Search Documents

Copper from Central Africa was well known to the Arab slave traders who depredated the country in the nineteenth century. By the 1870's slave raiding was so intense that the habits of the tribes were disrupted, and they no longer worked the copper deposits or made the crosses and bars of copper which had been their custom. In fact, the country had been greatly depopulated by the slave raiders. News of this horror was spread to the civilized world by missionaries and, in particular, by David Livingstone's writings. Whether to extend geographic knowledge, to suppress slavery or for national aggrandizement, the rush for African territory was on at the end of the nineteenth century. Cecil Rhodes at this time was established by his successes in diamonds and gold. He obtained the blessing of Lord Salisbury in 1889 to form the British South Africa Company under crown charter. His objectives were to occupy the lands north of the Zambezi for England and pay for development out of the country's mineral deposits. He planned to occupy the territory and close the gap to form an all-British route from the Cape to Cairo, one of his great dreams. With this master plan in mind he sent his agents into the field to make treaties with the tribes.

Jan 12, 1962

NEW MEMBERS The following list comprises the names of those persons who became members during the period Apr. 10, 1919, to May 10, 1919. BEAVER, JAMES J., Supt., Mech. Ore Loaders, Tennessee Coal, Iron & R.R. Co., Box 62, Bessemer, Ala. BLACKWELDER, ELIOT Geol. & Prof. of Geol., Univ. of Ill., Urbana, Ill. BRAECKE, GUSTAVE E., -Min. Engr., Mgr., Societe Curas et Soldado, La Carolina, Spain. BRINK, CYRIL GORDON, Reduction Officer, Charge of Reduction Works. Fairview Devonian Montrose Gold Mines, Ltd., P. O. Sheba, Transvaal, So. Africa. COMERFORD, JOSEPH S., Chief Chem. & Met., American Manganese Steel Co., New Castle, Delaware. DROSDOWSKI, N. C. V., Asst. Supt.,, The Spassky Copper Mine, Ltd., Karagandy, Akmolinsk, Oblast, Siberia. DUNGLINSON, GEORGE, JR., Asst. to Gen'l Mgr., Norfolk & Western Railroad, Bluefield, W. Va. FARAGHER, PAUL VANCE, Research Fellow on Light Metals, Mellon Institute, Pittsburgh, Pa.

Jan 6, 1919

By O. Chanute

In discussion of Mr. Macdonald's paper, I can say little more thau to add t~ the general acknowledgments of iguorae, and like several of the gentlemen who have preceded me, make one of those confessions which are thought to be good for the soul. Having had some experience in the erection of bridges during past years, I am aware that We yet need much information in order to proportion them to the best advantage. I would more especially like to emphasize three of the points mentioned by Mr. Macdonald, as among those upon which we lack knowledge; these are: first, the behavior of steel; second, the proportions of compression members; and, third, the influence of the size of a bar upon its strength per square inch. First, as to steel. While we all acknowledge this as the material of the future, our position map be said to be still one of expectaucy. Feu? engineers are bold enough to employ it largely in bridges, and those who do, find such serious difficulties in obtaining uniform grades of it, are so puzzled by apparent anomalies and unexpected phenomena, that it requires considerable faith and courage to apply it in large structural masses. A series of systematic experiments,

Jan 1, 1882

By E. P. Pfleider, W. D. Lacabanne

Rotary percussive drilling, vibro-drilling, vibro-rotation drilling, rotary pulsating drilling-all names that mean the same thing-are gradually appearing in mining literature. What is rotary percussive drilling? It is a combined system superimposing a rapid percussive impact on a continuous rotary action in an attempt to utilize the most desirable features of both methods. At present single and multiple carriage-mounted rotary percussion units are being used in the European coal mining regions. One well engineered unit is the Hausherr "Albo" rotary percussive drill, utilizing two alternately operating percussion pistons, and another is the multiple-unit, jumbo-mounted Salzgitter machine. Niisse & Grafer also manufacture rotary percussion drills.

Sep 1, 1955

By James R. Grage

The lead deposits of Missouri may be divided into three districts, the southwest, middle, and southeast. As too much time would be required to devote a detailed account to each district, only a description of the modes of occurrence of the lead ores in the southeast district will be given. The lead mining region proper of Southeast Missouri is embraced in an area of about twenty-five miles in width by about one hundred in length. The country embraced in this district is very broken, and traversed by ridges from one hundred to three hundred feet; in height, with an occasional knob rising higher. Porphyry forms almost the entire substructure of the region, with here and there outcrops of granite. The crystalline rocks were eroded into ridges and valleys before the deposition of the limestone took place. These porphyries are older than the Silurian limestones, and " belong (according to Pumpelly) to the Archaean (Azoic) formation, of which they may be the youngest member in Missouri. They are the near equivalents, in point of age, to the great iron-bearing rocks of Lake Superior, New Jersey, and Sweden."

By T. Inoue, T. Imaizumi

A simulation model has been developed to find out the possibility of improving the industrial closed-circuit wet grinding operations. The model involves a continuous tumbling mill in combination with a hydrocyclone to recycle the oversize material back to the mill. The mill is described by the breakage, i.e. the selection and the distribution, functions, co-ordinated with the diffusional mixing along the axis. The cyclone classifier is characterized by the partition function with allowance for the non-selective separation of part of the feed material into the underflow. The computer program developed incorporates an interactive capability to modify the operating conditions of the system whenever needed. The results are analysed for the operational conditions characterizing the mill and the classifier. Besides the steady state conditions some observations are also made about the dynamic responses of the closed circuit grinding system.

Jan 1, 1980

By C. Alstetter, V. Kerlins

By using alloys with subzero Ms temperatures, this investigation demonstrates that the amount of decomposition of martensite during the quench from austenite may be considerable and especially so in specimens of large cross -sections and high Ms temperatures. The activation energy for decomposition as measured dilutometrically is PREVTOUS investigations of the initial decomposition of Fe-C system martensite have invariably been limited to alloys having M, temperatures above a function of the amount of transformation which has taken place. The amount of transformation is a linear finction of log time. A correction term to the activation energy is derived for dilatometric measurements in which no end-point of the transformation is detected. room temperature. In such alloys the martensite is tempered during the quench to an extent dictated by the quench rate and temperature of formation. This tempering, called quench-tempering, Q-tempering, self-tempering, or auto-tempering, although frequently acknowledged, has not been studied or treated quantitatively. To do so one should obtain absolutely untempered martensite and study its decomposition. This as-formed martensite could be obtained either by extremely rapid quenching, requiring very thin specimens, or by lowering the martensite formation temperature range. The second alternative is more effective, because

Jan 1, 1963

By Ashbel Welch

Ashbel Welch, Lambertville, N. J.: Dr. Dudley has given the wear of steel rails under four different conditions. He arrives at the conclusion that the softer rails, or those that from their composition ought to be softer, wear better than the harder. But there is another condition which has an important bearing on the subject, and should not be overlooked,—the weight on a wheel. With the lighter weights of the past, the softer rails may have worn best; with the heavier weights of the future, the harder may wear best. Weights will probably be increased up to the capacity of steel to bear; then doubtless the harder steel will wear best. A leaden rail with ten pounds on a wheel might carry millions of tons, but with one hundred pounds on a wheel, it would be destfoyed by a few thousand tons. So in the days of iron rails, my experience was that the softer rails under light machinery stood better than some of the harder; but under heavy machinery the softer were much the most rapidly destroyed. It is doubtless the same with steel. The pounding motion of the wheels loosens or spreads the particles of a thin film of steel; the pull lengthwise on the rail de-

Jan 1, 1881

By W. R. Roser, F. E. Rizzo, Wu Hu

An insight into the mechanism of electrocrystallization of copper in simulated commercial acid electrolytes has been surmised from scanning electron microscope analysis of laboratory prepared specimens. The growth takes place in three overlapping stages. In he first, lasting approximately one hour at 200 amps/sq m, a propensity to epitaxial growth is observed. During the second stage a preferred orientation developed. The crystallography of the deposit showed a strong preferred orientation with the [111] direction normal to the surface. Triangular pyramids with (111) faces and (111) texture is a common result. In the third stage, occuring at longer deposition times, side growth, dendrite-like branching is common. The obsermtions have some elements in common with published results for highly purified electrolytes. Several significant differences were observed. The truncated pyramidal and block type growth discussed in he literature is suppressed under the conditions studied. The results are briefly discussed in terms of the screw dislocation, fault, and layer type growth mechanisms of crystal growth.

Jan 1, 1973

By Henry M. Howe

MY attention has been drawn within a few days to a series of articles in Volume XVIII of the Engineering and Mining Journal, 1874, by Mr. J. A. Church, in which it is stated, among other

Jan 1, 1875

By N. A. D. Parlee, I. D. Shah

THIS communication reports the results of some work done on the effect of gold, palladium, and platinum on the liquid-gas-solid equilibrium in the Ag-O system,1,2 see Fig. 1. Recently several investigators3, 4, 5 have reported the effects of gold, palladium, platinum, and copper on the solubility of oxygen in liquid silver. This communication represents only a portion of the work done here on the solubility of oxygen in liquid silver and liquid Ag-Au, Ag-Pd, and Ag-Pt alloyss—the greater part having already been reprted. The apparatus, materials, and procedures used were similar to those of earlier work.' l The main precautions observed in obtaining these freezing points at constant temperature and PO2 = 1 atm were as follows: 1) The points were approached very slowly from higher temperatures. 2) In the very near vicinity of the L-G-S equilibrium point precautions were taken to see that the melt was in equilibrium with oxygen at one atm. Equilibrium was considered to have been attained when no more absorption of oxygen was observed in the last 15 min at a fixed temperature. 3) In the case of these alloys, the freezing point of the melt at 1 atm of oxygen and the equilibrium amount of oxygen absorbed by the liquid "infinitesimally" above this point were determined by lowering the temperature in very, very small steps, equilibrating at

Jan 1, 1969

By Bashir Ahmed, Fred D. Wright

Numerous investigators have studied the various factors that influence the ultimate strength of model mine pillars, such as ratio of height-to-least width; restraint or friction on the top and bottom; 1,2 the effect of stress distribution in pillars on their strength;3 and the scaling factors involved in applying the results of model pillars to full-scale pillars. However, the load-bearing capacity of pillars after initial failure does not appear to have been investigated. Yet many mines employ methods in which small pillars or pillar remnants are left systematically; these pillars crush as mining progresses and, of necessity, affect the behavior of surrounding rock even after initial failure. The effect of such crushed or crushing pillars depends largely on their load-deformation characteristics. This chapter presents the results of a preliminary investigation to determine the load-deformation characteristics of a few model mine pillars to and beyond initial failure. Various investigators have also studied the elastic and viscoelastic behavior of mine structures. In such studies, computers are frequently employed to obtain numerical results by the finite difference or finite element methods. It would be entirely feasible to write a program that would approximate the load-deformation characteristics of pillars to and beyond the crushing stage if these characteristics were known. More accurate information on the induced stresses and deformations in overlying strata and on surface subsidence could be obtained, information which should result in better strata control by enabling the engineer to calculate more accurately the effects of changes in pillar spacing, size, and shape.

Jan 1, 1972

By Z. T. Bieniawski, E. Unal, H. Reginald Hardy

INTRODUCTION Rock bolts are a major means of support in underground coal mines in the United States. However, two of the most crucial problems facing the mining engineer today are that of finding a well defined and standard method for testing the anchoring ability of rock bolts, and of selecting the most suitable type of rock bolt and bolting pattern for a particular mine or specific mine section (Anon., 1982). Such selection requires not only an understanding of the behavior of the rock mass and the rock-bolt unit itself, but also a knowledge of the basic mechanisms by which rock bolts provide support while they interact with the rock mass during various field loading conditions. A recent study in this area has shown the inadequacy of present methods used in selecting and testing of rock bolts and the lack of clearly defined guidelines for safe and economical design of bolting patterns (Bieniawski, et al., 1980). The present paper describes a research study aimed at developing laboratory instrumentation and associated techniques for the evaluation of bolt-rock interaction. The instrumentation system developed, procedures followed during various experiments, and typical results from a series of studies carried out on mechanical bolts are presented. DEVELOPMENT OF THE ROCK BOLT TESTING FACILITY General A block diagram of the experimental facilities are shown in Fig. 1. The system consists of three main sections. The first

Jan 1, 1982

By Otto F. Pfordte

Although the subject has no practical bearing on the metallurgy of the present day, it may not be entirely uninteresting to note how the art of silver-lead smelting has been, and in a few remote districts of Peru is still practiced by an old method, and under conditions widely different from our own. The subject will be considered under the following subdivisions,. viz.: The general conditions; construction and plan of furnaces;, fuels and ores; method of working; furnace products and slags. The mineral region of Peru varies in altitude from 10,000 to 16,000 feet above sea-level, comparatively few mines being locatedh above or below these limits. The timber-line in the valleys is at about 12,000 feet altitude on the western slope of the mountains, and even there the supply of wood is not sufficient to be utilized as fuel for furnaces. The sides of the mountains are either bare or covered with a hard bushy grass, which is most luxuriant during the latter part of the rainy season, from February to April. Agriculture on the western slope rarely reaches above 12,000 feet, while on the eastern slope its limit is at 14,000 feet; and in either case the height named is reached only in sheltered places. Transportation is slow, being carried on mainly by llamas, donkeys and mules; the former (taking 100 pounds at a load) are almost

Jan 1, 1893

By W. C. Schafer

In tunneling or mining where hydraulic shields, moles, or rock boring equipment is used lasers such as those shown guide the production machine by providing a continuous and visible line and grade reference. In this application the laser may be mounted in the heading, preferably somewhere above spring line. If we view the circular heading as a compass in the vertical plane with 0º referencing at the crown of the heading and 180º on the invert, then it might be said that the laser may be mounted anywhere from 270º through 0º to 90º. The laser is generally mounted 2 to 3 ft off the wall or the crown of the heading by means of a bracket that may be attached directly to the liner plate. In cases where no liner plate is used, then brackets may be bolted directly into the ribs, or grouted directly into the rock. Once the laser is in position the beam is projected to the face. Two points must be surveyed upstream between the laser and the face which define line and grade. Targets may be suspended beneath each of these points approximately 2 to 3 ft. These targets may be circular or rectangular with a surface area which approximates 16 sq in. Each of these two targets should have a ½ to ¾ in. hole drilled directly in their center. When the laser is adjusted so that the beam passes through the holes in each of the two targets, the laser beam itself will parallel the center line of the tunnel and become a visible line and grade reference over the total beam projection.

Jan 1, 1970

By R. W. Raymond

This paper is simply a summary, prepared at the request of the Council of the Institute, of the report of Mr. Albert Ladd Colby, of South Bethlehem, Pa., presented at the New York meeting (October, 1896) of the Association of American SteelManufacturers, on " The Advisability of the Endorsement by the Association of the United States Standard Gauge, approved by Act of Congress, March 3, 1893, to the Exclusion of the Birmingham Gauge, the .Brown and Sharpe, and all Others:" a subject on which, at the Pittsburgh meeting (April, 1896) of the said Association, Mr. Colby had been appointed as a committee. The report favors the adoption, not of the United States standard gauge to the exclusion of others, but of a decimal system of gauging all materials in thousandths of an inch, thus doing away entirely with arbitrary gauge-numbers running in inverse order to the actual thickness. The American Institute of Mining Engineers originated this movement. The report of its committee on a standard wiregauge, presented in October, 1877,* recommended the abandonment of the system of fixed gauges for commercial use, and of the system of representing the diameters and sizes by numbers, and the adoption, in lieu thereof, of the system of expressing sizes in thousandths of an inch or fractions of a millimeter, and the use of the micrometer-gauge as a means of measuring sizes. In 1892 the American Society of Mechanical Engineers appointed a similar committee, and corresponding action was

Jan 1, 1898

By G. J. Wolga, W. W. Tyler, A. C. Wilson

THE physical properties of uranium have been reviewed by Katz and Rabinowitch.1 Their review includes thermal conductivity data for ternperatures above 375°K. Recently, Mendelssohn and Rosenberg' have published data on the thermal conductivity of uranium from 2" to 20°K. Our measuremerits indicate the temperature dependence of the thermal conductivity in the temperature interval from 20" to 300°K. Electrical resistivity and thermoelectric power were measured on the same sample. The material studied was normal uranium which had been heated at 700°C in a lead bath for 10 min and then quenched in a water bath held at 50°C. From this material a rod M in. in diameter and 2 1/2 in. long was machined. Two 0.040 in. holes were drilled into the rod 1 3/4 in. apart. Copper-constantan thermocouples for temperature and potential measurements were soldered to copper pins which were pressed tightly into these holes. Details of the equipment and experimental techniques used in making the measurements have been described elsewhere." Fig. 1 shows micrographs of a section of the sample studied. Fig. la was taken with unpolarized light and shows impurity inclusions, probably uranium carbide. Fig. lb, showing the same field, was taken with polarized light and gives some indication of the grain size and twinning within the grains. Experimental Results Thermal conductivity and electrical resistivity data are shown in Fig. 2. Table I shows values of

Jan 1, 1954

NAME AND OBJECT. SEc. 1. This Institute is incorporated under the Membership Corporations law of the State of New York ; its corporate name is American Institute of Mining Engineers; and its objects are such as are stated in its Certificate of Incorporation. ARTICLE II. MEMBERS. SEC. 1. The membership of the Institute shall comprise four classes, namely 1. Members ; 2. Honorary Members ; 3. Associates ; 4. Junior Members. All members shall be equally entitled to the privileges of membership, except¬ing that Honorary Members, Junior Members, and Members and Associates whose residences shall be outside of the United States, Mexico, and Canada shall not be entitled to vote. Members and Associates residing within the United States of America, Mexico, and Canada, and not in arrears for dues, shall be entitled to vote in person at the meetings of the Institute, or, as hereinafter provided for, by letter ballot. SEC. 2. The following classes of persons shall be eligible for membership in the Institute, namely : as Members, all professional mining . engineers, geologists, metallurgists, or chemists, and all persons actively engaged in mining and metal¬lurgical engineering, geology, or chemistry ; as Associates, all persons desirous of being connected with the Institute who in the opinion of the Board of Directors are suitable.

Jan 1, 1917

By Paul Giesecke

Since most modern metallurgical plants are operated continuously and on a large scale, successful operation at maximum efficiency demands that an accurate knowledge of the performance at each stage of the process be available at all times. Quantitative analyses provide the most practical process guides, and it is essential to have analytical procedures that combine accuracy and speed. In continuous plant operations, large losses may occur if the time interval between the development of trouble at any stage and its recognition and correction is great. Many metallurgical plants are using rapid colorimetric and spectrochemical methods of analyses for control purposes. So-called "color coppers" may be cited as an example of the colorimetric methods, in contrast with- the routine use of the ultraviolet spectrograph for the analysis of steels.42 By means of this more refined spectrochemical procedure, a complete quantitative analysis of the molten metal is obtained every few minutes. During the past two years the Physics Division and the Ore Dressing Laboratory of the American Cyanamid Company's Stamford Research Laboratories have collaborated in a study of the use of spectrochemical methods for the analysis of various metallurgical products. New methods have been developed, which have proved of practical value in plant operation. The following pages give a general review of the principles of spectrochemical methods and also the details of several specific analyses. Principles of Spectrochemical Analysis In general, it can be said that a visible light spectrochemical analysis can be performed for any ion or molecule that is naturally colored, or that can be made to react with another to produce a colored salt or complex. Whereas transmission measurements in the ultraviolet and infrared portions of the spectrum are most useful for the analysis of organic molecules, * visible light measurements are of particular value for metal salts. Such elements as copper, manganese, cobalt, nickel, iron, molybdenum, vanadium, chromium, phosphorus, mercury, zinc, lead, and a great many others, can now be determined with a high degree of sensitivity, accuracy and dispatch. From the simplest of qualitative determinations, color analyses have been improved to such an extent that, at the present time, through the use of recording spectrophotometers, hundreds of accurate quantitative analyses can be performed by a single analyst during an 8-hr. day after the standardization curves have been established for the ions to be determined.

Jan 1, 1947

By J. C. Jaeger, G. A. Wiebols, N. G. W. Cook

It is usual practice in engineering to design a stable structure by ensuring that the stresses in the elements of the structure are always less than their strength, which may be defined as the yield stress, the ultimate stress, or the fatigue stress, according to the type of the load. Such restrictive design is not practical in the design of underground excavations since the rock surrounding such structures is usually failed, but only occasionally does this give rise to instability of the structure. Thus, while the usual criterion for the design of a stable structure is certainly sufficient, it is not necessary for underground excavations. A proper understanding of the conditions necessary for stability is vital to the useful application of rock mechanics knowledge to the design of underground structures. Most tests on the properties and strength of brittle rocks are disrupted at or near maximum load by the rapid release into the specimen of energy stored in the resilience of the testing machine. This is in contrast with a phenomenon, which may be observed frequently, where the rock immediately surrounding an excavation is both failed and subject to stress. By postulating a complete stress-strain curve for rock, it can be shown that failure is unstable or stable, depending upon whether the stress-strain curve of the rock lies inside or outside the stress-strain characteristics of the applied stress. Stability is, therefore, a function of the stiffness of the system applying the stress relative to that of the failing rock. Many workers have established that the strength of rock specimens under a lateral hydrostatic confining stress varies linearly with confining stress, in a way which may be expressed by the equation CT=Co+K[o]3

Jan 1, 1972