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By René de Batz

From 1754 to the end of 1895 the production of gold in Russia had been approximately as follows: Kilogrammes. Russia proper (Finland and the Caucasus),. .. 890 The Ural Region,........505,386 Western Siberia,........116,937 Eastern Siberia,........1,218,372 Total,.........1,841,085 of the value of more than $1,200,000,000.

Jan 1, 1899

By JOHN A. MALONEY

AS noted in the February issue of MINING AND METALLURGY, an advisory committee to the Museum of Science and Industry of Chicago was authorized by the Institute's Board of Directors, with W. R. Wright of Chicago, former Director of the Institute, as chairman. Since that time the committee has been undergoing organization, and held its initial meeting at the Museum offices in Chicago on April 11 and 12. Functioning as consultants to the Geology and Mineral Industries branch of this new institution, the advisory committee is aiding in building an exhibit which will tell the story of geology, mining, and metallurgy to millions of visitors a year. Although patterned to some extent

Jan 1, 1932

By Milton Glicken

THE airborne geophysicist is a busy man these days. In his plane he may have the airborne magnetometer, the airborne scintillation counter, and the airborne electromagnetic surveying system. Each of these is an independent tool, but all require additional auxiliary equipment for locating the aircraft in space: recording altimeters and Shoran or aerial cameras. Now there is still another piece of equipment, the airborne magnetic gradiometer, an accessory to the magnetometer. To understand its uses, consider the function of the magnetometer itself. Aside from detecting magnetic ore, the airborne magnetometer finds greatest use in spotting intrusions of igneous material. Where there is enough contrast in magnetic susceptibility of igneous rock and adjacent formations, it outlines the intrusion. Certain minerals also influence the magnetometer directly, but with the exception of magnetite and possibly one or two others, their effect is weak and can be detected only when there is sufficient ore and the magnetometer flight passes very close to it. An igneous intrusion of infinite depth with vertical sides is represented on a magnetometer record by an anomaly, as in Fig. 1. Amplitude of the high depends on susceptibility contrast of the igneous rock. Generally speaking, the edge of the intrusion lies below the point of inflection of the curve, and this point, where the curvature changes from positive to negative on the magnetometer profile, would be near A in Fig. 1, with a counterpart, of course, on the other side. Location of the contact is one of the principal objects of the survey, but finding the precise point is not always easy, as inspection of the curve near A will show. Mineralization is often found at the contact zones, as at B. Magnetic effects, if detected, may be small, as in B', and when superimposed on the anomaly due to the instrusion they are very difficult to discern and analyze. Furthermore, if these small fluctuations are to be perceived by the magnetometer the vertical scale should be large. This increases the slopes of the anomaly and makes detection of small deviations and inflection points even more difficult. The airborne magnetic gradiometer was designed to help overcome these difficulties. What it presents is the first derivative of the magnetometer record with respect to time, that is to say, the slope at any point. Fig. 2 represents an actual magnetometer record (solid line) with the corresponding gradiometer record (dashed line) superimposed. Both records read from right to left. Vertical lines on the original magnetometer record are automatic steps designed to keep the pen from going off scale. The slope of any curve is greatest at the point of inflection or point where the curvature changes sign, and this point is a maximum (or minimum) on the gradi- ometer. The chief advantage of the gradiometer is that maxima or minima are much easier to see and to locate precisely; hence an accurate location for the point of inflection can easily be found. Note that points C and D are more sharply defined than C and D'. Similarly the small fluctuations of the original record, so important to the interpreter, are far more clearly shown at E, F, and G, than on the original record at E', F', and G'. Though not necessarily highs and lows on the gradiometer, they do show up clearly what would take a painstaking analysis to detect on the original magnetometer record. Will the gradiometer have a particular configuration which indicates an orebody? Not necessarily. The total intensity curve, or original magnetometer record, can display an orebody in various ways, depending on dimensions, orientation, latitude, and composition, as well as on direction, flight height, and instrumental sensitivity of the traverse. Where the total intensity can take on so many different shapes the gradiometer must vary too. It is generally recognized that interpretation of total intensity magnetometer records requires an expert analysis; the gradiometer can be of considerable assistance to the expert but it does not replace him. Mechanism of the gradiometer is simple. A Leeds & Northrup recorder in the aircraft records the magnetic gradient simultaneously with the total intensity, which is on another recorder. Fiducial marks are put on both records simultaneously and the speed of the paper through the recorders is kept the same on both. This makes it possible to place one record over the other for direct comparison. In the laboratory the flights are positioned on a map. Maximum and minimum points on the gradiometer, which can then be posted on the map at their proper locations, may be expected to fall along a trend crossing the direction of flight. Trends should indicate the edge of an intrusion, or some other important features, and when superimposed on the total intensity contour map help greatly to locate the points of inflection, or line of zero curvature.

Jan 1, 1956

By Zdzislaw Specht

THIS paper discusses elementary laws pertaining to seismic reflection methods and presents a general and simple criterion for determining the direction of dipping of a reflection horizon from observational data of distance and time. The important development of practical geophysics and the successful results obtained in America, Germany, and other countries, caused introduction of geophysical methods of prospecting in Poland. Of all methods, seismic prospecting has proved most successful in the area of the Carpathian foreland, where new oil reserves are to be expected. Because of the great depth of the sedimentary column in that area, rang-ing sometimes over 2000 meters, it was obvious that only the seismic reflection method could give reliable information regarding the structural features of these strata at such a depth. During the experimental surveys it appeared that the complicated geological conditions of that area do not always allow prediction of the depth and the angle of dipping of reflecting horizons, and for that reason information about the inclination of a given horizon has great importance in the determination of subsurface structure. Therefore the problem arises of obtaining from seismic reflection data reliable information as to the direction of dipping of reflecting strata, without any previous knowledge of the average velocity and depth of geologic horizons under consideration.

Jan 1, 1940

W. S. GRESLEY, Erie, Pa. (communication to the Secretary): A six-entry method of opening coal-mines is, or was a short time ago, practiced in the Connellsville coal-region; but Dr. Chance's method has a novel aspect; for while in the Connellsville region the main pillars are formed outside of two pairs

Jan 1, 1901

By W. V. Long, D. H. Reynolds, R. B. Bhappu

Equilibrium distribution coefficients were determined for some monovalent and polyvalent ions for several absorbing and exchanging media as functions of pH and initial ion concentration. Among ions studied were NH4 (I), K(I), Ni(II), Ce(III), Th(IV), and Mo(VI). Absorbents used were: ion exchange resins; a tertiary, and a quaternary amine in an inert solvent; and some activated carbons. The ions studied were in aqueous HCI, HNO3, H2SO4, or HC104 solutions. The classical mass action expression proved of little value in describing the variations observed. The data indicate that the determining factors in absorption and ion exchange may be the ionic species in the aqueous solution, which in turn depend upon pH, dilution, and perhaps other conditions. Three sorption processes have become prominent in recovering values from leach solutions. These are: 1) ion exchange, 2) solvent extraction (liquid ion exchange), and 3) physical adsorption by materials of high specific surface. In the first two of these processes the exchange reaction is considered chemical in nature, and is discussed in terms of the mass action principle. The third is considered a surface phenomenon and is discussed in terms of surface areas and various forms (Gouy, Stern, Grahame, etc.) of the Helmholtz double-layer theory. Generally speaking, we have found in chemical analysis and hydrometallurgical studies that there are close similarities between the three sorption processes, and also differences which are difficult to reconcile with any of the usual theoretical treatments. That others have experienced the same troubles is shown by the fact that usable processes, in chemical analysis as well as in hydrometallurgy, generally are discovered by empirical procedures. EXPERIMENTAL CONSlDERATlONS The gaps between theory and practice have allowed many conflicting statements to appear in the litera- ture. To learn, in particular, the behavior of some metallic ions on a cation exchange resin at a constant pH, equilibration studies were made over a wide range of concentrations.' Results are shown in Fig. 1 for four metals in hydrochloric acid solution on a strongly acidic cation exchange resin, AG 50W-X8 (Bio-Rad). The distribution coefficient, defined as D = amount of metal extracted per g of resin/amount of metal unextracted per ml of solution is seen to vary in a way to support all manner of reports about its behavior with changes in solution concentration. The metals used were chosen from those least likely to form stable chloro-complexes. The changes of slope in the various isotherms may reflect formation of unsuspected chloro-complexes of low stability (ion-pairing for example) whose concen-

Jan 1, 1967

By Robert Bakish

VARIOUS aspects of structure-sensitive corrosion of single crystals and polycrystalline aggregates of Cu,Au have been presented in papers by the author, in association with W. D. Robertson. Prompted by some observations in the course of these studies, a new approach to the problem was undertaken. Results of these new experiments are reported here. Thin slices, less than 2 mm thick, were prepared from single crystals 3.5 mm in diam grown by the Bridgman technique. The crystals were homogen- ized for 300 hr at 850°C. Crystals with no deformation, crystals deformed in tension to the yield point, and crystals deformed 20 pct in excess of the yield point were used. Crystals of several different orientations were studied. Slices were immersed for one month in 2 pct aqueous solution of FeCl3 and, subsequent to this immersion, were subjected to bending. Immersion and bending were carried out at room temperature. The size and geometry of the crystals did not permit accurate data on the loads involved. A most unexpected result was obtained in the process of bending these slices of Cu3Au crystals normal to the (110) plane. Completely brittle be-

Jan 1, 1958

By Walter E. Heinrichs

The following is a condensed version of an open letter addressed to Bil Gilbert of Sports Illustrated: Your article, "When a Law Fights a Law, Sports Illustrated. April 26, 1971, betrays considerable unfamiliarity with the subjects of ecology, social science, mining law and history. In a magazine as widely circulated as Sports Illustrated, an article of such a slanted nature misleads the general public.

Jan 1, 1971

By J. J. Gilman

Examination showed that characteristic cleavage step patterns are observed on the cleavage surfaces of undeformed, slipped, bent, twinned, compressed, and indented zinc crystals; and the effect of temperature is discussed. Dimples were seen to produce cleavage steps in a treelike pattern in otherwise undeformed crystals. The steps seem to originate when cracks intersect screw dislocations. IT has been known for a long time that the path of fracture in polycrystals may be discontinuous (see Jaffe, Reed, and Mannl for review). Recently, Kies, Sullivan, and Irwin2 have proposed, and given evidence, that crack propagation is discontinuous within individual crystals as well. Other evidence has been given by Low.' When discontinuous cracks within a crystal join together to make a macrocrack, the lamellae between each set of two cracks are torn somewhere, forming small cliffs. These cliffs appear as lines when the cleavage surface is observed microscopically.4,5 The lines have been called vein, tree, and riverlike markings by various authors, and they have sometimes been mistaken for fissures. The descriptive term cleavage steps is used in this paper. Cleavage steps vary in height over a wide range of values, from molecular dimensionsG to lor. and larger. Kies, Sullivan, and Irwin,2 as well as George,' have shown that the gross cleavage step patterns for plastics, polycrystalline metals, and for mono-crystals are sometimes similar. Thus, they depend mostly on the mechanical variables that prevail during cleavage and are relatively insensitive to the structure of the material. For example, parabolic markings2,7,8 sometimes result when cracks open up ahead of, and not coplanar with, the main crack front. If the advance crack has the same velocity as the main crack, their intersection line is a parabola, otherwise it is a hyperbola or an ellipse. The patterns are strongly affected by differences in crack velocities. This results in chevron patterns which point to the place of origin of the main crack. It is the purpose of this paper to demonstrate the existence of a mechanism of cleavage step formation which is a continuous rather than a discontinuous process. Also, certain characteristic step patterns are described, and the strong effect of temperature is shown. The specimens were zinc monocrystals (grown from 99.999+ pct pure metal). These were cleaved at room temperature and at — 196°C. Results and Discussion Cleavage step patterns are highly variable from point to point on a given specimen, as well as from one specimen to another. Although the patterns shown in the photographs are typical, they have been selected for graphic illustration. Figs. la and lb compare undeformed crystals that were cleaved at —196 °C and room temperature, respectively. Cleavage at room temperature (Fig. lb) resulted in a higher density of high steps (dark black lines) and enhanced the visibility of the fine background markings. Deformation by simple slip caused no marked change in the step patterns until the glide strain reached about 1.0. But, as Fig. lc shows, the density of high cleavage steps was greatly increased by large glide strains. Corrugations lying perpendicular to the slip direction may also be seen in Fig. lc. These are caused by deformation bands. The cleavage resistance of the crystal of Fig. lc was very high compared to undeformed crystals (estimated by the force on a needle required for cleavage). Striking and varied cleavage step patterns were observed on bent crystals. Two characteristic patterns that were observed on crystals bent at 25°C, and cleaved by reverse bending at —196°C, are shown in Figs. 2a and 2b. The first, Fig. 2a, consists of V-shaped lines similar to the parabolas of other materials2,7 Fig. 2b shows a pattern that is the equivalent of Fig. la, consisting of faint background lines with a few higher step markings. Cleavage of bent crystals at room temperature resulted in Figs. 2c and 2d. Now, the cleavage step lines show a strong tendency to follow one of two perpendicular paths. In Fig. 2c (bent once), many of the cleavage step components that lie parallel to the bend axis are assembled into irregular lines. In Fig. 2d (bent twice), the cleavage steps again tend to consist of two perpendicular components, but neither of the components is assembled into lines. Also, the step density is higher.

Jan 1, 1956

By ERIIL SCHROEDTER

THE death, on May 6, 1908, of Dr. Hermann Wedding, Privy Mining Councilor of the Kingdom of Prussia, and Professor of the Metallurgy of Iron and Steel at the Royal Mining Academy of Berlin, was a loss keenly felt by the whole metallurgical world. Not alone in his native land, but also in foreign countries did he enjoy an esteem of which the title of honorary membership in the American Institute of Mining Engineers, the United States Association of Charcoal Iron-Workers, and the (British) Iron and Steel Institute bears eloquent testimony. Hermann Wedding was born March 9, 1834, in Berlin. At the suggestion of Dr. C. J. B. Karsten, the veteran father of Prussian metallurgy and author of the first German text-book of the metallurgy of iron, lie turned his attention, after gradu¬ating from the gymnasium, to mining and metallurgy. In 1853, he began a practical course at the Malapane iron-works, in Upper Silesia. Subsequently, he studied at the Berlin Mining Academy, and received from the University in 1859 the degree of Doctor of Philosophy. A journey which be made to England, somewhat later, led to his undertaking a German translation, with revision and additions, of John Percy's classic treatise on the metallurgy of iron and steel, the publication of which, in successive installments, stretched through many years. In 1863, lie published, as a thesis in connection with his "Assessor's examination," an essay, entitled The Results of the Bessemer Process for the Production of Steel, and Its Prospects for the Rhenish and Westphalian Iron and Steel Industry, which revealed such ability and knowledge as to secure for him a call to the chair of metallurgy in the Berlin Mining Academy.

Jun 1, 1909

By Jerome F. Kuzmick

Condusions. From the work on aluminum powder, the following general con clusions can bc drawn: I. The physical properties of aluminum compacts, such as density. strength and ductility, increase with increasing pressure, up to the practicable pressure limits. 2. Good properties ill aluminum con pacts can be secured only by the use of high pressures, because it is neccssary to rupture the refractory oxide film on aluminum powder. 3. Considerable softening of the specimens occurs upon sintering. regardlers of the pressure used. General Conclusions 1. For relatively short-time sintering. molding pressure is a very important factor in the final physical properties of the sintered specimens. 2. The effect of pressure. is difierent for each metal, so that few general rules can be drawn that would apply to all metals. 3. In many cases, fur a particular metal powder and sintering temperature there is a critical pressure at which the best physical properties can be obtained. 4. The principles of cold work and in nealing and their effect on grain structure applied to massive metal also holds true for sintered metals. 5. Particle size, at least for electrolytic iron powder, does not have a. great effect on ultimate grain six. DISCUSSION [E. E, Schumacher presiding V.. V. Crane. *—I was particularly impressed with Dr. Kuzmick's work on tin IF not the illustration, particularly the Second one. a very good illustraition of hot preessing. in that

Jan 1, 1945

By J. H. Schulman, M. H. Buckenham

R. W. Christy (Manager of Sales, Sanitary Engineering Equipment, Link-Belt Co.) and C.D. Rubert (Barrett, Haentjens & Co.) — Messrs. King and Schepman have presented an excellent paper which outlines the general practice in the design of thickener mechanisms. Lifting devices, controls, special applications and underflow pumping arrangements have been reviewed in detail. Pumping arrangements were illustrated which eliminate the need for an expensive tunnel beneath the thickener floor. Most of those illustrated have the common feature of a relatively long underflow suction line extending from the hopper floor to the pump located on the bridge at the periphery of the tank. The authors limit these arrangements to comparatively dilute or thin slurrys. It is implied that dense and coarse concentrates, which are difficult to pump, cannot be handled unless a tunnel is constructed. Fig. 1 shows an underflow pump arrangement which negates the need for a tunnel but which permits the operator to convey a heavy dense slurry. The pump is mounted directly on the fixed hoist platform and the impeller is located at the base of the steel center column. Priming water is not needed. The column

Jan 1, 1963

By AIME

A present the colleges and universities are struggling to meet the responsibilities placed upon them by the return of the veterans from the armed forces to the educational institutions as well as the youth graduating from the high schools. The problems of meeting these responsibilities are complex and upon the shoulders of the educational administrators lies much of the burden. One of those educators who is in the midst of this situation is James Rowland Cudworth, dean of the College of Engineering of the University of Alabama and Chairman of the Mineral Industry Education Division, AIME, both for 1946 and 1947. He was born at Norwich, Conn., on Sept. 23, 1897, and like his father before him went to the Massachusetts Institute of Technology where he received his Bachelor's degree in 1921. His studies at MIT were mainly in the fields of geological and mining engineering. Why a New Englander studies mining is anybody's guess, but it may be due to a love of traveling to far places which so many New Englanders do. After graduating tinder the famed Waldemar Lindgren. Jim trekked to Mexico where he worked at Pachuca for the Cia. Real del Monte and at Charcas with the American Smelting and Refining Co.

Jan 1, 1946

By Fred C., Bond

IN CYANIDE milling, little attention has been paid to the effect of the viscosity of the mill solution on the extraction speed. The viscosity of the solution varies with the amount of dissolved salts present as impurities. These salts build up to a maximum depending on the character of the ore, the grade of cyanide used, the lime and salts added, and the impurities originally in the water. The viscosity will change from month to month and week to week as these factors vary; and that this variation affects the extraction is unquestioned, although methods for calculating it are lacking. The character of the ore is probably the most important of the four factors, as the amount of minerals present that are soluble in cyanide solution will vary constantly, and each variation affects the viscosity of the mill solution. When the cyanide consumption increases as the character of the ore changes, the viscosity of the solution will increase and the extraction will decrease, for the cyanide consumption is usually a measure of the impurities dissolved from the ore. In other words, as the difference between the total and free cyanide increases the extraction will decrease, other factors remaining constant.

Jan 1, 1926

Elected Died 1903 * ADAMS, CHARLES C. 1905 1884 *ADDY, MATTHEW 1896 1894 *ALLFN R B 1896 1874 *AMIOT, H 1892 1886 *AMSLER, CARL 1894 1895 *ÅNGSTROM, CARL 1901 1895 *ARMSTRONG, JOHN F 1898 1882 *ARNOLDS, HUGO 1886 1875 *ASHBURNER, CHARLES A 1889 1872 *ASIIBURNER, WILLIAM 1887 1883 *ATKINS, C M , JR 1885 1897 *AYERS, WILLIAM 1898 1885 *BABCOCK, GEO H 1893 1884 *BAILEY, EDWARD 1889 1880 *BAILEY, JACKSON 1887 1900 *BALLOU, FRANKLIN 1903 1886 *BARNES, F W 1892

Jan 1, 1910

By E. D. Gardner

AGAIN in 1945, the fourth year of World War 11, the American mining industry met the necessary demand made upon it for metals. Lack of labor prevented full production in some districts; maximum output, however, was maintained with the man power available. Development work and maintenance of mechanical equipment were neglected in favor of immediate production. Drafting of the younger men continued throughout the year, and the loss of personnel to war industries with higher wage rates continued up to "V-J" Day, Aug. 14. Labor shortages were more critical in 1945 than in 1944 though the man-power situation eased for some districts in the last quarter of the year. The trend in mining for the most part was to increase tons per man-shift by continued increased mechanization and refinements in methods and practices; larger equipment was installed where practicable. Labor shortages, together with the current higher wage rates, have advanced mechanization several years ahead of normal progress. The manpower shortage and the employment of inexperienced men had the effect of decreasing the average efficiency of the individual workman, but this condition was largely balanced by improved organization, greater efforts to improve labor relationship, and increased use of incentive pay systems. Safety instruction was emphasized, personnel contacts were increased, and more frequent foremen meetings were held to clarify contract agreements. Many of the large companies maintained schools to train green workmen.

Jan 1, 1946

By Ralph Hultgren

FEW phase diagrams of alloys composed of two transition metals have been adequately studied, probably because of the high melting points involved. Transition metals are the elements that have inner shells incompletely filled with electrons. They comprise groups IIIa to Villa of the periodic table, including more than half of all metals. We have chosen to study two systems whose comparatively low melting points allowed the alloys to be melted in a molybdenum resistance furnace. The nickel-palladium system proved to consist of a simple series of solid solutions, but iron-palladium manifested several remarkable features. The main characteristics of the latter diagram were decisively established, but lack of time prevented precise determination of phase boundaries. The gamma to alpha transformation in this system is unusual and warrants further study. Grigorjew1 determined the liquidus and solidus of the iron-palladium system by thermal methods. He found a minimum melting point, but no eutectic. He also found that palladium lowered the gamma to alpha and raised the gamma to delta transformation temperatures of iron, with a complete series of solid solutions existing between gamma iron and palladium. His measurements also indicated a compound or super-lattice near the composition FePd3. Jellinghaus2 found that annealing at 500° C. greatly increased the magnetic coercive force of an alloy of composition FePd. X-ray dif-fraction photographs showed that a tetragonal ordered phase had formed during the anneal.

Jan 1, 1939

By H. Morgolin, M. A. Greenfield, P. A. Farrar

In attempts to correlate mechanical properties with microstructure, it is desirable to determine the effect of ß grain size. Determination of 6 grain size is not a problem where a has precipitated at ß grain boundaries. However, in alloys which have been processed to produce an equiaxed a +ß structure the ß grain size is difficult to determine because ß grain boundaries do not etch. The ß grain size can sometimes be laboriously determined by searching for grains which have some a! outlining the 6 grains. This difficulty of ß grain size determination in equiaxed a + ß alloys can be overcome by heating below the ß transus temperature for a short time and water quenching. Fig. 1 shows the starting equiaxed a + ß structure of the Ti-5.25A1-5.5V-0.9Fe-0.5Cu alloy used in this investigation, and Fig. 2 shows the microstructure of the same sample water-quenched after heating 1 min at 1675"F, which is 25°F below the 0 transus. The heavily etched microstructure consists of some equiaxed a! in a structure showing considerable amounts of transformed ß. The ß grain

Jan 1, 1969

By Theodore B. Counselman

Of all natural resources, iron ore made into steel is the most important both in tonnage and value. The primary reason for the prosperity of the United States in the last century has been its pre-eminence in domestic supplies of iron ore and steel. The depletion of these reserves by two world wars and by the demand for richer blast furnace charges, as well as the constantly growing world- wide demand for steel, has fostered the recent quest for new iron ore mines around the globe. These developments have made a dramatic change in the iron ore picture of the world. It is the purpose here, however, to look briefly at the development of the United States iron ore industry, which has played such an important role in the events leading to the modern day boom in iron ore exploration.

Jan 7, 1965

By C. S. Barrett, D. F. Clifton

THE transformation that occurs in lithium and its solid solutions containing magnesium1,2 is similar in many respects to other diffusionless transformations of the martensitic type. This general similarity makes it desirable to investigate the transformation curves in detail. The current interest in the phenomenon of stabilization in martensitic transformations has created a need for a careful appraisal of possible stabilization effects in both cooling and heating transformations in lithium alloys. The effect of prior heat treatment on the temperature at which transformation begins and the effect of various temperature cycles in partially transformed alloys also merit attention. Limited data on some of these features were presented previously,' but the present studies have been made with improved apparatus, in which erratic fluctuations were smaller than in the earlier work, and include many independent determinations of certain critical observations. Material and Methods Geiger counter X-ray spectrometers were used: a Norelco instrument, original model, and a General Electric XRD-3. The low-temperature specimen holder has been described elsewhere." Specimens 10 mm in diam and 1.5 mm thick were held in firm contact with a copper block which was attached to the lower end of a stainless steel tube that extended up to a reservoir of liquid nitrogen. A heating coil on the tube permitted a controlled temperature gradient along the tube, so that desired temperatures and rates of heating and cooling could be obtained by controlling the heating current. The specimen was surrounded by an atmosphere of evaporated nitrogen in an insulated chamber having double cellophane windows. The temperature of the specimen was read by a thermocouple imbedded in it close to the irradiated area; the specimen could be held at constant temperature within 1°C for long periods. The body-centered cubic 200 reflection near 8 = 26" was used as the index of the amount of b.c.c. material present; occasional checks were made using the most suitable line of the low-temperature phase, the close-packed hexagonal 110 line near 8 = 29". Copper radiation was used throughout. A continuous record was made of the reflected intensities on a strip chart recorder, both when the peak intensity of a line was being followed and when the lines were being scanned at constant temperature. On the continuous recordings of peak intensity, periodic checks were made on the background intensity between the lines, and on the setting of the spectrometer for maximum intensity. The lithium-base solid solution containing 12.4 atomic pct Mg (33.3 wt pct) that had been used previously' was chosen, as it had a transformation range at relatively high temperatures, so as to permit wide temperature cycling within the range. Just prior to use a pellet was cut from the ingot,

Jan 1, 1951