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Elected Died 1895 *ABBOTT, AI ATTHUR 1908 1882 *ABBOTT, ARTHUR V 1906 1905 * ABE, MASAYOSHI 1909 1903 * ADAMS, CHARLES C. 1905 1905 * ADAMS, WILLAMS 1909 1903 * ADAMS, W. EDWARDS 1910 1884 *ADDY, MATTHEW 1896 1889 * AKERS, WILLIAMS 1906 1894 *ALLEN R B 1896 1905 * ALLEN, R. SCOTT 1906 1874 *AMIOT, H 1892 1886 *AMSLER, CARL 1894 1895 *ÅNGSTROM, CARL 1901 1887 * ARCHBALD, JAMES 1910 1900 * ARLETT, GEORGE H 1906 1895 *ARMSTRONG, JOHN F 1898 1882 *ARNOLDS, HUGO 1886 1875 *ASHBURNER, CHARLES A 1889 1872 *ASIIBURNER, WILLIAM 1887 1883 *ATKINS, C M , JR 1885 1905 * AUSTEN, PETER T 1907

Jan 1, 1917

By L. C. Aycock, J. Hunter, P. M. Lyons

In view of the unfavorable discovery trend that has set in during the past few years, it seems permissible to infer that the large, more easily found crude reserves in Louisiana are now known. Without doubt, many new producing areas will be located, but in the light of development during the past few years the majority of new areas probably will be found at greater depths and from relatively poorer sands. f Although sufficient reserves exist in Louisiana to last at the present rate of production for a considerable period, additional reserves must be found in more intensive development of the presently known structures. In order to ensure the greatest ultimate recovery from such structures, the most advanced technical methods must be employed in their exploitation. Wherever possible, cycling and repressuring plants should be installed. 'here are presently in Louisiana, especially in south Louisiana, a great many fields that contain gas-condensate reservoirs. These reservoirs cannot be produced for their liquid hydrocarbon content under present conditions without wasting an enormous quantity of gas and creating underground waste. Although some of these reservoirs are being produced, such production must be considered in the nature of a salvage operation rather than as a sound economic proposition. Such reservoirs, however, can become profitable ven- tures through the use of cycling and repressuring plants. Cycling operations now operating in Louisiana have increased the ultimate recovery from gas-condensate reservoirs anywhere from 10 to 30 per cent. Cycling operations will also provide a considerable reserve of gas, without which Louisiana cannot hope to develop any program of industrialization. During the past year, Louisiana attained the rank of third among the oil-producing states of this country. With a proper program of exploitation and development, and with emphasis on conservation, Louisiana can maintain this position for a great many years. Production On Dec. 31, 1943, oil and/or gas were being. produced in 52 parishes, or 81 per cent of all the parishes in the state. Thirty-three of the parishes produced oil and gas, 14 produced oil, and 5 produced solely gas. Tensas Parish in north Louisiana and Assumption Parish in south Louisiana formerly contained no producing fields but during 1943 joined the ranks of the producing parishes. Twenty-three new fields, including one rediscovery, were found during 1943-—a rate of discovery almost comparable to that of the preceding year. Eleven of these new discoveries were either gas or gas-condensate fields. Thus, the trend of development in finding new reserves was also comparable to that of 1942. Many reasons of considerable merit have been advanced to account for the discouraging lack of crude-oil reserves found during the past year. None are, however, completely satisfactory.

Jan 1, 1944

By J. Hunter, P. M. Lyons, L. C. Aycock

In view of the unfavorable discovery trend that has set in during the past few years, it seems permissible to infer that the large, more easily found crude reserves in Louisiana are now known. Without doubt, many new producing areas will be located, but in the light of development during the past few years the majority of new areas probably will be found at greater depths and from relatively poorer sands. f Although sufficient reserves exist in Louisiana to last at the present rate of production for a considerable period, additional reserves must be found in more intensive development of the presently known structures. In order to ensure the greatest ultimate recovery from such structures, the most advanced technical methods must be employed in their exploitation. Wherever possible, cycling and repressuring plants should be installed. 'here are presently in Louisiana, especially in south Louisiana, a great many fields that contain gas-condensate reservoirs. These reservoirs cannot be produced for their liquid hydrocarbon content under present conditions without wasting an enormous quantity of gas and creating underground waste. Although some of these reservoirs are being produced, such production must be considered in the nature of a salvage operation rather than as a sound economic proposition. Such reservoirs, however, can become profitable ven- tures through the use of cycling and repressuring plants. Cycling operations now operating in Louisiana have increased the ultimate recovery from gas-condensate reservoirs anywhere from 10 to 30 per cent. Cycling operations will also provide a considerable reserve of gas, without which Louisiana cannot hope to develop any program of industrialization. During the past year, Louisiana attained the rank of third among the oil-producing states of this country. With a proper program of exploitation and development, and with emphasis on conservation, Louisiana can maintain this position for a great many years. Production On Dec. 31, 1943, oil and/or gas were being. produced in 52 parishes, or 81 per cent of all the parishes in the state. Thirty-three of the parishes produced oil and gas, 14 produced oil, and 5 produced solely gas. Tensas Parish in north Louisiana and Assumption Parish in south Louisiana formerly contained no producing fields but during 1943 joined the ranks of the producing parishes. Twenty-three new fields, including one rediscovery, were found during 1943-—a rate of discovery almost comparable to that of the preceding year. Eleven of these new discoveries were either gas or gas-condensate fields. Thus, the trend of development in finding new reserves was also comparable to that of 1942. Many reasons of considerable merit have been advanced to account for the discouraging lack of crude-oil reserves found during the past year. None are, however, completely satisfactory.

Jan 1, 1944

By Leo Wolrnan

IN the relations that exist between capital and labor in this country, there is a bright as well as a dark side. After many years of distressing conditions of labor and a plentiful supply of propaganda, it is doubtful that the doctrine of the class struggle, however defined and stated, has been embraced by any influential and numerous elements of our population. Extreme and uncivilized methods of conflict, whether they be the labor spy as used by the employer or the sit-down strike by organized, labor, have come to be abandoned as the result of the pressure of sober and distinterested public opinion. Unwise terms of our law of trade unions and the unbridled zeal of its administrators show some slight signs of being revised in the light of 'experience and the protests of the law's own beneficiaries. At the point where labor policy touches economic conditions, the two powerful factions in the American labor movement appear to look with a less friendly eye on the bewildering succession of economic experiments and to have a deep nostalgia for a simpler and more prosperous economy.

Jan 1, 1938

By Harry Warren

THE Geology Department of the. University of British Columbia has undertaken the task of examining the ores from as many as possible of the gold mines of British Columbia. The object of this work is two-fold. First, it is known that detailed mineralographic studies are useful in attacking ore-dressing problems, and these studies are intended to be helpful to mill operators. Second, it is hoped that mineralogical and mineralographical studies will prove useful adjuncts to those of lithology and structure in throwing more light on problems related to the origin of the deposits. The paper shows that gold, for all practical purposes, is not present in an ore mineral in solid solution nor as a eutectic with any mineral; if the latter were true the gold particles would be distributed equally throughout that mineral. The gold occurs either as native gold or as a gold-silver telluride and is not distributed regularly through any mineral or minerals: The relationship between the gold or gold-bearing telluride and the associated minerals affords a means of classification that is not only simple but also appears to be directly related to the geological nature of the deposit, which may be summarized as follows: 1. Disseminated Gold Type. ;-Precious minerals in extremely small grains, which are distributed without regard to grain size, fractures or grain boundaries: (1) Hedley variety-gold in native form; (2) Surf Point variety-gold predominantly as telluride. 2. Veining Gold Type.-Precious minerals in grains of various sizes, which occur mainly along fractures and grain boundaries: (1) Cariboo gold quartz-gold in native form. (2) Waneta variety-gold as telluride.

Jan 1, 1937

By D. E. Light, J. Y. Somnay

The use of alkyl acid phosphates and their alkali salts as collectors for the uranium minerals brannerite and uranothorite was investigated. In particular a detailed flotation study was carried out using isooctyl acid phosphate as a promoter. Tests were conducted on an Elliot Lake ore analyzing 0.11% U 3 O 8, chiefly as brannerite, and approximately 9% pyrite. Pyrite was floated with conventional reagents; the flotation of brannerite from the sulfide tails was studied to determine the optimum pH and pulp density to employ with isooctyl phosphate. 4 uranium recovery of over 90% was possible with a selectivity index of 8.95 when these tails were floated at 17% solids and a pH of 1.7. The effect of various modifying agents was also investigated. Aluminum sulfate, lactic acid and sodium silicate improved the selectivity of collection yielding selectivity indices of 9.5 to 11.5. Ferric chloride was found to be a depressant for brannerite. A Bancroft ore which analyzed 0.13% U308, and contained uranothorite was also amenable to flotation using isooctyl acid phosphate. The composite uranium concentrate obtained assayed 0.41% U308 at a recovery of 95.3% and a ratio of concentration of 3.24. Previous investigations1,2 on the flotation of brannerite, pitchblende, uraninite and/or uranothorite from various Canadian ores showed that fatty acids, including oleic acid and tall oils, petroleum sulfo-nates and alkyl acid phosphates, were suitable collectors for these uranium minerals. Additional work carried out by the Mines Branch in Ottawa on brannerite ores from the Elliot Lake area3 used the tall oil Acintol FA-1, or FA-2, as a collector. A recovery of 92% of the uranium in a concentrate which contained about 55% of the weight and assayed 0.2% U3O8 was obtained from a feed of 0.1% U308 in this latter instance. Eigeles et a1.4 carried out flotation on pitchblende ores and found that the most promising results were obtained with alkyl acid phosphates and their alkali salts as collectors. Within the homologous series of alkyl phosphates, the best flotation characteristics were displayed by isooctyl phosphates. Further, isooctyl phosphate derivatives were much less sensitive to hardness forming salts than oleic acid, enabling all flotation tests to be made with tap water. This paper describes tests employing alkyl acid phosphates for the flotation of ores containing brannerite and uranothorite. The flotation work described herein was conducted in conjunction with the development of a leaching process for Elliot Lake, Ontario, brannerite ores. In this process pyrite in the ore was concentrated by flotation and roasted, providing sulfur dioxide which was used to produce sulfuric acid in situ in a liquid-solid extraction process. A 40% conversion to sulfuric acid was indicated at a leaching temperature of 80°C; this resulted in the extraction of 93% of the total uranium after a contact period of 6 hr. A rotary kiln was used as a leaching vessel. Preconcentration by flotation was studied in conjunction with the above process to reduce the bulk of solids for leaching and, consequently, capital expenditure. The materials and methods used in this study will be described initially. Then the results will be presented in two sections, the first dealing with the brannerite ore, and the second with the uranothorite. Finally an economic analysis of the results on the brannerite material will be made. MATERIALS AND METHODS The two ore samples examined were from uranium-producing mines. One was a brannerite ore, a uraniferous quartz pebble conglomerate from the Elliot Lake area, which contained 0.11% U3O8, 4.3% S and 4.5% total Fe. Mineralogical studies of similar samples indicated the presence of quartz, microcline, sericite, pyrite and minor quantities of rutile, pyrrho-tite and zircon. The other ore was from a biotite-rich pegmatite in the Bancroft area; feldspar, quartz and biotite formed the major gangue components. Uranothorite was the principal uranium mineral; the head assay was 0.13% U 3 O 8. Preparation of Feed: The ores were crushed to —10

Jan 1, 1963

By S. Webster, M. Karmis, C. Haycocks

Mining any seam can seriously affect subsequent operations in coal seams both above and below the one being mined. The effect is often detrimental to the recovery, cost and safety of mining the subsequent seams. This paper describes the ground control mechanisms involved in mining through a passive subsided zone or all actively subsiding trough. Data were extracted from case studies, primarily from the Appalachia region, for construction of empirical models to predict interaction problems that can occur in overlying seams. Inner-burden thickness, innerburden lithology, percentage extraction, lower seam height, time and overburden were analyzed to determine their effect on upper seam damage. Magnitude of upper seam subsidence was incorporated, together with a broad classification of rock types, to predict the type and range of damage that can occur in the upper seam. Results are summarized in graphically and nomogram form for use in. engineering design.

Jan 1, 1984

By W. J. Taylor

It is, perhaps, more important to put on record the particulars of experiments that are derided failures than those that are successful, as those of the latter class are certain to live, while the former may be lost sight of in a short time, and repeated by others. TO this end, I propose to give the particulars of a straight or no-bosh furnace just tried at the Chester (New Jersey) works, which was such a decided failure as to leave no doubt of the plan being wrong, and determining the necessity of a bosh of some kind, as of old. Some experiences during the past year led me to suppose that the bosh or belly of a furnace was unnecessary, and that the contraction of the walls toward the bottom for the stock to wedge in, in its descent, facilitated dirty walls and scaffolding; hence, irregularity and high fuel. I concluded, however, that a very shallow bosh for a skew-back support to the stock would be necessary, and that the proper place for this was in the tuyere-section, beginning just below the tuyeres and ending just above them, where there is nothing in the solid state but fuel, which is consuming, and no slipping or travel of stock takes place. The cubical capacity of a furnace of this design would necessarily be much less than in the old style, unless it was made very much higher. But I assumed that the loss of room for reduction could be overcome by making the size of the ore and stone charged much smaller, so that the gases would act more quickly. The next point was, what should be the size of the shaft, crucible, tuyere-circle, and tunnel-head for a given quantity of air? My first design was 12 feet diameter of shaft for 7000 feet of air, with a 9-foot crucible and 8-foot toyere-circle. This I soon reduced to 8-foot shaft diameter, which I concluded was large enongh for economical work, if regular travel of the stock on the walls could be maintained. I consulted with a number of experienced furnacemen and furnace-engineers, and the plan was well thought of by many of them; and, as I had also some offers of financial aid from them toward the risk of trying the experiment, my firm concluded

Jan 1, 1885

By G. B. Gould, F. M. Gibson

IN DECEMBER, 1934, the joint Committee on Fuel Values, of the American Institute of Minim and Metallurgical Engineers and the American Society of Mechanical Engineers, submitted a preliminary report, which briefly stated its conclusion that it was not possible to devise any formula for the valuation of coal, based upon the various physical and chemical properties, that would be generally applicable. That report also listed those chemical and physical properties of coal that are generally recognized to have some effect on its use in steam plants, and those physical characteristics of steam plants which affect, in one way or another the relative importance of the properties of coal used in them. Since then, the Committee has considered and discussed in greater detail the interrelationship of the properties of coal and plant characteristics. The conclusions of the Committee are summarized below, with certain recommendations regarding engineering procedure, which will promote the collection of more easily correlated observations with respect to this subject, and thus advance more rapidly the accumulation of data capable of general application.

Jan 1, 1936

By M. R. Louthan, C. L. Angerman

In polycrystalline Zircaloy-2 the orientation of zirconium hydride precipitates is influenced by an applied stress during hydride precipitation; hydride platelets are oriented nearly parallel to a compres-sive stress and perpendicular to a tensile tress. 1,2 A similar effect has been observed in the Ti-H system, where precipitation of the low-density hydride platelets occurred on habit planes made energetically favorable by the application of stress. 3 Recently, stress activation of hydride habit planes in zirconium and Zircaloy-4 was also demonstrated. The hydrides precipitated on {101l), {112l} and (2131) planes in both zirconium and Zircaloy-4; however, no platelets were found near the prism-plane positions in the Zircaloy-4 samples. Investigations at the Savannah River Laboratory, using polycrystalline Zirc_aloy-2 samples, have confirmed the (101l) and (1121) habit planes but also showed that the prism planes were active hydride habit planes. Using single-surface stereographic analysis and back-reflection Laue techniques, most of the previously reported habit planes for a zirconium were observed.4"1 and one additional plane, the (1013) plane, was noted, Table I. All the habit planes observed had the form (101l) or { 112l) indicating that these planes are the habit planes for hydride precipitation in poly-crystalline Zircaloy-2. The specimens used in these studies were cut from large-grained weld areas of seam-welded tubing and were hydrided in either a static steam autoclave at 400°C and 1500 psig or in a modified Sieverts apparatus at 400°C.

Jan 1, 1967

By N. S. Wagner

The production of lightweight aggregates in Oregon is a new industry, and, like all new enterprises, it is suffering from growing pains characterized by numerous, small operations some of which flourish for a short time and then cease altogether. Normally all industrial mineral products are produced in a highly competitive atmosphere. At the present time this condition does not exist to a very marked degree in the state because as yet producers have not saturated the constantly expanding market. This paper has been prepared with the intention of outlining very briefly the current status of the various products now being used as lightweight aggregates in Oregon. The present picture will surely change, perhaps quite radically within even a short space of time.

Jan 1, 1949

By Ralph H. Sweetser

MUCH progress in -blast-furnace construction and in the manufacture of firebrick for furnace linings has been made since the publication of Bulletin 130 of the U. S. Bureau of Mines on "Blast-Furnace Breakouts, Explosions and Slips, and Methods of Prevention," by F. H. Willcox in 1917. At the time of publishing this report comparatively little information was available to blast-furnace men as to the fundamental facts relating to the character of blast-furnace refractories. Some of the accepted theories of only a few years ago have been completely reversed. The mortality of blast-furnace linings used to be so great that nearly every furnace plant had one or more complete linings in the brick shed ready for use in case of a lining suddenly "going out"; it was generally accepted that a furnace could not "keep her lines" more than two or three years at best, and often a hot spot in the shell would develop, or a breakout occur in the hearth or bosh within a year or two after blowing in on a new lining. In some respects these frequent relinings were not so detrimental as to he a complete loss because they afforded opportunities to take advantage of advances in blast-furnace practice. At present the cost of relining has greatly increased, but the life of a lining has also increased. Anything less than five years on a lining is now considered a short blast.

Jan 1, 1932

Tooele Flue-type Cottrell Treater Discussion of the-paper of A. B. YOUNG, to be presented at the New York meeting, February, 1921, and printed to accompany MINING AND METALLURGY No. 162, June, 1920. HARRY V. WELCH,* Los Angeles, Calif. (written discussion).-The basic requirement in the electrostatic process of electrical precipitation is that gases containing solid particles in suspension are forced to pass through an electrical field consisting of an insulated high-potential wire, or other type of discharge member, and a grounded plate, or other, type .of collecting member. Commercial. operation and efficiency of precipitation are secured by electrical and structural arrangements to provide the maximum value of the variable factors modifying the degree of precipitation. That is to say: 1. A unidirectional flow, of high-potential current is vastly more effective in precipitation than a high potential alternating-current flow.

Jan 2, 1921

DISCUSSION, G. Derge and D. J. Girardi presiding N. A. Gokcen (Michigan College of Mining and Technology, Houghton, Mich.)—While the authors present very interesting results on the effect of sulphur upon the solubility of oxygen, they have not established convincingly the lines of two-fold saturation (the valleys in Fig. 2) and the ternary eutectic point. Their contention that sample S-7, upon melting at

Jan 1, 1954

By J. W. Onuscheck

The oxygen-fuel oil burner lance is a very useful tool at the Monessen B.O.F. It increases the overall flexibility of the operation. An additional 15,000 to 20,000 ingot tons can be produced at a given hot metal supply. It helps overcome sporadic drops in hot metal thermal values and/or supply. It results in increased yield, in particular, on high carbon heats where much yield was lost on reblow triggered slag reactions. The burner has also been adopted as a standard tool to aid burning in new vessel linings. Overall, steelmaking performance has improved with the use of standard preheat practice. Scrap charges up to 50 percent have been used routinely in times of extreme hot metal shortages, but the performance is weak in some categories. Development of a single step oxy-oil process is in progress. In this process, scrap and hot metal are charged as in the normal B.O.F. practice, but fuel oil is fired with the refining oxygen.

Jan 1, 1972

By E. M. Bennett

HISTORY In 1923 John Campbell Miles discovered the Mount Isa deposit after finding and submitting for assay some “unusual and heavy rocks”. Six months after submission he received the assays of his original samples which indicated high lead-silver values. The deposit area was isolated and unknown geographically and not served by even a rough country road. The isolation of Mount Isa coupled with the depression years had a strong influence on the rate of development of the area. These two factors resulted in a slow amalgamation of the early individually held leases and the lack of ready finance to begin serious mining of the deposit. Initially, surface lead-silver-zinc mineralisation was proved and diamond drilling to shallow depths showed the presence of a viable orebody. Limited underground development work was initiated and open cutting associated with glory holing commenced. Due to the metallurgical problems associated with the ore and due also to unsuspected change in metallurgical conditions as the ore deepened into what is known today as the transition zone, major problems of finance were recurring at frequent intervals. Despite low metal prices the development of the mine continued due to continuing infusion of capital. During the 1939-45 war years a surplus of lead was being produced in Australia, but a grave shortage of copper was apparent. About this time copper ore had been found to the hanging wall of the then known major lead orebodies. At the request of the Australian Government, lead production ceased and copper production commenced.

Jan 1, 1970

By Walter J. Johnson

The coals in northern Wyoming and Montana are free-burning and non-caking and range from lignite to bituminous C in rank. Strip and underground mining are employed to supply railroad, utility, industrial, and domestic fuel. The market area includes Iowa, Nebraska, Minnesota, North and South Dakotas, Wyoming, Montana, the Pacific Northwest, and western Canada.

Jan 12, 1953

By Helmut Thielsch

MeTallographic specimens whose surfaces are to be investigated are too thick to allow either light or electrons to pass through them for microexamination by transmission. This difficulty is overcome with optical microscopes by illuminating the surface through the objective lens. For electron microscopes best results are obtained by preparing thin replicas of the surface of the specimen, placing them in the microscope and passing the electron beam through them. Since electron microscopes represent a rather recent invention, they have found little application as compared with optical microscopes. This is true because, aside from the cost of new equipment and development of new techniques, some of the older replica methods necessitated the destruction of the surface from which a thin transparent replica was obtained. In other processes in which the surface is preserved, either too tedious a procedure is required, unsuited to "mass-production" requirements of industrial laboratories, or replicas of insufficient contrast and sharpness are produced. In general, investigations with the electron microscope involve five steps: (I) polishing the surface of the metal specimen, (2) proper etching of the surface, (3) preparing the suitable replica from the surface, (4) examination and phorography in electron microscope and (5) interpretation. Preparation of Metal Surfaces Usual metallographic polishing is generclly satisfactory. It is important though that the final polish be applied very carefully, since otherwise evidence of a small amount of deformation might show up even on relatively deeply etched surfaces. A high-power microscope should be used to determine the suitability of the polish and etch. This, of course, is not different from optical examinations, but in these, if a deep etch is used, the problem is less serious. It is frequently difficult to detect with optical microscopes poor polishing aside fiom superficial scratches before etching. Figs. I and 2 show micrographs of "well" and "poorly" polished nickel etched by immersing the sample for 20 min. in a solution containing 8 grams cupric sulphate in 40 C.C. of concentrated HCl and 40 C.C. of Hz0 (Marble's reagent). The sample shown in Fig. I was polished in its final stages for 5 min. on a carborundum wheel followed by ro min. on a rouge wheel, whereas the sample shown in Fig. 2 was polished only I min. on the rouge wheel. Generally, this procedure does not guarantee that the surface of the specimen will be either undistorted or deformed. It was applied here merely to show the effects Of good and poor polishing. To the experienced investigator, plastic deformation is

Jan 1, 1946

By Helmut Thielsch

MeTallographic specimens whose surfaces are to be investigated are too thick to allow either light or electrons to pass through them for microexamination by transmission. This difficulty is overcome with optical microscopes by illuminating the surface through the objective lens. For electron microscopes best results are obtained by preparing thin replicas of the surface of the specimen, placing them in the microscope and passing the electron beam through them. Since electron microscopes represent a rather recent invention, they have found little application as compared with optical microscopes. This is true because, aside from the cost of new equipment and development of new techniques, some of the older replica methods necessitated the destruction of the surface from which a thin transparent replica was obtained. In other processes in which the surface is preserved, either too tedious a procedure is required, unsuited to "mass-production" requirements of industrial laboratories, or replicas of insufficient contrast and sharpness are produced. In general, investigations with the electron microscope involve five steps: (I) polishing the surface of the metal specimen, (2) proper etching of the surface, (3) preparing the suitable replica from the surface, (4) examination and phorography in electron microscope and (5) interpretation. Preparation of Metal Surfaces Usual metallographic polishing is generclly satisfactory. It is important though that the final polish be applied very carefully, since otherwise evidence of a small amount of deformation might show up even on relatively deeply etched surfaces. A high-power microscope should be used to determine the suitability of the polish and etch. This, of course, is not different from optical examinations, but in these, if a deep etch is used, the problem is less serious. It is frequently difficult to detect with optical microscopes poor polishing aside fiom superficial scratches before etching. Figs. I and 2 show micrographs of "well" and "poorly" polished nickel etched by immersing the sample for 20 min. in a solution containing 8 grams cupric sulphate in 40 C.C. of concentrated HCl and 40 C.C. of Hz0 (Marble's reagent). The sample shown in Fig. I was polished in its final stages for 5 min. on a carborundum wheel followed by ro min. on a rouge wheel, whereas the sample shown in Fig. 2 was polished only I min. on the rouge wheel. Generally, this procedure does not guarantee that the surface of the specimen will be either undistorted or deformed. It was applied here merely to show the effects Of good and poor polishing. To the experienced investigator, plastic deformation is

Jan 1, 1946

By John Vasey

A shaft of 1690 m depth is currently being sunk to exploit a large copper sulphide orebody. The primary crusher chamber, main pump chamber and the other excavations on the crusher level were developed from the shaft during the sinking operation. The maximum principal stress is horizontal and has a magnitude twice that of the vertical stress. It increased linearly with depth and on the elevation of the crusher level, 1613 m below surface, the stresses induced by mining can exceed the strength of the rock. The development of a workable crusher level layout, and a crusher chamber design and support system are described. Excavation and support of the workings are detailed and a comparison of expected and actual results is made.

Jan 1, 1983