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By R. F. Shurtz

R. Duval (Mining Engineer, Ancien eleve de PEcole Polytechnique, Paris, France) I do not agree with the Eq. 3, reading: m =1/100- [(0.214x30.4) + (0.7B6 x0.00)] =6.5pct CaO If 0.214 and0.786 were proportions by weight, the equation would represent the well known mixtures law of the conventional arithmetics and 6. 5 pct CaO would be the correct average content. But it is not the case as the author states: "In samples consisting of single grains of mineral, those grains must, as already mentioned, be either of dolomite or magnesite. Since 78.6 pct of the deposit consists of magnesite and 21.4 pct of dolomite (excluding for present purpose the presence of other minerals), for any single grains picked at random the probability will be 0.214 that is it dolomite and0.786 that is it magnesite. In 1000 such samples the expected numbers of dolomite and mapesite grains will be 214 and 786 respectively." 0.214 and 0.786 would be proportions by weigbt under the necessary condition that all grains of dole mite and magnesite should have an identical weight. Obviously it is not the case, as the specific gravities are not the same for mapesite and dolomite and the volumes of the grains are different. Furthermore, because of these differences the conditions for a random sampling are not fulfilled and we are not authorized to state that the probabilities are, respectively, 0.214 and 0.786. The author however makes a simple application of Eq. 1: M = 1/n— ? fi x i . n Should we deduce that this relation is wrohg? Not at all, but when applying Eq. 1 you must not overlook what it actually. means. Eq. 1 gives a definition of the arithmetic mean of a total of n observed values Xi and nothing else. But the average conteht of a deposit has not the same significance. It is the ratio between the weight of concerned mineral in the deposit and the total weight of the deposit. As from 1000 particles the 214 of dolomite and the 786 of magnesite have not the same weight, the two definitions do not concur, and when applying Eq. 1 the result is an arithmetic mean of figures which has no connection with what is named average contentof a deposit. The situation is similar to the calculation of an average velocity. If a car travels a first mile over at 30 miles per hr and a second mile over at 60 miles per hr, when applying formula 1 you find as average velocity for the 2 miles: 30+60 ------- - 45 miles per hour. Many people calculate in this way and they do not realize that a mistake is involved. In fact the definition of he average velocity for the 2 miles is the quotient of the distance of 2 miles by the time (in hours) necessary for 2 miles travel, i.e.: 2 ---------- = 40 miles per hr. 1 + 1 30 60 In other words, the average volocity wanted is not the arithmetic but the harmonic average of the two velocities. The above mentioned bias in the calculation of the average contents of deposits is frequent, even in the assessments made by experienced engineers and is independant of what is named the sampling error. In order to supress the bias and to be able to use Eq. 1, you must apply a correction. An example on the subject can be found in an article by Duval et al. in the January 1955 issue of the ''Annales des Mines" (French), page 19. R. F. Schurtz (Author's Reply) Mr. Duval's position is quite correct. The proportions shown for dolomite and magnesite., respectively, of 0.214 and 0.786 are, in fact, proportions by weight uncorrected for specific gravity. In our day to day operation of producing magnesite from these mines at a very substantial rate, we do not normally make corrections for the difference between the specific gravity of dolomite and that of magnesite. If these corrections are made in Eq. 3 as shown in my article, then the numbers of grains turn out to be in proportions of 0.226 dolomite and 0.774 mapesite instead of the values actually shown in the equation. For the purposes of our work, and in view of the inherently low accuracy of the data, this correction was not deemed worthwhile making.

Jan 1, 1961

By P. Gordon

An isothermal jacket microcalorimeter, supplemented by metallographic, microhardness, and X-ray measurements has been used to study the isothermal annealing of high purity copper after room temperature tensile deformation. The amount of stored energy released during annealing has been measured as a function of deformation in the range 10.8 to 39.5 pct elongation. The data have shown the major heat effect to be associated with recrystallization and have allowed an analysis of the recrystal-lization kinetics and the calculation of activation energies of recrystallization. WHEN a metal is deformed plastically, some of the energy expended is dissipated as heat during the working process, while the remainder is stored within the metal in the form of lattice distortions and imperfections. During subsequent heating of the metal, the distortions and imperfections can be largely annealed out and the associated stored energy released as heat. It is apparent that measurements of the evolution of stored energy during such annealing may produce important information concerning the nature of the annealing mechanisms and the imperfections involved. Some excellent studies of this type have been made in the past, notably those of Taylor and Quinney,' Suzuki,2 Bever and Ticknor,3 Borelius, Berglund, and Sjöberg,4 and Clarebrough et al.5,6 None of this work, however, employed isothermal techniques, with the exception of the Borelius studies' in which only the early annealing stages were investigated. Since isothermal measurements, as compared with heating or cooling curve, have the merits that 1—they reveal the kinetics of a process more clearly, 2—the results obtained are more easily applied to theory, and 3—most fundamental investigations of annealing using techniques other than calorimetry have been carried out isothermally, it was considered important to apply calorimetry to the study of the isothermal annealing of metals. Accordingly, an isothermal jacket calorimeter of the Borelius type,' supplemented by metallographic, hardness, and X-ray measurements, has been used to study the annealing of high purity copper after room temperature tensile deformation. Experimental The microcalorimeter has been described fully elsewhere." Briefly, the specimen to be studied is placed in a constant temperature environment of virtually infinite heat capacity achieved, as shown in the drawing of Fig. 1, by means of a vapor thermostat. A high thermal resistance is provided between the sample and the environment and a sensitive differential thermopile (see Figs. 2 and 3) arranged with half its junctions in contact with, and thus at the constant temperature of, the environment, and the other half in contact with the sample. A reaction in the sample develops a small difference in temperature, AT, across the thermopile, which is followed by a recorder-galvanometer set-up as a function of time, t, and is converted to reaction heat per unit time, P, by the use of the equation AT P=a?T + b AT dt The constants, a and b, in Eq. 1 are determined by a simple calibration, making use of the Peltier heat developed by a small current run through the junction of a thermocouple located in an axial hole in the specimen (Fig. 2). In its present form, the limit of sensitivity of the calorimeter is a heat flow of 0.003 cal per hr. The copper used was the spectroscopically pure metal supplied by the American Smelting and Refining Co. in the form of 3/8 in. diam continuously cast rod, reported to be 99.999+ pct Cu. A small amount of the copper was available at the start of this work and is referred to hereafter as lot A. A second batch, lot B, was obtained later, most of the results described subsequently being for this lot. As will be seen, there is some indication that lot A was somewhat purer than lot B, but it is not known whether this difference was present in the as-received metal or arose during subsequent handling. The two lots of copper were remelted and cast into two 1½ in. diam ingots in vacuo, using high purity graphite crucibles and molds. The ingots were upset several times to break up the large cast grains, and then rolled and swaged to rods 0.391 in. in diameter, using several intermediate anneals with about 40 pct reduction in area between anneals. The penultimate anneal was 2 hr at 350°C. X-ray examination showed no marked general preferred orientation in the resulting rods. The grain structure typical of the two rods is shown in the micrograph of Fig. 4." It was found to be virtually im- possible to get an unambiguous measure of the absolute grain size in the two annealed rods because of the profusion of annealing twins and the lack of regularity of the grain boundaries. However, counts of the number of boundaries intersected per unit length along a random line on a polished section, making a correction for the proportion of boundaries (about half) estimated to be twin boundaries, gave a figure of about 0.015 mm for the average grain diameter. The grain size of the rod from lot A was about 5 pct smaller than that from lot B. The rods were cut into 1 ft long bars and these deformed in tension at room temperature to various total elongations in the range 10.8 to 39.5 pct. A strain rate of 1 pct per min was used. The deformed bars were then stored in a dry ice chest until such time as samples were to be cut from them. Five bars deformed as indicated in Table I were used for the subsequent tests. In all cases, all the calorimeter.

Jan 1, 1956

By Craig R. Barreft, Oleg D. Sherby

The steady-state creep characteristics of pure polycrystalline copper were studied in the temperature range 400" to 950°C and in the stress range 400 to 7000 psi. Tests were conducted in dry deoxidized hydrogen and all specimens exhibited high ductility before fracture. Two activation energies for creep were established as a function of temperature. Above about T/T, = 0.65, the activation energy for creep was 48,000 cal per mole whereas between 0.5 and 0.65 T, it was 28,000 cal per mole. The observed temperature dependence of the activation energy for creep follows the same trend as exhibited by the self-diffusion coefficient of copper in copper single crystals and silver in silver single crystals. It is therefore believed that the rate-cmtrolling mechanism in creep of copper in the stress and temperature range studied is diffusion-dependent and is probably associated with a dislocation-climb process. The low activation-energy region is attributed to enhanced volume difFusion from the presence of dislocations which act as short-circuit paths for diffusion. THERE is extensive experimental evidence1,2 that the activation energy for creep, Q,, for pure poly-crystalline metals tested at temperatures above one half the absolute melting temperature (0.5 Tm) is a constant and equal to the activation energy for volume self-diffusion, Qsd This equality is generally interpreted as meaning that creep in this temperature range is controlled by a dislocation-climb process. The existence of high-temperature creep activation energies not equal to the respective self-diffusion values has been suggested both theoretically3"5 and experimentally.6-8 Two examples of apparent nonequality between Q, and Qsd have been reported for the cases of silver7 and copper,' where activation energies for creep much lower than those for self-diffusion persist to rela- tively high temperatures (up to 0.6 T,). These observations suggest that dislocation climb may not be the only important process in the high-temperature deformation of these metals. That dislocation climb does indeed occur relatively slowly in these two metals due to their low stacking-fault energy has been suggested by many investigators.9-10 Although the creep behavior of copper has been studied extensively at low temperatures, the high-temperature activation energy for creep is not well-defined. The data of Feltham and Meakin8 indicated that Q, is temperature-dependent above one half the melting temperature, equaling a value of -30,000 cal per mole at temperatures up to 550°C and increasing to a value of -49,000 cal per mole at 700°C. No data has been reported above 700°C. The value of 49,000 cal per mole is very near the value of Qsd for copper reported by Kuper et al." as 47,100 cal per mole. In view of the lack of high-temperature creep data and the apparent temperature dependence of Q, for copper the present investigation was undertaken to determine the value of Q, over the temperature range of 400" to 950°C. It was hoped that such a study would clearly document the temperature dependence of Q, and yield significant information as to the nature of the rate-controlling creep mechanisms. MATERIALS AND PROCEDURES The material used in this investigation was high-purity OFHC copper. After rolling and recrystal-lization treatments spectrographic and chemical analyses showed only 0.0008 pct Ag, 0.0002 pctCa, 0.0002 pct H2, and 0.002 pct O2 as trace impurities indicating a purity of greater then 99.995 pct. Specimens were machined from cold-rolled sheet and the gage sections polished with 2/0 emery paper prior to annealing treatments. Annealing was done in both vacuum and dry deoxidized hydrogen atmospheres. No variation in creep strength was found as a result of the different annealing atmospheres. The final annealing temperature was either 700°, 800°, or 1000°C depending on the temperature range to be studied. These treatments resulted in average grain diameters of 0.03, 0.4, and 1.0 mm, respectively. The precise mechanical-thermal history of these

Jan 1, 1964

By W. E. STOKES

SOME extension of flying service to the mining industry occurred in 1938, particularly in Canada, where freighting activity radiated from Edmonton into the new northern mining districts. Again the airplane demonstrated its usefulness in getting new equipment rapidly into the field and in decreasing shutdown time while waiting for repairs. An 18-ton Caterpillar tractor with shovel attachment was disassembled, brought in by plane, and placed in operation at Berens River, Ont., within seven days after its de- livery at Winnipeg. At Central Patricia a mill breakdown required the replacement of a full mill head and trunnion with ball bearings, weighing 2700 lb. The Canadian Airways Junkers, termed the "flying boxcar," was called in from Yellowknife, 1300 mi. away, and the new installation was completed three days later.

Jan 1, 1939

By J. E. Brantly

THE oil-producing industry may logically be 'divided into four independent branches: (1) Acquisition of possible productive lands by lease, fee purchase, concession, or otherwise and the perfection of titles thereto. (2) Studies of the geology of the properties, leading to the location of exploratory wells. These involve reconnaissance and detailed surveys and the use of geophysical instruments, where conditions do not permit surface determination. (3) Drilling of exploratory or test holes and, later, exploitation wells. (4) Actual recovery of the oil from the wells by flowing, pumping, or other methods. These four divisions of the industry are unrelated in detail of accomplishment, but they are entirely complementary, one to the other, and must, in any efficient' organization, harmonize in their respective efforts toward the desired ultimate end. The relative order for the first two branches is not necessarily the proper one; in fact one should have knowledge of the favorable possibilities of a given property before it is acquired, and preferably, also, final opinions as to then proper location for an exploratory well, if such is justified in the light of

Jan 1, 1937

By Paul F. Kerr

The insufficiencies of our mineral resources are becoming well known, and the national political conscience seems to be troubled at last by our dependence upon mineral commodities which must come from other lands. This realization places increased responsibility upon the industrial, educational, and governmental groups whose task it will be to solve the problems of mineral supply. As we all know, from the time that man first sought mineral deposits until recent years, prospectors have been largely responsible for mineral discoveries. Today the era of the prospector is almost over. The human ants that have literally examined all accessible outcrops and have tested the gravels of nearly all stream beds in the United States have left undiscovered few worthwhile mineral deposits within the scope of their recognition. The pages in the history of mineral exploration are now being turned from the era of the surface prospect to the era of the hidden de- posit.

Jan 1, 1949

By C. R. Dale

IT IS the purpose of this paper to point out a number of the most common causes of crooked holes; to outline methods of drilling and straightening which to my personal knowledge have proved successful in numerous cases; to describe some of the characteristics of holes which, though not crooked in an exaggerated sense, may still cause serious mechanical trouble if not recognized and properly remedied; and to define clearly the part of oil-well surveying in the concerted effort operators generally are making to keep their wells straight from spudding to completion

Jan 1, 1931

By A. Ross Rornmel

ABILITY to speak effectively is one of man's most longed for and coveted abilities. It is the ability to stand on one's feet, transfer knowledge and thoughts to others, to reach an objective professionally or otherwise by leading groups through a channel of planned thought. Each day group speaking plays an important part in making or marring success, and the engineering profession often provides this opportunity and requirement. An ability to speak effectively develops courage, poise, confidence, and prestige for the speaker. The technical man cannot be reluctant to face an audience. He is often called upon to do this in presence of employees, supervisors, and other groups. His ability to speak effectively is as much a requirement as the fundamentals of his profession. The three fundamentals of effective speaking are: (1) Enthusiasm and Confidence. These are joined because of their close relation. (2) Preparation. This includes knowledge of the subject. (3) Presentation. By this is meant the features of delivery.

Jan 1, 1946

By I. N. Knapp

Introduction.—The spccial object of these notes is to describe the mixing, testing, and use of mud-ladened water for rotary drilling in such a way as to make them helpful to the driller, the operator, or the engineer in solving his own special drilling problems. The structures, apparatus and tools used are indicated in a general way. No attempt is made to describe the art of rotary drilling; only such descriptions as are necessary to make plain the use of mud are given. The information is the result of actual experience in drilling in Coastal Plain formations. The materials encountered in the wells drilled were unconsolidated sands, gravels, and clays, in which thin layers of sandstones, shell conglomerates, and shales began to appear at about 1,200 ft, in depth, although one well was drilled to 3,018 ft. without encountering any cemented or indurated materials. Unusual Conditions.—-The general surface of the ground where the drilling was done being hardly a foot above mean tide, and the daily tidal variation being about 15 in., it was found necessary to plank over the sod surface with 3-in. plank to work from. A 30 by 30 ft. planked area was sufficient to carry the derrick with equipment and 2,500 ft. of 4-in. drill pipe stacked in it. The derrick was set up 3 ft. on cribbed blocking arranged to spread the load over the planking. The engine, bailers, and pipe yard were also carried on 3-in. planking. Drilling 0utfit.—This consisted of a derrick, 20 by 20 ft. and 84 ft. high, two 35-h.p., "oil country" boilers, one double 8 1/4 by 10 in. reversible engine, two 10 by 6 by 12 in. duplex mud pumps, one 15-in. rotary, "hoisting works" with chain drive, hoisting block with line, crown block with pulleys, rotary jetting swivels, hose, complement of tools, pipes and connections, and a mud mixer, with engine. Hydraulic Rotary Drilling Method.—This method of drilling is an adaptation of Fauvelle'sl invention made in France in 1833 for drilling

Jan 1, 1915

By Bernard Moore

THE last few decades have witnessed the introduction of many new nonmetallic mineral products and changes in the use of many of those already well known. Among these is diatomite, formerly employed as a mild abrasive and, at one time, as the absorbent material in dynamite. Now nearly 100,000 tons a year are mined and milled into such things as filter aids, cement admixtures, insulants, fillers, absorbents, cosmetics, cleansers, etc. Pumice, commonly regarded as only an abrasive, is now also employed as an insulant, as light-weight aggregate and as a concrete admixture. With increasing use of insulants, light-weight aggregates, and acoustic stuccos and plasters in the building trades, both these mate-rials should find increased application. Very large deposits occur in eastern Oregon and have been studied by the U. S. Geological Survey in cooperation with the Oregon State Mining Board.

Jan 1, 1934

By C. Chiou, D. P. Seraphim

The effect of clustering on the superconducting properties of Al-Zn alloys has been studied by the ballistic induction techniques. The superconducting critical temperature, T,, changes when zinc-rich clusters are formed. The change in T, depends on the concentration and may be positive or negative, but always correlates with an effective decrease in the solute concentration of the alloy. Reversion after clustering effectively returns a 5 at. pct Zn alloy to the quenched state. These methods might be use&lly extended to the Al-Mg system, where X-ray data are difficult to obtain. In very dilute Al-Zn alloys, as in other tin,' indium, aluminum,2 or tantalums base solid solutions, there is a decrease in the superconducting critical temperature, Tc, roughly proportional to the temperature independent resistivity, i.e., -0.2°K per pS2cm. With increasing solute concentration, the T, generally reaches a minimum and then increases4 to a value well above that for the pure solvent. The change of T, with solute concentration follows an empirical formulation involving two constants which correlate with the scattering cross section of the impurities. As will be shown below, the Al-Zn alloys more concentrated than 1or2at. pct do not follow the empiricism, probably because they are unstable even when rapidly quenched.5 However, it seems possible to study at least the later stages of solute clustering by precise measurements of the 1', following various thermal treatments. A few experiments on quenched alloys, aged alloys, and tests on reversion are reported here. The heat treatments selected for obtaining the quenched and aged states were mainly deduced from the work of Dash and Fine.6 For the quenched state, specimens were homogenized at 480°C, quenched to -160°C, and immediately transferred and mounted in liquid nitrogen. Measurements on the superconducting properties and residual resistivities were then made at helium temperatures, after which the specimens were aged at room temperature for 3 to 5 hr, i.e., much longer than the time required for clustering to be essentially completed. The superconducting properties and residual resistivities were once again examined. To reach the reverted state of the A1-5at. pct Zn alloy, the aged specimen was heated for 5 min at 200°C and then tested as above.

Jan 1, 1963

By J. W. Halley

THE effects of tin on steel have become increasingly important because of the necessity of using poorly detinned scrap, tin cans, and terne plate, in the open hearth. Since a tin can contains about 1.5 per cent tin, it would be possible to have up to 0.75 per cent tin in steel made with a 50 per cent scrap charge. In order to use tin-containing scrap, it is necessary to know the effect of tin on various grades of steel. The following investigation is by no means comprehensive but covers a number of steels in which tin content is important. PUBLISHED WORK A number of investigations of the effects of tin on rolling quality and physical properties have been published. It has been found that tin increases strength and hardness and reduces ductility and notched impact resistance. The decrease in ductility and notched impact resistance becomes more marked as the carbon decreases. McKimm1 found no change in Olsen ductility, Rockwell hardness, yield strength, tensile strength or elongation in cold-reduced strip containing up to 0.124 per cent tin. A tin content of 0.15 per cent gave difficulties in rolling and increased the hardness but 0.21 per cent tin showed no change in properties from material containing very little tin. No explanation of this contradiction is offered. Andrew and Peile2 investigated steels containing 0.10 to 0.25 per cent carbon and up to 0.63 per cent tin. They found an increase in tensile strength 0f from 100 t0 200 lb. per sq. in. for each 0.01 per cent tin on normalized samples. The elongation and reduction of area were decreased and the notched impact resistance was reduced markedly. Quenched and drawn samples did not show embrittling if water-quenched from the draw temperature of 1148°F. (620°C.). They could find no evidence of tin under the microscope. Whitely and Braithwaite3 investigated the effect of tin on rail steel containing 0.55 to 0.60 per cent carbon. They found that 0.08 per cent tin caused a marked decrease in elongation, notched impact resistance and the degree of bend. The tensile strength was increased in some tests and not in others. Bolsover and Barraclough4 investigated the effect of tin up to 0.50 per cent on a 0.35 per cent carbon steel and on several alloy steels with from 0.30 to 0.40 per cent carbon. They found a comparatively uniform decrease in notched impact resistance with increasing tin on quenched and drawn samples. If the samples were quenched from the drawing temperature or reheated to the drawing temperature and quenched, the embrittling was much less severe. Steels containing molybdenum suffered much less embrittlement than other steels. EXPERIMENTAL WORK Effect of Tin on Low-carbon Rimmed Steel Increasing quantities of tin were added to four ingots of a heat of the following ladle analysis: carbon, 0.08 per cent; manganese, 0.39; phosphorus, 0.009; sulphur, 0.025.

Jan 1, 1942

By M. R. Daly

In a recent paper on Geologic Structure in the Cushing Oil and Gas Field, Oklahoma,l Carl H. Beal has pointed out some interesting peculiarities in the distribution of the hydrocarbons and the disposition of the "planes of separation" between the oil and the water (water surfaces). Mr. Beal's principal statements on this matter may be, summarized as follows: I. In every important dome in the Cushing field, which has not been complicated by folding along its sides, the oil area in each of the three oil and gas sands studied (Layton, Wheeler and Bartlesville) apparently extends farther down on the long axis of the dome than it does on the steeper sides. The result is that water is encountered at a lesser depth below datum plane (sea level) on the steep sides of the dome than along the ends where the beds are more gently tilted. II. In the Layton and Wheeler sands (to which the detailed study of water surfaces has been almost entirely confined), the water surface is not level, but dips at a gentle angle (maximum dip 100 ft. to the mile) away from the center of the structure. This inclination existed prior to development, and it has been rendered greater by the rapid extraction of oil and gas. To these statements, the following observations are added: The dominant structural feature in the Cushing field is a broad north and south anticlinal fold, along whose axis the domes are distributed (Fig. 1, p. 897), and the more important oil areas in each sand lie on the west side of the field. In many cases, gas has been forced to the east side of the structure, sometimes as far as the water line. From the distribution of the oil and gas bodies, Mr. Beal concludes that the hydrocarbons in this region probably migrated from the west or the northwest. It seems as if these different features would be susceptible of some

Jan 1, 1918

By Donald B. Gillies

THE great source of iron ore for the furnaces of this country has been the Lake Superior district. Ore was first discovered there in 1844, and the first shipments made via the Great Lakes in 1852 to a furnace at New Castle, Pa. The stream of ore from that region increased slowly to exceed a million tons in 1873, and did not reach 10 million tons until 1895. By 1901 it exceeded 20 million tons, and in 1907 over 40 million tons. Total Lake Superior output through 1948 was about 2500 million long tons. Outside the Lake Superior district are the Southern district, including mainly Alabama, Georgia, Missouri, and Texas; the Eastern district of New York, New Jersey, and Pennsylvania; the Western district embracing Wyoming, Utah, and California.

Jan 1, 1949

By E. J. KENNEDY

FEBRUARY 15-18 will be the outstanding dates of the month for members of the A. I. M. E., for then the 141st Meeting of the Institute is to be held in the Engineering Societies Building, at New York. What with 41 technical sessions, the Annual Business Meeting at 4 o'clock Tuesday afternoon,, two sessions of the Section and Division delegates, minor committee meetings, and the many luncheons and dinners, the Dinner-Smoker, Informal Dance, President's Reception and the Dinner-Dance, the opportunity will be limited to do- more-than cast sheep's eyes at New York's other multitudinous attrac¬tions until the meeting is over. The technical program is diverse but well organized. The sessions are almost equally divided among the four days, with ten on Monday, Tuesday, and Wednesday, and 11 on Thursday. The meeting opens Monday morning with registration. Be sure to attend to this detail. Failure to do so may have its repercussions at the meeting and throughout the year.

Jan 1, 1932

By Don M. Jackson, Robert W. Howard

Techniques for the epilaxial growth of single -crystal silicon carbide films on silicon were developed. The vapor-phase decomposition and bydrogen reduction of silicon tetrachloride (SiC14) and Propane (C3H8) resulted in clear films of silicon carbide, lip to seveval microns in thickness. The growth took place in a horizontal . silicon epilaxial reactor at 1100°C (pyrometer) at a rate of- 3000Å per minute. Electron diffraction and X-ray diffraction studies demonstrated that the films were single-cyrstal, ß -phase, or cubic silicon carbide. SiO2 film were used to mask areas of the silicon sur-lace in order that the silicon carbide might be grown in controlled geometries. Both n- and p-type films were grown on p-type silicon waters.. Heavily doped silicon films of the same conductivity type as the silicon carbide films were deposited over the silicon carbide in order to affect better probe contact to the structures. when n-type silicon carbide mesas were grown on p-type silicon substrates the de vollage-current relationships between films and substrates were that of junction diodes. These diodes showed a sensitivity to while light ill that the incident light increased forward- and reverse-satro,ation currents, P-type silicon carbide mesas grown on p-type silicon were ohmic rather than rectifying in their voltage -current relationship. No conclusions could he reached concerning heterojunc-tiou rectification in the structure. SILICON carbide is a semiconductor with many interesting properties. It decomposes at temperatures above 2200°C.1 It occurs in two general crys-tallographic forms—hexagonal (a Sic) and cubic (ß Sic)—with the cubic form having a forbidden-gap energy of 2.32 ev and the hexagonal form (specifically the 6H polytype) a gap energy of 2.86 ev.3 It behaves as an extrinsic semiconductor at temperatures approaching 5003C. It has been shown to have a high resistance to radiation damage4 and p-n junctions formed in Sic have been shown to radiate visible light under forward- or reverse-bias conditions. Epitaxial silicon carbide on silicon carbide has been successfully grown through the use of a variety of techniques, such as gaseous cracking of SiCL4 and CC4, nearly all of which require a deposition temperature above 1500°C.6 This paper will cover very recent work on the gas-phase deposition of highly ordered films of silicon carbide on high-quality silicon single-crystal substrates. The films have been shown to ex- hibit junction-rectification properties when geometrically isolated regions are electrically biased with reference to the silicon substrate. There will be no discussion of the mechanism of heterojunction rectification, but the methods of film fabrication, geometry control, and structural evaluations will be covered in detail. Electron diffraction, X-ray diffraction, and diode electrical properties were used to characterize the films and the junctions. GAS-PHASE DEPOSITION OF Sic The techniques for the deposition of silicon carbide films were a logical outgrowth of the standard silicon epitaxial process. The major premise followed was that, for any film to nucleate in an ordered fashion where there is considerable mismatch in lattice parameters (in this case 22 pct), an extremely clean, damage-free substrate surface must be presented to the gas stream. Thus a standard gas-phase HCl etching step was used to prepare the substrates for growth. A minimum of 5 µ of substrate-surface material was removed prior to the deposition of Sic overgrowth films. The techniques used for growing silicon carbide films were those of growing silicon alone, with the added injection of a hydrocarbon gas into the hydrogen and silicon tetrachloride gas stream. The hydrocarbon gases used thus far have been research-grade (99.99 pct) methane (CH4) and propane (C3H8). Propane ultimately gave the best results. The gas flows were controlled through a panel shown schematically in Fig. 1. A hydrogen main stream of 30 liters per min passed through the horizontal quartz-tube epitaxial reactor, while SiC14, C3H8, HC1, and doping gases were injected as side streams. The

Jan 1, 1965

By A. H. Tousley

Current problems in the cement industry are discussed and suggestions for solving them by modernization are made. Cement facility modernization is discussed in considerable detail with examples illustrating before and after conditions. Itemized are the improvements realized in better working conditions, better efficiency, higher production, lower costs, and better community relations. These improvements are related to the overall profitability of the particular plant or facility.

Jan 1, 1972

By Luis Toron, Salvador Cortes-Obregon

John D. Price (Colorado Fuel and Iron Corp., Pueblo, Colo)—The paper on the coal fields of the Oaxaca district as prepared by engineers Toron and Cortes-Obregon of the staff of the Bank of Mexico bears witness to the thorough and careful way in which the men associated with this organization perform their work. There is little to be added to their paper in way of discussion other than to confirm and amplify some of their statements. Since the only extensive and well-developed field of coking coal lies in the northeastern section of the country adjacent to Sabinas in the state of Coahuila, it follows that blast furnace plants would be located in that same region. Two such plants are now operating at Monterrey and Monclova, using coke produced at the Sabinas district mines. But the nearer of these two plants is 600 miles from Mexico City and even farther from the center of population. Transportation of products from these mills to the market area is therefore expensive, both because of the distance and the difficulty of the terrain over which it must be carried. The development of an integrated steel industry closer to the center of population has therefore long been a goal toward which the Mexican technicians have been striving. While the presence of coal of some grade has been reported in many of the states, and many ideas have been advanced regarding its possible uses in iron and steel production, deposits of anthracite in Sonora and the various coals of the Oaxaca district as reported on in this paper are the only ones that have been explored in a serious manner. The coking coal from the Mix-tepec zone appears to offer promise of producing a coke which could be used in a standard blast furnace. Several problems are indicated, however: 1—The ash in the coal is high as mined, but indications are that it can be washed to an ash content of 15 pct with a recovery of 70 pct of washed coal. 2—Such washing would increase the volatile content from 17.4 pct to about 20 pct, and in a byproduct oven this should give a coke yield of close to 80 pct with an ash content of coke under 20 pct. 3—A free swelling index of 5 appears low for a good coking coal, and below that of the coals from the Sabinas district, which show between 6 and 9. But washing of the coal should result in an improvement in this regard; in the United States coals from Utah with an index even lower than 5 have made a usable coke. 4—A coal with volatile as low as 17.4 in raw coal and 20 in washed coal would come close to being classed as a low-volatile rather than medium-volatile coal, and low-volatile coals are notorious for their high expansion properties. Several plants in the United States are making coke from straight medium-volatile coal of 26 to 28 volatile content, and one at Rosita,, Mexico, from coal of 25 volatile. But no plants to my knowledge are using coal as low as 20 volatile. Since the Rosita coal appears to be a borderline coal from the angle of its expansion properties the coking of one of the straight lower volatile must be approached with caution. 5—There are few coals possessing any degree of coking properties which cannot be used in coke production by careful attention to its preparation and blending. The fact that coals of other types are available in this same region make improvement through blending very possible. 6—There are other workable methods of reducing iron ore other than the conventional coke-blast-furnace method. These will not be discussed here but it is known that their use has been considered. The technicians of not only Mexico but also of the other Latin American countries are keenly aware of their natural resources and their national needs. This paper emphasizes the fact that the Mexican technicians are working on their problem and attempting to speed the day of self-sufficiency for their country. Salvatore Cortes-Obregon (author's reply)—I wish to thank Mr. Price for his kind remarks. The Mixtepec coal as shown in Table II has 30 pct ash and a free swelling index of 5, but when the same coal is washed to 15 pct ash it has a free swelling index of 8 to 9 and the volatiles increased from 17.4 to 20.7 pct. A satisfactory coke has been produced from blends made in the Mexican laboratory using at least 40 pct of the Mixtepec coking coals with the other Oaxaca non-coking coals. Koppers in Germany report good coke obtained from the Oaxaca coal with a blend of 80 pct Mixtepec coal. Consideration is being given the possibility of using methods other than the conventional blast furnace for the reduction of iron ore near the Oaxaca area; electric furnaces appear promising. The non-coking coals could be used to produce cheap electric energy and the coking coals to make metallurgical coke.

Jan 1, 1955

By H. J. Fraser

LIKE a runner catching his second wind, the mining geologist in 1944 has had some opportunity to appraise the result of three years of active and intense search for the metallic sinews of war and peace. The war period has been one of physical activity and accumulation of new data but has not so far resulted in the announcement of any profound or revolutionary theoretical concepts or techniques. Most technical publications during the year have been either descriptive or statistical. A review of accomplishments during the war years, although affording some measure of satisfaction in individual cases or regarding production of certain metals or' ores, is far from justifying any feeling of complacency regarding the growth of the profession either in fundamental knowledge or in application. During 1944 an abundant supply of all metals and minerals flowed steadily to smelters and fabricating plants. Also, during this and preceding years, adequate stock piles for war needs, in view of the improved foreign and domestic supply situation, were accumulated in many metals in such quantities that the mining industry has become concerned not with the problem of supply but with the effect these accumulated stocks, if maintained, might have on the postwar market. These considerations culminated in the enactment by Congress of the Surplus Disposal Act, which, admittedly a tempo-

Jan 1, 1945

Book Review MAN-TO-MAN: THE STORY OF INDUSTRIAL DEMOCRACY. By John Leitch, Phila¬delphia, Pa. The B. C. Forbes Publishing Co., New York, 1919, 2.19 pp., 7 1/2 X 5 in. $2.00. "Man to Man" is a short, well-written, well-printed, easy to read and very interesting hook. It is an account of a method introduced into more than twenty industrial plants to give the workers a share in managing their own troubles. It is not a panacea for labor troubles and strikes, but neither have existed where the new method has been tried. The scheme is, in a word, to organize the working force like the government, having a cabinet composed of the executives, a senate composed of foremen, and a house composed of men elected by fellow workers from all departments. This governing machinery takes up all complaints of workers, investigates, reports, and settles. The increased profits due to economy and increased production from this cooperation are divided 50-50 between the company and the men. Experience has shown that, since inattention, tardiness, irregularity, and inefficiency tend to reduce their profits, all men very quickly, after once convinced of the sincerity of the management in their scheme of cooperation, eliminate them because it is for their personal profit. Astonishing results have been attained, including higher wages, greater output, lower unit costs, great reduction in labor turnover, elimination of waste, an increased loyalty and a waiting list of employees even in periods of labor shortage. Profit sharing as such and stock ownership as a benefit to industrial relations are discussed briefly and illuminatingly, although they are not believed by the author to he the best way to bring about the human relation between those who work,for and those who work with money. The author is not against unions but does not believe the union is the best medium for improving industrial relationship. The look is nowhere dogmatic but is always forceful and convincing and, being well written, is very entertaining. It is doubtful if "Industrial Democracy" is the right expression for the solution of the problem but certainly anything that will place on the shoulders of labor some of the responsibility of industry and will increase production is tine much-to-be-desired desideratum. It is a. contribution to the solution of our biggest problem and should be read by everyone who employs men and who has been worried by the labor turnover. P. E. B.

Jan 7, 1919