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WE must begin by defining what we mean by the Copperbelt. This term is generally used to denote that region of Northern Rhodesia in which the copper mines of that territory are situated. The first published use of the term Copperbelt we have been able to trace dates back to 1905. The African World of December of that year contained an article entitled "The Great Northern Copper Belts of Rhodesia." The next reference we have traced is in 1909 in an article in the Transactions of the Geo- logical Society of South Africa. It began to be used generally in the late twenties and by 1929 was in common use to denote the region which today contains the existing large copper mines of Northern Rhodesia. The first of three accompanying maps is a very simple outline map of Africa showing where Rhodesia is within Africa, and where the Copperbelt is within Rhodesia. The second is a larger scale map of the Copperbelt itself. It will be seen that within the present Copperbelt there are six producing mines. Two of these are new and four are relatively established, having started operations between the two world wars. The Copperbelt also includes a town- ship called Ndola, which is not a mining town, but a railhead on the main line. This town has developed primarily as a result of the mining industry in the neighborhood. It describes itself as the Gateway to the Copperbelt and is shortly to become a refining center.

Jan 5, 1957

By R. L. Langenheim

Cooperative education for engineers is based on the premise that theory and practice are inseparable in training men for the engineering profession, and the two must be advanced simultaneously in order to train men most successfully and efficiently. The teaching of theory obviously should be done by the college but the practice must be obtained in the field where the application of the theory is made. The ideally trained engineer is one that knows theory, can apply the theory to practice, can direct, and work with, his fellow men. The old four-year plan of training engineers does a fair job of teaching the underlying theory of engineering but neglects entirely the training necessary for application of the theory, except through laboratory experiments, and the training in adjustments necessary to direct and work with men. An engineer, like a lawyer, doctor, dentist or other professionally trained man, cannot practice until he has had practical experiences that give him a knowledge of the other phases of his profession. The doctor serves as an interne, the lawyer reads law in the office of a practicing attorney, and the engineer must enter the profession as a laborer or as an apprentice, unless he has had the advantage of a cooperative education. Cooperative education provides the opportunity for the coordination of practical and theoretical training for the engineering profession throughout the period of training and thus eliminates many that are unfit to enter the profession, giving them an opportunity to seek other fields for which they may be better fitted, and reduces the overhead in industry that results from a large turnover of men not fitted for the profession. The Cooperative Plan Cooperative education in engineering is no longer an experiment. It was inaugurated at the University of Cincinnati in 1904 by Dean Herman Schneider, and has worked successfully ever since. Over twenty schools offer this type of education and many thousands of young men have had the opportunity to receive their technical training under this plan. Under the cooperative plan a student attends class for a period of eight weeks, then enters industry for eight weeks, maintaining this schedule

Jan 1, 1937

By A. B. Young

The difficulties encountered in the preparation of the lead smelter charge for the blast furnace and in the roasting and sintering of the ores, and the expert means taken for the preparation of these materials since the introduction of flotation concentrates into the lead smelter charge, have been described by W. H. Eardleyl and R. A. Wagstaff.² Function of Roasters and Blast Furnaces The lead smelter has first its roasters and its sintering devices, of which the primary object is the removal of sulfur from the ore or from the charge. The blast furnace follows; its function being the elimination of the gangue material left in the charge—the elimination of the insoluble, the iron, the zinc and the lime from the metallic lead. The secondary object is the separation of copper from the lead. A lead blast furnace is a sensitive apparatus. The materials composing the charge must be marshalled in certain proportions before they will make a fluid slag which will separate from the metallic lead. The silica, iron, lime and zinc must be put together in proportions that usually do not mist naturally in the ores, therefore fluxes are necessary. Function of the Flotation Cell The flotation cell—-speaking from the standpoint of a lead concentrate—has taken over part of the work hitherto performed entirely by either gravity concentration or the lead blast furnace. It has eliminated gangue from the concentrate and separated waste products from the lead. In so far as it has done that, it has usurped some of the function of the lead blast furnace; and it is much cheaper to run a flotation cell than a lead blast furnace. The effect in Utah, and it will be similar to effects in other districts. has been to remove a great deal of the gangue by means of flotation, whereas in the old clays it was eliminated by means of sme1ting. In this district, as in others, the insoluble content of the ores has been greatly out of proportion to the iron and lime content to make a proper slag

Jan 1, 1928

By C. T. Van Winkle

MINE fires are always dangerous and are frequently accompanied by loss of life during the period of confusion which is apt to follow their discovery. In metal mines, fires may result from the accidental ignition of some combustible material, or they may be of spontaneous origin resulting from the rapid decomposition of sulphide. They occur frequently enough to demonstrate the need of some special equipment and a general plan for controlling them, in addition to measures for their prevention. Nearly all the large copper mines have had fires, and the methods of fighting them have been well described in recent papers, notably-by C. L. Berrien,1 R.. E. Tally,2 and others in discussion. The Copper Queen mine has many shafts, which are connected by underground workings. The deeper parts are ventilated by fans, but in the shallower portions natural ventilation through numerous connecting raises or shafts is sufficient. There have been several fires in the past few years, of which all are extinguished but one, and that is under control. These notes cover particularly the preparations that are being made-to check a new fire, partially or temporarily, and to facilitate the escape of workmen in the interval before a definite plan of fighting it can be established. A fire may occur in a shaft or station, or in some working father away. In case of fire in an upcast shaft, the gas would escape to the surface and the immediate result would probably not be dangerous to workmen, as they could escape by other shafts. In a downcast shaft, however, the gas would be distributed very rapidly throughout a large portion of the mine, and men might easily be trapped and asphyxiated. A fire in mine workings, drift, raise, or stope, would be dangerous in a degree, but the draft there is likely to be less strong than in a shaft and probably a smaller area would be invaded by the fire gases.

Jan 1, 1918

By J. E. Schaefer

A summary of oil and gas development in Ohio for 1936 is necessarily brief and, in some details incomplete, owing to the lack of a central state agency for the collection of data and statistics on well drilling and production. The information used in this report was compiled from the records of the several companies operating in the state. Drilling activity in Ohio increased during 1936 as compared to the two preceding years. During the year 1157 wells were completed, as compared to 1022 wells in 1935 and 1055 wells in 1934. However, in spite of this increase in drilling activity, both oil and gas production declined for the year. Activity by Fields Trenton Sand Field.—The Trenton sand field is located in 15 counties of northwestern Ohio, trending from Toledo on the north, south and west through Findlay into Indiana. About 40 years ago the Trenton field was one of the most important oil-producing fields in the United States, but it has declined to a position of minor importance. During the year 1936 there were 52 completions in this field—29 gas wells, 19 oil wells and 4 dry holes. Clinton Sand Field.—The Clinton sand is by far the most important gas-producing field in the state. Production is located in small pools separated by nonproducing areas, on a band of varying width reaching from Cleveland on the north to Lawrence County on the Ohio River on the south. During 1936 a small pool of patchy character was developed in Butler township, Knox County. Seventeen wells were completed in the Clinton sand, of which 13 were gas wells and 4 were dry holes. The average initial production secured per well drilled, including dry holes, was 1,288,000 cu. ft. The average depth of the Clinton sand was 3000 feet. A gas well was completed in lot 9 of Franklin township, Tuscarawas County. Production was found in the first Clinton sand at a depth of 4354 ft. The initial open flow after shot was 828,000 cu. ft. and the rock

Jan 1, 1937

By David N. French

In a recent paper, Miyoshi, Hara, and sugimotoL have shown that hardness increases and crack resistance decreases with polishing time in tungsten car-bide-cobalt alloys. They attribute the changes in hardness and crack resistance to cold working in these alloys. More recently Exner2 explains the decrease in crack resistance with the amount of material removed (polishing time) by suggesting that polishing removes a high compressive residual surface stress due to the initial grinding operation. He cites previous work on steel to show grinding can induce surface compressive stresses but offers no direct experimental measurements to support this in cemented tungsten carbides. In recent work we have observed changes in residual stress in the W C phase as measured by X-ray diffraction techniques with changes in polishing conditions.3 As a result of the work of Miyoshi et al.,L a brief study was undertaken to investigate the effects of polishing and grinding on the residual stress in the WC phase and have been reported.4 A single composition of tungsten carbide —10 wt pct Co was used. Two initial conditions were studied: an annealed condition with about -30,000 psi residual stress from the differences in thermal coefficients of expansion of WC and cobalt and, on the same specimen, a surface ground with a 150 grit diamond wheel. Stress was measured in the WC phase using X-ray diffractometry as a function of the amount of material removed by metallographic polishing with 6 diamond paste. The results are shown in Fig. 1. Two things are noted, 1) polishing with 6 p diamond paste has little effect on the annealed sample and 2) the magnitude of the grinding stress is markedly reduced as material is removed. By the time 0.1 mil is removed the surface has a metallographic polish satisfactory for light microscopy examination. Thus the surface, even though polished, can still retain most of the stress due to grinding. Since WC is itself slightly ductile, it seems reasonable that high compressive stresses can be generated in the surface by the plastic deformation accompanying grinding. Exner2 suggests, by analogy with steel, that as a result of grinding both WC and cobalt in the

Jan 1, 1970

By E. M. Norris

In the summer of 1917 it was decided to fireproof the main Tramway hoisting shaft of the Anaconda Copper Mining Co. at Butte, Mont. The shaft has three hoisting compartments and one pump compartment; it is timbered with 12 by 12-in. (30.5 by 30.5-cm.) fir timber, and is 2475 ft. (754 m.) deep. Subsidence and displacement of the surrounding country rock had produced exceedingly heavy ground, and had carried the shaft out of line, in several places, by as much as 2 ft. (0.6 m.) displacement. Constant repairing and realigning of the timbers had been necessary in order to maintain clearance for the cages. The most feasible method of fireproofing, therefore, seemed to be to cover the timbers with a coat of concrete applied with the cement gun. The cement gun, which is operated by compressed air at ordinary mine pressures, feeds a mixture of sand and cement through a hose to a nozzle having a water connection. The mortar in fluid form is thus sprayed upon the prepared surface in thin layers, which can be built up to any desired thickness. The cement gun can be set up at any convenient point; satisfactory results have been obtained with the nozzle a distance of 500 ft. (152 m.) from the gun. The shaft was thoroughly overhauled and the timbers put in the best possible state of repair. Between the 1000 and the 1400 levels, much loose ground lay against the shaft timbers on the north side; this was breast-boarded back and a 30-in. (76-cm.) reinforced-concrete retaining wall was erected, leaving a space of 12 in. (30.5 cm.) outside the shaft timbers to allow for future movements of the ground. For convenience in handling men and materials, it was arranged to concrete the auxiliary hoisting-cage compartment and the pump compartment first, using the cages of the main hoist to serve the cementing crews. The auxiliary cage was then available while the remainder of the shaft was being concreted. A tight partition of 2-in. (5.08-cm.) plank was erected between the auxiliary and the adjoining hoisting compartments, for better protection of men riding on the cages. The application of concrete made this

Jan 1, 1920

IN THE December issue of MINING AND METALLURGY, attention was drawn to the February meeting of the Institute. The plans of the Committee on Arrange-ments have progressed considerably since that date, so that further announcements may now be made. The Mining Methods Committee has definitely arranged for at least three sessions. One of these will be devoted to a discussion of various methods used in sampling large low-grade ore deposits; a second will have for its leading subject underground transportation and mining practice as developed by the Anaconda Copper Mining Co., and the third will be devoted to the coal industry, particularly in reference to the percent-age of economic recovery under various conditions. The Mining Methods Committee will also hold a committee meeting, which will be open to all members, for the purpose of a discussion in reference to the symposium on mining methods which it proposes to hold at an early meeting. The Petroleum and Gas Committee is planning a two-day symposium. A tentative program was printed in the November number of MINING AND METALLURGY, and this, with a few changes, still indicates the plans of the committee. E. L. DeGolyer, vice-chairman of the committee, says Mining engineers and geologists should make every effort to attend the February meeting and hear the symposiums on foreign oil possibilities which have been arranged by the Petro-leum and Gas Committee of the Institute. No such comprehen-sive consideration of this subject as that planned has previously been attempted. This matter is extremely important to all persons who are users of petroleum or its products, and in our present civilization this classification includes every individual, but it is particularly important to the engineer who directs the production and use of power on a large scale. The United States produces currently about two-thirds of the world's oil but consumes more than it produces. We must look .to outside areas for part at least of our petroleum requirements and the future market, because even American oil will be influ-enced largely by the ease and freedom with which this outside supply may be secured. It is important to you to know something of foreign prospects and conditions under which they may be developed.

Jan 1, 1922

By Valentin R. Garfais

The world's petroleum production in 1928 is estimated at 1,322,896,-000 bbl., an increase of about 62,000,000 bbl. over 1927, as compared with an increase of over 133,000,000 bbl. in the previous year. The daily average was close to 3,600,000 bbl., of which the fields on the American continent produced about 84 per cent. The most important development during the year has been the partial success of the attempts to temporarily control production without appealing to legislation and, as a consequence, the increasing realization that, in order to reach a permanent cure for this situation, some form of legislation is necessary to' make possible the conservation of the oil supply and the stabilization of the industry. The importance of such a control over American production is not merely local but worldwide, as the American oil supply is now and for years to come will be the controlling factor of the industry. United States.—Production in the United States, which in 1927 increased about 15 per cent. over the previous year, remained practically stationary in 1928, the total being estimated at 902,000,000 bbl., or 68.2 per cent. of the world's output. This uniformity in production during the last two years was due primarily to the curtailment of output from wells already drilled, it being estimated that the available or shut-in production at the end of the year was close to 500,000 bbl. per day, or equivalent to the combined production of Venezuela and Russia, the countries ranking second and third. Venezuela.—With a production estimated at 106,000,000 bbl., Venezuela has trebled its output in the last three years. The increase in 1928 was 43,000,000 which placed this country as second in rank, a position which it should easily maintain for years to come. The output could have been considerably larger had not the oversupply in the United States made it advisable for Venezuelan operators to enter into tentative conservation agreements. Russia.—In Russia, production has doubled in the last five years, and reached a new peak in 1928 with an output estimated at 87,800,000 bbl., or an increase of 10,000,000 bbl. over the previous year. Difficul-

Jan 1, 1929

By d&apos, C. Antonio, S. H. Reichman

In the course of our studies of the annealing behavior of vapor-deposited silver films we have determined the electrical resistivity as a function of annealing temperature for films in the thickness range of 630 to 3240A. Fig. 1 shows the resistivity of the silver films vs film thickness in as-deposited and annealed conditions. The films were prepared by depositing 99.999 pct pure silver from molybdenum boats onto Vycor substrates. Deposition was conducted at a residual pressure of 5 x 10"6 Torr at rates of 20 to 408, sec-'. Thicknesses were determined using a multiple-beam interferometer. During annealing, resistance was measured using the four-probe method. Measurements were made every 5°C during two consecutive anneals to 300°C under a continuous vacuum of 2 x X6 Torr. The heating and cooling rates during annealing were approximately l° and 2°C min-', respectively. Typical resistivity vs temperature curves are shown in Figs. 2 through 4. There is an inflection point evident at 120°C on Fig. 2, the first anneal of a 3240A film. This inflection point was found on all films above approximately 1!00A on both first and second anneals. Below 1400A the inflection occurred at approximately 180°C. Figs; 3 and 4 show the first and second anneals of a 1370A film. The inflection point occurs at 180°C on the first anneal and approximately 120°C on the second. Our interpretation of this phenomenon is based on oxygen liberation from the film surface. It is well-documented that the presence of oxygen on silver surfaces causes a reversible increase in resistivity.1"3 The liberation of this oxygen, for example during vacuum annealing, would therefore cause a decrease in resistivity as observed on Figs. 2, 3, and 4 as a change in slope. This is accounted for by the decomposition of Ag20 on the film surface. The free energy of AgzO becomes positive between 125" and 225°C.4 The thickness dependence of the inflection points can be explained as an orientation effect. The films used in this study were preferentially oriented with their (111) planes parallel to the Substrate.''~ In addition it has been sten that the thinner films, below approximately 1500A, possess a decided "hill and valley"

Jan 1, 1969

By N. D. Gerald

The mathematical analysis, which is an essential part of this paper, has revealed the interesting fact that contrary to the opinions of many, determinate and measurable economic factors are largely responsible for the price of crude oil. It should, however, be well understood that the results of this analysis are applicable, without qualification, only to the particular period and market studied. There are certain peculiarities of the petroleum industry which make the consideration of its economics very difficult, and at times practically impossible. Noneconomic factors often become highly important and have serious economic effects, which make unqualified predictions based on economic data extremely hazardous and ill advised. However, in spite of the attendant difficulties there are many problems, especially in price analysis, to which approximate solutions must be made for the proper guidance of public and private policy, but their limitations should be kept clearly in mind. An understanding of the nature of prices is of fundamental importance for a number of purposes. Measurement of the motivating factors giving rise to trends and other price movements is essential to forecasting for the intelligent engineering and financial administration of the industry. The fixing of prices, maintenance of an intelligent industrial dictatorship, or the making of other industrial adjustments, demand, for success, an accurate understanding of their probable consequences. The establishment of a system of equitable relations within an industry, or between industries, by methods other than the natural competitive ones, requires a thorough knowledge of the price structures and the nature and trends of the normal and basic prices of their products. This research has shown that in this case, even though the statistical records are only fair, quantitative economics offers a direct and satisfactory approach to the problems of economic consequences dependent on the reactions of mass intelligence. A consideration of commodity prices naturally leads to costs. The true cost of petroleum is so complex and elusive that its accurate deter-

Jan 1, 1934

By W. M. Hirthe, E. H. Greener, D. R. McCann

It has been proposed1'2 that, at low temperatures, point defects are a strengthening factor in inter-metallic compounds whereas, at high temperatures, the deformation is diffusion-controlled and, therefore, an increase in the concentration of point defects tends to soften or increase the plasticity of a compound. More recent investigations, including those of Bloem and Kroger' on PbS, Kramers and smith4 on TiO, and Nadeau5 on LiF, have extended this concept to ionic crystals. Rutile (TiO2) is a tetragonal transition metal oxide which has a defect structure over at least the compositional range. The defect in near-stoichiometric rutile is either an oxygen ion vacancys or a titanium ion interstitial.' This investigation does not contribute to resolving the defect question but either defect would satisfy the results obtained. Six specimens having the same orientation, see Fig., 1, utilized in an independent investigation1' were cut with a diamond saw from a single-crystal boule purchased from the Linde Co. Three specimens were annealed in air at 1200°C for 4 hr and slowly cooled to room temperature in a period of 12 hr. The remaining specimens were reduced in a vacuum of l0 mm Hg at 1200°C for 4 hr and cooled at the same rate in vacuum. The reduced specimens were weighed before and after reduction and, assuming the weight loss to be oxygen, the corresponding oxygen-to-metal ratio is 1.998. All specimens were chemically polished and etched utilizing the techniques described by Hirthe, Adsit, and Brittain." The specimens were embedded in acrylic resin and mounted on a leveling vise in a Kentron micro-hardness tester. A 200-g load was applied to a Knoop indenter with a descent time of 18 sec and a dwell time of 20 sec. Eight indentations were made on a near (171) surface, approximately 3 deg from the (lii) plane, for each orientation of the major axis of the indenter relative to the crystal structure. The dependence of microhardness on orienta-

Jan 1, 1963

By E. Keller

Some years ago the writer's attention was called to the fact that rolling-mill scales from auriferous copper do not have the gold content proportional to the gold contained in the copper from which they are derived.' So, later, he made a few simple experiments, which are described herewith. In order to test the gold movement on the changing surface of a copper plate under the influence of oxidation, plates 6 in. by 8 in. by 1 in. (15.2 cm. by 20.3 cm. by 2.5 cm.) of converter copper, refined, of 99.29 per cent. purity, and leaded copper with a content of 95.65 per cent, copper, were obtained. Ten cuts were made through the thickness of the plates along the longitudinal center and the silver and gold content ascertained in each of the 10 samples in both plates, as shown in the accompanying illustration. The assay results, recorded in Tables 1 and 2, show that the gold distribution is relatively uniform in both plates, while silver has greater variations, especially in the leaded plate. The plates subjected to oxidation were placed in a red-hot muffle for about 2 hr., two small scarifiers being used as supports. Arranged alongside each other, they nearly filled the width of the muffle, and so were practically under equal conditions of heat and draft. The accurate observance of the time was not possible, however, because of other work, but the time of the exposure of each plate in a pair was identical. At the end of each period, each plate was plunged into water and completely freed of scale, which was carefully collected, dried, weighed, and analyzed. Samples of the plates had also been taken of the molten metal and duly analyzed. Table 3 contains the analytical data for the two plates and their several sheets, or layers, of oxide scales. These figures show that in the oxidations of the converter copper the silver is fairly uniform, while the gold is highly irregular and especially low in the first layer. In the oxidations of the leaded copper plate, the silver and gold contents are variable; however, this irregularity is due to two different causes. The

Jan 1, 1919

By Rudolf Kudlich

THE problem of eliminating the hazards of hoisting in mines has been with us since the industry passed its earliest stages, when coal and ore could be won from surface working and tunnels. At first, safety devices were introduced as means of decreasing the amount of labor necessary, to produce the mineral, or to increase the amount that could be obtained from a certain opening. For example, crude, ladders replaced winding footpaths or steps cut into the walls of the pit or shaft, decreasing the distance it was necessary to carry the product to the surface and eliminating, to some extent, the hazard introduced by the precarious footing afforded by such paths and steps. Later, instead of being carried from the pit on the backs of men, the product was hoisted in buckets or baskets on a rope passing over a pulley or around a windlass. Thus the capacity of the pit was considerably increased, and the hazard due to making many trips up and down the shaft was eliminated. From such beginnings accident prevention in mine hoisting advanced with the importance of the industry, until at present hoisting compares favorably with other branches of the mining industry with reference to safe practices. As in the other branches, this progress has been accomplished along two general lines-by legislation, rules, and education, and by the installation of safety devices. Though due credit must be given the former, it is not so satisfactory as the latter. Legislation, to be effective, requires a policing and inspection system to guarantee enforcement, such as we cannot hope to inaugurate. Rules may be satisfactory so long as the employer controls the labor market, and dismissal or some other form of discipline is an effective means of insuring obedience to the rules; but where labor demand is in excess of the supply, or where labor organizations are in control, such measures are not effective. An educational campaign will draw attention to hazards and may awaken a desire to avoid accidents by exercising the proper care.

Jan 2, 1922

By N. A. McKinnon, J. H. Auld, A. M. Marshall, R. A. Coyle

IN making a study of the slip deformation and strain hardening of single crystals of aluminum, it has been found that considerable information additional to that provided by the usual metal-lographic techniques can be obtained by the use of the microfocus X-ray method described by Schulz.1 This technique has been applied to crystals both in the state as-grown by the strain-anneal method and after they have been subjected to increasing amounts of plastic strain. Kelly and Wei" have recently reported the use of this method for a study of lineage structure in aluminum single crystals grown from the melt. The crystals, prepared from aluminum of 99.99 pct purity supplied by British Aluminium Co. Ltd., were grown in the form of flat tensile specimens with a gage section of 0.3 by 0.1 in. and a gage length of 2.3 in. The microfocus X-ray tube used provided a focus of approximately 50 half width. Examination of a large number of as-grown crystals showed no sign of any macroscopic defects in the majority of cases. However, occasionally crystals grown by the strain-anneal method did show defects similar in nature to those shown by Kelly and Wei to occur in crystals grown from the melt. In some other cases a more regular appearance of black and white lines, corresponding to valleys and ridges, respectively, in the lattice, was obtained, Fig. 1. This particular crystal was slightly deformed as the lines when present in the image of an as-grown crystal are only barely visible. The angle of tilt of the blocks is of the order of 3. It seems likely that these tilt boundaries arise during the growth of the crystal due to the specimen not being perfectly flat on the hearth of the furnace and straightening under its own weight at the elevated temperatures. For the deformation studies the crystals were strained in a Polanyi-type tensile machine. A typical photograph taken after 1.2 pct elongation of a single crystal oriented with its axis fairly close to the center of the stereographic triangle is given in Fig. 2. The reflection, which is from the (111) planes, is traversed by two systems of parallel lines. These have been identified as traces of the primary (111) slip plane and the (110) plane perpendicular to the primary slip direction. The latter lines correspond to kink bands which could not be detected by the ordinary techniques of

Jan 1, 1958

By Porter W. Shimer

As is well known, cast-iron borings are a mixture of small particles of iron with more or less of finely divided graphite, separated from thc surfaces of these small particles during the process of boring. The amount of graphite thus mechanically mixed is, in all cases, quite large enough to cause serious difficulty when the problem is to obtain an average sample of a given lot of borings for carbon determination. This difficulty arises from the necessity of obtaining a uniform mixture of the heavy and comparatively coarse borings with the finely divided and light graphite, and of removing a sample for analysis without disturbing the uniformity of this mixture. It was first sought to overcome this difficulty by having the horings made very fine, so that they might have more nearly the size of the particles of graphite. It was not practicable, however, to secure this uniformity of size, since much of the graphite is in the form of the finest dust. At all events, the duplicate determinations of rarbon in these fine borings, made with every precaution by combustion in oxygen, frequently showed differences too large to be accounted for in arty other way than by imperfect sampling. Very coarse borings were also tried with the idea that the graphite separated from these large and heavy pieces would perhaps be inappreciable ; but it was found that quite enough was separated to vitiate the results. Various methods of mixing were tried, both in the bottle and on glazed paper ; but in all these mixtures it mas found that duplicate samples seldom colitained the same proportion of the mechanically mixed graphite; and when they did, there could be no certainty that it was the true proportion. All this was shown many times over by the failure of duplicates to agree closely, the differencheing sometimes so much as 0.20 per cent. It was finally clear that nothing was to be hoped from these methods. Even if we could secure a perfect mixture containing in every part its due proportion of graphite, it would run a great risk of being destroyed the moment a spatula was inserted to remove a sample: for the least agitation causes some of the graphite to fall through between the coarser borings.

Jan 1, 1886

By W. H. Eardley

It is increasingly evident that the excellence of blast-furnace operation to a great extent depends upon the preparation of the products fed into the furnace. The preparation of these products is carried on largely in the roasting and sintering departments. Prior to the building of flotation plants in Utah and other western states for the treatment of lead-zinc ores, the gravity concentrates received at the Midvale smelter amounted to about 4000 tons per month, containing 24 per cent. lead and 10 or 11 per cent. zinc. This product was about 20 mesh—that is, 45 per cent. of it would be plus 20 mesh and the balance minus 20 mesh. About 1000 tons of pyrite per month, containing 5 per cent. lead and 10 per cent. zinc, was also received. These products were sent to the multiple-hearth roasters for calcining, after which they were sent to the Dwight-Lloyd machines for sintering with other ores. The sintering charge passed over the machines but once. The first flotation products received consisted of a wet, sticky, muddy mass, containing a large amount of moisture, up to 19 or 20 per cent., and it was almost impossible to feed them with any degree of regularity, if at all, through our standard feeders; but the amount of flotation product received during the first year or so was relatively small and it virtually lost its identity by being mixed with a large amount of jig and table concentrates. As the quantity of flotation products increased, more efficient filtering was accomplished and the moisture greatly reduced. Flotation Products Received At the present time the Midvale plant receives about 4300 tons per month of flotation product running 60 per cent, lead and 4.5 per cent. zinc, 85 per cent. of which is minus 200 mesh and contains about 8 per cent, moisture; and 4000 tons per month of pyrite of similar fineness, running about 2 per cent. lead and 3.5 per cent. zinc, containing about 10 per cent, moisture. The lower moisture greatly reduces the difficulties of handling, making it possible to run a 100 per cent. flotation feed on a multiple-hearth furnace without serious mechanical troubles. The calcine, however, would contain nodules and balls of unroast,ed concentrates, sulfur elimination

Jan 1, 1928

By S. E. Bretherton

(San Francisco Meeting, September, 1915) DURING the year 1878-79, Anton Eilers, who was then interested in the lead smelting and refining business near Salt Lake City, Utah, made a somewhat radical departure from the regular practice at that time, which was to use but little lime in the slag, with a high percentage of iron. Lime was not only a cheaper flux than iron, but it enabled the metallurgist to make a more siliceous slag, an economical advantage in smelting where the smelting companies had to purchase either iron or lime to neutralize the excess silica, and penalize the ore shippers accordingly. The larger amount of both lime and silica in the slag also made it of lighter specific gravity, and a better separation of the metals and mattes was secured. This change in the formation of slags for lead smelting was brought about by Anton Eilers, prior to the Leadville mining excitement of 1879. We must also give Mr. Eilers credit for the general introduction of the hollow water-cooled cast-iron jacket for the blast furnace. Again referring to the use of more lime and less iron in the formation of slags,. there is no doubt but that it prevents the formation of a great many so-called "sows" in the lead crucible, such as were made in the early history of lead smelting in the Rocky Mountains; these sows consisted of lead, iron, arsenic, sulphur, copper, and other metals, including gold and silver, mixed with unconsumed fuel, and often, after vain attempts to cut them up or melt them to a suitable size for handling, were buried in the slag clumps to get them out of-sight. Another advantage derived from the adoption of high-lime slags. when smelting ore containing arsenic is the production of less speiss (a by-product heavier than matte, resulting from careless operation of the furnace, the lead being driven out of the crucible and sows built up). This speiss, while usually not as rich in precious metals as matte made at the same time, is too valuable to be thrown away; but it is difficult to treat, and it was thrown away or piled on the slag clumps in the pioneer clays of lead smelting in this country.

Jan 8, 1915

By Carville E. Sparks, Rollin Farmin

Edward Thomas (U.S. Bureau of Mines, Washington, D. C.)—This excellent article on an ingenious and successful installation of wooden rock bolts loses much of its effectiveness through an attempt by the authors to establish the general adaptability of this type of support. Possibly because they have only local experience as a guide, they imply erroneously in the first paragraph that the Bureau of Mines has been opposed to wooden bolting, although later in the article reference is made to a Bureau publication on the subject. In 1947 the Bureau of Mines decided to sponsor experiments in roof bolting in coal mines because the experience of the St. Joseph Lead Co. had indicated that this type of roof support appeared to be a roof-fall accident-prevention measure that might be adopted and also effect economies in operating cost. Justification for this belief has been borne out, particularly in coal mining. This program has been carried out under the following general program: 1—The Roof Control Section of the Bureau of Mines has advocated and initiated underground experiments under controlled conditions with many different ideas related to rock bolting since 1947. In no instance has cooperation in developing an idea been refused, no matter how ridiculous it may have seemed at first glance, if it has been requested by a mining company. 2—The Bureau of Mines has no police powers over the selection of roof-support devices and seeks none. 3—At the request of an operator, the Bureau of Mines will make comparative tests on various types of bolts underground and will submit resultant data for the operator's consideration. 4—Wherever possible, the Bureau publicizes successful installations, so that others may benefit from this experience; however, it is careful not to discriminate between manufacturers of bolts or bolt-installation equipment. Unsuccessful experiments probably should also be publicized, but from a practical standpoint it is usually not feasible. In other words, the role of the Roof Control Section of the Bureau is in line with the original purpose for which the Bureau was first organized: to serve industry through gathering, analyzing, and disseminating factual data. It would seem to be logical that the starting point for any experimentation on roof bolts in coal mines should be the time-proved practice of the

Jan 1, 1955

By Norman J. Gibbs, John Sroka

INTRODUCTION At the point a company decides to begin mine development and wishes to convince lending institutions that the proposed operation will return their borrowed funds, plus interest, over the terms of the loan, communications between lender and borrower are crucial. The importance of the mine feasibility presentation should not be underplayed, especially as new projects continue to increase in size, complexity, and cost. While the content and emphasis of a report to the lender will vary according to the particular project and type of debt financing sought, there is a general base of information upon which all such studies are built. THE PROJECT'S TECHNICAL ASPECTS Here, the object is to satisfy the lender that he will not be unduly exposed to technical risks as a result of the physical scope of the project. Reserves The feasibility report submitted to financial institutions should include an adequate description of the geologic setting, mineralogy, ore types, and reserves broken down into such recognized categories as proven/probable/possible or measured/indicated/inferred. Rather than a bald statement of reserves, lenders prefer to have detailed information on: History of exploration Drilling, both percussion and core, with core recovery, drill hole spacing, analyses, and continuity of mineralization Bulk sampling, with core assay comparisons Overburden, with stripping ratios Specific methodology of reserve calculation, and Geologic reserves vs. mineable reserves. As a rule of thumb, a lender would prefer to see that reserves in the proven class alone are sufficient to support operations at the design rates until the borrowed funds are repaid. (See also Schreiber above in this Chapter.) Mining The rationale for adoption of a particular mining technique should be presented as well as descriptions and justifications for: Preproduction development Preliminary mine plan, with forecasts of grades and material movements Geotechnical test work which influenced decisions Mining recoveries and efficiencies Major equipment, with type, model, rating life, spares, replacement schedules, utilization, and productivity Manpower requirements and work schedules Design assumptions Ore stockpiling and blending Environmental requirements, and Waste disposal Processing If a new ore body is to be developed or a new process used, it is important to provide details of test work, scale up, and extrapolation factors. A basic process description with a summary of the studies which justify the intended processing route should be included with the following data:

Jan 1, 1985