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By H. E. Mauck

The many factors that control bumping must be carefully studied for each coal seam where bumps occur, and specifications known to exclude bumping should be incorporated in the mining plans. This calls for complete knowledge of the seam's characteristics and its adjacent strata, and in many instances these characteristics are not revealed until the seam is actually mined. Pressure and shock bumps, the two general types, occur jointly and separately. In this discussion no differentiation will be made. Whether pressure or shock, they are treated as bumps, and both must be eliminated. Bumps in mines have occurred in several places throughout the coal fields of the world. A study of many of these occurrences indicates that geologic characteristics, development planning, and mining procedure have contributed. But more specifically, there are conditions usually associated with bumps: thickness of cover, strong strata directly on or above the seam, a tough floor or bottom not subject to heaving, mountainous terrain, stressed and steeply pitching beds, and the proximity of faults and other geologic structures. Mine planning should incorporate these known factors (not necessarily in order of importance): 1) Main panel entries should be limited to those absolutely necessary to ventilate and serve the mine. This reduces the span over which stresses may be set up that will later throw excessive pressures on barrier and chain pillars when they are being removed. 2) Barrier pillars should be as wide as practicable so that they will be strong enough to carry the loads thrown on them when final mining is being carried out. 3) Pillars should never be fully recovered on both sides of a main entry development if the barrier and chain pillars are to be removed later. The excessive pressures placed on the main chain and pillar barriers by arching of the gob areas can result in bumping when these barriers are being removed. 4) Full seam extraction is better accomplished by driving to the mine boundary and then retreat-drawing all pillars. If there are natural boundaries in the mine—such as faults, want areas, and valleys —retreat should be started there. 5) Pillars should be uniform in size and shape. The entire development of the mine should call for uniform blocks with entries driven parallel and perpendicular. Only angle break-throughs should be driven when necessary for haulage, etc. 6) For better distribution of rock stresses and reduction of carrying loads per unit area, both chain and barrier pillars should be developed with the maximum dimensions. 7) Pillars should be open-ended when recovered. If they are oblong, the short side should be mined first. Both sides of a block should not be mined simultaneously, but under no circumstance should the lifts be cut together. 8) Pillar sprags should not be left in mining. If they are not recoverable, they should be rendered incapable of carrying loads. 9) Pillar lines should be as short as practicable. (Three or four blocks are adequate). Experience has shown that rooms should be driven up and retreated immediately. The longer a room stands, the more unfavorable the mining conditions. This contributes to bumping. 10) Pillars should not be split in abutment zones (high stress areas lying close to mined out areas) and if slabbing is necessary, it should be open-ended. 11) Pillars should be recovered in a straight line. Irregular pillar lines will allow excessive pressures thrown on the jutting points. Experience has shown that the lead end of the pillar line can be slightly in advance. 12) Pillar lines should be extracted as rapidly as possible. This appears to lessen pressures on the line and render abutment zones less hazardous. 13) Extraction planning should call for large, continuous robbed out areas. Robbing out an area too narrow to get a major fall of the strata above the seam tends to throw excessive pressures on a pillar line. 14) Timbering in pillar areas should be adequate but not excessive. Too heavy timbering or cribbing is likely to retard roof falls and throw excessive weight on the pillar line. 15) Experience has shown that when pillar lines have retreated 800 to 1000 ft from the solid, bumps can occur. Because this distance may vary in different seams, impact stresses should be studied for each individual condition. In any event, extra precautions should be taken against bumps in this area. This list of controlling factors may or may not be complete. It probably is not, but it covers most of the problem's significant aspects. The question is whether or not bumping can be eliminated. The answer is that bumping can be minimized and possibly eliminated if these and other established factors are thoughtfully considered and incorporated in the mining and extraction plans. If a mine has already been developed or the pattern set so that little change can be made, then it will be necessary to adjust to the most nearly practicable system that can incorporate the known factors.

Jan 1, 1959

By J. Murray Riddell, George A. Morrison

THIS paper is a companion to the one by George A. Morrison on Mining a Deep Limestone Mine in Ohio.[+] Barberton is 8 miles west of Akron, Ohio, and 23 miles south of Cleveland. The underground mining of limestone at Barberton constitutes the world's deepest limestone mine. The stratigraphy is as follows: 0-20 ft. Loam, clay, sand and gravel. Water bearing. 20-40 ft. Fractured. sandstone. Water bearing. 40-110 ft. Sandstone with interbedded shale, slightly fractured. Water bearing. 110-314 ft. Sandstone with interbedded shale, slightly fractured. Water carrying. 314-2197 ft. Shale with occasional seams of sandstone, which varies in thickness from a few inches to 4 feet. Dry. 2197-2247 ft. Limestone. Dry. 2247-2742 ft. Dolomitic limestone. Dry. 2742-2767 ft. Salt. Dry. 2767- Dolomitic limestone. Dry. All of the strata dip to the southeast, about 0.5 per cent from the horizontal. The top 110 ft. of the crust is water-bearing. The rock strata are naturally fractured to a depth of 314 ft., sufficient to allow the passage of water. In the shaft-sinking operations, a stra was encountered at a depth of 520 ft., and flows of methane gas were pierced at depths of 1350 and 1952 feet. Specifications for the mine plant called for, in part, the sinking of two vertical shafts and a hoisting plant capable of producing at the rate of 300 tons per hour. No. I shaft is 550 ft. west of No. 2 shaft. Each shaft measures 8 by 17 ft. outside of steel. General features of the design (Fig. I) are: Principal set members, 6-in. H-section; connecting angles (studdles), 3/8 by 4 by 4-in. angle irons; spacing of sets, 8 ft. centers; spacing of bearer sets, generally, 160 ft.; bearers, of 12-in. I-beams. Each bearing set featured a concrete ring about the periphery of the shaft, steel to rock, and 8 ft. in height; permanent guides, 6 by 10-in. long-leaf yellow pine, 85 per cent heart. THE SHAFT-SINKING OPERATION The preliminary shaft-sinking work consisted of driving interlocked steel piling about the exterior of the shafts to depths of 35 and 32 ft., respectively, and of such horizontal dimensions as to ultimately permit the pouring of a concrete collar 2 ft. in horizontal thickness. Following the pouring of a shaft collar, a temporary wooden headframe for shaft-sinking purposes was erected. The head-frame, while ordinary, featured: (I) a storage pocket of 300 cu. ft. capacity with truck servicing facilities, and (2) pneumatically operated dump doors, which were actuated by the hoistman, thus caring for the dumping of the "ball-and-chain"

Jan 1, 1944

SEC. 1. The membership of the Institute shall comprise seven classes, namely: 1. Members; 2. Honorary Members; 3. Senior Members; 4. Associates; 5. Junior Members; 6. Rocky Mountain Members; 7. Junior Foreign Affiliates. All shall be equally entitled to the privileges of membership, excepting that no member of any class whose residence shall be outside of the United States of America, except those residing in Mexico and Canada, shall be entitled to vote. SEC. 2. Members: A person to be eligible for election or transfer into the. class of Member must be at least 27 years of age and must have had at least six years' employment in the practice of engineering, mining, geology, metallurgy, or chemistry, during at least three years of which he must have held positions of responsibility in one or more of these fields. This shall not apply to Rocky Mountain members. SEC. 3. Honorary Members: Each candidate for Honorary Membership must be recommended by at least ten Members and must be elected by ballot at a meeting of the Board of Directors by the unanimous vote of the Directors present; provided, however, that the number of Honorary Members shall at no time exceed twenty. Such election shall automatically act as a transfer of such member from any other class of membership to which he may belong. SEC. 4. Senior Members: The Directors may, at the special request of any Member or Associate who has reached the age of seventy years and who has paid dues for thirty years, transfer such Member or Associate to the class of Senior Member; and in special cases may waive either the requirement as to age or as to the number of years for which dues have been paid. SEC. 5. Junior Members: A person to be eligible for election to the class of Junior Member must be qualified -through education or experience to hold a subordinate position in engineering, mining, metallurgical, geological or chemical work. He shall be not more than 33 years of age at the time of election. .SEC. 8. Associates: A person eligible for election or transfer into the class of Associate shall be one, who, in the opinion of the Committee on Admissions and the Board of Directors, is suitable for such election or transfer by reason of his interest in or connection with mining, geology, metallurgy, or chemistry. SEC. 7. Rocky Mountain Members: Membership in a special class of life memberships without annual or other dues and without right to receive the printed literature distributed to other members or the right and privilege of wearing the official badge of technical members, is given to all members of the Rocky Mountain Club at the time of consolidation. These special Rocky Mountain memberships shall be claimable by any member of the Rocky Mountain Club, not already a member of the Institute, availing himself of the privilege within ninety days after mailing of notice to him, by the Secretary of the Institute. SEC. 8. Junior Foreign Affiliate: Upon appropriate action by the Board of Directors and with its approval, members in good standing of any technical society having its headquarters outside of the United States of America, Canada, or Mexico,

Jan 1, 1940

By AIME AIME

FRIEND recently remarked that the career of Scott Turner is characterized by Work and Wild -A Ducks. To these might be added Accomplishment and Persistent Fishing. All of these elements are manifestations of his character. The diversions-hunting and fishing-are in the nature of the proverbial trolley conductor's holiday, for many of Turner's years have been spent in the outdoors, often in distant lands, as in Spitzbergen, where the ducks pictured below were bagged. The election of Scott Turner to the presidency of the Institute marks the culmination of a quarter century of membership, during the last two years of which he has been vice-president. He was born at Lansing, Mich., on July 31, 1880, and received his A.B. at the University of Michigan in 1902, with a B.S. and E.M. at the Michigan College of Mines in 1904. Since then he has been granted two honorary degrees, D.Sc. from the Colorado School of Mines, and D.Eng. from the University of Michigan, but he still prefers to be called "Scott" rather than "Doctor." Government service was not a new experience for Turner when he was appointed Director of the U. S. Bureau of Mines by Secretary Hoover in 1925, for his first employment after graduation was as Field Assistant in the U. S. Geological Survey in Oregon and Idaho. This was followed by work in Tombstone, Ariz.; then his first foreign engagement in 1905-6 as superintendent of the San Pablo Gold Mining Co. in Panama. Various field experiences followed, though there was an interlude in work of a kind that few mining engineers ever experience. This was in technical journalism, for in 1906 he was

Jan 1, 1932

Robert T. Hill, Washington, D. C.: Having studied very minutely the geology of the district referred to by Prof. Branner, I beg to state that his quotation of my classification of the Cretaceous deposits of Arkansas is not the one which I originally gave,* nor is it the one which has since been published and is now generally accepted.? I did not assign ally of the Cretaceous formations of Arkansas to the " middle Cretaceous,"

Jan 1, 1898

By W. A. Backofen, R. L. Fleischer

Single crystal, bicrystal, and polycrystal tensile tests of aluminum at 4.2°K, 77°K, and 300°K have been used to examine the role of grain boundaries in the deformation process. Results indicate that a grain boundary may affect the extent and slope of easy glide. The stage II hardening rate, on the other hand, is independent of the presence or absence of grain boundaries. This conclusion allows the size of the region of multiple slip caused by an incompatible grain boundary to be determined. For the size of bicyystal sample used in this study, multiple slip occurs in about half of the cross section. PREVIOUS studies of the stress-strain characteristics of bicrystals of face-centered-cubic metals have been limited to aluminuml-5 at room temperature. Recent results, however, indicate that the stress-strain curves of single crystals of such metals may be separated into at least three stages6 in which different deformation processes are occurring7 provided testing is done at sufficiently low temperatures.' Since for aluminum a well-defined stage II develops only below room temperature, previous studies have not been able to relate effects of grain boundaries to all of the three stages of deformation. It is therefore to be expected that low-temperature deformation of aluminum single crystals and bicrystals should clarify the effects of grain boundaries on the different processes of deformation. EXPERIMENTAL PROCEDURE Single crystals and bicrystals were grown from the melt by the standard techniqueg with aluminum reported by Alcoa to be 99.993 pct pure. Ridges in the boat were used to guide the grain boundary during growth, assuring that the boundary would bisect the sample.10 The rate of furnace motion during growth was 1.0 cm per hr. During growth zone purification resulted, as evidenced by the ability of the first material to freeze to recrystallize at room temperature following severe deformation. Samples were approximately 4.4 X 6.6 mm in cross section and 103.5 mm in length between grips. Samples were annealed at 635" i 5°C for 40 hr and furnace cooled over a 7-hr period. They were then electropolished in a solution of 5 parts methanol to 1 part perchloric acid at a current density of 15 amp per sq dm for about 30 min at temperatures below 0°C. Tensile testing was performed at 295" (room temperature), 77" (sample in liquid nitrogen), and 4.2"K (sample in liquid helium) on the hard-type machine indicated schematically in Fig. 1. The machine con- sists basically of a tube surrounding a rod; one end of the sample is attached to each member, and the rod is pulled up the tube to extend the sample. The rod is rigidly mounted and is moved vertically by a system described by asinski." The pulling force is measured continuously by an electrical strain gage load cell, and the relative displacement of the tube and rod is also recorded continuously by a soft cantilever beam with electrical strain gages. Maximum stress and strain sensitivities were ±2g per sq mm and * 3-10-5. In all tests the strain rate was approximately 5.10-5 per sec. The thin wires in the tensile apparatus introduce softness, which may be corrected for, however, by measuring load vs displacement with the sample replaced by an elastic member. For loads greater than 15 kg the spring constant is 1.875.106 g per cm. The flexible wires also served to reduce substantially the large shearing forces which may arise in the case of grips having horizontal rigidity.'' As in any gripping system, however, bending moments will arise in the course of deformation by single slip. Engineering stress, s = (load)/(original cross-sectional area), and strain, E = (increase in length)/ (original length), are used for stress-strain curves unless otherwise indicated. Tables list resolved shear stress, T=mo and shear strain ? = dm, where m is the usual Schmid resolved shear stress factor for the primary slip system at the start of deformation. The first group of samples to be described forms an isoaxial set, all of the crystals making up the single crystals or bicrystals having the same tensile axis, the orientation of which is indicated by the cross in Fig. 2. For this orientation the primary slip plane and slip direction make angles of 45 deg with the tensile axis and the Schmid factor m has its maximum possible value of 0.5. Rotations about the tensile axis are indexed by means of an angle 0 between the small-area surface of the samples and the projection of the primary slip direction onto the cross section, as defined in Fig. 3. In single crystals, values of 0 were 0 and 90 deg, while in bicrystals 0 values were (0 deg, 180 deg), (90 deg, 270 deg), and (0 deg, 90 deg) as indicated in Fig. 4.

Jan 1, 1961

By Edmond S. Miksch

The morphology and growth rate of ice grown in supercooled water are markedly affected by convection of the water. A dendritic ice sheet with water flowing past the dendrite tip exhibits deflection of the dendrite spine toward the upstream direction, accelerated growth of secondary spines on the upstream side, and suppression 01" secondaries on the downstream side. Flow causes a thin disk to become corrugated, the corrugations being parallel to the flow. Flow causes an increase in the growth rate of the ice. IF a small seed of ice is placed in slightly supercooled water, it grows initially as a disk with the axis of the disk parallel to the c axis of the ice crystal.' It appears that growth in the c direction is inhibited, while growth occurs with equal facility in all directions in the basal plane. It appears that growth rate as a function of interface temperature is very nearly equal for all directions similarly oriented relative to the c axis. Subsequent to the discoid growth, branching occurs and dendrites develop. The primary dendrite spines grow parallel to the six equivalent a axes of the crystal. Secondary, and in some cases, tertiary spines also grow in these directions. The highly anisotropic: dendritic growth indicates that there must be some finite difference of growth rate for different directions in the basal plane. These differences must be quite small, however, since if they were large, the discoid mode would not occur. Hence, it was expected that the dendrite growth direction could be deflected from the crystallographic direction by perturbation of the thermal field at the dendrite tip. Experiments were done in which perturbation of the thermal field was accomplished by causing the supercooled water to flow past the dendrite tip. The flow direction was perpendicular to the c axis of the crystal, and was perpendicular to the primary spine of the unperturbed crystal. Supercooled water was supplied by a 15 cm cubical copper box, which was refrigerated and insulated so it could cool water to temperatures down to —2oC, and maintain the temperature constant to O.l°C for the duration of a run. A lucite channel of rectangular cross-section, 12 by 24 mm, was mounted horizontally in the box, with one end open so water could flow into it, and the other end leading out through the wall of the box to a length of tubing leading: to an orifice plate 123 cm below. cnunMn s MIKSCH, MemberAiMe, formerly Research Associate, Research Associate, Fig. l(b)—Vertical section of apparatus A horizontal cross-section is shown in Fig. l(a), and a vertical section is shown in Fig. l(b). Means for observing the ice are shown in Fig. l(a). Collimated light passes through the ice sheet and forms an image on the ground glass screen. A lucite box containing dry air was employed to prevent condensation. Ice of the desired orientation was provided by the seed holder shown in Fig. l(b). This device was made of lucite, and had a reservoir in which ice could be frozen by placing it in a freezer. This reservoir com-unicated with the outside only through a narrow gap between two sheets of lucite. The seed holder (after ice had been washed off its exterior) was immersed in the tank of supercooled water, the narrow gap terminating in a slot in the top of the flow channel. Ice growing through a thin water layer in the gap between the two sheets of lucite was oriented so its c axis was perpendicular to the sheets. This orientation is an application of a growth phenomenon2 which causes ice growing along a smooth solid surface in supercooled water to orient itself so its c axis is normal to the surface. After the ice grew into the channel, further orientation was necessary, since the direction of the a axis

Jan 1, 1970

By J. Murray Riddell, George A. Morrison

This paper is a companion to the one by George A. Morrison on Mining a Deep Limestone Mine in Ohio.‡ Barberton is 8 miles west of Akron, Ohio, and 23 miles south of Cleveland. The underground mining of limestone at Bar-berton constitutes the world's deepest limestone mine. The stratigraphy is as follows: 0-20 ft. Loam, clay, sand and gravel. Water bearing. 2-40 ft. Fractured sandstone. Water bearing. 40-110 ft. Sandstone with interbedded shale, slightly fractured. Water bearing. 110-314 ft. Sandstone with interbedded shale, slightly fractured. Water carrying. 314-2197 ft. Shale with occasional seams of sandstone, which varies in thickness from a few inches to 4 feet. Dry. 2197-2247 ft. Limestone. Dry. 2247-2742 ft. Dolomitic limestone. Dry. 2742-2767 ft. Salt. Dry. 2767- Dolomitic limestone. Dry. All of the strata dip to the southeast, about 0.5 per cent from the horizontal. The top 110 ft. of the crust is water-bearing. The rock strata are naturally fractured to a depth of 314 ft., sufficient to allow the passage of water. In the shaft-sinking operations, a stra- turn of oil-bearing sandstone one foot thick was encountered at a depth of 520 ft., and flows of methane gas were pierced at depths of 1350 and 1952 feet. Specifications for the mine plant called for, in part, the sinking of two vertical shafts and a hoisting plant capable of producing at the rate of 300 tons per hour. No. I shaft is 550 ft. west of No. 2 shaft. Each shaft measures 8 by 17 ft. outside of steel. General features of the design (Fig. I) are: Principal set members, 6-in. H-section; connecting angles (studdles), ? by 4 by 4-in. angle irons; spacing of sets. 8 ft. centers; spacing of bearer sets, generally, 160 ft.; bearers, of 12-in. I-beams. Each bearing set featured a concrete ring about the periphery of the shaft, steel to rock, and 8 ft. in height; permanent guides, 6 by 10-in. long-leaf yellow pine, 85 per cent heart. The Shaft-sinking Operation The preliminary shaft-sinking work consisted of driving interlocked steel piling about the exterior of the shafts to depths of 35 and 32 ft., respectively, and of such horizontal dimensions as to ultimately permit the pouring of a concrete collar 2 ft. in horizontal thickness. Following the pouring of a shaft collar, a temporary wooden headframe for shaft-sinking purposes was erected. The head-frame, while ordinary, featured: (1) a storage pocket of 300 cu. ft, capacity with truck servicing facilities, and (2) pneu matically operated dump doors, which mere actuated by the hoistman, thus caring

Jan 1, 1946

By K. R. Waugh, Barbara S. Brown, D. W. James

AN electronic data-processing system is described which permits rapid, accurate, low-cost processing of strain-dependent damping data utilizing equipment normally available within the service facilities of most large laboratories. On analyzing the record of a stress-dependent damping test, the operator usually measures the double amplitudes at several points on the decay curve. The logarithmic decrement is then calculated for decay between consecutive amplitudes. These values of 6 are plotted against the corresponding maximum surface shear stress, T, which is proportional to the average of the two amplitudes between which is calculated: where d is the specimen diameter. The period of the vibration is not necessarily constant during decay; thus, each cycle must be counted. A decay curve may extend to, perhaps, 1000 cycles, and at least two curves are always obtained for each specimen or set of conditions. It can, therefore, be seen that manual analysis of decay curves is both tedious and costly in terms of man-hours. Furthermore, the resolution of the record is often such that accurate measurement of amplitude is extremely dif-

Jan 1, 1969

By William M. Shepard

The Tintic mining districts of central Utah com- prise one of the major silver-lead producing areas in the United States. Ore valued at nearly $450 million has been produced from these districts since the initial discoveries, in 1869, of veins cutting the Silver City monzonite stock. Subsequent production from the famous manto-type "ore runs", which characterize the Main Tintic district, was followed during the past 40 years by discovery of the blind orebodies of the East Tintic district, including the famous Tintic Standard mine and the most recent discovery, the Burgin mine, currently being brought to full production by Kennecott Copper. The occurrence of blind orebodies of exceptional size and grade in both the Main and East Tintic districts has made this area a field laboratory of major importance for the study of geochemical dispersion halos and alteration features associated with known ore, and has led to the discovery of additional concealed orebodies. The larger share of the basic data-gathering and interpretation has been done by members of the U.S. Geological Survey who have been studying the Tintic mining areas since before the turn of the century. These studies have been supplemented and expanded by the geological staffs of the local operating mining companies, by exploration geologists and by students.

Jan 4, 1966

By Robert Steinitz

Soft iron parts for magnetic applications, particularly pole shoes, constitute a major portion of the ferrous products of powder metallurgy. The residual pores in pressed and sintered parts reduce values such as the magnetic permeability but service experience extended over a number of years has proven beyond doubt that in many instances the lower density of powder parts is not prohibitive to their use as replacement of machined magnetic parts. The magnetic requirements for pole shoes, particularly the permeability, vary within wide limits, especially with the relative size of the air gap in the finished assembly. The overill permeability of an assembly, is given by the formula where is the permeability of the core material, I the total length of the magnetic path, and a the length of the air gap. Fig I shows the variation of the overall permeability with the permeability of the core material, calculated according to Eq I for an air gap of I pct of the total length of the magnetic circuit. It is readily recognized that to use core materials hav- A

Jan 1, 1949

AT the Tulsa meeting of the A. P. I., the following reso-lutions, expressive of the policy of that organization, were among those adopted: RESOLVED, That we endorse the conclusion of the Federal Oil Conservation Board in its report of September, 1926, that the prevention of the waste of gas incident to the pro-duction of oil is of paramount importance in the conserva-tion and economical production of oil, and the president of the Institute is requested to appoint a committee of seven to devise and suggest to this board, or the executive com-mittee, such measures as will enable the industry, while continuing to meet the consumption requirements for pe-troleum and its products, to conserve in its natural state such reserves of petroleum as may not then be required for consumption. RESOLVED, That the president of the Institute appoint a committee of seven to formulate and recommend to this board or its executive committee, at the earliest practicable date, a program of legislation; Federal and State, to be advocated by the Institute giving sanction and effect to agreements by oil producers for the curtailment of produc-tion in pools where and during periods when there is over-production, having for their purpose the economical and orderly production of oil.

Jan 1, 1927

By P. A. Beck, S. Kohara, M. N. Parthasarathi

IT has been shown1,3 that many observed phenomena related to annealing textures in f.c.c. metals can be adequately accounted for, at least in a qualitative way, by considering the orientation dependence of the boundary mobility, without any hypotheses concerning preferred orientation of nuclei. It was noted1 that this approach is particularly successful in the common cases of primary recrystallization in highly cold-worked polycrys-talline metals, where nuclei occur in great abundance, and that in the other extreme case, where the number of nuclei is very limited, or even only a single crystal is grown, the orientation dependence of boundary mobility has only a small effect, or none at all, on the orientations resulting from annealing. Recently Dunn described examples3-6 where observed secondary recrystallization textures apparently cannot be accounted for on the basis of oriented growth alone, but also require oriented nuclei, or at least the absence of nuclei in certain orientation ranges. In general, the great difficulty in correlating the preferred orientation of recrystallized grains with that of nuclei is inherent in the fact that nuclei are by nature very small, and that they are usually identifiable as "nuclei" only after growth, i.e., after they have already been subject to growth selectivity. An investigation was carried out by Liebmann and Lücke,' and also a very similar one by Graham and Cahn,' to obtain quantitative information on the orientation depend- ence of boundary migration rates in the recrystallization of slightly deformed aluminum single-crystal rods or plates, in which artificially nucleated recrystallized grains of predetermined orientation were grown. Liebmann and Lücke foupd maximum boundary mobility for boundaries across which the misorientation corresponded to a rotation of 40 deg around a common [Ill] axis, in accordance with earlier conclusions.9,1 Also, they confirmed that such an orientation relationship predominates among crystals growing into slightly extended single crystals from presumably random artificial nuclei. On the other hand, Graham and Cahn found no preferred orientation among crystals grown in a similar manner. It is not as yet known how these observations may be reconciled with each other. The view has been expressed in various papers5'10,21 that selective growth based on the orientation dependence of boundary mobility is not in itself sufficient to account for the formation of sharp re-crystallization textures, such as those often observed in highly deformed polycrystalline metals after annealing. The present work was undertaken to ascertain whether or not it is possible to obtain a sharp re-crystallization texture in a case where random nuclei are assuredly present in large numbers. It was previously found1' that high-purity aluminum crystals rolled 80 pct on the (110) plane in the [1T2] direction, when suitable precautions are taken, may be annealed for periods of about 1000 sec at 350°C without recrystallization. It was also found that the reluctance to recrystallize in this case is due to the scarcity of material in sufficiently deviating orientations to serve as nuclei. By using such a matrix,

Jan 1, 1959

The Year Book of the Institute is mailed with this Bulletin. Its membership lists, both alphabetic and geographic, are corrected to Jan. 1, 1918, but its list of officers is revised inn accordance with the elections in February, 1918. The amendment to the Constitution, relating, to qualifications for membership, adopted at the same time, is also inserted in its proper place. We would call attention to the Honor Roll, heading the list of membership. This includes the names of those whom we know (in February, 1918) to be on active military duty, as well as those who are rendering emergency service to the Government in other branches. We are aware that the list is not complete, and shall be grateful for information as to any omissions or corrections. Because of the rapid movement of the military members, their addresses have been omitted from the alphabetic list. Mail addressed to such members, and sent to the office of the Institute, will be forwarded to the best of our information at the time.

Jan 3, 1918

By H. F. Silliman, Daniel R. Hull, John R. Freeman

IN the normal operation of a brass-rolling mill, sheet and strip has, for the most part, been finished in comparatively thin gauges, involving a substantial amount of coldwork and a considerable number of anneals. This condition has been disturbed by the prep0nderance of cartridge brass, which is not rolled to thin gauges, and particularly by brass for artillery cartridge cases, on which the mill may finish its work at a thickness between 0.400 and 0.900 in. Obviously, the amount of rolling and the number of anneals to which such a product can be subjected are small compared with strip that is carried to a thickness of a few hundredths of an inch. As a result, critical examination into the internal condition of metal has been made on an extensive scale at a stage of manufacture that would not, in normal times, have been chosen for complete inspection. Under these conditions, a type of defect has been recognized that is not seen at thinner gauges. It might be more accurate to call it the appearance of a defect, since it refers to an apparently laminated, discontinuous structure, which, in fact, does not exist as such, and disappears after suitable treatment. For this reason it has been called a phantom lamination, which the authors consider an appropriate term. It is the purpose of this paper to describe the phenomenon and the conditions of its occurrence and, at least tentatively, to discuss its nature and cause. Great numbers of phantoms may be found in 2: 1 brass, either hot-rolled or cold-rolled. They are also found in 70-30 brass, sometimes when hot-rolled and generally when cold-rolled. It is not believed that phantoms are confined to these alloys but this paper is limited to them for the purpose of description. HOT-ROLLED 2:I BRASS For illustration, therefore, a typical cake of hot-rolled 2: 1 brass has been chosen. This was rolled to a slab 7/8 in. thick, from a casting 5 in. thick by 24 in. wide by 18 in. high, which was believed to have been sound. After hot-rolling and cooling, the slab was sheared and a portion of such a shear cut is shown in Fig. 1. It would be difficult to convince anyone viewing this specimen that the metal was not unsound. The impression would be confirmed by the appearance of a tensile break, as shown in Fig. 2. This is an ordinary tensile-test piece from metal just described. Although there was nothing in its tensile strength or elongation that suggested unsoundness, it appeared run through with pipes and laminations. To question the reality of such a condition would imply questioning the obvious. But, considering the history of the metal, it w0uld be difficult to believe that it could be so bad as it appeared. It seemed reasonable, though, that if the defects were what they appeared to be, they could be traced back from the sheared or broken face.

Jan 1, 1945

THERE are three chief production zones of tungsten ore in China. In the Province of Kiangsi mines are located at Kanchow, East River, and West River. Their combined production is understood to amount to 300 to 350 tons of ore per month, and their original exportation is made through the port of Kiukiang, largely to Shanghai. The second zone is in Kwangtung Province, the mines there being at Tayulin. Produc-tion reaches about 200 tons per month and cargo is gen-erally exported through the port of Hong Kong. In the Province of Hunan approximately 25 tons of ore are produced monthly in the mines at Ton-on. Tungsten ore from Kiangsi and Kwangtung Prov-inces is generally about 70 per cent WO, (tungstic acid), while that from Hunan is of lower quality, run-ning about 65 per cent WO3. Kiangsi ore is received from the mines in 100-1b. and Hunan in 224-lb. gunny sacks. No repacking is done except as it is made neces-sary by the condition of the sacks. Kiangsi Province contains the Chinese districts pro-ducing the largest amount of salable wolframite or tungsten. Many districts west and south of Kiangsi have been found to have wolframite deposits.-Com-merce Reports.

Jan 1, 1928

Discussion of the paper of C. W. Goodale and J. H. Klepinger, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 50, August, 1913, pp. 1935 to 2010. PROF. JOSEPH W. RICHARDS, South Bethlehem, Pa.:-Mr. Chairman, I would like to call attention to one valuable feature of the paper which may interest some: I have worked a good deal with the Pitot tube, and have always had difficulty with what is called the static end of that apparatus, so much so that I became almost hopeless of securing good results with it. I find here, however, what is stated to be a perfectly satisfactory static end for the Pitot tube, satis factory under probably all conditions. I congratulate Mr. Klepinger on the design of that tube and the consequent improvement he has made in the technical measurement of the volumes of gases. I would also like to ask if the total volume coming out of the chimney per day could not be computed by chemical analyses of the SO and SO2 in the gases, and calculation on the basis of the known weight of.. sulphur going out in a day; so that the Pitot tube measurements . could be checked by a method independent of measurements in the flues. J. H. KLEPINGER :-I think the volume of gases could be determined in that way. Those of a chemical turn of mind would go. about it so, but I am not enough of a chemist to follow that method, and consequently I always look at the mechanical way to obtain the results.

Jan 11, 1913

By Robert Steinitz

SOFT iron parts for magnetic applications, particularly pole shoes, constitute a major portion of the ferrous products of powder metallurgy. The residual pores in pressed and sintered parts reduce values such as the magnetic permeability but service experience extended over a number [ ] of years has proven beyond doubt that in many instances the lower density of powder parts is not prohibitive to their use m replacement of machined magnetic parts The. magnetic requirements for pole shoes particularly the permeability, vary within wide limits, especially with the relative size of the air gap in the finished assembly. The overall permeability of an assembly, µ, is given by the formula [ ] where µm is the permeability of the core material, l the total length of the magnetic path, and a the length of the air gap. Fig 1 shows the variation of the overall permeability with the permeability of the core material, calculated according to Eq I for an air gap of 1 pct of the total length of the magnetic circuit. It is readily recognized that to use core materials hav-

Jan 1, 1948

By Arthur Notman

THE matters I had intended to present to you ap-peared in the March 12 issue of Engineering and Mining Journal over the signature of George J. Young, so that although I should like to talk to you for about three hours on this subject, unfortunately it has all been done before. The subject originally sug-gested to me was the trend in mining methods. You will find that fully set forth much more clearly than I could hope to do, in Mr. Young's article, so that I shall confine my attention to a few points of interest in specific cases. You are undoubtedly familiar with the problem that was presented to the Miami Copper Co. when they had exhausted their so-called high-grade orebody. They had what appeared to be a large tonnage of material which their preliminary development work and such drilling as was done indicated contained one per cent copper or a-little over, and how to mine that profitably by underground methods was the question. It was somewhat complicated by the fact that the nature of the ground made them doubtful of their ability to cave it successfully. It was unquestionably harder ground than that of the more highly mineralized sections of the Miami and Inspiration- ore zone which had been mined. However, they had kept very accurate and complete records of past accomplishments and knew what they had to work with and what modifications with respect to costs would be necessary in order to solve this problem. Under the old method of working, they were extract-ing about 71/2 tons per man employed in the mining department; that is to say all labor, direct and indirect required to put the ore in the mill bins, and this, with the grade of ore which they had, resulted in a satis-factory financial outcome. Under their modified method now in use, they have raised that output per man to 29 tons per man shift. That is almost four times what they were doing with the old method.

Jan 4, 1927

By W. A. Vine

When a hole is made in a stressed solid, such as rock pierced by mine openings, equilibrium of the solid is destroyed. To restablish that equilibrium the stress condition in the rock surrounding the opening becomes rearranged. This rearrangement may or may not develop local stresses in the vicinity of the opening which exceed the elastic strength of the rock. Since stability of the opening depends, therefore, on the strength of the naturally occurring rock surrounding the opening, this rock is an engineering material of construction, and all rock affected by the associated opening or system of openings may be considered a structure. The term invert is chosen to describe the formation of the structure built from the inside, as it were, and a consequence of mining rather than an entity built for a purpose. By definition, an invert structure is formed when openings are made underground and is com- posed of that material on the solid side of a rock-air interface wherein the stress condition is affected by the associated opening or system of openings. The shape of an invert structure is never clearly defined; the skin of the structure may be mapped, and even described, but the boundary of the structure within the solid rock mass must be arbitrarily set.

Nov 1, 1955