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THE Institute of Metals Division opened its series of meetings by a session* on lead, R. S. Dean be-ing in the chair and G. 0. Hiers acting as vice-chairman. A large and representative audience listened to the papers in the abstract and contributed an inter-esting and fruitful discussion. The main points of these papers and discussion are given below: In the absence of Carl E. Swartz, the summary and conclusions of his paper, "A Study of the Lead-Tin-Cadmium System with Reference to Their Use as Solders," were read. Swartz investigated a number of alloys in the lead-tin-cadmium system and prepared a diagram representing the solidification ranges of these alloys. He also made tensile strength tests of joints made with these alloys, and compared these with joints made with ordinary lead-tin solder. The tests showed solders containing cadmium were equally strong as the lead-tin series and that the cadmium alloys were suit-able in other respects for use as solders. In general, solders of the composition near to the ternary lead-tin-cadmium eutectic appeared to be the best for most soldering work although compositions widely differing are desirable for special purposes. The lead-tin-cad-mium solders are finding a market particularly in the fields requiring lower solidification temperatures than common solders. Mr. Darby opened the discussion and asked whether it was a fact that the lead-tin-cadmium solders were more useful than ordinary solders on galvanized and tin-plated sheet. C. Smith said he thought it to be a fact that galvanized sheet was more easily soldered by the lead-tin-cadmium solders than common lead-tin-solder. Continuing, Mr. Smith showed lantern slides of his own investigation of the thermal diagram and recommended the 70 per cent lead, 20 per cent cadmium, and 10 per cent tin for general employment. He thought the author did not differentiate between wetting and alloying and pointed out that wetting was more a ques-tion of the flux than the metal. In some cases a definite alloy was formed by soldering and in some no evidences of alloying were found. Illustrating the former case he showed slides and demonstrated that failures always took place longitudinal with the brittle compound alloy and transversely across the solder itself.

Jan 3, 1928

By John Chipman, A. M. Samarin

It has been long known that the gas evolved during the boil in the open-hearth furnace is mainly carbon monoxide associated with smaller quantities of other gases. A number of attempts have been made to determine the precise effects of carbon and oxygen content of the bath, and of other factors, such as temperature, upon the evolution of carbon monoxide. In his investigation of the carbon-iron oxide product in liquid steel, Hertyl showed that the value of this product at equilibrium could be approximated by plotting the value of the product observed in open-hearth reactions against rate of carbon elimination, and extrapolating to zero rate. The results of this study showed a slight but definite effect of temperature upon the carbon-iron oxide reaction. Experimental studies of the evolution of gases from rimming-steel ingots have not yet attained the degree of precision necessary for an exact understanding of the effects of pouring temperature, carbon content, and iron oxide in the metal upon the composition of these gases. Klinger2 showed that the gas consists mainly of carbon monoxide, and that considerable variation in its composition occurs during the solidification of the ingot. In order that these variations may be understood in their proper relationship to the progress of solidification of the ingot and the segregation that accompanies solidification, it is essential to have a knowledge of the condition of equilibrium in the several chemical reactions by which the gases are being formed. It is also necessary to understand the effects of temperature upon the equilibria, and further, to know the manner in which the temperature of the liquid metal within the ingot changes as the skin of the ingot is being built up. The reactions in which we will be chiefly interested are those involving in the one case the oxides of carbon, and in the other case steam and

Jan 1, 1937

By F. W. McQuiston, L. J. Bechaud

3.2-1. Introduction. Much has appeared in the technical literature on theory of sampling (18, 37), weight of sample required in relation to particle size (28), probability of error in sampling (3), and statistical analysis of sample data (20). Each industry, whether it be copper, iron ore, or coal, has its own standards and methods. All of the rather extensive theoretical treatments appearing in published literature on sampling apply to material already on hand such as coal, iron ore, or copper concentrates in rail cars, or in moving streams such as on conveyor belts. The attempt usually is to apply statistical techniques in order to improve reliability and precision in sampling, and to reduce differences between the analyses of seller and buyer. In contrast to this type of sampling, very little has appeared in the literature on sampling a virgin deposit from the metallurgical point of view. Perhaps it would he more descriptive to designate this point of view as "Gm-metallurgical," since geology is inextricably interwoven with metallurgy in gaining an understanding of the complexities of a deposit, eventually leading to a definition of mineable reserves, with the development of a flowsheet and engineering criteria for the planning of a successful and profitable operation. The degree of cooperation between these two departments often determines whether the processing plant is a success at the inception of operations, or whether expensive changes and modifications must he made, with the plant finally reaching rated capacity at some later date. The first concern of the metallurgical department should be to establish proper accreditation of the samples which will be used in any ore-testing campaign. It should he made mandatory, as part of operating management policy, for the responsible metallurgist to he aware of the significance of the samples and to become intimately knowledgeable in all aspects of metallurgical behavior and response to treatment of all varieties of ore in the deposit under consideration.

Jan 1, 1968

By N. S. Greensfelder

THE firing of explosive charges by electricity dates back to 1745 when a Doctor Watson is said to have used an electric spark for igniting gunpowder. His method failed in practical application because, to ignite blasting powder, heat must be applied for a period longer than the duration of an electrostatic spark; Wheatstone found that this does not exceed 14000 sec. The usual result, therefore, of an electrical discharge in gunpowder is to scatter the grains, without igniting them. Benjamin Franklin partly overcame this difficulty by confining the powder and crushing grains that lay in the line of discharge. In 1822, after the primary cell had been discovered by Volta, Robert Hare, professor of chemistry at the University of Philadelphia, noticed the heating of a short piece of wire placed in the circuit of a voltaic battery. Later work by Oersted, Faraday, Wheatstone, and Henley resulted in the development of the magneto blasting machines. Fulminates of gold and silver are thought to have been discovered by Cornelius Drebbel, about 1600. Pepys, in his diary for November 11, 1663, recounts a conversation with Doctor Allen, who told him about aurium fulminans "of which a grain ... . put in a silver spoon and fired, will give a blow like a musquett and strike a hole through the silver spoon downward, without the least force upward.1," This fallacious belief that explosives act downwards only, is still held by many who should know better. Fulminate of mercury was discovered by Howard in 1799. J. Shaw of Philadelphia is said to have invented a fulminate-of-mercury cap in 1814; his idea was later adopted by gunmakers in England and France. The principal advantages of

Jan 9, 1922

By Karl Sundberg

ElectRical investigations carried out in regions containing sedimentary rocks showed that sediments generally are good electrical conductors, a fact which at the present time is used for structural investigations by electrical methods. It is of fundamental importance, not only for these investigations but also for electrical prospecting in general, to know the electrical properties of various soils and rocks. It will be useful, therefore, to discuss this question with the hope that the general points of view discussed in this paper will perhaps be completed by further observations and determinations of material from various localities. This paper is based principally on the study of literature, and the purpose is primarily a discussion of the main factors that determine the electrical conductivity of soils and rocks. It will follow, however, that the factors discussed here also frequently decide how far a certain orebody can be regarded as a good electrical conductor compared with the surrounding rocks. All rocks are more or less porous, and the pores are filled with liquids and gases. Their electrical conductivity, therefore, depends on the following factors: 1. The electrical conductivity of minerals composing the rock. 2. Electrical conductivity of the liquid filling the pores. 3. Proportion of the volume of liquid filling pores of the rocks to the solid rock material. 4. Shape of the pores. 5. Arrangement of the particles of gas and liquids. 6. Temperature. Dry minerals, with the exception of certain ore minerals, are complete nonconductors from the point of view of applied geophysics; in the present investigation we deal with rocks which have no conducting minerals, and factor 1, therefore, is not important. The same is true of soils. The liquids contained in soils and rocks in most cases are waters, sometimes oil. As oil is a nonconductor of electricity, the impregnating waters will determine the electrical conductivity of soils and rocks.

Jan 1, 1932

By J. E. Tobey, David R. Mitchell, J. H. Kerrick

DETAILED knowledge of purchase specifications established by coal consumers is essential to the successful design and operation of a coal-preparation plant. ANTHRACITE Specifications should be considered by both the consumer and the producer as guide posts outlining a certain path for both to follow. Plants differ, therefore specifications must differ to meet the varied requirements. Specifications are not of themselves a "cure all" or an assurance of complete satisfaction in fuel utilization. Specifications should not be regarded as a license to engage in an orgy of buying any and all coals that may happen to fall within their limits. This would lead to the-indiscriminate mixing of coals which may vary in their burning characteristics. Different coals of equal grade tend to be individualistic in their burning characteristics. Rather, specifications should be used to help simplify coal selection, to reduce the actual number of coals used over a given period; in other words, to have a stabilizing influence on coal or customer turnover. In the final analysis, the use of too many coals per year in a plant is costly to both the consumer and the producer. Too many sources usually result in higher operating and maintenance costs for the consumer and higher sales costs for the producer. Finally, the statement included in the report accompanying the comprehensive Coal Selection Charts prepared by the Coal Committee of the National Association of Purchasing Agents, and released in 1938, is significant. This Committee worked diligently for a period of 15 years seeking to find a scientific and reliable method for selecting coals. The two following paragraphs are quoted from its report: More important is the fact that no ready-made classification or set of specifications can possibly replace the judgment and resourcefulness of an experienced combustion engineer, or fuel technologist, nor the usual need for full scale plant tests under the exact conditions of use before a final decision is made . . .

Jan 1, 1943

Coal was known in this county before 1819, but there is no record of its use before that year. In that year a furnace, the first one built in the northwestern countries, was put in blast on Bear Creek; it was built to use coke and its first blast was with this fuel, which was made in heaps, but the blast was too weak and the furnace chilled after two or three tons of iron had been made. Charcoal was then substituted, and this use of coal ceased.1 In November of the same year a resolution was adopted urging state aid for a road from Kittanning to. Hamilton, New York: "that this road will increase the trade and industry of the whole county, between Pittsburgh and the New York line; and that our soil will in consequence be better tilled, our mines of coal, of iron and of salt, be better wrought, etc."2 In 1828 an advertisement of lands situated near Freeport on the Allegheny River and contiguous to the canal nearly completed between the Kiskiminitas and Pittsburgh stated that they contained "large and never failing springs, Coal in abundance, and a great deal of Fine Timber."3 In 1830 there were said to have been 24 salt wells in this county producing 327,000 bushels of salt, chiefly on the Kiski and Allegheny Rivers. In 1837 there were a number of wells in the vicinity of Freeport. As all the salt works on the Conemaugh River, were using coal long before 1830,4 it is safe to say that a considerable tonnage of coal was used for some years in these plants. In 1837 a tract of land in Clarion Township having a new saw mill and abounding "in Stone Coal" was offered for sale,5 and also one in Toby Township having "an abundance of the best quality of iron ore and stone coal."' In 1839 an advertisement in the Pittsburgh Mercury said

Jan 1, 1942

By J. B. Austin, R. H. H. Pierce

IN developing a consistent picture of the thermal expansion of the commercial chromium steels, which cover a range of, carbon contents, it is desirable to know the expansion in the limiting case of the binary, carbon-free, iron-chromium alloys. We have, therefore, determined the thermal expansion of a series of five special alloys, ranging in chromium content from 3 to 10.5 per cent, with not more than 0.03 per cent carbon, over a temperature range extending beyond the transformation region; this low carbon content enables us to draw reasonably reliable conclusions as to the behavior of the carbon-free system. Moreover, the measurements serve to determine the beginning and the end of the alpha-gamma transformation; and they emphasize once more the fact that a transformation temperature determined by any method in which the specimen is .cooled at an appreciable rate is apt to be seriously in error, particularly if the metal contains a transformation-retarding element such as chromium or managanese. The lag, or undercooling, observed at the ?-a transformation is explained in terms of the influence of temperature on transformation velocity; the rather unusual shape of the ? loop is attributed to a change with temperature and with composition of the distribution of chromium between the alpha-iron and gamma-iron solid solutions. The exact composition of the alloys which were obtained through the courtesy of Dr. W. Rohn, of the Heraeus Vakuumschmelze A-G., is given in Table 1. Determinations of the linear thermal expansion and of transformation temperature were carried out in the vacuum dilatometer previously described,1 using a rate of heating and of cooling of 3.0° to 3.5° per minute unless otherwise stated. Magnetic susceptibility, which was measured in studying the rate of transformation, was determined with a magnetic balance, which also has. been described.2

Jan 1, 1935

By Herbert H. Kellogg

DEPOSITS of high-silica kaolinite clays occur at many places in central Pennsylvania. These white clays were formed apparently by weathering of argillaceous quartzite and limestone. Their geology, distribution and use have been reported by Leighton.1 The larger deposits have been mined from time to time, and the clay, after washing to remove coarse sand, has found use as rubber filler, foundry clay, and in white cements. In general, the clay from these deposits contains too much grit (quartz) to be useful as paper filler, and the silica content is too high to make it useful as china clay for ceramic ware. Gravity methods for the separation of quartz from these clays have failed because of the extremely fine size of the quartz grains, but by the methods of froth flotation described in this paper these sandy kaolins can be made to yield a purified kaolinite that has a chemical composition close to that of good-grade Georgia kaolins, and is free enough from grit to be used as a paper filler. As by-products of the separation, a fine (-325-mesh) sand assaying 95.5 per cent Si02, and a very fine (-3-micron) clay are produced. The possible ceramic uses of these products are being investigated at The Pennsylvania State College. EXPERIMENTAL PROCEDURE The Sample.-The clay sample used in these tests was obtained from a small mine near Tyrone, Pa. It had already been washed to remove coarse sand, and represented the finished product of this small mine and washery. Microscopic examination showed that the clay was composed almost entirely of the minerals quartz and kaolinite, and that the quartz was present mostly in particles larger than one micron, while the kaolinite particles generally were less than 20 microns in size. The kaolinite and quartz particles were physically separable by blunging the clay in water with a suitable dispersant. Preparation of Flotation Feed.-By the addition of NaOH in an amount equal to 3 lb. per ton of solids, the clay was completely dispersed in water. Flotation feed was prepared by allowing a dispersed suspension (10 per cent solids) of the clay to stand for the period of time required for a 2.5-micron particle of quartz to settle from the top of the container to the bottom. After this settling period the suspension was decanted from the settled solids. The settled solids were redispersed in water and the separation was repeated once. The two fine fractions were then combined. Thus the clay was divided into a fine and a coarse fraction by size separation at approximately 2.5 microns.* The fine fraction was found to have a considerably lower sand content than the raw clay (Table I), and was not treated further. The coarse fraction formed the flotation feed for all the tests described in this paper.

Jan 1, 1945

By L. C. Glenn

In the preparation of this paper the writer has drawn freely upon the writings of Orton, Munn, Shaw, Mather, Miller, Hoeing, St. Clair, Jillson, and others, as well as upon his own personal knowledge of the fields of both states. It is to be regretted that certain data gathered by him and his assistants last fall are not available for publication. Oil in Tennessee A few wells drilled for brine for salt making in Tennessee between 1820 and 1840 obtained oil, but no definite search was made for oil until just after the close of the Civil War. Active drilling was then begun in Overton and counties southwest of it on the eastern half of the Highland Rim. A number of strikes were made at shallow depths in the basal part of the Mississippian but the wells were soon exhausted and abandoned. Drilling was revived, about 1892, when the Spurrier district in Pickett County was developed and was followed by the Riverton district in the same county in 1896. A pipe line was laid from the Wayne County, Ky., fields and about 60,000 bbl. of oil were run before a very heavy slump in the production, a failure to find an extension of the field, and excessive local taxation caused the removal of the pipe line in 1906. There was then no production in Tennessee until the discovery, in 1915, of oil near Oneida, Scott Co., at about 950 ft. (289 m.) in fissures in the Newman or St. Louis limestone. This field, however, soon failed and was abandoned. In 1916, oil was found at Glen Mary, Scott Co., in the Newman limestone at a depth of 1232 ft. (375 m.) A number of wells have since been drilled there, some of which were dry while others, close by, were produccrs. The largest one yielded, at first, about 340 bbl. per day and produced for several months, when it suddenly went dry. Several of the first wells began at 6 or 8 bbl. per day and are still maintaining that output. Production is from a fissured part of the limestone and varies greatly in accordance with the size and extent of the ramification of the

Jan 1, 1921

By R. B. G. Yeo

The effects of alloy additions on the M, and A, temperatures of an Fe-22.5 pct Ni alloy have been determined. Increasing amounts of titanium, colum-bium, vanadium, and silicon raise and then lower M,while raising A, cmtinuously. Cobalt raises both M, and A,. Aluminum has little effect on Ms but raises A,. Chromium md nickel lower M, and A,. It is proposed that elements raise M, in accordance with their effect on the Ae3 temperature of iron until the lattice becomes stiffened against the shear transformation so that M, is then lowered. An anomaly, first pointed out by Zener,1 arises in steels when the addition of elements, such as molybdenum and tungsten, which raise the Ae3 temperature, also lower the M, temperature.2'3 During the development of a series of martensitic precipitation-hardening (maraging) steels, the effect of several elements on the transformation of austenite to martensite was studied. The results show that under suitable conditions several elements which raise Ae3 also raise the M, and A, temperatures. PREPARATION OF MATERIALS STUDIED A series of alloys was made in which cobalt, titanium, columbium, vanadium, silicon, aluminum, molybdenum, chromium, and nickel were added to an iron base containing 22.5 pct Ni. The compositions of the alloys prepared are given in Table I. The residual manganese contents of the heats were in the range of 0.030 to 0.35 pct, silicon 0.05 to 0.1 pct, carbon 0.0008 to 0.009 pct, and nitrogen from 0 to 0.004 uct. The allois were made as 50-lb induction heats starting with electro-iron and electro-nickel, melted in air to oxidize impurities. Additions of silico-manganese and ferro-silicon were made after which the power was turned off to allow the products of deoxidation to rise and be skimmed from the surface of the melt. The furnace chamber was pumped down to a pressure of 5 p and the charge was heated to 2900°F for the addition of other alloying elements. The heats were poured into five 10-lb ingots, making successive alloy additions to each. The ingots were soaked for 2 hr at 2300°F and hot-worked to 3/4-in.-diam bars. This stock was heated to 1500°F for 1

Jan 1, 1963

By Donald O. Rausch, Robert H. Merrill

12.1 -1. Introduction. Problems concerning slopes in soils and rock generally arise in connection with road cuts and open pit mines. The angle at which a slope will safely stand is of major economic importance to both the road designer and the open pit operator. Stable slopes in soils and rock are evaluated through two fundamental approaches, namely, soil mechanics and rock mechanics. The approach selected to make this evaluation depends upon the material in the slope. For the purposes of this chapter, only slopes totally in soil or totally in rock are considered. By definition, soils are unconsolidated accumulations of solid materials produced by mechanical and chemical disintegration of rocks or the accumulation of sediments (28); rock is defined as the hard, compact, natural materials composing the crust of the earth (10). The basic factors affecting slopes in soil or rock are similar, although rock strengths are orders of magnitude greater than soil strengths. In general, the strength of large masses of soil depends upon the texture of the soil, the particle size, cohesion, and resistance to tensile and shear stress; the strength of large masses of rock depends upon the strength of the rock and the defects, such as faults, fractures or joints, that intersect the rock. Further, some of the defects in rock are cemented or uncemented, and may be filled with materials that are strong or weak compared to the rock. In slopes of either soils or rock, the stability is presumed to be a function of the slope height, slope angle, the size of the excavation, and the stresses imposed on the soil or rock by tectonic and/or gravity forces, earthquakes, or other static or dynamic forces. In addition, both soil and rock slopes are affected by static and dynamic water pressures in the pores of soils or permeable rocks or in the defects in the rock behind the slope. Visual observations of slope failures also indicate that both soil and rock can deteriorate with time, and this deterioration may be caused primarily by weathering (27).

Jan 1, 1968

By M. Muskat, R. D. Wyckoff

The general problem of the simultaneous movement of water and oil in a connected sand is of considerable practical interest from two points of view. First, there is the situation usually described as "edge-water encroachment." Here the water in the sands contiguous to and flanking the oil sand begins to enter the latter as the oil is removed and the reservoir pressure declines. The physical questions involved concern an understanding of the mechanism of the advance of the water and its control, so as to aid the oil recovery rather than to hinder it. In so far as the entry of the water into the oil sand means at least the partial replacement of the oil from the region of the encroachment by the advancing water, it is quite appropriate to consider this type of situation as one of natural water-flooding. For the present discussion, however, we are primarily interested in the problem of artificial flooding. Here the water is deliberately injected into the oil sand with the intention of displacing the oil and removing it through prearranged output wells. For the practical development of such a procedure rather large areas are included in the flooding program and the injection and output wells are arranged in regular patterns or networks, which are felt to be most favorable for a high oil recovery. Although remarkable success has already been obtained in such flooding programs, especially in the Bradford field of Pennsylvania, essentially by the application of the lessons of practical engineering experience, a more thorough physical analysis of the problem appeared to offer promise of leading to results of some interest and value. Another phase of the problem, which stimulated both the experimental and mathematical analysis, is that it is susceptible in large measure to empirical field tests. It, is in itself but an example and illustration of the general theory of the flow of dead (gas-free) liquids through porous media, in which the authors have been interested for the last several years. From the point of view of its applicability to actual petroleum technology problems, however, water-flooding is a particularly favorable

Jan 1, 1934

By R. S. Archibald

The subject of this paper is particularly appropriate, since Daniel C. Jackling was active in early exploitation of taconites on the Mesabi Range and contributed greatly to their later economic development. After his success in developing the low grade porphyries in the West he looked for more worlds to conquer, and so undertook the concentration of low grade taconites, from which he hoped to produce commercial ore. Mesabi Iron Co., organized in 1919, actually did produce merchantable sinter from taconites in 1922. The enterprise did not prove commercial at the time, as cost of production was high and the surplus of iron ore in the Lake Superior District already contributed to a low market price, but this same property has since been developed by Reserve Mining Co. The work done by Jackling had much to do with the success of this later venture. Iron ore was first discovered on the Marquette Range in Michigan in 1845. The first ore from this range came from the old Jackson mine in Negaunee in 1848. During these early years this property and others on the Marquette produced limited tonnages for transportation to Lower Lakes and for consumption by charcoal furnaces in the area, where a plentiful supply of hardwoods furnished the charcoal for iron smelting. The Marquette and other ranges tributary to Lake Superior did not produce much ore for transportation to Lower Lakes until the locks at Sault Ste. Marie were constructed, but from the time the first lock at the "Soo" was completed in 1855 these ores were transported through the locks to consumer centers in the East. The Marquette Range has a history of continuous production from 1848 to the present day. In 1877 the Menominee Range was discovered at the location of the old Penn Mines near Vulcan, Mich. There were further discoveries of ore on the old Menominee Range and at Florence, Wis., in 1880 and at Iron River and Crystal Falls, Mich., in 1882. Penn Mines continued in operation from the date of their discovery until they were finally exhausted by Pickands-Mather in 1945, but operations still continue on the Menominee in the Crystal Falls and Iron River districts. Ore is shipped to a lake port at Escanaba, Mich.

Jan 1, 1960

By David E. Hyatt, Christopher H. Cox, Franklin T. Davis

INTRODUCTION The composition of water used in the flotation process has always been of primary interest to the flotation metallurgist. It is by alteration of the chemistry of the water introduced to the process that flotation separation is effected. In only a few cases has it been necessary to treat available water prior to use in the process. In the past, flotation tailings were treated for the removal of solids via the tailings dam and water decanted from the dam was either recirculated to the process or discharged to the surface water system. The choice of recirculation or discharge was based upon water availability, effect of recycle water on the process, and economic considerations. The Federal Water Pollution Control Act Amendments of 1972 have charged the United States Environmental Protection Agency with establishing effluent limitations from point sources of discharge into the navigable water of the United States. A detailed study, sponsored by EPA, of the water of ore processing plants took place in 1974 and 1975 and guidelines for these plants will presumably have been published by the time this paper has been presented(1). The action of many of the individual states preceded the EPA in this attempt to regulate the quality of the water discharged from industrial point sources. Even with recycle of tailings water, some water is discharged from tailings dams into the substrata and at least one state is currently preparing guidelines for the quality of water discharged into the substrata.

Jan 1, 1976

By J. B. Stubbins, D. F. Coates, K. L. McRorie

Twenty-two pit slides that occurred in two Canadian open pit mining properties are analyzed. Information on the results of laboratory tests of the rocks and a brief description of the geological environment are also presented. One deduction from the study is that slides seem to be predictable by using established theory. This corroboration indicates that, contrary to normal mining practice, the appropriate slope angle should vary with the height of the wall. In addition, if the general ground water level around an open pit can be reduced, the appropriate slope angles of the walls could then be increased by a determinable amount. The ultimate objective of these investigations is to determine the relationship between the percentage probability of failure of any slope designed with specific strength paraheters. With this relationship it would then be possible to determine optimum slope angles. Because of changes in various economic factors, open pits are now being mined to much greater depths than previously. The need to keep stripping ratios low without endanrrerine.-- lives and equipment provides a strong incentive to determine the maximum practicable wall slopes. Applied research work is currently being conducted to establish the methods for analyzing optimum slopes.

Jan 1, 1963

By P. W. Bridgman

During the war, the Navy undertook the construction, under my direction, of an experimental gun embodying features designed to lessen the cost and time of production. These experiments were initiated after representations as to their desirability had been offered by myself, by the Naval Consulting Board, and by the National Research Council. The first drawings were made in June, 1917, and the experiment was completed in November, 1918. For the sake of clearness it will pay to recapitulate briefly the fundamental idea of gun construction. It is well known that if a hollow cylinder is subjected to internal fluid pressure, the maximum stress occurs in the inside layers, the outer parts carrying much less than their due share of the stress. This inequality of stress is more pronounced the thicker the walls of the cylinder. If such a cylinder is pushed to the elastic limit, failure in elasticity will take place long before the outer lagers have reached the limit of their capacity. Economical use of the material would demand, however, that all parts of the cylinder reach the limits of their capacity simultaneously. This may be brought about, at least in cylinders of not too great thickness, by producing in the inner layers an initial compression, and in the outer layers an initial tension. The effect of internal pressure is at first to relieve the compression of the inside layers, while increasing the tension of the outside layers. If the initial stresses are properly distributed, all parts of the cylinder will reach their elastic limits simultaneously, thus giving a cylinder of maximum strength for its weight. In gun construction as hitherto practiced, this initial distribution of stress is produced either by winding the inner tube with wire, a common English practice, or by shrinking hoops over the inner tube, which has been the standard American practice. Either process is long and expensive, particularly with the larger guns, 12- or 14-in., which require

Jan 1, 1922

By C Gunther

Secondary minerals are the result of a process of concentration and enrichment and are commonly richer than the primary minerals of the same deposit. Secondary ores that contain abundant sulphides are commonly dibtinguishable in the field from primary ores; this distinction is more difficult with ores that carry a small quantity only of sulphide minerals, and microscopical examination of the ore in thin section is advisable in all doubtful cases. It is frequently difficult, and in some cases impossible, to determine the primary or secondary character of quartzose gold ores. The safest guide is the presence or absence of gaseous or fluid inclusions in association with the ore minerals; such primary association coupled with a lack of traces of oxidation is indicative of primary origin. Any ore that carries traces of oxidation, such as iron stains, dendritic oxides of manganese, kaolin and so forth must be considered to have been acted upon by surface agencies, and secondary enrichment must be suspected. Further examination, however, may indicate that the contained value is primary, and, therefore, persistent in its vertical distribution. The manner of occurrence of secondary minerals is frequently characteristic; secondary minerals, being due to the action of surface waters, are commonly found in cracks through earlier minerals, or as crusts lining vugs or surrounding nucleal masses, or in general, in some distribution later than and not conforming to the arrangement of the primary minerals. Secondary sulphides are often found as soft black pulverulent masses or coatings, although they frequently occur well crystallized or as

Jan 1, 1932

By Martin T. Broome

INTRODUCTION The Luanshya Mine is situated in the southern part of the Zambian Copperbelt. The copper ore deposit is stratiform, and is preserved in a synclinorium known as the Roan/ Muliashi basin. Roan shaft (formally called No.14 shaft) is located at the eastern end of the syncline and is theoldest of the presently operating hoisting shafts, being sunk during the 1930's. It presently hoists some 45 per- cent of the total Luanshya Mine production. A cross-section through the shaft is shown in figure 1. The ore formation on the south limb is unmined on this section because until recently it was believed that such mining might cause damage to the shaft. This paper examines the influences of adjacent mining on this so-called 'shaft pillar', and describes the mechanics of subsidence of the pillar itself. GEOLOGY AND STRUCTURE Figure 1 shows the general form of folding in the vicinity of Roan shaft. The north and south limbs of the main syncline approach parallelism, with the bottom of the trough fairly smoothly rounded. The axis of the - trough plunges to the west-north-west at 6° - l0°. A brief summary of the major lithologies present in the Roan basin is given in table 1, however, the performance of the overall structure during progressive mining of the ore horizon is controlled by the following features in addition to the mining method. Intraformational Contacts These are characteristically weak in most geological environments. The BC/RL7 contact is an unconformity between moderately weak quartz-biotite schists below (unconfined compressive strength 40 - 80 MN/M 2), and strong quartzites above (U .C .S. 170-200 MN/M2) Subsequent formations are conformable, and planes of weakness are generally the result of contrasting lithology (see below). Weak Interbeds The Rt7, RL6, RL5, RL3 and RU2 horizons consist predominantly of quartzitic rocks, i.e. conglomerates, quartzites and argillites, and as such are generally strong and considered suitable for the positioning of development. Between these however, lie two much weaker dolomitic horizons, the RL4 and RU1. The Rt4 is the main hangingwall aquifer, and must be drained prior to mining. Drainage results in an extremely weak, blocky cavernous horizon which usually requires support if exposed by development. Similarly, the RU1 formation is comprised mainly of dolomites and dolomitic arqillites which are weak and cavernous. In the eastern part of the Roan/

Jan 1, 1981

By C. F. Willis

Many of the failures in vocational education are due to the fact that the educational methods were not designed to the capabilities, habits, and environments of those to be trained; rather they were based on the policy that education is education and lessons are lessons, whether for youngsters of fifteen or for men of forty. Vocational education among miners involves, first, a study of the men themselves, their habits, and the use of their leisure time; second, a study of the differences between the methods of teaching required for men and for children. Certain fundamental requirements of training methods for miners are reasonably universal and may be applied with success to any ordinary mining community. The rate of labor turnover is another consideration; it would be useless to design a four-year course for men who remain in one place only a few months. Length of Course The first consideration should be the length of the course. Few mining communities have a sufficiently stable population to make it possible successfully to carry on a course for over a year. While some men might complete a four-year course, the number is comparatively small compared with the number to whom a shorter course would be of service, and it is better to raise the standards of education even a little for a large number than to raise them to a high level for a few. It is perfectly possible to attain both objectives by arranging the courses in small units; all the units, when grouped together, should comprise a fairly complete course, yet any one unit should be complete in itself and of benefit to the workman. It should not take many of these units to make a miner or a timberman out of a mucker; but to do this the course should be short, because muckers seldom stay in one place long. By grouping a number of these units together it Would be possible for a miner to become a shift boss or a shift boss a foreman, and so on. As far as possible the units of the course should not be dependent on those preceding or following. The workman understands the completed job but he is not accustomed to carrying on several jobs at the same time and

Jan 1, 1920