Search Documents

By W. G. Fischer, S. R. Felde

Trona ore at the Westvaco, Wyo., mine of FMC Corp. has been obtained by room-and-pillar methods since the mine began operation. The flat- lying, 10-ft thick trona (Na2CO3.NaHCO3.2H2O) is covered by 1500 ft of weak shale and sandstone, and extraction of pillars on the retreat quite often throws large amounts of weight onto development workings. Weak shales in the roof and floor fail rapidly, and the mine ribs slough to such an extent that mining often becomes very difficult. When this occurs, efficiency goes down, costs go up, and the risk to men and machinery increases greatly. Difficult mining conditions in the early '60s forced a re-evaluation of all presently known mining techniques in bedded deposits. Many room-and-pillar mining plans were compared with the system in use at that time, but none of them offered a better solution to the roof control problem. Longwall techniques were also seriously considered, but machinery was not available that would cut the hard trona seam and still maintain the productivity obtained from room-and-pillar sections. However, since roof control in the longwall methods appeared to be more satisfactory than that found in room-and-pillar techniques it was believed that a new technique using the longwall principle and based on rock mechanics should be tried rather than previously known pillaring methods.

Jan 4, 1966

By H. U. Schutt, J. M. Toguri

REGARDLESS of the degree of purification effected during the electrorefining of copper, a danger of re-introducing impurities exists in the operation of melting and casting of the refined copper. Logically only a combination of the purification and casting operation would remedy the situation. A well-known method of metal purification is the "Gross"-type process, whereby a volatile halide is produced, purified, and decomposed.' In the present case, this concept was used to remove the impurities rather than to form possible volatile copper halides. The object was to produce volatile halides of the impurities present and distill these away, leaving high-purity copper. It is interesting to note that such techniques are used in spectrographic procedures in order to shorten exposure time and enhance the density of impurity lines.' In the present investigation, copper hydroxy fluoride was used, since the temperature of decomposition of copper hydroxy fluoride and the melting point of copper nearly coincide. The fluorine released by the thermal decomposition of copper hydroxy fluoride purges the molten copper. Copper hydroxy fluoride was prepared by dissolving high-purity copper in nitric acid and adding hydrofluoric acid and ammonium hydroxide in the required proportions. The melt was made in a high-purity graphite crucible heated by an induction furnace. Trial experiments showed that impurities can be introduced from the crucible material. Therefore, preceding each cast, the crucible itself was cleaned by decomposing copper hydroxy fluoride and discarding the residual copper. Best experimental conditions were obtained by adding 30 g of copper hydroxy fluoride to 500 g of nor-

Jan 1, 1967

By Frederick Burbridge

The Morning silver-lead-zinc mine of the Federal Mining & Smelting Co. is about 'two miles northwest of Mullan, Ida. The lode is a metasomatic fissure vein. The orebody is approximately 2000 ft. long within the bounds of the property and varies in width from knife edge stringers to 50 ft. It has been developed to a depth of 3600 ft. and stands nearly vertical in Revett quartzite, which .strikes north 65" west. The high-grade veins and lenses are generally mixed with waste (siderite, quartz, and quartzite). The average grade of ore to sorting plant in 1921 was 4 oz. silver per ton, 8.6 per cent. lead, and 4.1 per cent. zinc. Wall rock stands only a short time without timbering. The minimum angle of gravity flow is 45". The ratio of waste sorted out to ore is 6 per cent. No gases are generated underground and temperature has no influence on mining operations. Fresh air is forced down the air raise and up the main shaft. Drifting and Stoping Main drifts 12 ft. wide and 13 ft. high are driven every 200 ft. (vertically) and are connected by raises 125 ft. apart. These raises consist of three compartments (chute, tramway, and timber slide) and are for the purpose of ventilation, access, and hoisting supplies to stopes. Ground is stoped between raises. Chutes are placed every 25 ft. for drawing off ore broken in stopes. Waste for filling is obtained from waste raises off the stope in walls or waste is dumped from the level above down the chute compartment of raises, which is bulkheaded so that waste can be drawn off at any floor as required. Timbering Posts and caps for square sets (varying in diameter from 6 to 24 in.) are cut to length in a sawmill on the surface. No preseratives are used. Timber is taken on a flat car along drifts to a raise nearest the working place and hoisted as required. Practically no timber is salvaged for

Jan 1, 1925

By T. T. Read

In discussing the taxation of mining enterprises, it is desirable to place limits of both time and space on the field of discussion. For our present purposes it seems best to limit consideration to taxation of mining enterprises in the United States, and to further limit the subject to taxation under approximately current conditions. Even with such limitations the field is large enough, since in this country we have, in most regions, a number of taxing powers; so that state, county and village tax systems must ordinarily be considered, in addition to our national or federal taxes. Nor is it possible, in discussing United States mineral taxes of today, altogether to pass by similar taxation in earlier periods, or related systems in other countries. It is perhaps hardly necessary to remind you, at the outset, that each age in the history of the world displays its own system of public revenues, and that the taxation systems of today are everywhere different from those of older times. Theories as to taxation have varied according to the economic basis of the society in which they were formulated, and our ideas as to justice in taxation fluctuate with changes in social conditions. The word taxation is used in a fairly definite sense today, but you have only to glance into the history of taxation to find that the paragenesis of ore deposits is a fairly simple subject as compared to the paragenesis of taxation systems.

Jan 1, 1932

By B. Silliman

THESE ores occur in the Laurentian rocks in the town of Clifton, St. Lawrence County, New York. The Clifton Mining Company have opened these magnetites upon their estate of 23,000 acres, on the waters of the Grasse River, an affluent of the St. Lawrence, which flows for about nine milt",3 across the estate, exposing a section of the formation, and affording ample water-power at numerous points. In approaching this district from De Kalb Junction, upon the Watertown and Ogdensburg Railway, the observer passes from the zone of the specular ores, which abound to a great extent in Jefferson County, across a belt of non-metal-liferous limestones, continuing for some miles intermingled with metamorphic rocks, and gradually giving place to heavy beds of granitic and porphyritic gneiss, the weathered surfaces of which present a gray and rough appearance, from the washing out of the feldspar; leaving the quartz very prominent, and completely disguising the real character of the rock, which, when freshly broken, has a lively reddish appearance from the predominance of flesh-colored and red feldspar. Beds of fine-grained quartzite appear also intercalated in the granitic gneiss. These are the dominating rocks of the magnetite region, but the magnetite is always found, so far as the speaker's observation extended, associated with beds of calcite, carrying hornblende, black and green, biotite, and brown garnet interspersed with yellow and magnetic pyrites. The strike of these rocks is about northeast, and their dip about 40' to 45' southeast

By Cornelius Kelley

VOLUMES have been written about the organizing genius of American industrialists. American methods of production are being studied by the manufacturers of other nations to ascertain the prac-ticability to foreign adaptation. Mass production and the mechanization of industry have become terms of popular understanding and significance. Our people think, act and talk in terms of economic nomenclature. Under these circumstances is it not a matter of supreme importance that Americans themselves should make an analysis of their own situation? National supremacy has been but a transitory event. Wealth has had no fixed abode, and commerce has followed no permanently established route. One hundred and fifty years, viewed from the abstract idea of time, is but a moment in the fact of continuous or successive existence, yet it measures. the cycle that has witnessed the growth of America from a struggling embryonic union of thirteen colonies estab-lished along the Atlantic seaboard to the nation of un-rivalled proportions, vast wealth, huge enterprises and productive energy that now exists beneath the protec-tion of and renders allegiance to the flag that but then had been created. To appreciate fully the significance of what has occurred, it is necessary that there should bee an understanding of the basic factors that have con-tributed so largely to the realization of our present situation. Among the most important were: First, the establishment of a government that was founded upon the principle of affording the widest pos-sible opportunity for individual effort and accom-plishment. Second, there existed a virgin territory of vast extent, endowed by nature with elements of potential wealth far exceeding that possessed by any other like area upon the globe.

Jan 8, 1928

By P. Bouéry

This account of a contrivance which has been found serviceable in practice may be of interest to engineers, and especially to those engaged in hydraulic mining. In that process, one feature which seems at first sight to possess little significance, is highly important in its effects—namely, the regular supply of water to the " giants." The chief condition of this regularity is an even flow in the pipe-line from the penstock to the nozzle.' This, of course, requires that the penstock be kept full. Any considerable surplus of water, overflowing at the penstock, is a simple waste, unless it be otherwise utilized in the sluices. At all events, it does not affect the delivery of the nozzles. But a deficiency at the penstock may admit air into the pipe; and this may produce hydraulic recoil, injuring the line by incessant vibrations, giving rise to leaks, and even to blow-outs, and (when a partial vacuum exists at the time of the fracture) the collapse of the pipe. An accident of this sort in our main pipe-line, occasioned partly by a settling of the ground and partly by the presence of air in the pipe, led to the employment of the device here described. The line referred to is made of 30-in. pipe, successively reduced to 18 and 15 in. in diameter, for the supply of two giants. By reason of the causes above mentioned, the 30-in. pipe burst more than 1,400 ft. from the penstock, and, despite the air-valve, the 30-in. pipe was collapsed to such a degree that one length of it, next to the penstock, was squeezed together and positively swallowed by the main pipe, through which it traveled for 750 ft., piercing through a short elbow on the way. This remarkable result was undoubtedly the effect of the vacuum suddenly produced when the pipe burst.

Jan 1, 1907

By William Fraser

SINCE the operative word in the subject on which I have been asked to speak is "international," I need hardly emphasize before such an audience as this that it is one which calls for some discretion on my part at the present juncture of world affairs, since, in some respects, it may not be devoid of a controversial aspect. For though the war is over, it has left behind it a sorry state of health in the political and economic complex of the world we live in; and however different may be the impact of these factors on each of us, yet none of us can any longer hope to devise a system or policy to escape from much of its controversial heat, or evade the obligation of doing what we can to diminish it. I would like, therefore, to consider with you how one great form of world enterprise whose range is coextensive with material civilization itself-that is, the Petroleum Industry-can make and is competent to make, a contribution to international health; for it is now an agreed commonplace that oil is arterial in the world's system and we need no telling that a healthy body needs healthy blood. Before embarking on my subject, let me assure you that I have no need to be told that this country before all others-and for obvious reasons is the major sounding board of opinion in matters affecting most aspects of the petroleum industry-technical, economic, national and international (but, may I please add parenthetically, not to the exclusion of quite a

Jan 1, 1947

By Joseph Pogue

PRORATION in the petroleum industry has come to mean a method for curtailing the production of crude petroleum by artificial effort, and it is in this sense that the term is employed throughout this paper. Although a contrived curb on supply has been invoked at various times in the past in particular fields and to meet specific situations, it is not until the past few years that this procedure has become general and assumed a dominant role in the oil business. In the sense that we now understand it, proration had its inception in the Seminole area of Okla-homa in 1927, from which time and place the practice spread to include practically all the flush oil fields of the country, especially those of California, Kansas, Oklahoma and Texas. At present there is perhaps no phase of the oil business that commands more attention than proration, nor one that engages more time and effort on the part of executives in the business. The practice of proration, indeed, has not only become an integral part of the policy of most companies and operators, but it has also taken on the aspects of a "movement" involving two schools of thought with considerable feeling, and at times some bitterness, on both sides. In this atmosphere it is difficult to find calm, dispassionate consideration of proration, for most discussions are either vigorous exhortations by its proponents, or else sharp condemnations by its opponents; although it appears that the majority of the industry is clearly "in favor of" proration. It is hoped that this analysis will be taken as an attempt to appraise the movement as an economic force, without bias and without regard to the incidence of the conclusions upon any preconceptions that the industry may entertain.

Jan 1, 1932

By E. M. Frizzell

Introduction In 1956, the first mobile crusher was installed in a limestone quarry in Hover, Germany. These early mobile crushers solved the problem of wet and soft ground conditions that did not permit the use of haulage trucks due to the high cost of building and maintaining the haulage roads. Quarry operators also wanted to take advantage of continuous belt conveyor haulage systems and the resulting cost savings. European mines, particularly the coalfields, are in soft materials that allow use of bucket wheel excavators and their following continuous haulage system of belt conveyors. Quarry operators, with this background knowledge of belt conveyors in mining, easily accepted the conveyor concept, once in-pit mobile crushing solved the problem of size reduction of mine-run-rock required for conveyor application. Four years after the initial mobile crusher installation, the first report published on the subject appeared in the December 1960 issue of Mining Engineer (Kochanowsky, 1960). With this early background and basis for direction, mobile in-pit crushing and conveying have increased to more than 74 installations. The capacity, type of crusher, and material being processed appear in Table 1. These data in Table 1 indicate that experience to data has been heavily influenced by limestone installations of less than 1 kt/h (1102 stph). Most of these installations were directly fed by a mine face excavator because of the limestone quarry ground conditions. Crusher Configurations Crushers systems developed to date have varying mobility capabilities. These range from fully mobile units that are used continuously in this mode to fixed, permanently located in-pit crushers. The following terms are presented to help distinguish the range of mobility within the configurations of "mobile" crusher systems planned or now in use. Mobile Crusher The crusher works at the mine face, is directly fed by an excavator, and moves in unison with the excavator on its own transport mechanism as the mining progresses. An example is the unit delivered in 1976 to Yamama Cement Co. in Reyadh, Saudi Arabia.

Jan 1, 1986

By G. Carman Ridland

IN conjunction with a geological investigation of the silver-bearing veins at Contact Lake, Northwest Territories, Canada, a survey was made with a Geiger-Müller counter of the gamma-ray emissions from the rocks in the vicinity of the mine workings. Discontinuous pitchblende veins have been encountered occasionally in the silver-bearing fissures, and the geophysical survey was undertaken with the hope that abnormally high gamma-ray intensities, if detected, might lead to larger and more continuous pitchblende discoveries. Before the instrument was used at. Contact Lake, preliminary tests were made, first with laboratory specimens at Princeton University, and later over known pitchblende deposits at the Eldorado property, LaBine Point, N.W.T. The Geiger-Müller counter, as adapted for field use, is described; the technique of transporting and operating the instrument is outlined; and the general precautions to be observed are discussed. The results obtained at Great Bear Lake show that the instrument is capable of detecting not only a pitchblende ore shoot in a shear zone, but also the mildly radioactive "host rock" at a considerable distance from the ore body. Hence, use of the Geiger-Müller counter is urged, not just for the detailed search for an ore body in a shear zone, but for the detection of possible radioactive "host rocks" in large-scale reconnaissance surveys of unexplored regions made by prospectors and members of federal geological survey parties.

Jan 1, 1944

By N. P. Peterson

THE Castle Dome copper deposit is of the porphyry type and occurs in a body of quartz monzonite intruded into the pre-Cambrian formations and possibly into the lower part of Paleozoic limestones. The hypogene sulphide minerals include pyrite, chalcopyrite, and a little molybdenite, sphalerite, and galena. Pyrite and chalcopyrite are disseminated or occur in small closely spaced veins. The hypogene mineralization shows distinct zoning in the distribution of pyrite and chalcopyrite, so that the mineralized area can be subdivided into pyrite and chalcopyrite zones. Supergene enrichment, though not extensive, played an important part in the formation of the ore body, the chalcopyrite zone being the protore. Several thin, gently dipping, diabase sills occur in the mineralized area, and the copper content of the rock in and near these sills is substantially higher than average. The formation of the ore body was caused by the combined effects of three forces: I. Zoning of the hypogene mineralization, 2. Richer copper metallization associated with the diabase sills, and 3. Supergene enrichment.

Jan 1, 1947

By John W. Cloud

IN 1877 the Pennsylvania Railroad Company removed an old bridge from its line at Duncannon, Pa., built intermediate piers and erected shorter spans of the Pratt truss type, which had previously been in use on another portion of the road. The design of this truss would not admit of diagonals larger than 1 5/8 inches diameter, and in order to stiffen the bridge somewhat steel rods were introduced for the main diagonals in the first and second panels, 1 5/8 inches and 1 3/8 inches diameter respectively. These rods were threaded without upsetting, and by the ordinary formulae the strains were of the same intensity upon both, viz., 16,000 pounds per square inch with the maximum loading. The other main diagonals in the truss are 1 5/8 inches diameter, and of iron. It was specified for the steel rods : Elastic limit, - 45,000 lbs. Tensile strength, - 80,000 lbs. Elongation, - 20 per cent. The steel was procured without difficulty, and it allowed a factor of safety of 2 3/4 at elastic limit, while a similar factor of 2 1/2 had for a long time been successfully used for iron. In the course of three years, from time to time, six of these steel rods broke, three of them being 1 3/8 inches in diameter, and three 1 5/8 inches in. diameter. The broken rods were tested, and three of them. analyzed at Altoona to ascertain the cause of failure, and what modi¬fications should be made in the steel for such service. Examination showed that all the rods were broken in detail close under the nut. The threads were well cut and properly rounded at the root. In testing the rods micrometer screws,. reading to .0001" with electric bell to signal the contact, were attached to the test pieces, and by this means the modulus of elasticity and elastic limit accurately obtained.

Jan 1, 1881

By J. E. Powers, T. D. Taylor, N. E. Wood

A computer program has been developed to simulate a gas transmission 1ine operating under transient conditions. The program was developed by application of the basic mass and momentum balance equations. The nonlinear equations thus obtained were transformed by the method of characteristics and finite-difference techniques to make them suitable for machine computation. Three tests of the computer program were made. In each of these, the initial condition was assumed to be steady-state flow, the inlet density was held constant at the initial condition, and the outlet mass flow rate was varied with time. One test was theoretical in nature, but the others were made for direct comparison with actual field data. Results of the tests are presented in graphical form. INTRODUCTION Theoretical investigations of the transient flow of gas in long pipelines have been limited in number. In 1951, Olds and Sage4 developed a gaphical method of solving the nonlinear flow equations describing transient gas flow in a long pipeline. Research in this field at the U. of Oklahoma was initiated by Nelson1 in 1956. Nelson utilized a computer to solve numerical equations involving a lengthy trial-and-error procedure, and his results have been reported in the literature? It does not seem likely that Nelson's method can be extended to the analysis of transient behavior of pipeline networks; therefore, the investigation to be discussed in this paper was undertaken to improve and extend the previous work. The following discussion presents, briefly: (1) the basic differential equations governing transient flow, (2) transformation of these equations into a form suitable for machine computation. (3) role of boundary conditions in the calculations, (4) a very brief description of the computer program which was developed to simulate the pipeline and (5) results of tests of the computer program.

By J. Parke Channing

THE caving system of mining is that method of removing the ore from an underground body in which the top is first attacked and mined out and the capping, or roof, as the case may be, is allowed to fall in or "cave" and fill the space formerly occupied by the mined ore. It is applicable, generally, to large orebodies where the ore is relatively soft. We may say, within moderate limits, that when ore is removed the surrounding ground either caves in or remains open. For example, in mines like the Lake Superior amygda-loid copper mines, when the lode is removed there is left a void which remains open for many years; on the con-trary, mining a Lake Superior soft hematite ore, however carefully it may be done, always produces a caving of the surrounding rocks. We may say, with propriety, therefore, that the caving system is applicable to that type of ore deposit in which the surrounding rock readily caves. Another factor which governs the use of the caving system is the value of the ore itself. Admittedly, any form of caving will not extract 100 per cent. of the ore, and in the case of a very rich orebody it is often desirable to get out every pound of the ore with as little dilution as possible. Under these conditions, some other method of mining, such as that by square sets and filling, is indicated and should be followed. We may say, however, that, looking at it broadly, in the United States the caving system of mining is generally used for the removal of soft hematite and for the so-called "porphyry" coppers. In both cases this method is used where open-pit mining is not possible.

Jan 1, 1922

By Ernest E. Thurlow

The western coal industry, long overshadowed by the petroleum and metallic minerals industries, has been revitalized by several new coal mining operations, with the promise that this is only the beginning of a tremendous surge in production of coal that will carry into the next century. The content of this paper is confined to the coal fields and recent developments in eastern Montana, northeastern Wyoming and western North Dakota. The area is commonly referred to as the Powder River-Fort Union region although the Powder River Basin and the Fort Union formation are separate entities and are not coextensive. Coincidentally or otherwise, the extent of the subbituminous part of the coal region coincides approximately with the Powder River Basin. Environmental considerations together with the low sulfur content of much of the western coal have triggered demand since this coal could not compete at present with eastern and midwestern coal solely on a delivered-cost-per-million-btu basis. However, increasing costs of underground mining and the comparatively thin seams of the eastern and midwestern deposits may soon bring a balance to these costs regardless of the sulfur content. Another factor which has made western coal competitive at this time is the use of the unit-trains to significantly reduce the cost of transportation. Fast loading and unloading facilities and trains of 100 cars or more in turn-around service are the keys to success in this effort.

Jan 5, 1974

By John W. Tieman

Coal is a term applied to vegetable matter which, through geological processes of heat and pressure, has had both its physical and chemical properties changed. Because its chemical composition is variable, geologists classify coal as a rock rather than a mineral. Peat represents the initial stages in the development of coal, although not classified as coal itself. PHYSICAL PROPERTIES OF COAL The physical properties are concerned with the characteristics of coal in its natural state, or prior to its end use as a fuel. For example, the hardness of coal determines the maintenance cost on coal handling equipment; the specific gravity of coal determines the coal preparation techniques used in a cleaning plant as well as the capacity of coal bins, boats and size of cargo, and other coal storage facilities. The physical properties are, of course, dependent upon the chemical constituents that make up coal, and thus all properties are interrelated. Specific Gravity The specific gravity of a body is the ratio of the weight of the body in air and the weight of an equal volume of water. The specific gravity of pure coal ranges between 1.25 and 1.70, generally increasing with rank. The most important use of this physical characteristic is the part that it plays in the cleaning of coal by wet wash methods. The basic principle on which these operate is that the specific gravity of coals differs from their associated impurities and that there is a relationship between the velocity of the fall of particles in water and their density. Since the specific gravity of slate is around 2.5 and pyrite is about 5.0, pyrite and slate will fall to the bottom of a container filled with water more rapidly than coal. If the water is given a pulsating motion by

Jan 1, 1973

By George L. Heath

It may at first appear doubtful that any further ideas can now come from such a well-trodden soil, when we consider that the ground of the subject has been so thoroughly gone over in many of its phases and that observations have been recorded in technical journals, ever since the days when Luckow and his cotemporaries brought the electrolytic deposition of pure copper to the position of an exact scientific method. Certain facts, however, which seem worthy of note, have come under the writer's observation during an extended use of the method in a large refinery, involving frequent tests of refined Lake and electrolytic copper, and thousands of assays of native copper concentrates and tailings. This work has required a careful study of the conditions suited to the assay of refined copper, and of ores and tailings— conditions which must be varied for each particular case to secure the best results. Especially is this true when we come to the exact determination of pure copper in the high-grade refined metal of the present day. Very slight traces of impurities (especially tellurium, selenium, bismuth, tin, arsenic and antimony) seriously injure the properties of copper, notably its electrical conductivity. The increasing demands of electrical science and construction lead to the conclusion that the analysis of all high-grade American coppers, at least, has become, and must be in future (in or-

Jan 1, 1898

By R. G. Garlick, M. Garfinkle

It was observed for several bcc metal crystals that the Knoop hardness anisotropy was dependent essentially on the direction of the lung axis of the indentor alone and not on the plane of indentation. The generality of this observation was tested for an fcc md an hcp metal and an ionic crystal. For cubic crystals, this observation was valid; for the hcp structure, however, the planes of indentation did have an effect on the hardness anisotropy, although this was not nearly as significant as the direction of indentation. Because the direction of indentation is the only significant crystal-lographic parameter necessary to describe the hardness anisotropy, it is possible to represent the anisotropy of single crystals on the standard stereographic triangle. THE commonly observed1, 2 periodic variation of indentation hardness with crystallographic direction on the high-symmetry planes of various single crystals has been inadequately related to the physical or mechanical properties of the crystals examined. In fact, the hardness anisotropy curves for the various planes of a particular metal crystal, as is illustrated in Fig. 1, are uncorrelated and appear in the literature3, 4 as unrelated observations. Attempts to correlate hardness anisotropy curves with specific physical properties can be generally divided into either mechanistic or nonmechanistic approaches. A nonmechanistic approach would be to devise a mathematical expression that could describe the various hardness anisotropy curves. Such a relation could then be compared with the known anisotropy of various physical properties to determine which contribute to the observed hardness anisotropy. No such mathematical expression has been found in the literature.

Jan 1, 1969

By R. U. Jackson

FACED with rising costs, the mining industry is looking to new methods and equipment to supply the relief necessary for profitable operation. Conveyor transportation is rapidly taking a superior position to motor tramming in underground mines because of lower installation, maintenance, and operating costs. Haulage is always a critical problem in underground mining. The ease of operation and flexibility of a haulage system can have an important effect on ultimate mining cost. With the average tenor of ores on the downgrade, larger tonnages are required for the same metal recovery. This selection of a tramming system can be the key to a successful, paying plant. Because this shift is being made at an ever advancing rate, it may become necessary to tailor mining operations to the transportation system, rather than to select a haulage system fitting set mining methods. In choosing a haulage system, the relative costs of the various methods are of the greatest importance. Adapting the mine to one or the other type of tramming is not considered in the cost analysis, and very likely would make little difference, outside of location of drifts and raises. In the cost sheet, the problem presents recommendations for a conveyor installation and a comparison of equipment, installation, operation, maintenance, and power costs are made. Under the track haulage estimate, no allowance was made for dumping equipment at the shaft pocket or bin. If this equipment was added to the balance sheet, the additional

Jan 1, 1952