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By H. W. Weart, D. J. Mack

SINCE the first recognition of eutectic solidification as the simultaneous formation of 2 solids from one liquid,1 many complex structures thus produced have been observed. Despite many attempts to ascertain it, however, the detailed mechanism by which these structures develop remains obscure. In an attempt to clarify the origin of eutectic structures, the study described in this paper was undertaken. The broad objective of the study was to investigate the effect of different solidification conditions on the structure of single eutectic grains. It was expected that the eutectic structure would thereby be isolated for study, but preliminary experiments revealed another structure within each grain. When a literature surveye revealed only 1 previous mention of the subgrain structure,' it was decided to determine the origin of the structure and to study its response to various growth conditions. Before presenting the details of the investigation, it is apropos to distinguish carefully among the 3 structures produced during eutectic solidification. This is especially desirable in view of the apparent confusion existing in the literature concerning the structures in a eutectic specimen. The confusion is due largely to the existence of the subgrain structure noted above which is easily mistaken for the grain structure. In the following paragraphs, an effort is made to distinguish the 3 structures by briefly describing their origin during solidification, even though the results are thereby anticipated slightly. The 3 structures produced during eutectic solidification are the grain structure, the colony structure, and the eutectic structure, each one contained by the one preceding it. The grain structure is analogous to the polycrystalline structure of a metal or inle-phase alloy in that each grain grows from a single nucleus. A somewhat broader interpretation is needed here, however, because of the presence of 2 phases in each grain. Since in most eutec-tics particles of 1 phase are dispersed in a matrix of the other, a grain may be taken to be the region in which the matrix phase is monocrystalline.*

Jan 1, 1959

By Joseph S. Malesky

The discovery and development of explosives mark one of the most important findings in the history of civilization. Without explosives our vast economic enterprise concerning the mining of coal, copper, iron, aluminum, and various other ores could not function. Explosives are used in all kinds of construction works, in the razing of old buildings, blasting of trenches, driving of tunnels, and in many other instances common to our everyday life. For these reasons explosives are rightfully referred to as the forerunner of progress. An explosive may be defined as a substance (usually a mixture) that, when flame or shock is applied, yields readily to rapid combustion or oxidation, accompanied by the formation of such relatively large quantities of gases as to produce much violence and pressure which, in turn, react against their surroundings and cause what is termed an explosion. By their very nature the action of explosives is destructive and disruptive of adjacent materials. Decomposition of explosives can occur through deflagration, which is rapid burning or combustion, as in the case of black powder, or through detonation, which is an almost instantaneous disruption, as in the case of dynamites and blasting agents. HISTORY OF BLASTING WITH EXPLOSIVES At one time workmen obtained stone blocks for building by grooving the rock with crude picks, driving wooden wedges into niches in the rock, and pouring water on the wedges; the swelling of the wood forced out the blocks. As late as the 17th century, fires were placed against the face of rock to crack it, and water was sometimes dashed on the heated rock to shatter it by sudden cooling. The progress of our country is synonymous with advancement of the improved manufacture and extended use of explosives. Coal had been

Jan 1, 1981

By J. Charles Miller

NATURAL carbon dioxide has recently been exploited in the United States in consequence of oil and gas developments in the Western States and the growing demand by transcontinental and transoceanic shippers for solid carbon dioxide. The discovery by drilling of commercial deposits resulted in consideration of its geographic and geologic distribution and occurrence. Its wide distribution in nature is evidenced by its occurrence in the atmosphere, hydrosphere and lithosphere. The question of origin of carbon dioxide involves consideration of theories similar to those concerning natural hydrocarbons, although available evidence favors an inor-ganic rather than an organic source. Areas favorable to development of commercial production appear to be those in proximity to igneous rocks or in the vicinity of decadent volcanic activity, where, it has long been known, the gas is evolved either free or dissolved in the waters of furnaroles, geysers or mud pots. Structure contour maps are presented showing the Wagon Mound anticline in New Mexico and the Farnham anticline, Utah. A well drilled on the latter supplies gas to a 20-ton plant manufacturing solid carbon dioxide at Wellington, Utah, on the Denver and Rio Grande R.R., whence it is shipped to surrounding territory and to the West Coast. Before funds are invested in a plant for the manufacture of liquid or solid carbon dioxide, whether supplied by wells or springs, an effort to ascertain the volume of gas available is advisable. The use of present methods of estimation of gas reserves with modifications to account for the quantity absorbed by any water present in the produc-ing formation is recommended. The Farnham anticline is used as an example and computations are made of the probable volume of gas originally present in the struc-ture. No attempt was made to compute reserves in the Niland area, California, for the reason that in such areas it is believed the volume is indeterminate.

Jan 1, 1937

By J. M. Callow

THE results obtained by pneumatic flotation throughout the country on all classes of ore, and. the tonnage now being treated by this particular method, speak for themselves. Its advantages over the so-called agitation process are now established by facts and data from practice. The comparative efficiency of a rapidly revolving paddle, as a means for aerating an ore pulp, and of a cycloidal or turbine blower for the same purpose, would seem to be so obvious as to leave no room for discussion. Practitioners in this art are to be congratulated on the acquisition of the valuable literary contributions that have recently been made on the theory of. flotation by Messrs. Ralston, Van Arsdale, Taggart and Beach, and others, and the very valuable and able articles, by Messrs. Laist and Wiggin on "Flotation Concentration at Anaconda, Mont.," by, Dr. Rudolf Gahl- on the "History of Flotation at Inspiration," and by David Cole on "The Advent of Flotation in the Morenci District." It is not within the province of this article to attempt an answer to the various issues raised in regard to the theory, or to defend the one advanced by me a year ago. But since discussion usually benefits the profession, a reply will be made to some of the statements made by the last-named writers. COMPARATIVE SENSITIVENESS AND ATTENDANCE Concerning 'the article, "Flotation Concentration at Anaconda, Mont.," by Laist and Wiggin, a little explanation is in order. It should be stated that; with the exception of about 24 days at the end of the testing 'period, the Callow experimental plant at Anaconda was not run under my direction. This perhaps accounts for some of the conclusions drawn on page 562 of the descriptive paper. The conclusion that the use of acid seems to be of considerable advantage, calls, for some comment. While the tests conducted by the Anaconda Copper Co. do show acid to be, of considerable benefit, this is a consequence of using acid sludge as a flotation agent. My belief has always been that the Anaconda

Jan 2, 1917

By Norman Weiss

THE need for more efficient utilization of labor in the metal-mining industry has been the subject of several recent editorials in the mining press, and one attractive possibility for such improvement lies in the designing of future milling plants particularly with economy of man-power in mind. We are accustomed to think of mill design as the selection and coordinated arrangement of process equipment, but if labor is to be efficiently utilized it must be given early consideration in planning the new mill. There are three good reasons for economizing in labor: (I) to reduce costs, not only in the form of wages but also in housing, hospital, welfare, and other obligations that a company accepts when a new man is added to the payroll; (2) to prepare for recurrent periods of manpower shortage, during which a well-designed plant can manage to get along with skeleton crews; (3) because a milling plant that must depend upon an inordinately large labor force for its operation and maintenance is certain to be inefficient in other respects, for many of the shortcomings in design that make necessary the excessive use of labor are generally not corrected merely by having too many men. A simple example of this is a poorly designed ore-feeding system: if this is inadequate to the extent that one man must be constantly unclogging feed chutes, it may help the situation to put two men or three at this task instead of one, but the feed rate will still be inconstant. First of the factors that affect labor saving is the location of the mill. This is often determined by transportation costs alone, and as a result the mill may be placed close to the mine regardless of the nature of the terrain. The designer must then adapt his layout to the conditions, favorable or not. This happens often at small properties, where capital investment may seem more important than operating expense. In most instances, however, a mill site carefully selected for the advantages it gives the designer in laying out the plant is the most economical in the long run, even if it involves a slight increase in cost of ore haulage. Given some freedom of choice, the design engineer may be able to find just the piece of ground that provides the proper gradient for the needs of the flowsheet, permits installation of essential yards and trackage, and perhaps supplies an excellent site for a tailing dam. Further justification for having placed the mill not too close to the mine sometimes emerges only years later as an opportunity to treat ores from other properties. When it is known from the beginning that the new mill will serve a number of scattered mines, a free choice of mill site is naturally stimulated. The most important single factor in limiting the labor requirements of a mill is its materials-handling system for bring-

Jan 1, 1946

By George H. C. Norman

A NUMBER of methods have been developed for the determination of the dust concentration in air, some of which have been reported as very efficient and for research may be more satisfactory than the method about to be described. In practical mine use, however, the accurate research equipment is unwieldy and requires a high degree of technical skill to manipulate it. Also, it gives less general practical information to the operator in the same length of time than the method described here. Moreover, it is doubtful whether at the present stage of affairs the results obtained from the precise methods have any more practical significance than those obtained with simpler and more portable apparatus, which can rapidly give a sufficiently reliable indication of the relative dust hazard. HISTORY OF DUST DETERMINATION IN ONTARIO The first record of mine-dust determination in Ontario is given in an article by Dr. J. H. Elliott,' in which he records a few dust counts made with the Palmer spray apparatus. There were insufficient data from which to draw any definite conclusions or reasonably compare with present-day counts using the konimeter. The first konimeter dust sampling was started in the Porcupine district in 1926, using light-field counting without adhesive and with no sample treatment before counting. A method of semidark-field counting was used from about 1928 to 1931 and dark-field illumination was adopted permanently about December 1931. The konimeter has been continued as the principal means of dust sampling in the mines of Ontario, where South African practice has been adopted because in South Africa most careful study has been given the problem of silicosis, and very complete records of work done there are

Jan 1, 1937

By G. F. Comstock

A serious disagreement as to the effect of titanium on the hardenability of steel exists in published references to this subject. Kramer, Hafner and Toleman reported1 that acid-soluble titanium decreased the hardenability, with multiplying factors less than unity according to Grossmann's system for calculating hardenability from the composition. Crafts and Lamont, on the other hand, showed2 how titanium increased the hardenability, with multiplying fdctors up to nearly I.; for about 0.1 per cent titanium, though reducing the hardenability with higher titanium. Their data, however, were obtained almost exclusively from steels containing more than 1.4 per cent manganese, and thus should be considered as applying mainly to manganese steels. Likewise, the results of Kramer, Hafner and Toleman regarding titanium are subject to the limitation that although they eliminated the effect of the insoluble titanium compounds from their calculations, they did not make a similar correc- tion for the carbon that was combined with titanium and therefore occurred in a similarly ineffective form. It is suggested by the literature referred to that titanium may have different effects on hardenability, depending on the mode of its occurrence in the steel. The different effects on strength, ductility, etc., have already been discussed by the author.3 In the present discussion some comparisons, on the basis of hardenability as revealed by the Jominy end-quench test, are given between three titanium and two non-titanium steels heat-treated in the same ways, and between other titanium steels heat-treated in several different ways. Comparison of Plain-carbon, Vanadium and Titanium Steels The five steels used for these experiments were cominercially melted and rolled products received in the form of 1.5-in. rounds from three different mills. Their analyses are given in Table I. Steels 2, 3, and 4 are from the same basic electric heat1 containing 0.009 per cent of phosphorus and the same amount of sulphur. They were made by adding aluminum and low-carbon ferrotitanium to different ingots. No. I is a plain carbon

Jan 1, 1947

By G. F. Comstock

A serious disagreement as to the effect of titanium on the hardenability of steel exists in published references to this subject. Kramer, Hafner and Toleman reported1 that acid-soluble titanium decreased the hardenability, with multiplying factors less than unity according to Grossmann's system for calculating hardenability from the composition. Crafts and Lamont, on the other hand, showed2 how titanium increased the hardenability, with multiplying fdctors up to nearly I.; for about 0.1 per cent titanium, though reducing the hardenability with higher titanium. Their data, however, were obtained almost exclusively from steels containing more than 1.4 per cent manganese, and thus should be considered as applying mainly to manganese steels. Likewise, the results of Kramer, Hafner and Toleman regarding titanium are subject to the limitation that although they eliminated the effect of the insoluble titanium compounds from their calculations, they did not make a similar correc- tion for the carbon that was combined with titanium and therefore occurred in a similarly ineffective form. It is suggested by the literature referred to that titanium may have different effects on hardenability, depending on the mode of its occurrence in the steel. The different effects on strength, ductility, etc., have already been discussed by the author.3 In the present discussion some comparisons, on the basis of hardenability as revealed by the Jominy end-quench test, are given between three titanium and two non-titanium steels heat-treated in the same ways, and between other titanium steels heat-treated in several different ways. Comparison of Plain-carbon, Vanadium and Titanium Steels The five steels used for these experiments were cominercially melted and rolled products received in the form of 1.5-in. rounds from three different mills. Their analyses are given in Table I. Steels 2, 3, and 4 are from the same basic electric heat1 containing 0.009 per cent of phosphorus and the same amount of sulphur. They were made by adding aluminum and low-carbon ferrotitanium to different ingots. No. I is a plain carbon

Jan 1, 1947

By A. K. Mukherjee, J. E. Dorn

A modified Peierls model is Presented for the rationalization of the asymmetric plastic behavior of single crystals of bcc metals. The model assumes that the asymmetry of slip arises from a tendency toward asymnetric splitting of the a/2[111] screw dislocation. The approach differs from former theories however insofar as it assumes that the splitting is so minor ttut only the core energy is modified and that no real partial dislocations exist. As a consequence, the concepts of a line energy of a partial dislocation, interaction between partial dislocations, constriction energies, and stacking fault energies are not invoked. Instead the present analysis is based on a specialization of the Peierls mechanism which assumes an asymmetric dislocation core which is modified by the effective stress and permits cross slip. The theoretical predictions on the stress-temperature -strain rate and orientation relationship agree qualitatively with the limited experimental data that are currently available. Additional experimental work over wider ranges of conditions is suggested to provide more complete evaluation of the possible validity of this theory. RECENT experimental investigations on the low-temperature thermally activated deformation of bcc metals have confirmed the existence of several unique orientation effects. These will be described with the aid of the standard stereographic projection shown in Fig. 1. If slip were determined exclusively by crystal symmetry, the deformation characteristics would be symmetrical about X; = 0 and independent of whether the specimen were subjected to a tension or a compression stress, regardless of what combinations of slip planes might be operative. Experiments, however, reveal that neither of these symmetry based predictions are valid. A schematic representation of the commonly observed asymmetry of both the yield stress and the plane of slip is shown in Fig. 2. A reversal of the direction of stressing results in an inversion of the asvmmetric behavior. 1) Asymmetry bf Yielding. A detailed investigation on the asymmetric yielding in an Fe-2.7 pct Si alloy was repoEted by Tabka, Tikeuchi, and Furubayashi,1 Similar trends have been observed by Keh and Nakada on iron,' Stein on molybdenum,3 Bowen, Christian, and Taylor4 on columbium, Sherwood, Guiu, Kim, and pratt5 on Ta, Cb, and Mo. The degree of asymmetry not only depends on the atomic number and alloying but, in all cases that have been examined, it also increases with a decrease in the test temperature. 2) Asymmetry of the Slip Plane. Asymmetric $I-~: curves of the type shown in Fig. 2 have been found for several Fe-Si alloys6-8,1 and columbium.4 There is general agre_ement that near X: = 30 deg slip occurs by the [111](211) mode so that ?1 = 30 deg. As X; decreases it appears that [111](211) to [111](101) cross slip takes place leading to slip band traces on intermediate planes. And as xi approaches 0 deg, sharp

Jan 1, 1970

By H. K. Work, G. H. Enzian

In the manufacture of steel for commercial purposes, the deoxidation practice used, i.e., the method and degree of deoxidation, is an important factor affecting the structure and mechanical properties of the finished steel. Deoxidation practice exerts a pronounced influence not only on the soundness of the ingots but also on the reaction of the steel to a number of mechanical and thermal treatments. The first mentioned effect of deoxidation is more or less obvious and was first demonstrated, though perhaps not fully appreciated, by Robert Mushet when, in 1856, he added speigeleisen to low-carbon bessemer blown metal. In 1861. Bessemer patented the addition of one pound per ton of silicon to his blown metal to "cause the metal to lie quietly in the mold." The second effect of deoxidation-—that is, the effect on the properties and behavior of the steel—is, one might say, more subtle, and certainly not as well understood as the first, although in many cases it is the more important consideration. This paper is limited to a discussion of only the second effect of deoxidation and: in particular, to the effect on the strain-sensitivity of low-carbon steels. General Discussion Originally it was thought that the function of a deoxidizer was to combine with the oxygen present in the steel as iron oxide and prevent its subsequent evolution as a gas. -More recently it has been realized that a deoxidizer does more than this. Frequent reference has been made to the effect of deoxidizers on the nitrogen in the steel, and some attention has also been paid to hydrogen. As a consequence of the above situation any study of deoxidation must be concerned with the gas content of the steel and the effect of the deoxidizer on the gases involved. The term "gas content" as used here refers to gases extracted from steel during melting in vacuum rather than to elements present in steel in the gaseous state. The extracted gases, at least in the case of oxygen and nitrogen, are generally accepted to be products of decomposition of oxides, nitrides, or other more complex compounds. The manner in which deoxidation affects the gas content of steel and the significance of gases in steel have been and still are subjects of considerable speculation. No attempt will be made here to give a complete discussion of the literature on this subject but a few references will be cited for purposes of illustration. N. Hamilton1 found a correlation between the oxygen content of alloy steel and the behavior of the steel during tube piercing. Davenport, Bain, and others associated oxygen with aging properties of steel while Köster5 and a number of others6-lo made similar claims for nitrogen. Daniloff, Mehl, and Hertyll stated that "deoxidation decreases the susceptibility of steels to aging directly

Jan 1, 1945

By Gunnar Thaning, Borje Bjorkvall

At LKAB Central Division for Metallurgical Research at Malmberget, Sweden, fired pellets are examined in respect to mechanical and reduction properties. The paper deals with descriptions of the test methods. It also involves the rationale for the choice of these tests. Their correlation to the blast furnace operation will be examined. The mechanical tests used are the ISO-tumbler test and the cold compression strength test. Concerning the metallurgical properties, experiments have shown that some superbasic pellets in particular have different disintegration properties in different temperature ranges. Pellets which have favorable reduction properties when tested under isothermal reduction at high temperature may disintegrate to a large extent under low temperature reduction. This is also valid for some types of acid pellets. Consequently, it was found to be necessary to determine the reduction strength both at high and low temperatures. In the low temperature range, the disintegration is measured by tumbling the pellets in soft reducing conditions at 600°C in a modified Linder test equipment. The high temperature reduction strength is determined under load in the Burghardt-Grebe equipment. However, in order to get more information of the high temperature strength, LKAB intends to introduce a softening test. The tendency of high temperature disintegration will also turn up in the swelling test. The swelling properties are examined according to a procedure developed at LKAB. In this test the pellets are subjected to free swelling without mutual contact. The reducibility of the pellets is recorded in the swelling test.

Jan 1, 1974

By Richard W. Smith

KYANITE, long known to occur in Georgia, did not excite commercial interest until about 1930. Investigations revealed two main types of deposits: (1) separate kyanite crystals embedded in mica schist; and (2) crystal aggregates of kyanite associated with quartz in small and very irregular veins. The second kind at first sight appeared to be the best source of supply. Large boulders or dornicks of kyanite with more or less quartz were found on the surface at many places throughout the Piedmont and Highland sections of the state, but prospecting failed to disclose a sizable vein. These dornicks seem to be a surface accumula-tion from small veins or lens-shaped masses not more than one or two feet thick, and with a horizontal extent of not' more than a few feet. The larger surface accumulation of kyanite dornicks, where not too badly stained by iron oxide, may prove to be marketable, but it is extremely doubtful whether a vein large enough to mine will ever be found. In 1932 deposits of the kyanite-mica schist were known to occur in two places northwest of Clarkesville, in Habersham County. In 1934, at the request of and in cooperation with the Georgia Geological Survey, the United States Geological Survey made a thorough investigation2 of the deposits and found that the two known areas of kyanite-mica schist in Habersham County were but a part of an unsymmetrical, U-shaped belt (Fig. 1) with a western limb extending into Rabun County and somewhat longer than the eastern limb. The total length of the belt is about 30 miles. The width of outcrop ranges from 100 ft. to 1/4 mile or more. Deposits of kyanite-mica schist of very doubtful commercial importance were found in several other counties. Only the deposits of this kyanite-mica schist belt in Habersham and Rabun counties will be discussed in this paper.

Jan 1, 1936

By A. E. J. Engel

INDUSTRIAL talcs and ground soapstones both include earth materials of different chemical and mineral compositions. In general, the industrial talcs are composed of silicates that contain appreciable amounts of magnesia. Generally talc, the mineral, is a predominant or at least common constituent. Talc, the mineral, is a hydrous magnesium silicate, with a suggested theoretical formula H2Mg3 (SiO3)4 or H2O.3MgO.4SiO2, which postulates 63.5 pct SiO2, 31.7 pct MgO, and 4.8 pct H20.11 Actually different single grains or leaves of pure talc have variations in water content ranging from 3.5 pct to more than 7 pct, as well as slight differences in the proportions of MgO and Si02.16 Only a very small percentage of the ground industrial talcs produced in the United States approaches the composition given above (see Table 1). The purer talcs invariably occur as alteration products of magnesium carbonate rocks. Some of these relatively pure talcs include compact, massive types largely mined in California, which are designated as steatite.38,58 In general, steatites cannot contain in excess of 1.5 pct CaO, 1.5 pct combined FeO and Fe203, and 4 pct A1203. The less pure varieties of massive talc and mixtures of magnesian silicates are commonly called soapstones, or merely talc. Many industrial earth products classified as talc or as soapstone contain a variety of minerals, especially serpentine (H4Mg,Si2O9), chlorites (hydrous magnesium, iron, aluminum silicates), tremolite (Ca2Mg5H2[SiO3]8), anthophyllite ([MgCa]SiO3), diopside (CaMg[SiO3]2), and quartz (SiO2). The carbonates calcite (CaC03), dolomite (CaMg[CO3]2), and magnesite (MgCO3) are also present in some industrial talcs and soapstones. Some of these minerals, as well as sulphides, sulphates, and iron and manganese oxides, if present at all or in excess of minute amounts, may alter the composition of the industrial talc sufficiently to restrict materially its use or to lower or destroy its value. These factors are discussed in a subsequent section of this chapter.

Jan 1, 1949

By T. Egleston

The manufacture of charcoal in kilns was declared many years ago, after a series of experiments made in poorly constructed furnaces, to be unprofitable, and the subject is dismissed by most writers with the remark that in order to use the method economically the products of distillation, both liquid and gaseous, must be collected. It is asserted with truth that the number of kilns required for a large production of iron would be so great that it is doubtful whether any works would be justified in making the necessary outlay for their constructiou, but it can also be asserted with equal truth that for any such production in a given locality the use of charcoal as fuel would be eqnally unjustifiable. It appears to have been forgotten that there were other manufactures besides iron in which large amounts of charcoal were used, but these consumers seen] to have been guided entirely by the results of the experiments of the iron men, who necessarily made the largest qnantity of it. Some authors speak in a doubtful way of the quality of the charcoal produced, and a few concede that with great care good charcoal can he made in kilns, but that most of the workmen do not like kiln 'charcoal. This is the real secret of the opposition to this method of manufacture. Most of these objections were written when charcoal was the most important fuel used by the iron manufacturer, and when what was a largeproduction of iron for several furnaces was less than that produced by a single modern one, in localities where other fuels can be had. Almost all that has been written on the subject related to the use of the fuel for the manufacture of iron in the blast furnace, where very peculiar properties are required, and where the qnantity produced is limited by the height of the furnace, and this in turn by the crushing resistance of the charcoal. A large production was, therefore, only possible when the best and hardest woods were used. Of all these objections there is not a single one which is not eqnally applicable to any method of charcoal manufacture, whether it be meilers, pits, or furnaces. Until recently, therefore, the manufacturers of charcoal iron

Jan 1, 1880

By Edward O’Toole

THe Pocahontas district occupies the extreme southern end of West Virginia, principally McDowell, Mercer and Wyoming counties, and a part of Tazewell county, in southwestern Virginia. The first record of the coal field is a report by Prof. J. P. Lesley, of Pennsylvania, about 1880, in which he mentions a coal opening at the upper end of Abbs Valley, Tazewell county, Va. C. R. Boyd, a mining engineer of Wytheville, Va., published a series of articles in 1881, mentioning coal on Indian Creek, Tazewell county, and on Horse Pen creek, which coals, he stated, extended toward the Ohio River. He also mentions the Abbs Valley coal reported by Lesley. In 1881, F. J. Kimball (who became president of the Norfolk & Western R. R. in 1883)) after examining the Scott mine in Abbs Valley, went northward across Abbs Valley Mountain to the place now known as Pocahontas, where he located what has since been called No. 3 vein of Pocahontas coal. In November, 1882, Jed Hotchkiss and others prepared a cross-section of the Flat Top Mountain coal measures, some notes on which were published by Mr. Hotchkiss, between 1880 and 1892, under the title of " The Virginias.' In May, 1881, the Norfolk & Western R. R. was organized through the purchase of the Atlantic, Mississippi & Ohio R. R., an old line running from Norfolk, Va., to Bristol, Tenn., with branches from Petersburg to City Point and from Glade Springs to Saltville. At that time, charters had been granted for three railroads tributary to the New River Valley, but their proposed routes would indicate that the promoters were concerned with minerals, timber, and a connection with the Chesapeake & Ohio R. R., rather than the development of any coal in the Pocahontas district. One of them was projected to extend up Bluestone River a short distance, but not far enough to reach the coal in the Bluestone Valley, and a little grading was done for a narrow-gage road between New River Station and a point in Giles county, Virginia, near the West Virginia line. All charters and railroads in this district were acquired by the Norfolk & Western R.R.

Jan 1, 1925

By Whitman E. Brown, Louis J. Erck

The installation in 1948 of a Hum-phrey~ spiral concentrator section at the Hill-Trumbull plant of The Cleve-land-Cliffs Iron Co. is the latest commercial method on the Mesabi Range being used for the recovery of fine iron ore. In two stages of concentration 84 spirals treat approximately 120 long tons per hour of minus ? in. ore. These spirals augment the production of the heavy-density plant which recovers the plus 36 in. iron from the plant crude ore. Structure of the ore is such that, when crushed, about 50 pct of the plant crude is minus ? in. size. After de-sliming in a 66 in. Akins classifier, grinding the classifier product in a ball mill and again desliming in a 78 in. Akins classifier about 15 pct of the crude ore remains to be treated in the spiral plant. Overall recovery of the ball mill feed in the Hill-Trumbull spiral plant during the 1948 season was about 53 pct of the weight and 66 pct of the total iron content. Of the actual feed delivered to the spirals from the 78 in. classifier 64.9 pct of the weight was recovered containing 73.7 pct of the total iron. The average analysis of the spiral concentrate is 55.05 pct Fe and 14.83 pct SiO2. An average of mill assays during the 1948 season is given in Table 1. The Hill-Trumbull plants treat both wash ore and jig-type ore. During the 1948 season spirals were used only on the fine sizes of jig-type ore. At times the deslimed minus ? in. size is of sufficient grade to warrant bypassing the spirals but in the main the fine size is delivered to the 48 first stage spirals and thence to the 36 cleaner or second stage spirals. In the past several years numerous Mesabi Range ores in the fine size cate- gory have been tested by a wide variety of beneficiating equipment. The prodigious amount of research devoted to the recovery of values in the fine ore reflects the dire need of the iron industry to squeeze the last possible unit of iron from the mined ore and to develop suitable equipment and processes to satisfactorily concentrate the leaner horizons as they are encountered in the process of mining. Large governmental and private appropriations have been allotted, new laboratories built, research and technical staffs increased, and operator-manufacturer cooperative agreements applied to hasten the solution of the problem. The University of Minnesota, at its Eighth Annual Mining Symposium in January 1947, dedicated as its objective the bringing to light of technological developments in iron ore beneficiation. Papers were given at that time relating to processes being developed. Specifically, these papers reviewed flotation, Baum jig, selective media concentrator, Hardinge concentrator, Dorrco sizer, heavy media concentration, Hydrotator, and the Humphreys spiral. The Cleveland-Cliffs Iron Co., after encouraging results from tests in a small pilot plant using one full size spiral, made the first commercial installation of Humphreys spirals on the Mesabi Range at their Hill-Trumbull mine, Taconite, Minn. This company

Jan 1, 1950

By G. W. Jones

THIS paper describes experiments in which eight test samples of gelatin dynamite were fired in three different types of apparatus and the quantity and composition of the gaseous products of detonation determined. The special dynamites were so prepared that the oxygen balance of the samples varied from -35.0 to +6.0 g. per 100 g. of explosive, including the wrapper. By means of this graded series of explosives, the relation between oxygen balance and gaseous products of detonation could be studied explicitly. The effect of varying oxygen balance on explosive strength has been discussed in another paper.1 The apparatus employed in the work described in the present paper included (1) the Bichel gage, a steel bomb of 15-1. volume; (2) the Crawshaw-Jones confined detonation apparatus, a steel cannon from which the explosive is fired into a pipe of 90-1. volume; and (3) the Hercules tank, an apparatus in which the explosive is confined in a quartz block which is placed in a steel tank of about 4500-1. volume. A full description of the apparatus is given later. VARIABLES AFFECTING COMPOSITION OF DETONATION PRODUCTS The character of the detonation products of commercial explosives is governed in part by the same factors that affect the combustion products from explosive mixtures of air with gases or vapors. In either case, combustible materials-namely, carbon, hydrogen, and sometimes sulfur-are present and combined variously. In an exploding gas mixture the combustibles are oxidized by oxygen in the admixed air, whereas with explosives the necessary oxygen is provided by oxygen-carrying materials in the explosive ingredients.

Jan 1, 1928

By Millard K. Shaler, Sydney H. Ball

During the past 50 years the attention of mining-men has been turned to Africa, and within the past decade prospecting-expeditions sent into Central Africa have resulted in the open-ing-up of several mines. Having recently spent two years in the Belgian Congo for the Societe Internationale Forestiere et Miniere du Congo, it is our purpose to outline briefly the mining-conditions in that part of Central Africa. Before it became, in 1908, a Belgian colony, this region was known as the Congo Free State. 11. Location and Area. The Belgian Congo lies in southwestern Central Africa, west of the continental divide, as illustrated in Fig. 1. It has a coastline of but 20 miles on the Atlantic, but widens rapidly eastward to points 5 north and 14 south of the equator. Its area is 908,000 sq. miles, which is almost one-quarter that of the United States and Alaska, or more than one and one-half times that of Alaska. Stated in other terms, its area is nearly one-third that of the United States, exclusive of Alaska and the insular possessions, or more than that of all the United States east of the Mississippi river. III. Topography and Drainage. From north to south, Africa is made up of three topographic elements: 1, the Atlas mountains, a highly-accentuated region

Jan 1, 1911

CHARLES CATLETT, Staunton, Va.-A great many important things have been said in an interesting way but the most startling, to me, is that for 25 years, the price has been in the neighborhood of $1.00, with a minimum of 86 cents and a maximum of about $1.25. It is evident that during all that time the price was inadequate. The amount paid to be divided between the land owner, the capitalist, and the laborer was too limited or too irregular to permit of a healthy condition; yet it is evident that the enormous industrial development of this country was fostered by this very cheap coal, probably the cheapest that has been provided in quantity in any country. I entered the coal business when the price was lowest and my interest and sympathy went out to the man who spent his days in the dirt and foul air of a mine and I was filled with schemes for helping. But at the end of the year, after exercising every economy and in blissful ignorance of proper depreciation and obsolescence, there was still only a profit of 1 cent per long ton for what I think is one of the best coals in the world, the best grade of New River coal. We are now paying a great deal more than we did a few years ago and probably will continue to pay more for some time; but any one who thinks we will not have low prices again is very young or very forgetful. Yet we must have larger profits if the industry is to be healthy, if the three parties to the production are to get adequate returns and be in shape to provide the improvements which will be needed to take the place of and supplement the man-power. This will come when the men are making so much money that the operator wants to replace the man by a machine, and when the operator is making so much money as to be in a shape to make the improvements. He will not put in machinery unless the machinery will save money. We have got to pay a higher prime cost for coal, but engineering skill will teach us how to handle it better and use it more economically, and the ultimate result ought to be of advantage to the public.

Jan 3, 1920

By G. H. F. Gardner

The velocity and attenuation of elastic waves in sandstones were measured as a function of both pressure and fluid saturation. A large change occurs in these quantities if water is added and the rock is not compressed, but the change is small if the rock is subjected to a large overburden pressure. Measurements were made by vibrating cylindrical samples in both the extensional and torsional modes at frequencies up to 30,000 cycles/sec. Formulas were derived which enable the attenuation of dilatational waves in dry rocks to be deduced from the data. Similar experimental methods were used to investigate the properties of unconsolidated sands. Velocities were found to vary with the 1/4 power of the overburden pressure and attenuations to decrease with the 1/6 power. The effects of grain size, amplitude and fluid saturation were studied. Formulas by which the effects produced by a jacket around the sample may be calculated were derived. The practical application of these results to formation valuation is discussed. INTRODUCTION The attenuation of elastic waves in the earth has been of interest to the seismologist and geophysicist for many years, but only recently to the petroleum engineer. Engineering interest has been brought about by the success of velocity logging devices, for it is possible by modification of these instruments to measure the attenuation of sound waves in addition to their velocity and, hence, deduce the mobility of formation fluids as well as the porosities of the rocks which contain them. The main problem is to decide whether field measurements can be made with sufficient accuracy to be of practical use. This problem can only be solved after we know the magnitude of the attenuations which are typical of the earth at various depths. The logarithmic decrement of a fluid-saturated rock is the sum of a "sloshing" decrement and a "jostling" decrement, the former caused by the mobility of the fluid contained within the rock and the latter by the granular framework of the rock. Sloshing decrements can be calculated' using Biot's theory, but the jostling losses are less well understood. The present paper reports an experimental investigation of jostling losses in consolidated and uncon- solidated sands, particularly with respect to the effect of overburden pressure and fluid saturation. Born' showed that the decrement of a sandstone may increase dramatically when only a few per cent by weight of distilled water is added, and that the additional loss is proportional to the frequency of vibration. His measurements were made with no compressive stress on the framework of the rock. M. Gondouin3 investigated similar phenomena for fluid-saturated plasters but also did not compress the samples. In the present paper it is shown that compression of the framework reduces this effect, so that at depth the jostling decrement of a sandstone may be expected to be almost independent of fluid saturation and frequency. Decrements for many sedimentary rocks have been given by Volarovich,4 but all for the state of zero overburden pressure. Anomalously low velocities have been logged in shallow unconsolidated gas sands. Results of the present investigation confirm that these velocities are not caused by correspondingly high attenuations, because the jostling decrement in a packing of sand grains is small and much less than in a consolidated sandstone at the same depth. Velocities in sands have been measured by Tsareva5 and by Hardin6 as a function of pressure, but the corresponding decrements do not appear to have been measured previously. The widely used "resonant bar method" of measuring velocities and decrements was employed. Comments on variations of this technique have recently been published by McSkimmin.7 The main novelty of the present technique was the application of pressure to the samples. It was found possible to do this by placing the apparatus inside a pressure vessel, provided the conditions leading to large additional losses were avoided. These conditions are discussed below. EXPERIMENTAL TECHNIQUE Cylindrical samples were caused to vibrate in both the extensional and torsional mode of vibration and the amplitude of vibration was measured as a function of frequency in the neighborhood of a resonant frequency. The resonant frequency, fr, is related to the corresponding elastic modulus by the formulas where E and N are Young's modulus and the modulus of rigidity, p is the density of the sample, and A the wavelength of the vibration.

Jan 1, 1965