The study of waters associated With oil and gas began more than 50 years ago and has been well recognized by operators, engineers, and geologists for about 30 years. It appears unnecessary at this time to recite the history of oil-field water analysis; suffice to say that it has proved its worth many times to the production engineer suddenly confronted with water problems in producing oil and gas wells. Chemists and geologists have studied the possible origin of these waters and as Yet the subject is unsolved in many important phases. There are both local and regional problems connected with the explanation of concentrations and character- istics peculiar to each field, each subsurface zone and each province. Criteria useful in postulating the Occurrence of oil Or gas in One province completely fail when applied to another, and data carefully prepared and analyzed from one field may be actually misleading when applied to another. Correlation of water with its reservoir zone or formation has been one of the applications of oil-field water analysis of greatest direct value to the engineer. The concentrations and characteristics of the waters are essential to the engineers and geologists making interpretations of electric logs in this region. The behavior of water under conditions of reservoir temperature and pressure is dependent to a great degree upon its concentration and characteristics, and thus important to the reservoir engineer. With the advent of secondary recovery methods in the Rocky Mountain region the characteristics and treatment of water will become increasingly important. Premises upon which Correlation Is Based A brief review of the geochemical history of oil-field waters will suffice to present the premises upon which correlations of the waters are based. Sedimentary rocks which are now stratified were first sediments in seas, lakes and streams. These sediments were filled interstitially with connate water. With burial the sediments were compressed arid consolidated, integrated and indurated into bed rock and much of the connate water was dispelled. Following the formation of bed rock the strata were sub-

Jan 1, 1949

By Carl H. Samans

The attention of physicists and metallurgists has been directed toward the study and explanation of the deformation textures in metals for the past 15 years. In 1920 N. Uspenski and S. Konobejewskil were first able to show that the symmetrical X-ray diffraction effects that had been previously reported by E. Hupka2 and others in metal foils were caused by a directed arrangement of the crystallites. Since then, the systematic study of textures resulting from the application of the pure forces of tension or compression to polycrystalline materials has been supplemented by many investigations on deformed single crystals, which have greatly added to our knowledge of deformation. However, despite the valuable information secured from these comparative studies only four investigations upon cold-rolled single crystals of any of the face-centered cubic metals have been reported in the literature. This lack of quantitative data is especially unfortunate because of the much greater practical significance of rolling textures and their effects in both cold-rolled and annealed materials. This investigation was undertaken for the purpose of specifying the deformation of rolled single crystals in the hope that such information might later facilitate the explanation of polycrystal-line textures. Of the four studies that have been made upon cold-rolled single crystals, only two are of any quantitative value. S. Tanaka,3 working

Jan 1, 1934

By J. E. Johnson

Discussion of the paper of Mark A. Amnion, presented at the Cleveland meeting October, 1913, and printed in Bulletin No. 70, October, 1913, pp. 1167 to 1 79. J. E. JOHNSON, JR., Ashland, Wis.:-Mr. Amnion's paper is of great value and it is not with any desire to reflect. on it that I wish to make some comments on the use of the scleroscope. We obtained one on trial some months ago and made very extensive tests with it, but without getting very satisfactory results. The readings on good car-wheels and bad ones were just about the same, but the factor in its use most likely to produce erroneous results is a variation in the thickness of the specimen being tested. In order to find out something on this subject we cut a thin disk, about -1,: in. thick, off a brass rod; then one 0.25 in. thick, and another about 1 in. thick, put the surfaces of all in about the same condition and tested them with the scleroscope. The readings varied widely; the resilience of the anvil evidently entered to a very high degree on thin pieces. By putting a soft cushion between such a thin specimen and the anvil, and forcing it up against the tube, the softness of the cushion cut off the resilience of the anvil and the results were more like those of the thick specimens. After a thickness of 1 in. was passed, the specimen seemed to have mass enough so that the resilience of the anvil no longer played an important part, and above that thickness results on different materials would be comparable, even though the thicknesses differed. But in order to get comparable results on thin specimens the thickness of those being tested should be the same. I should like to ask how the variations introduced in this way were overcome, so as to get strictly comparable results. Mr. AMMON :-.I have not had much experience in that, but the scleroscope is simply an indication of the surface harden-

Dec 1, 1912

By R. E. Reed-Hill, W. H. Hartt

High-purity magnesium single crystals, oriented with basal plane parallel to stress axis, were deformed in tension at room temperature so as to form second-order (1011)- (1012) twins. Investigation by optical and replica electron microscopy revealed that these twins can support very large internal strains approaching 1000 pct and that fracture follows as a direct consequence of these strains. At low strains the basal plane within (10i1)- (10i2) twins rotates with increasing deformation until it becomes approximately parallel to the twin boundaries. This rotation is not consistent with deformation by basal slip in the double twin, but may be rationalized in terms of nonbasal slip. Observations also indicate that basal slip in the primary (1011) twin, prior to second-order twinning, may contribute to this rotation. Deformation markings that are difficult to interpret in terms of slip on previously observed systems were noted in the twin bands. A possible means of rationalizing these markings is to relate them to grain boundary shear. The fracture associated with these twins is thought to initiate by formation of voids at the twin boundaries. These grow into microcracks, with ultimate fracture occurring by tearing of the interconnecting regions. THE significance of deformation and fracture along second-order (10i1)-(10i2) twins in polycrystalline magnesium1-' and many magnesium alloys4 was discussed in a previous paper.5 It was noted that this double twinning mode effectively controls the room-temperature deformation and fracture of magnesium single crystals, oriented with the basal plane parallel to the tensile axis. Reed-Hill and Robertson6 observed that, although these crystals may fracture at a macroscopic strain of less than 1 pct, shear strains up to 1000 pct could occur within (1011)- (10i2) twin bands. They concluded that the fracture was "ductile" and resulted from concentrating the deformation into a very small volume. The present research was undertaken to obtain a better understanding of the deformation and fracture associated with these twins. EXPERIMENTAL TECHNIQUES The experimental procedure involved straining high-purity magnesium single crystals in tension at room temperature. Specimens were oriented so that the applied stress direction was within 2 deg of the [1010] crystal axis. The specimen cross section was rectangular with faces closely parallel to (1210) and (0002). The specimen preparation and testing procedures have been described in detail elsewhere.5 Second-order (1011)- (1072) twins nucleated during straining were studied using optical and replica electron microscopy techniques. For the latter, cellulose acetate-carbon double replicas were employed. Observations were made on the (1210) crystal surface, which is the plane of shear for twins of this type. In addition to the single crystals, some investigations were carried out on longitudinal polycrystalline specimens. These were obtained from high-purity magnesium plate with a texture in which the basal planes of the grains tended to be nearly parallel to the specimen axis. All. polycrystalline specimens were annealed prior to testing in order to produce a coarse grain structure, permitting Laue back-reflection X-ray photographs to be obtained from grains of interest. EXPERIMENTAL RESULTS a) Deformation Within ( 101 l )-( 1072) Twins. Fig. 1 is an optical micrograph demonstrating the extent of the plastic deformation that can occur in (1011)-(10i2) twin bands. Notice at the lower left corner of the photograph the large displacement of the dark band (a polishing step) where it crosses the twins. The shear strain in the twin band at this position was computed to be 700 pct, using the ratio of step width to twin thickness. It was previously shown5 that (1011)- (1012) twin bands are often composed of small, separate twins aligned close to the macroscopic habit plane. Fig. 2 is an electron micrograph from near the upper end of the twin band in Fig. 1. This illustrates that the twin habit often does not coincide exactly with the macroscopic band habit, but may be inclined at a slightly smaller angle to the matrix basal plane. Figs. 3 through 6 are electron micrographs of the twin band in Fig. 2 illustrating successive steps in the development of deformation inside the band. A twin band such

Jan 1, 1969

By J. R. Stack, H. H. Alexander

Prior to 1915, numerous attempts were made to treat tin concentrates in the United States, but for various reasons they were unsuccessful. Tin ore is said to have been found in nearly every state, but none of the deposits has proved to be of commercial importance. An annual output of a few hundred tons in Alaska is the only domestic production; hence any considerable production of tin in the United States must be from foreign ores. The most promising occurrence of tin was found in the Black Hills, S. Dak.; in the early development stage, it was called the Cornwall of America. Associated with the tin is tungsten The story is told that an exceedingly fine specimen of the Black Hills ore was sent to England to encourage stock promotion; the desired effect was produced until a skeptic chipped off a small piece, which the analysis showed to be wolframite. First Attempts at Smelting One of the first promising attempts at tin smelting in the United States was made by R. T. White at Bayonne, N. J., in 1903. Mr. White, after spending some time in England studying the methods of tin smelting, organized a company called the International Tin Co., and erected a plant to treat tin concentrates from the Straits of Malacca. About the time the plant was completed, the English Government placed an export duty of 40 per cent. ad valorem on tin concentrates exported to other than British smelters, which duty made it impossible to operate this plant so the enterprise was abandoned, As this export duty is still effective, the only source of tin-ore supply for the United States is the Bolivian concentrates. Bolivian Tin Concentrates Unlike the alluvial placer deposits, nearly all Bolivian tin occurs in lode deposits and some of the highest grade ores contain only a small

Jan 1, 1924