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By Kenneth Robertson

ALL, strangers visiting this district are struck with the peculiar manner in which the pig-iron is graded. There are eleven regular grades, besides which, when gray forge is ordered, one-half of Nos. 1 and 2 Mill are shipped. Occasionally there is another grade Known as Silver Mill, which is made so seldom that I cannot describe it, and have no sample to exhibit. Most of you have found it difficult to grade properly and uniformly under the simpler system which obtains elsewhere, and can consequently readily imagine the increased difficulty with us. Each furnace employs an " expert," and even with this precaution, the system is not conducive, at all times, to amicable relations between buyers and sellers. I am told that it was adopted at the time Southern irons were seeking a market; but it still remains, although the time has come when our iron is sought for and has obtained for itself a place in the markets of the country. The grades are as follows:

Jan 1, 1889

EUGENE WESLEY SHAW,* Washington, D. C. (written discussion ?).-Studies of the probable future production of oil wells and fields-particularly those in the nature of the recent work by Lewis and Beal, having the object of increasing the percentage of recovery-rank, in both practical and theoretic value, very high, if indeed they do not outrank all other petroleum investigations except structural surveys. Even such surveys, although saving untold millions that might have been spent in prospecting unpromising territory, may have less ultimate value than generally supposed, for it may perhaps be argued that much if not most of the condemned territory will sooner or later be tested-some is already productive-and the most that can be rightly claimed is the recovery of cream first; also that the consumption of the richest portions first cannot be extenuated, as it might with some resources, on the ground that if the best is not taken now it will deteriorate.

Jan 5, 1918

By John Mills

THREE case histories from professions other than engineering will serve to introduce ideas basic to this discussion. Case (1) Date, about 1900. A young man, B. D. from a three-year graduate course in a prominent divinity school, was for two years a successful pastor of a small church; then friction over theological matters arose with a fundamentalist deacon of the "Bible belt" type. He resigned, returned to his university for a four-year medical course, interned for two more, and thereafter was successful and apparently happy as a physician. We may assume that he was converted in early adolescence and vowed himself to service as a minister. Acceptance of his announced career by parents, friends, and teachers plus his own determination confirmed his choice until illiberal criticism threatened his usefulness and he awoke to the fact that his inner needs were not along the direction in which inertia and his conscience had constrained him.

Jan 1, 1947

Abbott, Argyle Campbell 1209 Sherwin Ave, Chicago, ILL. '29 Almstrom, Adne A., Student, Met. Engrg, Washington State College Pullman, Wash. '29 Ankedinoff, N., School of Mines, Univ. of Utah Salt Lake City, Utah. '30 Apter, Robert F., Student, McGill Univ Montreal, Que., Canada. '30 Bailey, Donald G 798 1/2 Kensington Rd., Los Angeles, Cal. '29 Baker, Kenneth B., Met, Aluminum Co. of America Pittsburgh, Pa. '29 Barger, Thomas, Student, Univ of North Dakota Grand Forks, N D '23 Bartholomees, Geo. C Box 304, Bonne Terre, Mo. '29 Bates, Walter, Student, Univ. of Utah, School of Mines . Salt Lake City, Utah '30 Bobb. Russell V. . 16 College Ave., Houghton, Mich. '29 Boswell, John C., Stripping Asst, Fairbanks Exploration Co Fairbanks, Alaska '29 Brandenburg, E. C., Student, Univ of Kentucky 112 Church St, Lexington, Ky '29 Brannen, John, Chemist, Assay Office, Consolidated Min & Smelt Co. of Canada, Ltd , Tadanac, B. C , Canada '29

Jan 1, 1923

COLUMBIA LOCAL SECTION STANLY A. EASTON, Chairman, FREDERIC KEFFER, Vice-Chairman, L. K. ARMSTRONG, Sec.-Treas., P. O. Drawer 2154, Spokane, Wash. The fifth annual meeting of the Columbia Local Section was held in Wallace, Idaho, November 19-20, 1915, with headquarters at the Samuel Hotel. The afternoon session scheduled for November 19, was adjourned to give the members an opportunity to hear the testimony in the case between the Alameda and Success mining. companies on trial in the Superior Court of Shoshone County. The Success Company offered some excellent mine models and maps and furnished some interesting testimony. In the evening a technical session was held at which Stanly A. Easton presided in the absence of the Chairman and Vice-Chairman of the Section. The following papers were read: Progress in Ore Dressing By D. W. Buckby,.. Mine Accounting for Small Mines, By J. E. Chapman. Zinc Smelting and Smelter Rates, By W. E. Henry.

Jan 2, 1916

By Donald N. H. Chi, Henry E. Perlee

Accident cost data bases for all mining sectors covering the period 1975 through 1980 have been created on the PDP-11/70 and VAX-11/780 computers at the Bureau of Mines Pittsburgh Research Center. The total expected costs of the following tangible elements are computed: (a) loss in personal income; (b) compensation of wages from State, Federal, and union funds for disabling injuries; (c) benefits for injuries resulting in death or permanent disability; (d) medical treatment and hospital care; (e) investigation of a fatal accident; and (f) production loss due to accidents involving fatalities or amputation injuries. Each cost record computed contains a reference to the original record in the Health and Safety Analysis Center (HSAC) accident files to permit concurrent analysis. The intended applications include examinations of annual trends in mine accident statistics on the basis of economic loss. This provides an additional perspective on mine accidents. Various examples of the use of these data bases are presented.

Jan 1, 1983

By R. E. Reed-Hill, W. H. Hartt

High-purity magnesium single crystals, oriented with basal plane parallel to stress axis, were deformed in tension at room temperature so as to form second-order (1011)- (1012) twins. Investigation by optical and replica electron microscopy revealed that these twins can support very large internal strains approaching 1000 pct and that fracture follows as a direct consequence of these strains. At low strains the basal plane within (10i1)- (10i2) twins rotates with increasing deformation until it becomes approximately parallel to the twin boundaries. This rotation is not consistent with deformation by basal slip in the double twin, but may be rationalized in terms of nonbasal slip. Observations also indicate that basal slip in the primary (1011) twin, prior to second-order twinning, may contribute to this rotation. Deformation markings that are difficult to interpret in terms of slip on previously observed systems were noted in the twin bands. A possible means of rationalizing these markings is to relate them to grain boundary shear. The fracture associated with these twins is thought to initiate by formation of voids at the twin boundaries. These grow into microcracks, with ultimate fracture occurring by tearing of the interconnecting regions. THE significance of deformation and fracture along second-order (10i1)-(10i2) twins in polycrystalline magnesium1-' and many magnesium alloys4 was discussed in a previous paper.5 It was noted that this double twinning mode effectively controls the room-temperature deformation and fracture of magnesium single crystals, oriented with the basal plane parallel to the tensile axis. Reed-Hill and Robertson6 observed that, although these crystals may fracture at a macroscopic strain of less than 1 pct, shear strains up to 1000 pct could occur within (1011)- (10i2) twin bands. They concluded that the fracture was "ductile" and resulted from concentrating the deformation into a very small volume. The present research was undertaken to obtain a better understanding of the deformation and fracture associated with these twins. EXPERIMENTAL TECHNIQUES The experimental procedure involved straining high-purity magnesium single crystals in tension at room temperature. Specimens were oriented so that the applied stress direction was within 2 deg of the [1010] crystal axis. The specimen cross section was rectangular with faces closely parallel to (1210) and (0002). The specimen preparation and testing procedures have been described in detail elsewhere.5 Second-order (1011)- (1072) twins nucleated during straining were studied using optical and replica electron microscopy techniques. For the latter, cellulose acetate-carbon double replicas were employed. Observations were made on the (1210) crystal surface, which is the plane of shear for twins of this type. In addition to the single crystals, some investigations were carried out on longitudinal polycrystalline specimens. These were obtained from high-purity magnesium plate with a texture in which the basal planes of the grains tended to be nearly parallel to the specimen axis. All. polycrystalline specimens were annealed prior to testing in order to produce a coarse grain structure, permitting Laue back-reflection X-ray photographs to be obtained from grains of interest. EXPERIMENTAL RESULTS a) Deformation Within ( 101 l )-( 1072) Twins. Fig. 1 is an optical micrograph demonstrating the extent of the plastic deformation that can occur in (1011)-(10i2) twin bands. Notice at the lower left corner of the photograph the large displacement of the dark band (a polishing step) where it crosses the twins. The shear strain in the twin band at this position was computed to be 700 pct, using the ratio of step width to twin thickness. It was previously shown5 that (1011)- (1012) twin bands are often composed of small, separate twins aligned close to the macroscopic habit plane. Fig. 2 is an electron micrograph from near the upper end of the twin band in Fig. 1. This illustrates that the twin habit often does not coincide exactly with the macroscopic band habit, but may be inclined at a slightly smaller angle to the matrix basal plane. Figs. 3 through 6 are electron micrographs of the twin band in Fig. 2 illustrating successive steps in the development of deformation inside the band. A twin band such

Jan 1, 1969

By L. S. Castleman, R. Resnick

The self-diffusion coefficient of columbium has been measured over the temperature range 1535o to 2120°C, using the radioactive isotope Nb95 as the tracer. The data for the temperature dependence of the self-diffusion coefficient are best fitted by the equation D = (12.4 ± 0.8) exp [(-105,000 ± 3000)/RT] cm2/sec. THE increasing need for high-temperature structural materials has stimulated considerable interest in the properties of columbium, since it is a strong, ductile metal with a high melting point—in the vicin- ity of 2450oc.l One fundamental property which has not heretofore been measured is the self-diffusion coefficient. The self-diffusion coefficient plays an important role in theories of oxidatioq2 creep,' sintering4 and other phenomena. Accordingly, the investigation reported in this paper was undertaken to determine the value of the self-diffusion coefficient and its temperature dependence by the use of Mb95.

Jan 1, 1961

By John V. Beall

The Glidden Co., a newcomer to the mining industry, will be putting on stream its Lakehurst mine and concentrator this spring. Ilmenite-bearing placer sands will be mined and concentrated in a spanking new combination gravity, magnetic and high-tension separation plant. Glidden, well known as a paint, chemical and food manufacturer, consumes titanium dioxide as pigment in its paint business. The commodity is produced at the company's Adrian D. Joyce Works in Baltimore from ilmenite purchased in India and Australia, The Lakehurst operation, handily located in Ocean County, N. J., will dampen any deficiencies in quantity or price which might occur from foreign suppliers. This objective is no overnight concoction of The Glidden Co., because the move at Lakehurst was preceded by an attempt to start up in Florida. That project was abandoned when it was found that the titanium dioxide values were largely in rutile-a mineral which does not lend itself readily to the digestion process of the Baltimore chemical plant.

Jan 1, 1962

By R. L. Fullman

IN the investigation of metallurgical transformations and the relationships between microstructure and properties of metals, it frequently is desirable to obtain a measurement of the relative amounts of the various phases present and of the mean size of particles into which each phase is dispersed. The relative amounts of the phases can be measured by the classical methods of area, lineal, and point analysis,1-5 in accordance with the principle that the volume fraction of a phase, the fraction of a polished cross section occupied by the phase, the fraction of a random line occupied by the phase, and the fraction of randomly arrayed points occupied by the phase are all equal. The validity of this relationship depends only on the attainment of a truly random sample of area, length, or points, and not on the size, shape, or distribution of the particles constituting the phase. Smith and Guttman8 have derived a relationship between the interface area per unit volume S, and the measurable quantities L., the interface length per unit area on a cross section, and NL, the number of interfaces per unit length intersected by a random line. Their equation, Sv = — L8 = 2NL is also valid regardless of the distribution of particle sizes and shapes. In contrast to the situation concerning measurement of relative fractions of phases and of interface area, the measurement of particle sizes in opaque samples has not been subjected to a complete analysis. It has been common to measure some lineal or area dimension of particles on a polished cross section and to use the mean value as a qualitative measure of particle size. In the present paper, quantitative relationships are established among the various mean dimensions on a polished cross section and the actual dimensions of the particles present. Particles of Uniform Size Spheres: If a metal sample contains particles of a phase a dispersed in the form of spheres of uniform size, a polished cross section through the sample will reveal circular areas of phase a with radii from 0 to ?, the radius of the spheres. Consider a cube of unit dimensions to be cut from the sample. If a cross section parallel to one of the cube faces is examined, the average number of particles per unit area (N,) equals the number of particles per unit volume (Nv) times the probability p1 that the plane would intersect a single sphere positioned at random within the unit cube. Since, of the various possible positions for the cross-sectional plane over the unit length from top to bottom of the cube, only those positions existing over the length 2r would lead to the plane intersecting the sphere, the probability of intersecting a single sphere is just 2r. N8= Nvp1 = Nd-2r [1] Applying the equality of area and volume fractions, the relationship is found between sphere size and average area s of uniform spheres intersected by a random cross section, 4 - f = NV V = Nr . — pra = N s = Nd . 2rs S = —pr2 [2] A similar analysis reveals the average traverse length across spheres of uniform size when random lines are passed through the sample. If a randomly oriented unit cube is cut from the sample and a randomly positioned line is passed through the cube parallel to a cube edge, the number of spheres intersected by the line (Nl) equals the number of spheres per unit volume times the probability p1 of the line hitting a single randomly placed sphere in the cube. Since possible positions of the line occupy unit area, and possible positions for which it will pass through the sphere occupy an area of pr2, the probability of the line hitting a randomly placed single sphere is pr2. NL = Nv p1 = Nvpr2 [3] Combining this relationship with the equality of volume and lineal fraction, the desired relationship is obtained between radius and mean lineal traverse length -i, for spheres of uniform size. 4 - - 3 l=4/3r [4] Circular Plates: Consider a sample containing particles of a phase a in the form of circular plates of uniform radius r and thickness t, where r >> t. If the plates are randomly oriented, as in a sufficiently large sample of a fine grained polycrystalline material, area and lineal analysis may be carried out with parallel cross-sectional planes and lineal traverses. If the plates are not randomly oriented, it is necessary to randomize the orientation of the cross-sectional planes and traverse directions. Let a unit cube be cut from the sample, and a cross-section plane be passed through the cube parallel to one of the cube faces. The number of plates cut by the cross-sectional plane per unit area is equal to the number of plates per unit volume times the probability of a plate intersecting a single randomly positioned and randomly oriented plate in the cube. If J is the component of the plate diameter in the direction normal to the cross-sectional planes, the probability of a plane cutting a single randomly oriented plate is equal to J, the mean value of J for all possible orientations of the plate. Let 4 be the dihedral angle between a plate and the cross-sectional plane, and let p?, d? be the probability that a plate makes an angle between 4 and ? + d? with the cross-sectional plane. Then for ran-

Jan 1, 1954

Some years ago it was my good fortune to inspect some coal properties in Germany, and the most striking impression I received on my trip was that in that country every one in the coal industry, miners and operators, was proud of the fact-not apologetic about it-and that industrially coal was looked upon as a King. The explanation, of course, was that at least 90 per cent of the entire mineral value produced in Germany was from coal, and that it was the very foundation of the nation's industrial life. The feeling was so different from that existing in the United States among those engaged in producing coal that it made a profound impression on me, and many times since then I have speculated about the reasons for the difference in opinion in the two countries. Here, of course, our units are much smaller and more numerous, there is not so large a proportion of technically trained men, and we have the American trait of depreciating the things we do at home; but among those not actively

Jan 1, 1935

The Howe Memorial Lecture, in memory of Henry Marion Howe, Past President of the Institute, was authorized in April, 1923, as an annual address to be delivered by invitation under the auspices of the Institute by an individual of recognized and out- standing attainment in the science and practice of iron and steel metallurgy or metallography, chosen by the Board of Directors upon recommendation of the Iron and Steel Division. The follow- ing were the Howe lectures and lecturers for the years indicated: 1924 What is Steel? By Albert Sauveur. 1925 Austenite and Austenitic Steels. By John A. Mathems. 1926 Twenty-five Years of Metallography. By William Campbell. 1927 Alloy Steels. By Bradley Stoughton. 1928 Significance of the Simple Steel Analysis. By Henry D. Hibbard. 1929 Studies of Hadfield's Manganese Steel with the High-power Microscopa By John Howe Hall. 1930 The Future of the American Iron and Steel Industry. By Zay Jeffries. 1931 On the Art of Metallography. By Francis F. Lucas.

Jan 1, 1937

By M. F. Goudge, R. V. Tomkins

Sodium sulfate is an important chemical raw material that is being used in ever increasing quantities in modem industry. It comes on the market mainly in three forms: (1) Salt cake (Na2SO4), a relatively crude form of the anhydrous salt containing up to 3 pct impurities, and comprising about three-quarters of the North American production; (2) anhydrous sodium sulfate (Na2SO4), a refined form containing less than 0.3 pct impurities; (3) Glauber's salt, the decahydrate (Na2SO4.10H2O) containing 55.9 pct water of crystallization. Competing with salt cake from natural sources is byproduct salt cake from a number of industrial operations. For instance there is Mannheim cake resulting from the manufacture of hydrochloric acid by the reaction of salt (NaCl) and sulfuric acid in Mannheim furnaces; rayon cake, a high-quality product, resulting from the process of making rayon by the viscose process; chrome cake from the processing of sodium chromate to dichromate; phenol cake from the manufacture of phenol; also byproduct sodium sulfate resulting from the conversion of lithium sulfate to lithium carbonate; from the processing of sodium tetraborate to boric acid; from converting sodium formate to formic acid; and in the manufacture of cellophane. Sodium sulfate is also obtained as a byproduct in the manufacture of isosebasic acid. In addition strong competition has resulted from imports of byproduct salt cake from the chemical industries of a number of highly industrialized European countries. However in recent years due to technological changes the output of byproduct salt cake is rapidly diminishing and the natural deposits are becoming the most important source of sodium sulfate used in North America. For instance, the production of hydrochloric acid in Mannheim plants has become obsolete and thus the greatest single source of byproduct salt cake will disappear. Also viscose rayon is meeting strong competition from nylon and other synthetic fibers and production of byproduct salt cake from this source may do little more than remain at the present level. These factors together with increasing demand for sodium sulfate point to increased production from natural sources. In 1958, 36 pct of the total United States production was derived from natural sources and in addition 97,000 short tons was imported so that over 40 pct of the total consumption was supplied by natural sources whereas in 1953 the proportion was only 24 pct. The rapid growth in production is shown in Table 1. Principal Sodium Sulfate Minerals There are many minerals in which sodium sulfate is a constituent but those of commercial importance at the present time, and consisting wholly of sodium sulfate in either the hydrous or anhydrous states, are mirabilite and thenardite. Minerals of potential importance but consisting in part of compounds other than sodium sulfate are glauberite in which sodium sulfate is combined with calcium sulfate, and blödite in which sodium sulfate is combined with magnesium sulfate. Mirabilite (Na2SO4.10H2O) the decahydrate, consists of 24.8 pct SO3, 19.3 pct Na2O, and 55.9 pct H20. It is a colorless to opaque, soft, water-soluble mineral with a slightly bitter taste. It has a hardness of less than 2 and a specific gravity of 1.48. It forms long needle-

Jan 1, 1960

By P. K. Lucke

One of the interesting features connected with the great continental uplift, which formed the table land of Mexico, is the great depth to which oxidation and secondary enrichment of orebodies occurred. This table land lies at altitudes ranging from 4000 to 7000 ft. (1219 to 2133 m.) above sea level. Several cases could be cited of oxidized zones in copper and lead mines which reached depths of upward of 1500 ft. (457 m.) below the surface, and it is universally admitted that the oxidized zone in a mine is limited by the permanent water level. Mexico, however, like many other countries in which deserts occur, is visited at rare intervals by tremendous floods, which sometimes cause variable water levels over long periods. The following cases bear out the idea, and lead to interesting conclusions of commercial value. My paper demonstrates that carbonates of ores may occur below water level and sulfides above, and I will endeavor to explain the causes of the phenomena in certain specific instances. Case I.—Fig. 1 in this case shows that sulfides of lead remained

Jan 1, 1920

By A. C. D. Chaklader, Ashok K. Kakar

The basic density equation originally dericed ' to predict the increase in density of a compact of spherical particles with the progressive deformation at the points of contact has been further modified to include the yield strength of the material. This has been done by assuming that the contact areas grow to stable sizes under a fixed stress which is equal to three times the yield strength. The final equation has the form: where Do and D me the initial and final bulk densities of the compact, u is the applied pressure, and Y is the yield strength of the material. This equation was tested with the data obtained on spheres of lead, K-Monel, and sapphire. The calculated yield strength t~alues for lead and sapphire are within the range of values reported in the literature. A few of the earliest hot pressing models proposed to explain the mechanism by Murray, Livey, and williams2 and then by McClelland3 are based on a plastic flow mechanism. However, more recent investigations suggest that the overall densification process is a combination of several mechanisms, such as particle rearrangement, fragmentation, plastic flow, and stress-enhanced diffusional creep. While fragmentation and particle rearrangement are considered to be responsible for the densification in the early stages,"475 it has been concluded that the final stages of hot pressing are controlled by stress-enhanced diffusional creep.516 The manner in which the densification takes place, i.e., by fragmentation, particle rearrangement, plastic flow, or stress-enhanced diffusional creep, would depend upon the type of material, the temperature, and the stress level used during the hot-pressing experiments. Metal compacts can be expected to have a much greater contribution from plastic flow than ceramic oxides. Also, plastic flow would be a significant contributing factor to densification at high temperatures and high stresses. Most of these works, directed towards elucidation of densification mechanism, have dealt with kinetics of the process. The results of most of the authors vary from one another and they have proposed either new empirical or semiempirical equations to fit their data. The densification rate was found to vary with the type of the powder, shape and size of the powder, initial packing density of the compact, and a few other factors such as rate of heating, pressure, and so forth. Beyond the initial stages, the densification process has been considered to be as time-dependent flow, controlled by a diffusional process, e.g., Nabarro-Herring creep. Palm our, Bradley, and johnson' have attempted to use modified creep rate equations to interpret the data of densification under hot-pressing conditions. Beyond the initial stages, however, the densification would be controlled by a process depending upon the temperature, pressure, and size of the powders. It is the authors' belief that such densification cannot be exclusively controlled by a single process and so attempts should be made to study some observable phenomenon like microstructure, yield strength, and so forth. The emphasis of this work has been toward studying the densification problem from a more fundamental point of view. Some of the principal variables, like initial packing density, mode of packing, and size of the powders, have been controlled to a great extent. The total strain produced on pressure application (instantaneous) in such a case can be considered to be due to plastic and elastic deformation. The elastic component of the strain can be determined by decreasing the load to the initial value. The strain remaining then can be correlated with the contact areas produced by deformation and the corresponding applied load. In a previous paper,' the possible deformation behavior of spheres in a compact has been theoretically analyzed and experimentally tested. The change in contact area radius a relative to the particle radius R was related to the bulk density and the bulk strain for simple and systematic modes of packing. Tt was found that a density equation relating the above parameters can be represented by: where D and Do are the bulk densities of the compact at any value of a/R and a/R = 0, respectively. This basic equation should hold for any material as it was derived from geometrical considerations alone. An attempt has been made in this work to include the yield strength in the above density equation, so that a knowledge of the properties of any material can be used in predicting the densification behavior during the hot-pressing process. THEORETICAL CONSIDERATTONS The deformation of two spheres in contact under a static load can be compared to the deformation occurring between a hard spherical indentor and the flat face of a softer metal. Tt has been shown theoretically by both ~encky~ and lshlinskyg and experimentally by ~abor" that, for a material incapable of appreciable work hardening, the mean pressure required to produce plastic yielding (for deformation occurring between flat face and a hemispherical indentor) is approximately equal to three times the elastic limit, Y, of the material (in tension or compression experiments). Tabor has further observed that the same relationship is valid in the case of work-hardening materials, if the elastic limit at the edge of the indenta-

Jan 1, 1969

By George S. Rice

INTERESTING developments going on in European coal mines look to: (1) increasing mechanization; 12) concentration of mining; (3) improvement in safety appliances; and (4) studies in bettering roof supports and. incident to this, studies of the way a roof behaves under different conditions of support and methods of mining and back-filling. Mechanization and concentration off mining is being adapted to a considerable extent in Great Britain coincident with the development of conveyors. Belt conveyors, shaker-pan conveyors, and a combination of the two are used. For pitching seams not steep enough for the coal to run in station-chutes, the. shaker-pan conveyor is more popular. For large outputs from a contiguous face, the double-unit system of face layout-that is, the conveyors meeting at a common point-is favored.

Jan 1, 1934

By J. S. FINLAY

OPERATING a "muck stick" never appealed to me. It always seemed a terrible waste of energy to "put rocks in the box" by hand-particularly when my own personal energy was involved. But during the past forty years, there have been periods-more or less extended when I was compelled, against my finer instincts, to muck or quit eating. For about the same length of time, I have devised schemes to make mucking faster and more painless. There was always something mechanically wrong with these designs-too many;" parts to wear out and need replacement, and excessive cost incidental to a complicated mechanism. The idea of a shovel unit comprised of a single, rigid assembly which would roll from a digging to dumping position solved the problem of simplicity and durability. Ingersoll-Rand's utility engine provided a splendid power plant, small enough and powerful enough for the job. In the machine finally developed, known as the Eimco-Finlay loader, roller chains are preferred to gears for power trans-

Jan 1, 1935

By L. D. Ricketts

AN older man looks back, perhaps wistfully, on a long and rather active experience, and possibly a popular and brief glimpse of some contrast between past and present may hold your attention for a few brief moments and prove useful. In the late nineties an engineer was .called on to de- sign and build two copper ore concentrating mills of 400 tons average daily capacity. There were larger mills than this at Washoe and elsewhere, but a 400 ton' mill was a large one as mills went over thirty years ago, and one might say a large mill of those days could crush a ton of copper ore in 216 seconds. In the mills I refer to steel construction and the conveying belts were introduced into the copper industry and rein- forced concrete came shortly after. Since then we in the West have ever been faced with a constantly de- creasing tenor in the grade of our copper ores and a constantly increasing demand for our product, and we have therefore been obliged to call for far larger castings and finished machines than were formerly used. The mechanical engineer has also enabled us to accomplish notable economies in power generation and distribution. Ore handling and crushing have been simplified and through the introduction of reagents to induce physical or chemical reactions, or both, our older methods have been vastly improved or even supplanted by new and better ones and our recoveries greatly improved.

Jan 1, 1929

By AIME AIME

I would like to ask Bob Merrill whether he considers that horizontal concave curvature of a slope has any stabilizing effect, such as Jenike 1 suggested several years ago. The stabilizing effect is due to the restraint offered to radial movement by the curvature. We found in laboratory tests that if we constrained the rock with the same stresses as those measured in the pit then it would sustain a maximum stress about two or four times greater than when the same rock type was unconstrained. We are therefore definitely of the opinion that a constrained situation in a slope is favorable towards stability.

Jan 1, 1967

By Sir John Cadman

IN THE changed circumstances which now confront the world, an international open-door policy is the only way to keep pace with the world's demand for oil. You may rest assured that as far as the British Empire is concerned, American capital for the develop-ment of oil resources is welcome, and little obstruction will be found in the way to permit the use of foreign capital in the group of countries which constitute the British Empire. In the war days we worked in close cooperation and harmony, but in disbandment of the Petroleum War Service Committee, when the war ended, I feel that it left its task unfinished. In the wake of war there appeared a ghost of war-time conditions in the form of belief that Great Britain was straining to corner the petroleum resources of the world. I am certain that if the war-service committee had continued its work in the period of reconstruction the real story would be known and this sinister ghost would have long since vanished before the truth.

Jan 2, 1922