Search Documents

By New kensington P. A, W. L. Fink, H. R. Freche

The investigation of aluminum alloy systems prior to 1923 was severely handicapped by the low purity of the best aluminum available. However, by that time, the electrolytic purification of aluminum had been developed by the Aluminum Company of America,(1)† and in May, 1923, there was initiated, under the direction of E. H. Dix, Jr.,(2) a program for the investigation of the aluminum-alloy systems using the purest electrolytically refined aluminum. Up to the present time 15 papers (3) have been published, most of which are on the binary aluminum systems. Work is now in progress on the ternary systems, and it seems probable that most of the future work will be on ternary systems. Therefore this survey of the binary aluminum systems investigatcd up to the present time (the sixteenth paper of the series) concludes the first phase of this program. Certain qualitative relations between corresponding portions of the various binary diagrams as well as between different parts of the same diagram were noted some time ago by R. S. Archer.(4) In the present paper these relations and others are considered quantitatively by the application of well-known thermodynamic equations or by newly discovered empirical relations. No attempt will be made here to present the history of the development of the thermodynamic equations defining equilibrium or their application to metallic systems, although a list of references is given at the end of this paper for those who are interested in this phase of the subject. Two thermodynamic equations, which will be employed extensively in this paper, are: loge x1 = - L/RT + C

Jan 1, 1934

By S. H. Penn

Preliminary experimental evidence seems to preclude the use of unlubricated mechanical force drills on the moon. Measured values of the coefficients of friction and adhesion between metallic and nonmetal-lic solids have been shown to increase in an ultra-high vacuum environment. The paucity of real knowledge of the influence of a hard lunar vacuum upon interacting solid surfaces, relegates current proposals to sample the moon with a mechanical force drill, to the equivalent of wildcatting on earth. Within a few years, drilling will be attempted on the lunar surface with tools that have been designed with parameters that are normally considered for most conventional terrestrial drills. Lunar drills must be light in weight, portable, have reasonable penetration rates, low manpower requirements, etc. Although the initial equipment cost is expected to be high, this will probably not be a critical factor. Early lunar drilling will be limited to shallow holes with depths of 10 ft or less. The primary function of these holes will be to furnish samples of lunar surface materials but they may also be utilized for other purposes, such as geophysical experiments. Instruments may be installed in them capable of measuring thermal diffusivity, gamma radiation, etc. As sampling will be the primary objective of the earliest holes, sample contamination is a parameter that effectively excludes such otherwise promising techniques as explosive or plasma jet drilling. The most desirable method is probably some form of mechanical force drilling that has the capability of operating in the extreme lunar thermal environment (125° to 37S°K), high vacuum (10- l3 torr range), and low gravity.

Jan 1, 1968

By E. T. Dumbles

Prof. Edward Orton, in his Report on the Occurrence of Petroleum, Natural Gas and Asphalt Rock in Western Kentucky, thus clearly states his ideas of the universal dissemination and rare accumulations of the bitumens:I "We need to bear in mind that the various members 'of the bituminous series are abundantly and almost universally distributed among the unaltered sedimentary rocks of the earth's crust. The valuable accumulations of these substances are rare, it is true, but one can scarcely go amiss' of petroleum, asphalt or gas, at least in small quantities, among the stratified rocks that retain their original structure." Speaking of the Ohio valley, he adds: "A fifth of one per cent. of petroleum, if distributed through a thousand feet of rock, would make a total to the acre, or square mile far beyond any production that has ever been realized from the richest oil field, and -percentages of this amount are not only not rare to find, but are even hard to miss." Dr. F. W Clarke in his Data of Geochemistry (Bulletin No. 491, U. S. Geological Survey, 1911), discussing these views of Orton with similar views of T. Sterry Hunt and Szajnocha, says that they "lead to the conviction that the formation of bitumens is a general process and by no means exceptional. Wherever sediments are laid down, inclosing either animal or vegetable matter, there bitumens may be produced." The organic origin of the bitumens, including petroleum, Gas long been an accepted fact with nearly all geologists, but the method, place, and time of the transformation into petroleum or other bitumen is still under 'discussion. Dr. Orton says? "The statements now presented........bring before us two main views as to the origin of petroleum, viz.: " (1) Petroleum is produced by the primary decomposition of organic

Jan 1, 1915

By C. A. Stetefeldt

It will be of interest to compare the statistics of the gas-producer plant at Aspen, Colorado (recorded by Mr. W. S. Morse in a paper read at the Montreal Meeting, February, 1893*), with those at the Marsac mill, Park City, Utah, where such a plant was first introduced by the writer in July, 1890. In both mills a Stetefeldt furnace is used for roasting; but the Marsac mill has the old-fidsdshioned revolving dryers, while at Aspen, shelf-dryers are at hand. At Aspen, separate Taylor-producers are provided for the Stetefeldt furnace and the shelf-dryers; at the Marsac mill one 7-foot producer supplies gas to both the furnace and the dryers. Hence, in the latter case, the quantity of coal consumed for each apparatus can only be estimated, based upon the relative consumption of wood before gas was introduced. According to Mr. Wilson's statement, the relative consumption of wood in the Stetefeldt furnace and the revolving dryers was as 3 to 2. In the year 1892 the Marsac mill put through the dryers and the Stetefeldt furnace the following quantities of ore and salt (approximate dry weights) : ore, 22,800 tons; salt, 2262 tons. There were consumed in the Taylor-producer 2,714 tons of Rock Springs coal. We may thus make the comparative estimate as follows: Table Showing the Consumption of Coal per Ton Of Ore and Salt at the Marsac and Aspen Mills. Marsac. Aspen. Difference. Pounds. Pounds. Pounds. Drying ore and salt,.... 86.63 72.22 14.41 Roasting ore,.....142.40 117.44 24.96 Total,.....229.03 189.66 39.37 In making a just comparison a number of items must be taken

Jan 1, 1894

By Frank Robertson Van Horn

In June, 1911, the writer spent a few days in studying the economic geology of the vicinity of Park City. During this rather hurried visit a number of specimens of ore were collected, which have since been examind. The results of these investigations show that bournonite (PbCu-SbSa) is present in the ores in greater or less quantity. This fact has never before been reported, as far as can be learned. The failure to recognize this mineral is due to its similarity to tetrahedrite, with which it has probably been confused during a long period of years. Jamesonite (Pb2sb2s6) has been reported from the region in a rather doubtful manner, but the writer has seen it in notable amounts from several mines, and can offer the first analysis of this mineral from the district. Calamine (HzZn2SiO5) was found at one mine and has never been ecognized and reported from the district. Geogbaphy and Geology Park City, Utah, is located at an elevation of about 7,000 ft. above sea level on the eastern slope of the Wasatch mountains. It is situated approximately 25 miles southeast of Salt Lake City. ' The geology and ore deposits have been described in detail by Bout well and Woolsey.' The mines visited are situated south-southeast from the town. The Silver King Coalition mine is located in Woodside gulch about 1 mile southeast of Park City, at an altitude of about 8,100 ft. The other mines visited were the Daly West and Quincy, which are in Empire canyon about 2 miles sontheast of the town, at elevations of 8,300 to 8,500 ft. respectively. The Daly Judge tunnel goes into the mountain from Empire canyon about 1 mile south of the city, at an altitude of 7,700ft.

Jan 1, 1915

By L. C. Uren, E. J. Bradshaw

This paper presents the results of a group effort by a number of University of California students and faculty members, and the authors attach their names primarily in the capacity of editors and interpreters of the data thus assembled. In addition to the writers, the following individuals have made substantial contributions in time and effort in the conduct of this research: Dr. A. J. Carlson, Associate Professor of Petroleum Engineering; J. E. Gosline, University Research Assistant; C. F. Bedford, G. W. Mikulasek and H. S. Conder, senior and graduate petroleum engineering students; H. Bachman, G. Spencer and G. W. Gard, mechanicians in the Department of Mining and Metallurgy. Acknowledgment is also due the Research Board of the University, the Department of Mining and Metallurgy, and Prof. F. H. Probert, Dean of the College of Mining, for continued cooperation in securing mechanical assistance and funds for the purchase and assembly of apparatus. Significance of the Pressure Gradient The expulsion of petroleum from its reservoir sand doubtless is due to expanding natural gas intimately associated with the oil, to the hydrostatic pressure of encroaching edge waters, and to gravitational influences. These forces may operate independently or collectively. In any case they subject the fluids stored within the reservoir sands to elevated pressures, thus causing movement of oil and gas through the productive formations toward the lower pressure of the well outlets. This movement is opposed by pore friction, capillarity and adhesion: resisting influences brought to bear by the reservoir sand on the moving fluids. The magnitude of the resisting force is influenced directly by the viscosity, surface tension and density of the oil, as well as by the properties of the gas. The more rapid the rate of flow, the greater will be the resistance offered, and the greater will be the energy consumed.

Jan 1, 1932

By David H. Browne

The trite maxim that man is a tool-using animal might nowa-days be amended by saying that man is a tool-choosing animal. The chipped flint, at first all-sufficient, gave way to hammered bronze, and that, in turn, to wrought-iron and steel. As our knowledge of metals increases, we learn to specialize; we temper and anneal; we alloy and intermix; and we fashion for ourselves a metal suitable to our necessities. The knowledge of the properties and uses of the various metals and their alloys has become the capital of every constructive engineer, and the currency of every intelligent brass-founder aid blacksmith. Prom year to year, the specifications of the designer become more rigid, and the steel-maker is forced to study more closely the qualities obtainable by changing the treatment, or altering the composition, of his metal. Of making alloys there is no end. We have heard much, during the last decade, of manganese-steel and chrome-steel, of aluminum and tungsten, of titanium- and silicon- and copper-steels, and of every conceivable union into which steel could be coerced or cajoled. Without denying to each of these alloys novel and valuable properties, it. must be admitted that, of all alloys, the one which shows the greatest range of adaptability, and has met the largest measure of popular approval, is nickel-steel. Introduced to public notice by Mr. Riley, in 1889, its field of usefulness has been rapidly enlarged, until, at the present day, the use of nickel-steel is as thoroughly recognized as that of carbon- or manganese-steel. Concerning the properties of nickel-steel numerous articles have appeared in the technical journals. For the man in a hurry, who wishes to look up the properties and limitations of nickel-steel, these articles might almost as well be in the lost

Jan 1, 1900

By Samuel L. Hoyt

Cemented tungsten carbide, a product of a branch of metallurgy which has never possessed more than a relatively minor interest and importance, has recently commanded the attention of engineers, industrialists, financiers and men of business. New methods, new opportunities, new goals, never before considered, have suddenly been brought within the scope of practical realization. It is these results that attract the interest of the world, but we, as engineers and metallurgists, will have equal interest in the product itself and in that branch of metallurgy from which it comes. It seems appropriate, therefore, to speak today on Hard Metal Carbides and Cemented Tungsten Carbide, as the latter represents one of the outstanding developments of recent date in non-ferrous metallurgy. We are interested in the hard metal carbides as a group of related metallic substances and in cemented tungsten carbide as the leading representative of the metallurgy of this group. The literature of this general field is limited, and, bearing this in mind, it seems advisable to attempt to cover the field broadly and to correlate the subject matter, rather than to present a detailed account of any one of its phases. Our annual lecture lends itself admirably to this plan. The quickened interest in cemented tungsten carbide, once its potentialities were recognized, the many sides to the problem of developing the manufacture and use of this new product, and the desire to economize as much as possible in the time of development, have brought many into this work, both in this country and abroad, notably the Osram Lamp Co. and Friedrich Krupp in Germany and the General Electric Co. in this country. It would be presuming too much to attempt to speak too broadly of the present state of the art and science of the hard metal carbides and my remarks arc guided largely by the work done in the General Electric Co., and by our associates in the Carboloy Co. Even here the activities of many in these two groups have centered around the utilization of cemented tungsten carbide, which is outside the scope of this talk. To those whose work is represented in this lecture, it is my pleasant duty to acknowledge their assistance and advice. To Dr. Zay

Jan 1, 1930

By R. L. Mauger, P. E. Damon

Potassium-argon dating of the late Mesozoic and Cenozoic intermediate to acidic plutons and volcanic rocks of Arizona and northern Sonora demonstrates the existence of two distinct magmatic episodes. The earlier episode begins in late Campanian time and dies out before the middle Eocene. Following a quiescent period in middle and late Eocene time, magmatism increases in Oligocene time, becomes most intense at the Oligocene-Miocene boundary and dies out as the Pliocene is approached. Pliocene magmatism is primarily confined to extrusion of post-orogenic basalts. The late Mesozoic-early Cenozoic magmatic pulse is essentially confined within the limits of the classical Laramide orogeny (Laramie through Wasatch time). The mid-Tertiary pulse is contemporaneous with the mid-Tertiary Basin and Range orogeny. The Laramide provides an excellent specific example of Umbgrove's concept of the pulse of the earth and in general his concept appears to be meaningful. Copper porphyry mineralization is time-congruent with Laramide magmatism and there seems to be no doubt as to the existence of a genetic relationship between the two phenomena. Two origins are tenable: direct accumulation of the copper sulfides in the copper porphyry liquid magmatic environment; or, introduction of the mineral constituents entirely from a larger source magma when the host rock is already crystalline. Transgression and regression of the epicontinental seas provide an excellent indicator of orogeny and epeirogeny. There was an overall transgression of the epicontinental seas from early Triassic time through the Turonian epoch in early late-Cretaceous time. Thereafter, there is a relatively continuous regression of the seas until the present time. Both the earlier transgressive episode and the later retreat are intermpted by temporary but distinct reversals. These interruptions can be correlated with classical orogenies. There are six distinct orogenies so indicated in the Mesozoic-Cenozoic eras. These occur at approximately 35 to 40 m.y. intervals. The regression of the epicontinental seas following the Turonian epoch was contemporaneous with the deepening of the Pacific ocean basin over the Darwin Rise. As the Darwin Rise was collapsing the East Pacific Rise was being elevated. The Western United States, situated on the eastern flank of the East Pacific Rise, was upwarped and tilted toward the east. Epeirogeny is the primary consequence of processes that operate on a global scale. Orogeny is an exothennic process that is limited in space and is treated here as a secondary consequence of epeirogenic-initiated warping. The off-campus buildings of the University of Arizona Geochronology Laboratories rest on the volcanic rocks of Tumamoc Hill. From this hill, the observer may obtain a beautiful view of typical Basin and Range topography. The city of Tucson lies below, contained within the broad Santa Cruz basin and surrounded on all sides by characteristic NW-SE trending ranges towering as much as 7000 ft above the valley floor. Since the senior author arrived in Tucson eight years ago, a great deal more has been learned about the geochronology of this and neighboring basins and ranges. For example, the volcanic rocks underlying the laboratory at Tumamoc Hill were shown on the state geologic map as Quaternary basalt. A student of the senior author has demonstrated that the so-called basalts are in fact alkali-andesites (Halva, 1961), and we now know that these alkali-andesites or doreites (Mielke, 1965) are of early Miocene age rather than Quaternary age (Bikerman and Damon, 1965). Is it any wonder then that geologists disagree on the nature and time of Basin and Range volcanism, plutonism and tec-tonism? The plain fact is that few definitive Cenozoic fossil sites were available upon which to base a chronology and geologists were forced to guess the ages of rocks in order to achieve the semblance of a time classification. We have now made considerable progress in developing a K-Ar chronology for the volcanic and plutonic rocks of the Basin and Range (Bikerman, 1965; Damon and Bikerman, 1965; Damon et al, 1964 and 1965; Mauger et al, 1965). It is the purpose of this paper to point out the main features of this chronology and to discuss the relationship of magma-tism to orogeny-epeirogeny during post-Turonian time. We will also discuss probable relationships during

Jan 1, 1967

By H. B. Pulsifer

.ABOut 1.5 varieties, or tnodifications, of the best rnagnesiurn available were prepared and subjected to etching tests, then examined for micro-structure. Of the 30-udd etching reagents that were tried, nearly half, mostly ammonium salts, etched the metal satisfactorily. The surfacing and etching of magnesium is shown to be a very simple and quick operation. The density and hardness of magnesium were determined. The most interesting new observations relate to the finding of the hexagonal etch figures, the crystal laminations, and the fact that the metal is plastic, cold, when restrained or quickly deformed. Under slowly applied pressule cold metal deforms slightly, then shears to fracture without plastic flow. The chief structural features of magnesium arc presented in two reduced photographs and 30 photomicrographs. Materials Tested There are only two sources in the United States from which new metal can be procured: the American Magnesium Corpn. and the Dow Chemical Co. No pronounced structural or property differences in the metals from these two companies were disclosed by the work of this investigation. The following materials were obtained from the manufacturers: 1. Massive crystals of distilled metal (American Magnesium Corpn.). 2. Rods of hot-extruded metal, ½-in. squares and 5/8-in. rounds (American Magnesium Corpn.). 3. Sheet magnesium, 0.005-in. thick (American Magnesium Corpn.). 4. Cast stick metal, 13/8-in. dia. (Dow Chemical Co.). 5. Magnesium-aluminum alloy, hot-rolled plate, ½-in. thick (American Magnesium Corpn.). From these materials, were prepared: 6. Sections from a furnace-cooled ingot made from clistilled crystal. 7. Cold-strained pieces from (6), (4) and (2). 8. Pieces cold-squeezed to fracture from (6), (4) and (2). 9. Hammer-struck pieces from (6), (4) and (2). 10. Steam-hammer struck pieces from (6), (4) and (2). 11. Sections from furnace-cooled ingot of the magnesium-aluminum alloy.

By John Vasey

A shaft of 1690 m depth is currently being sunk to exploit a large copper sulphide orebody. The primary crusher chamber, main pump chamber and the other excavations on the crusher level were developed from the shaft during the sinking operation. The maximum principal stress is horizontal and has a magnitude twice that of the vertical stress. It increased linearly with depth and on the elevation of the crusher level, 1613 m below surface, the stresses induced by mining can exceed the strength of the rock. The development of a workable crusher level layout, and a crusher chamber design and support system are described. Excavation and support of the workings are detailed and a comparison of expected and actual results is made.

Jan 1, 1983

By G. Ferrara

In process and plant simulation, more reliable prediction of industrial results and evaluation of data for designing purposes may be attained by the combined use of (a) modeling and simulation of ore characteristics and (b) modeling and simulation of integrated plant operations. The systems for modeling and simulation of ore characteristics are discussed as well as the conditions in which their use may be necessary (complex structure of the ore-body and variability of the ore fed to the plant). Two examples, for coal and bauxite run-of-mine (ROM), are reported. The procedure of linking the process unit models and the approaches for the solution of integrated systems are indicated. A general-purpose program for the simulation of integrated plant operations is described, and some examples of its use are reported.

Jan 1, 1984

By S. G. Malghan, A. L. Mular

Size distribution and surface area measurements play an important role in the characterization of crushed and ground granular materials properties. This paper outlines sampling methods of granular materials followed by a detailed treatment of principles of size and surface area measurements of a wide range of sizes from crushers feed to ball-mill ground sub-micron particles. Currently available equipment for size distribution and surface area analysis is described and critically examined with respect to advantages, range of application and precautions in their use. Equipment for on- stream size analysis is also evaluated. Finally, a list of criteria are given for selection of particles size and surface area measuring devices for a particular application.

Jan 1, 1982

BECAUSE gold is a compound mineral praised by philosophers and all wise men as being of the highest perfection among all mixed minerals, and because of its great beauty, it is the universal opinion that it possesses extraordinary powers which are beneficial to man. For this reason it is the thing esteemed most highly in this world, after living creatures. Hence, I, too, in order to honor it, wish to begin by speaking of it now rather than of any of the other metals, and I wish in particular to tell you of its generation and of its most obvious qualities, for, although it is a metal very widely known and one that is desired and sought after by all kinds of persons, I know of few who take the trouble to find out what its substance or natural form may be. But, in order that you too may not be one of those who know it only by name or by the appearance that it shows outwardly to us, I tell you that its original and peculiar materials are none other than elemental sub¬stances, with the quantity and quality of each proportioned equally one to the other and very finely purified. From this union of elements which are of equal force there is born a pleasing and perfect elemental mixture,* and then after fermentation and decoction the elements finally become

Jan 1, 1942

By E. B. Olds, Burt. B. P.

THE mines of the Consolidated Coppermines Corporation are at Kimberly, in the Robinson mining district, White Pine County, Nevada. [ ] The blanket-like ore body is a disseminated copper deposit occurring in monzonite porphyry and, in general, is thoroughly fractured, altered, and soft. Contained in the porphyry ores of the extreme westerly end of the ore body are pendants of hard garnetized limestone. A younger monzonite porphyry underlies the ore-bearing porphyry, which in turn rests on limestone and shale. Block caving is the standard method of mining. Because of the undulating top and bottom contours of the ore body, the main haulage level was selected and driven at an elevation calculated to be the most economic depth below the major tonnage sections of ore. Fig. I shows a general section of the Emma Nevada ore body taken through its long axis, which lies roughly in an east-west direction. Mine openings in either type of porphyry require heavy timbering and constant maintenance and repair, particularly in horizons at or near the ore body contact. Where the ore lies close to the haulage level, slusher hoists and scrapers are used to transport horizontally the ore to the main haulage drift (Fig. 2). For the extraction of high-lying ores, a system of branch raises is used; and the ore is mined by gravity. Slushing methods are used also on the high-lying ore-body fringes. Slusher drifts are often driven from the fringe branch raises that have already served their purpose, in order to minimize the cost of the preparatory work in mining the thinner portions of the ore body (Figs. 3 and 4). When a block of ore is developed and undercut, it is economical to mine it as rapidly as the ore will cave efficiently; and this procedure often presents safety problems because of men with equipment working in a relatively congested area. The single-track main haulage drift is about 1 ½ miles long, and lateral haulage drifts are driven under the ore body at intervals determined by the height of the ore body above the haulage level. In order to minimize repair and maintenance, the

Jan 1, 1946

By T. E. Leontis, F. N. Rhines

THE oxide scale that forms upon magnesium at elevated temperatures is nonprotective in the sense that the rate of oxidation is constant and thus does not decrease with the growth of the scale as it does with other common metals. This generality was first stated by Pilling and Bedworth1 and has been verified by Suzuki2 and by Scheil.3 Pilling and Bedworth argued that the nonprotective characteristic could be predicted from the fact that magnesium oxide occupies less space than does the metal from which it springs, wherefore the scale is not expected to cover the metal so completely as to exclude all direct access to the atmosphere. Linear oxidation is thought by Scheil to be common to all cases where the reaction occurs at the oxide-metal interface. According to Suzuki,2 the product of high-temperature oxidation in the air is MgO contaminated with no more than traces of a nitride. When the metal is allowed to burn freely a fume composed of cubic crystals of Mg04 is given off. Delavault5 observed that excrescences form upon liquid magnesium and alloys in the course of oxidation. Beyond this it is known that the use of atmospheres containing small quantities of sulphur dioxide6 or carbon dioxide serve to retard the oxidation of solid magnesium and that beryllium7and calcium8 minimize the oxidation of molten magnesium exposed to the air. Many studies have been devoted to the nature and rates of "protective" oxidation, as exemplified by the cases of copper and iron, wherein the rate is characteristically parabolic. The theory of parabolic oxidation is well developed.9 Linear oxidation, on the other hand, has received but little attention and the theories proposed by Pilling and Bedworth and by Scheil have yet to withstand careful examination. There exists no comprehensive survey of the high-temperature oxidation of magnesium (or of any other metal that exhibits linear oxidation) over a broad range of temperature, under a variety of atmospheric conditions and covering a large group of alloys. It has been the purpose of the present investigation to provide such a survey, with the object of gaining a fuller understanding of linear oxidation, especially as applied to magnesium. EXPERIMENTAL PROCEDURE AND RESULTS The experimental studies undertaken were of two kinds: (I) measurement of the rate of oxidation as influenced by the

Jan 1, 1946

By John C. Branner

No precise geographic limits can be given for the zinc- and lead-region of North Arkansas. In general terms it lies N. of the Boston mountains and W. of the St. Louis, Iron Mountain and Southern railway; but the prospecting and the development of the ore-deposits have not gone far enough to outline more than vaguely the areas over which workable deposits are to be expected. The tardiness of the development of the region is due in part to its topography, as a hilly and partly mountainous country, through which there have been no railways until recently. There is no longer any doubt, however, about the existence in that region of large bodies of zinc-ores. I. General Geology. The general geology of the region is, in the main, quite simple, but that of the ore-deposits is less so. The zinc-regions of North Arkansas lie about the southern flanks of the Ozark dome. The rocks are approximately horizontal, but have a gentle southward dip away from the axis of this dome. Figs. 1, 2 and 3 show the broad features of the to-. pography and geologic structure. South of the zinc-region, the sandstones and shales of the lower Coal-Measures form the north-facing escarpment of the Boston mountains. Beneath the Coal-Measure rocks are the limestones and cherts of the Lower Carboniferous; and these rest upon Silurian and Ordovician beds. The uppermost beds (Coal-Measures) have been cut into by erosion along the mountain-slopes so that their edges or outcrops have a meandering or dendritic form. The same thing happens with the Lower Carboniferous beds; but these, haying been more or less protected by the overlying Coal-Measured, have broader bases, and cover a much larger area. In places,

Jan 1, 1902

By Thomas Clagett

THE Pocahontas coal field comprises the area in Tazewell County, Va., and Mercer and McDowell Counties, W. Va., in which Nos. 3 and 4 Pocahontas seams of bituminous coal are mined. It is a mountainous region with ridges rising 300 to 1000 ft. (91 to 305m.) above the very narrow valleys and, except for some poorly kept farms along the tops of the ridges and the area occupied by the mining and coking plants and villages, is wooded throughout. First shipments were made from Pocahontas in 1883. There are now, about 100 mines, 95 per cent. of which are drift mines. At the end of 1920, approximately 298,000,000 gross tons of coal had been produced and 35,000 acres of coal mined. No. 3 seam is from 4 to 10 ft. (1.2 to 3 m.) thick, but the change is gradual and the thickness fairly uniform in any particular locality. It has a streak of bone, about 2 in. (5 cm.) thick, io which the coal adheres on both sides. In parts of the field this bone is replaced by hard slate, usually from 2 to 4 in. thick. The seam has a slate or fireclay bottom and a draw-slate top. No. 4 seam is from 65 to 80 ft. (19.8 to 24 m.) above No. 3 seam, and of minable section only in the western part of the field. It is from 3 to 8 ft. thick and has two streaks off bone, each from 1 to 2 in. thick. It has a fireclay or slate bottom and is overlaid by from 4 to 24 in. of a laminated coal and slate, locally termed "black rash," which is separated from the coal seam by about 3 in. of slate. This "black rash" averages about 25 per cent. ash, but contains some clean coal. The coal in both seams is quite soft. Cleavage sufficiently well defined to exert an influence on the mining is rare. Overlying strata are slates, shales, and sandstones, the sandstones predominating, extending from .30 to 1000 ft. above No. 3 seam. The strata directly above the. draw slate of No. 3 seam, or "black rash" of No., 4 seam, and up to the first sandstone are usually slates or shales, about 10 ft. thick over the

Jan 5, 1922

By D. T. Peterson, F. A. Schmidt, J. D. Verhoeven

The velocity of mig-ration of these solutes in thorium metal due to a high amperage dc current was measured at several temperatures. All three solutes migrated in the same direction as the electron flow. Diffusion coefficients were combined with the migration velocities to predict the steady-state concentration profile. Electrotransport was shown to be an effective method of removing carbon, oxygen, and nitrogen from thorium and resistance ratios several times larger than for crystal bar thorium were achieved. However, the maxirnum attained purification was well below the predicted values, apparently due to some form of contamination. THE migration of solutes in metals when a high current density dc current is passed has been known for many years. This phenomenon has been the subject of a number of reviews published in recent years.l~* Many of the earlier investigators of electromigration of interstitial solutes interpreted the direction and velocity of migration on the basis of a charge on the solute particle. This interpretation is unclear because, in a given experiment, one cannot separate the contributions to the force moving the solute which arise from the charge on the solute in an electric field gradient and the momentum transfer from the scattering of the electrons or holes. There have been only a few quantitative measurements of interstitial migration velocities and some of these have been characterized by poor accuracy or by errors in the analysis of the experiment. The electrotransport mobilities of carbon, nitrogen, and oxygen in thorium were determined by observing the rate of movement of a discontinuity in the concentration profile. This method was used by Carlson el a~.~ to determine the mobilities of interstitial solutes in yttrium and its advantages are discussed in that paper. The specimen is essentially a pair of semi-infinite, bar-type diffusion couples. The electro-transport velocity was measured by observing the displacement of the mean concentration point in a measured length of time. The diffusion coefficients were calculated by the Grube method from the concentration profile. The transport mobilities and diffusion coefficients can be used to predict the concentration profile in an electrotransport experiment of a given time, current density, and specimen length. At long times a steady state will be reached such that the natural logarithm of the concentration of each solute varies linearly along the bar with a slope which is equal to the velocity of the migrating solute divided by its diffusion coefficient. The estimation of the purification potential of electrotransport is discussed by ~erhoeven.' A comparison of the concentration profile and the purification which should be expected from known solute velocities and diffusion coefficients with that which is obtained in an experiment can be very useful in indicating whether the maximum possible purification has been achieved. EXPERIMENTAL METHOD The apparatus used in this study consisted of a sample chamber which was equipped with two electrodes, a sight glass, and a flange for mounting to a high-vacuum system capable of obtaining pressure of 2 x lo-? Torr. The chamber was made of stainless steel and was 4 in. in diam and 6 in. long. The seal between the electrodes and the chamber was made with "0" rings and compression bushings. The thorium specimens were threaded and screwed into tantalum "U"-shaped adapters attached to the ends of the electrodes. This arrangement is shown in Fig. 1

Jan 1, 1967

By H. B. Pulsifer

ABOUT 15 varieties, or modifications, of the best magnesium available were prepared and subjected to etching tests, then examined for microstructure. Of the 30-odd etching reagents that were tried, nearly half, mostly ammonium salts, etched the metal satisfactorily. The surfacing and etching of magnesium is shown to be a very simple and quick operation. The density and hardness of magnesium were determined. The most interesting new observations relate to the finding of the hexagonal etch figures, the crystal laminations, and the fact that the metal is plastic, cold, when restrained or quickly deformed. Under slowly applied pressure cold metal deforms slightly, then shears to fracture without plastic flow: The chief structural features of magnesium are presented in two reduced photographs and 30 photomicrographs.

Jan 1, 1927