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By J. N. Anderson

Developments in reverberatory furnace practice at Noranda over the period 1928 to 1953 are described. Features of interest are increasing furnace tonnage from 700 to 2000 tons per furnace day, the use of the suspended basic roof, and improvements in furnace fuel ratio. Points of comparison and contrast between Canadian and American furnace practice are given. OPERATIONS at the Noranda smelter have been described in a series of papers published between 1930 and 1945.1-4 In the present paper the development of reverberatory furnace practice over the 25 year period from the beginning of operations up to the present time will be reviewed and current furnace practice will be described in some detail. Particular attention will be given to those features which are characteristic of Canadian practice: first, the use of the suspended basic roof; second, the deliberate driving of furnaces to give tonnages in the range of 1400 to 2000 tons of solid charge per furnace day; and third, the continuous operation of furnaces at high tonnage for many years without any extended shutdown for repairs or rebuilding. Finally, points of comparison and contrast between reverberatory furnace practice in Canada and the United States will be discussed. The Noranda smelter, which started in December 1927, was built for the reduction of ore from the Horne mine where early development had shown a comparatively small tonnage of rich cop-per-gold ore of a grade and character which would require direct smelting. The smelter was designed for a capacity of 1000 tons of ore a day and originally consisted of eight roasters, two reverberatory furnaces, and two converters, together with necessary auxiliaries. The discovery of a large new body of ore in 1928 made it necessary to increase both the size and the scope of the reduction plant. A mill which was ultimately brought to a capacity of 3000 tons a day was built for concentrating low grade ore and in addition the capacity of the smelting plant had to be greatly expanded, so that for the next fifteen years every effort in the smelter was directed toward achieving maximum tonnage. Because the layout and design of the smelter made it impracticable to add a third furnace, it was necessary to increase the tonnage on the two original furnaces by improvements in furnace design and operation, roasting and converting equipment being added as required to meet the demands of increased furnace capacity. The smelter tonnage, which reached a peak in 1941, was curtailed in 1944 when it became necessary to operate on a one-furnace basis because of a reduction in the output of the Horne mine due to a shortage of labor. Two-furnace operation at a moderate tonnage was resumed in 1949. In the early years the smelter tonnage was made up almost entirely of Noranda ores and concentrates. However, since 1937 an increasing tonnage of ores and concentrates from other mines has been treated in the smelter. In recent years, with decreased production from the Horne mine, copper concentrates from several mines in the district, treated on a custom basis, have formed an important part of the smelter tonnage. A review of developments in reverberatory furnace practice at Noranda falls naturally into the following four periods: 1—1928 to 1935, the early years; 2—1935 to 1944, the period of greatest change and development; 3—1944 to 1949, one-furnace op-

Jan 1, 1955

By J. L. Fitch, B. G. Hurd

The presence of gypsum in samples subjected to standard core analysis introduces serious errors in the measurement of water saturation and porosity. The magnitude of these errors, depending upon the type of analysis procedure used, has been evaluated experimentally and theoretically. Water-saturated pore volumes determined by vacuum distillation or retort procedures may be too high by as much as 48 per cent of the volume of gypsum present. The maximum error in this value determined by Dean-Stark extraction with toluene is 36 per cent of the gypsum volume. If pore space is measured by a Boyle's law type porosimeter the maximum erorr due to gypsum is 38 per cent of the original gypsum volume present. The conscientious core analyst may eliminate the errors caused by gypsum by either of two methods. He may apply suitable corrections for the water of crystallization removed from gypsum, or take special precautions to prevent dehydration of gypsum during core cleaning and alzalysis procedures. These alternatives are discussed and methods for obtaining reliable core analysis data are proposed. Gypsum (CaSO4 . 2H2O) occurs as a common mineral in many of the world's sedimentary basins. In addition to its presence as primary bedded evaporitic deposits, it is often found as secondary replacement zones and pore-fillings in host rocks. That it may cause false indications in porosity, both on neutron logs and in standard core analysis, has been generally recognized. False porosity interpretations from neutron logs result because the chemically bound water in gypsum attenuates neutrons as effectively as free water. Errors in core analysis result when gypsum is dehydrated prior to or during the analysis. Vacuum retort procedures used by many laboratories to determine fluid saturation and porosity effect a complete removal of water of crystallization from gypsum. The crystal water, distilled and collected with free water from the sample, is counted as water-sat11rated pore space. Dehydration of gypsum results in a decrease in volume occupied by calcium sulfate and a corresponding increase in pore volume. Thus, if gypsum is dehydrated by sample cleaning and drying procedures, subsequent porosity measurements with gas expansion or compression instruments will be high. The qualitative effect of gypsum on porosity determinations by retort procedures was discussed in a recent article by Bynum and Koepl3. They concluded that since false porosity was interpreted as being water saturated, determinations of oil content were not affected. Others in the industry, however, have pointed out that porosity values are often used with values of water saturation determined independently, e.g., from electric resistivity logs in making reserve estimates. Values of water saturation calculated from the formation resistivity using the Archie equation, S4= are actually low if values of are high due to gypsum. In this case, false porosity values due to gypsum could cause serious errors in calculations of oil-in-place. This investigation was made to determine quantitatively the effect of gypsum on porosity values determined by different core analysis procedures. EXPERIMENTAL PROCEDURES Dehydration of Gypsum The extent and rate of removal of water of crystallization from gypsum under conditions encountered in core analysis procedures were studied. Taken for the experiments were three types of relatively pure, naturally occurring gypsum, viz. selenite, satin spar and massive gypsum. Although all samples probably contained trace chemical impurities, each type lost the theoretical amount of water upon complete dehydration. An automatic recording thermobalance, similar to one described by Mauer2, was used to obtain dehydration rate data for samples heated in dry air. Water

By A. W. Ruff

In the last ten years large gains have been made in the field of blasting. These gains have been both in the theoretical and in the practical application of explosives. One of the most publicized changes in the practical application of commercial explosives is the now-prevalent use of ammonium nitrate and fuel oil. The new water-compatible mixture of ammonium nitrate and TNT should also have a large field of application. Most of the theoretical gains have been concerned with the actual rock breakage obtained with explosives. In the last ten years, large gains have been made in the field of blasting. These gains have been both in the theoretical and in the practical application of explosives. One of the most publicized changes in the practical application of commercial explosives is the now prevalent use of ammonium nitrate and fuel oil. The new water-compatible mixture of ammonium nitrate and TNT should also have a large field of application. Most of the theoretical gains have been concerned with the actual rock breakage obtained with explosives. EXPANDING-GAS-BUBBLE THEORY There has been an outstanding change in the conception of how an explosive produces rock failure. The early theory which explained rock breakage was correct for some of the first force-producing agents such as quicklime. When a drillhole was filled with quicklime and water added, the material expanded and steam was generated. The expanding material and the steam exerted a slowly increasing pressure on the sides of the drillhole. The force broke the rock by splitting. Because a great quantity of gas was produced by the deflagration of gunpowder, the same process of the gas pressure splitting the rock was assumed to take place. Even after 80 years of use, the rock-breaking action of all high explosives was thought to be caused entirely by the expanding gas bubble which tore and split the rock. Fig. 1 shows a vertical section through an exploding spherical charge of high explosive. It illustrates the early theory which attributed the entire breakage to the expanding gas bubble. The basic idea of this theory is that the breakage started at the explosive charge and progressed toward the free face. REFLECTED-WAVE THEORY me expanding-gas- bubble theory has gradually been replaced by the reflected-wave theory. The reflected-wave theory explains rock failure by explosives in the following manner: The enormously high gas pressure in the drillhole produces fracturing of the rock on the sides of the drillhole. The fracturing around a 1 1/2-in. diam drillhole is usually confined to an area with about a 6-in. diam. In the fractured area, the pressure of the gas is reduced until the force on the walls is no longer capable of fracturing the rock. Although the gas pressure does not continue to fracture the rock, the pressure imposes a high impact stress on the wall rock. In addition, a pressure or seismic pulse is produced in the rock. The pulse is probably entirely a compression pulse when originally produced in the rock. But, with distance, part of the energy of the compression pulse is transformed into a tension pulse which follows the compression pulse. The explosive charges and burdens used in conventional mine blasting are such that the tension pulse of the original wave is probably too small to be considered in a practical evaluation of the theory. The compression pulse is transmitted through the rock with no associated fracturing.

Jan 1, 1961

By R. N. Thurston, E. A. Nesbitt, G. Y. Chin

A general relalionship between the amount of glide shear (due to slip) and the macroscopic shape change has been developed. Since the deformation can be large, finite strain analysis is employed. In this treatnzent, the shape change is expressed by a deformation gradient matrix, F - [axi/aXj1, where X and x refer to the initial and final positions of a particle. This matrix is readily evaluated in terms of the amounl of glide shear, a , and the direction cosines of the slip-plane normal and the slip direction for a single active slip system. In the case of deformation from slip on several systems, the product F(a) of the several deformation gradient matrices is first calculated. Then, by assuming that the final configuration is reached by a long series of small shears of magnitude a, occurring more or less alternately in the several slip sys- IN problems of crystal plasticity, it is often necessary to relate the amount of glide in the operating slip systems to the macroscopic strain components. This relationship is relatively simple when only small strains are considered. In this case the separate strain contributions from several slip systems are additive. Such a procedure is incorrect in the case of large plastic deformation. To the authors' knowledge, no general treatment of the latter problem has appeared in the literature. In specific instances, Mark, Polanyi, and schmid3 have derived the relationship between glide and axial elongation during tensile pulling of a single crystal when only one slip system is active. A similar relationship for duplex slip was worked out by v. Goler and Sachs.4 Taylor and Elam5 have also studied in detail problems of large plastic deformation. Due to uncertainties as to the slip systems at the time, terns, the final deformation gradient matrix can be obtained. Mathematically, the problem is reduced to finding the limit of F(dN as N — m while a — 0 in such a way that the Product Na = 0, a ftnite conslant designatzng the accunzulated amount of shear. It turns out that this limit is simply , where F, is the matrix whose elements are the coefficients of a in the F(a) matix. Application is made of the present treatment to a fcc crystal of Perlrzalloy compressed on the (110) plane and contrained to elongate zn the [112] directzon. In addition, it is shown that one rnay readily obtain from the general analyszs the well-known formulas relating elongation, amount of glide shear, and amount of lattice rotation for crystals deforming by single and double slip under tension. however, they were mainly concerned with proving that slip occurs on {111}(110) systems in fcc metals. The present general treatment arose out of recent investigations of magnetic anisotropy in cold-worked Fe-Ni alloys6 as well as some related problems in strength anisotropy of single crystals.' Detailed application of the general analysis will be provided in the case of a Permalloy single crystal compressed on the (110) plane and constrained to elongate only in the [112] direction. It will be seen that, as expected, the small strain approximation leads to significant errors after moderate straining. It will also be shown that the present general treatment yields the formulas of Mark et al. and of v. Goler and Sachs in those specific cases. GENERAL CONSIDERATIONS Consider a homogeneous deformation in which a material point initially at moves to both positions being referred to the same set of Cartesian axes. Such a deformation can be

Jan 1, 1967

By R. I. Jaffee, H. R. Ogden, D. J. Maykuth

IN THE past year, Jaffee and Campbell&apos; and Finlay and Snyder2 reported on the mechanical properties of titanium-base alloys, some of which were in the same ranges of composition as are covered in this paper. In this paper, evidence confirming that given by Finlay and Snyder on the effects of carbon, oxygen, and nitrogen on titanium will be presented; and, in addition, new data will be given on the effects of these elements on the flow properties and phase transformation of titanium. Materials and Preparation of Alloys The preparation and general properties of iodide titanium have been adequately described elsewhere.&apos; , As-deposited iodide titanium rod, prepared at Battelle, of Vickers hardness less than 90 was employed as the base metal in the present work. This was the same material as that used by Finlay and Snyder.2 The probable analysis reported by them for standard quality metal holds here also: N 0.005 pct, 0 0.01 pct, C 0.03 pct, Fe <0.04 pct, A1 <0.05 pct, Si <0.03 pct, and Ti 99.85 pct. Carbon was added in the form of flake graphite supplied by the Joseph Dixon Crucible Co. Oxygen was added in the form of c.p. grade TiO, powder, produced by J. T. Baker Chemical Co. Nitrogen was added in Ti3N4 powder, supplied by the Remington Arms Co. Individual ingots weighed 7 or 8 g. Carbon, oxygen, or nitrogen was added by placing the corresponding powder in a capsule made from as-deposited iodide titanium rods and melting the capsule with the balance of the charge. The charge was are-melted with a tungsten electrode on a water-cooled copper hearth under a partial vacuum of very pure argon (99.92 pct minimum). Melting was practically contamination free. Vick-ers hardness increases of less than 10 points were normal for unalloyed iodide titanium control melts. Nitrogen analyses of are-melted iodide titanium showed a nitrogen content of 0.005 pct, about the same as is present in the as-deposited rod. No tungsten pickup was found in a melt of iodide titanium analyzed for tungsten. Weight losses in melting nitrogen-free alloys were very small and varied consistently from nil to 0.015 g (0 to 0.2 pct). This permitted the use of nominal composition for these alloys. Chemical analyses made for carbon, which can be analyzed conveniently by combustion methods, justified this procedure. Where nitrogen was added, considerable splattering took place. Here it was necessary to analyze for nitrogen by the Kjeldahl method. The ingots were hot rolled at 850°C to about 0.045 in. thick. After hot rolling, the strips were descaled by mechanical grinding, and then given a cold reduction of 5 to 10 pct to insure a uniform thickness throughout the length of the specimen. The edge strips and the tensile strips were annealed in a vacuum of 1x10-4 mm Hg pressure for 3 1/2 hr at 850°C and furnace cooled. Methods of Investigation Hardness Measurements: At least five Vickers hardness measurements were taken using a 10-kg load on each sample in the following conditions: (1) top and bottom of each ingot, (2) top and bottom surface of as-rolled and annealed sheet, and (3) on cross-section of annealed sheet and all quenched specimens. Tensile Tests: Tensile tests were conducted on Baldwin-Southwark testing machines having load ranges of 600 or 2000 lb. Tests were made on 1-in. gauge-length specimens, 3 1/4-in. overall length, 1/2 in. wide, 0.040 in. thick, with a reduced section 1 1/4 in. long and 0.250 in. wide. Two SR-4, A-7 strain gauges, one mounted on each side of the specimen, were used to measure the strain over a limited range to determine the modulus of elasticity. After the modulus of elasticity readings had been taken, load vs. strain readings were taken, using only one strain gauge, at increments of 0.0001 in. until the yield points were passed and then at 0.001-in. increments to the limit of the strain-gauge indicator (0.02 in.). Strain readings above 0.02 in. per in. were taken every 0.01 in., using dividers to measure the strain between the 1-in. gauge marks until the maximum load had been reached. Crosshead speed, when using the SR-4 gauges, was 0.005 in. per min, and, when using dividers, 0.01 in. per min. Flow Curves: Flow curves were determined using the true stress-true strain data obtained during the tension test. The usefulness of this type of information has been dealt with very adequately elsewhere by L. R. Jackson,&apos; J. H. Hollomon,6 and many others. Flow curves of true stress vs. true strain could be converted to the more conventional cold-work curve of 0.2 pct offset yield strength vs. percentage of cold reduction by means of the transformation, 1/1 = 1/1-R, where R is the fraction reduction in cold working. Thus, the true strains corresponding to percentage reduction can be calculated, and the 0.2 pct offset yield strengths scaled off the — 6 curve by taking the true stresses corresponding to the values of 6 + 0.002 strain. Heat Treatment: For the transformation studies, the alloys were heat treated in a horizontal-tube furnace using a dried 99.92 pct argon atmosphere, and quenched into water. Essentially no contamination was found after several hours of heat treatment at temperatures up to 1050°C. Metallography: Specimens were prepared in the

Jan 1, 1951

By J. P. Smith

Permian salt measures carry extensive lenses of soluble potash salts in north central Germany. Potash deposits of Oligocene age are found in the Upper Rhine Graben of Alsace (France), and in the Catalonian Basin of Spain. These deposits are found in a wide range of structural settings. Reserves are large, and the production of potash salts is an important phase in the economy of each of these countries.

Jan 1, 1950

A few years later another gazetteer said of Virginia: "The Ouasioto Mountains are 50 or 60 miles wide at the Gap. These mountains abound in coal, lime and free-stone." The Gap was the Potomac River. "Copper, iron, black-lead, coal, marble, limestone &c are found in this country."&apos; In the Morris papers, in Louisa and Goochland Counties, some records of operations in 1797 and 1798 have been preserved. These are: [ ]

Jan 1, 1942

By GEORGE W. HARHIS

IN the earlier period of anthracite-ruining, much coal was wasted, both underground and in the culm-banks on the surface. Such waste is common in the development of new mining districts, in which, as a rule, only the richest material can be profitably treated. In the anthracite-region, special causes operated to increase this evil. The mines were generally operated under 20-year leases, and royalties were paid upon such coal only as was actually marketed. The lessees consequently cared for immediate profit only. They were- not bound to win all the coal they exposed, or to leave it in such condition that their successors could win it. Nor was it their interest or duty to educate consumers in the use of their product. The market called for coal of large sizes ; and such coal they furnished, throwing away the rest. Any pains taken by them to bring about a more rational use of coal by their consumers would have borne fruit, after their leases had expired, to the benefit of somebody else. A full statement of the situation wits given in 1893, in the report of the State Commission, appointed in 1889 to investigate the subject.` That body included the names of Heber S. Thompson, William Griffith and the late Eckley B. Coxe.2 Its report gives special attention to the utilization of the old culm-banks.

Nov 1, 1905

By AIME

COAL, its acquisition and consumption, has loomed large enough in the lives of many of us at one time or another, not from a technical standpoint, perhaps, but on a utility basis, to keep the house warm and the plant going. The Chairman of the Coal Division was much like many of us in that respect until after his graduation from Northwestern in 1928. Then he went to work as geologist for the Zeigler Coal Co., investigating strip coal possibilities in western Illinois, and also did research in the microscopy of coal at the Illinois Geological Survey. His interest in coal was originated and stimulated by Gilbert H. Cady, of the Illinois Geological Survey. With his advice, and with the co-operation of M. M. Leighton, Survey chief, the results of his research work on the mineral constituents of coal at the Survey were accepted as a thesis for his doctorate which he received from Harvard in 1935. Nine days before the Christmas of 1906, Clayton Garrett Ball was born at Wauconda, Ill. His father was professor of geology at Northwestern until he retired in 1946; retirement didn&apos;t lessen his active interest in his profession; he&apos;s still teaching geology at the University of Kansas City. So it was only natural for Clayton to study at Northwestern. In 1937, following a year&apos;s connection with the Bell &

Jan 1, 1948

By Sherwin F. Kelly

Twenty five years of exploration has shown that the "geophysical dollar" is worth $1780 in the Orange Free State, $1488 on the Witwatersrand, $85 in Sweden, $28,000 in the Transvaal and $3500 or more in the U.S.

Jan 6, 1951

By Walter Gaby

L. C. GRATON, Cambridge, Mass.-May I ask, in connection with one point in the summary, to what extent the author regards actinolite equivalent to tourmaline as an index of high-temperature and presumably magmatic conditions of deposition of the accompanying sulphides? W. E. GARY.-I merely advanced the idea that the mineral actinolite might have some such significance. In the copper deposit at Braden in South America, the ore occurs in an andesite breccia which is cemented by a matrix of sulphides, quartz, and tourmaline. Tourmaline is a high-temperature mineral, and when we find it associated with ores, these are regarded as having come from a volcanic or deep-seated source, hence a primary hypogenetic deposit. Thus we can count on greater continuation of the ore with depth than in some other kinds of deposit, and I thought that the actinolite, being also a high-temperature mineral, might have some such bearing in the case of Mount Morgan. I did not advance this idea as a final conclusion from a study of such phenomena, but thought that it might bear some discussion in view of the fact of the peculiar occurrence of this mineral in a notable orebody. It also occurs with the copper ores at Ducktown, Tenn., and in both cases may only be due to general regional metamorphism.

Jan 12, 1916

By Richard P. Rothwell

REVOLING slime-tables with stationary sprays and oscillating brushes have for many years been a favorite apparatus used for working slimes in German dressing-works, often displacing Rittinger tables and the many variations of Cornish buddles. The difficulty of building these tables larger than 5 1/2 meters (17 feet) in diameter, increasing the cost and making them unwieldy, rendered it necessary also to concentrate the slimes in several operations, because the travel over so short a length of hearth would not suffice for close concentration. A preliminary sizing is effected in a system of spitzkasten. Herr C. Linkenbach, general manager of the Ems Lead and Silver Works, Germany, devised a buddle, in 1878, which has since worked well and found much favor in Germany, and has been in one instance copied here, at Colorado Springs, without any credit having been given to the original inventor. Linkenbach&apos;s plan has been to reverse the functions of the table and the washing apparatus of the old German revolving table. He makes the tables stationary and rotates the washing apparatus,, thus enabling him to save in power, and, within certain limits, to increase the dimensions of the table, without in any way affecting its durability or materially increasing its cost. In its earlier form, the buddle was single, and that type is still

Jan 1, 1883

By A. J. Goss, M. Tanenbaum, W. G. Pfann

THE purification of two metals, antimony and tin, by zone refining is described, and a reciprocating method of passing molten zones through a straight ingot, which effects a considerable economy of time and apparatus, is discussed. Antimony has been used extensively as a doping agent in germanium and silicon. More recently, it has become important in the preparation of new semiconducting compounds such as InSb, GaSb, and AlSb. High purity is especially necessary in this latter use, since the antimony may comprise as much as 80 pct by weight of the compound. Antimony is generally available in a commercial form of about 99.8 pct purity. Column 1 of Table I is a typical emission spectra analysis of commercially available 99.8 pct antimony. Zone refining has been quite successful in increasing the purity of such samples. Columns 2 to 4 of Table I are analyses of an ingot of the antimony of column 1 after the passage of seven molten zones in an atmosphere of nitrogen. The ingot length was 9 1/2 in.; the mean zone length was 2 in.; convection was the only means of stirring. The column headings are sample locations in inches from the leading end of the ingot. The results illustrate both the merit and a limitation of zone refining. It is seen that four of the five impurities—nickel, arsenic, lead,

Jan 1, 1955

By Alf Holmelid

Until recently the only automatic control of electric parameters in submerged-arc furnaces has been electrode control with electrode current or electrode impendance as controlled variables. Elkem Research and Development Centre has delivered this kind of control for a long time, both stand- alone controllers and control algorithms incorporated in an integrated computer control system. In recent years we have noticed increasing interest in more sophisticated electric control. Results both from pilot-plant experiments and from production furnaces show that proper electric conditions in the furnace are more important to the furnace operation than was assumed earlier. Optimal electric conditions lead to lower power consumption per ton of metal and allow use of cheaper raw materials Besides, power contracts and the market situation lead to more frequent change of load on the furnaces. Therefore it is important to vary the load in a way that allows proper electric conditions to be maintained. Based on this renewed interest in electric control, Elkem Research and Development Centre has carried out a project, starting with analysis of existing electric instrumentation and control algorithms for electrode control, and ending up with an integrated electric control strategy including power-demand control as shown in Figure 1. In this paper we will give a resume of this work and present a new integrated control strategy put into operation for the first time in June 1983. [ ]

Jan 1, 1984

By B. C. Craft, T. J. Johnson, H. L. Kirkpatrick

Petroleum engineers are displaying considerable interest in the problems of cementing oil wells, especially in the Gulf Coast and California areas, where steep temperature gradients are encountered and where wells are being drilled to greater depths. Deep drilling, that is, at depths in excess of 7000 ft., has been undertaken in these areas only in the last few years and with this trend oil-well cementing requires more technical treatment. It is not the purpose of this paper to describe the scope and application of cement operations in the oil industry or to give the standard specifications, methods of sampling and testing of portland cement. The various testing methods have been described by the American Society for Testing Materials1, Uren2, Tickell and Wankowski3 and Rakestraw and Parsons4. The latter authors (pp. 50-58) have also described in detail the methods of cementing. The authors realize that it is impossible to reproduce in the laboratory the scale of forces and dimensions that exist at great depths, but an attempt has been made to scale down these dimensions proportionally. The selection of problems to be studied was based largely upon the practical questions asked by several of the largest operators in these fields. All cements used in these experiments met the specifications of the American Society for Testing Materials.

Jan 1, 1935

GEO. F. COMSTOCK,* Niagara Falls, N. Y. (written discussion?).-This interesting paper throws additional light on a question about which differences of opinion have apparently existed in the past, and the writer would like to record in this connection the agreement of his experience with that of Primrose and Prof. Smart in regard to the effect of quenching on the properties of gun-metal bronze. The writer&apos;s results have been published, so that there is no need for a detailed report, here, but his in-vestigations resulted in showing that both gun metal and manganese bronze are ruined by quenching in water from a red heat, apparently because they cannot stand the strains produced by the sudden cooling. The lines, mentioned by Prof. Smart, in a polished and etched section of the quenched metal have also been noticed by the writer, who however has not found them any different in quenched specimens than in annealed specimens. Since they appear only after etching, it would seem most probable that they are merely grain boundaries in most cases, though Prof. Smart&apos;s idea that they are indications of strains is by no means impossible. Fig. 1 shows how these lines appeared on the author&apos;s speci-mens of annealed gun metal, etched with ammonia and hydrogen per-oxide, and magnified 100 diameters.

Jan 11, 1919

Weiss Transit and Level The illustrations shown are the transits and levels manufactured by the Weiss Instrument Co. of Denver, Colo:, and they state that city and mining engineers are securing satisfactory results. It is claimed that their patented prismatic telescope gives increased illumination with an astronomical eye-piece. The prisms are set in a milled seat for this purpose, and cemented in so they can never come loose or out of adjustment. All adjustment for collimation is clone with the cross-hairs. This telescope is 8 in. long for magnifying power of 20 diameters against 12 in. for regular old style. The field is 1° 45&apos; with a clear aperture of 1 1/8 in. The standards are 4 ¾ in. high from plate; to center of telescope axis. Weight 10 lb. Fig: 2. FIG. 1. FIG;. 3. The Light Mountain Transit of the same type, Fig. 1, has a telescope 6 ½ in. long, magnifying power 17 diameters; field 2° 15&apos;; clear aperture 1 1/16 in.; weight 9 lb. The Mine Transit made by this ?company is interesting because it may be sighted directly down a shaft.. The principal advantage claimed for this type is the arrangement by means. of which vertical&apos; sights can be had without an additional telescope.. As illustrated in Fig. 2 the telescope is in the position of a regular transit, and used exactly the same.

Jan 10, 1915

By J. C. Draper

Duquesne Light Co.&apos;s Portal No. 3 mine, in the Warwick group of mines in Southwestern Pennsylvania, was started in June 1965 with battery- powered tractor-trailer face haulage. The area as- signed to Portal No. 3 encompasses over 8000 acres of coal and will be developed by driving a set of main entries through the center of the tract in roughly a westerly direction, and sub mains on a 45º deflection angle in roughly a northerly direction (Figs 1 & 2). In the original planning these sub mains were to be at a 90º angle with the mains, but difficult roof conditions necessitated a change in plans. The entries and crosscuts are driven 18 ft wide in the normal Sewickley seam which varies between 46 and 56 in. high. The mine bottom is a strong shale and in average, cool or dry outside conditions stands up well for rubber-tired haulage equipment, but when the outside conditions are hot and humid, the bottom becomes soft and muddy. This condition lessens as the mine faces are advanced further from the portals because the condensation will then take place principally on the surfaces of intake entries outby the working areas. To aid the situation, an air cooling system was installed and is used as conditions dictate.

Jan 7, 1968

By Ajoy K. Ghose

INTRODUCTION Longwall mining made its debut in Indian coal mining scene around 1900. Despite this headstart, the application of the method has been slow and halting. Currently, there are some 16 operating longwall faces only in different Indian coalfields contributing to perhaps less than 3 percent of the total underground coal production. Ambitious plans for expansion of longwall mining notwithstanding, apprehensions on the cavability of Indian coalmeasure roof rocks and some unsavoury experiences with face collapses in caved longwalla have impeded wider adoption of the technique. Between 1960 and 1983, some 41 caved longwall faces were worked in Jharia, Raniganj, Karanpura and Korba Coalfields in India, of which 6 faces reportedly had collapsed(1). The first powered support longwall face was started in August 1978 at Monidih colliery which marked a major step forward in the introduction of advanced technological system in Indian coal industry. This paper attempts to analyse critically the experiences with longwall ground control in caved longwall faces in India. Experiences from powered support faces at Monidih, Dhemomain and Pathakhera are synthesized to provide an appraisal of the present status of caved longwall faces under the Indian coalmeasure roofs, which thus far have been characterised as “massive”. The geotechnical site factors at the powered support faces are evaluated and conclusions drawn on the pre-assessment of caving characteristics and support resistance required at the faces.

Jan 1, 1984

By W. V. Kotlensky, H. E. Martens

In an earlier communication, Ref. 1, the authors presented the tensile properties and the changes in crystal structure and microstructure for pyrolytic graphite tested at 2750°C. It was suggested that changes in the structure may have an effect on the tensile properties of this material. Accordingly, tensile tests were run on a series of specimens, from one block of pyrolytic graphite, some of which were hot-worked by being strained at 2750°C, others of which were tested in the as-deposited condition. According to the manufacturer, General Electric Co., the polycrystalline material was deposited at 2100°C on a substrate of synthetic graphite by decomposition of a dilute natural gas mixture. The as-deposited material had a density of approximately 2.19 g per cc, and as shown in Fig. 1 had a structure of medium size growth cones which were regenera-tively nucleated. All specimens had a gage section 0.75 in. long by 0.06 in. wide by 0.1 in. thick with the thickness direction perpendicular to the basal planes. The testing method and equipment used have been previously described, Ref. 2 and 3. For both the hot-working and the testing the load was applied parallel to the basal planes; a cross-head speed of 1.5 x l04 in, per sec was used. All heating was done in an atmosphere of bottled helium.

Jan 1, 1962