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The General Committee met in the Treasury Building at Washington on Oct. 6 and 7. At the first meeting, Cornelius P. Kelley was appointed chairman, and Paul Armitage, secretary. Sub-committees were ap-pointed on Invested Capital, Mine Valuation, and Depletion and De-preciation. On Oct. 7, the reports of these committees were submitted to the General Committee and were referred to the Executive Committee. A motion was carried that the Executive Committee he constituted a permanent committee to continue the work of the Committee, with full power to acid to and increase its membership, that. as thus increased, it should constitute a permanent organization to act- and cooperate with the Treasury Department in matters of mining taxation under the Federal Income and Excess Profits Tax Laws. Thereafter the Executive Com-mittee met and formed a permanent committee as follows: Cornelius F. Kelley, chairman, 42 Broadway, New York City. J. L. Darnell, office of the Commissioner of Internal Revenue, Wash-ington, D. C. J. Parke Channing, 61 Broadway, New York City. Walter Douglas, 99 John St., New York City. R. V. Norris, 542 Second National Bank Bldg., Wilkes-Barre, Pa. J. E. Spurr, Engineering and Mining Journal, 10th Ave., and 36th St., New York City. W. G. Swart, 808 Selwood Bldg., Duluth, Minn. J. P. Finley, 45 Cedar St., New York City. W. A. Williams, Bartlesville, Okla. F. S. Peabody, Peabody Coal Co., McCormick Bldg., Chicago, Ill. Matthew C. Fleming, 71 Broadway, New York City. H. B. Fernald, 54 Wall St., New York City. William G. Mather, Cleveland, Ohio. Walter Fitch, Eureka, Utah. Arthur Thacher, 900 Security Bldg., St. Louis, Mo. John P. Gray, Coeur d'Alene, Idaho. Paul Armitage, secretary, 233 Broadway, New York City.

Jan 12, 1919

By Mark Sheppard

DURING the winter of 1937, the writer visited a West Virginia stone quarry at which the overburden is stripped hydraulically. The quarry is in a bed of limestone, about 200 ft. thick, which outcrops on a hillside above a small river; the quarry face is 175 ft. high. The top of the stone is cut in all directions by erosion channels, which are filled with a tough, red clay. Some of the larger channels are 30 ft. deep and 8 ft. wide. The thickness of the clay overburden ranges from a few inches to 10 ft., the average being estimated as less than 3 feet. The topography of the district is rugged, and the hillside above the quarry face is not suited to the use of the usual mechanical methods of moving dirt. Until hydraulicking was started 10 years ago, the over- burden was dug by hand labor, dumped to the quarry floor and transported to the dump in quarry cars. Cleaning deep channels was a slow and expensive process. When hydraulicking was started, the top of the quarry face was over 200 ft. above the level of the river. The pipe line was carried in a semi- circle around the top of the quarry about 200 ft. from the face and about 50 ft. above it. As there is no adequate supply of water above the quarry, the water must be pumped from the river. As quarrying progressed the pipe line was moved until the discharge points are now over 300 ft. above the river. Water is pumped from the river by a four-stage centrifugal pump having a 5-in. intake and a 4-in. discharge. It is direct-connected to a 200-hp., 2300-volt, 1760-r.p.m. induction motor. At 1760 r.p.m. the rated capacity of the pump is 750 gal. per minute under a head of 600 ft. The pump is installed in a house of frame construction on the river bank, about 10 ft. above normal water level, which also houses the pump for the mill-water supply. Above the pumps are hoisting bays into which the motors are raised whenever the river reaches flood stage. An 8-in. suction line, equipped with a strainer and a foot valve, takes the water from a concrete sump at the edge of the river. The pipe line from the pump consists of 1750 ft. of 8-in. spiral steel flanged pipe and 800 ft. of 4-in. spiral steel flanged pipe. The connection from the pump

Jan 1, 1938

By V. F. Marsters

THE oil-producing territory of Peru is confined to the province of Tumbes and the department of Piura, located in the extreme northern end of the republic and adjacent to the southern border of Equador. The first real production came from Zorritos field, located on the shore line and in the province of Tumbes. The production of this territory was soon exceeded by that of the Negritos field, also located along the shore line and in the northwest corner of the department of Piura. Talara, lying a short distance north of the original or early producing area was made the shipping port. This field was developed by the London Pacific Petroleum Co.; it is now-operated by the International Petroleum Ltd. (Toronto, Canada). A little later, the Lobitos field came into prominence; it was first exploited by the Lobitos Oil Co. At present, it is operated by the British Oilfields Ltd. This field is located between Talara, on the south, and Zorritos, on the north. It is now the second largest producing area in the country, the Negritos being by far the largest both in area and production. In other parts of Peru, there have been periods of desultory prospecting, particularly in the department of Puno. This work was carried on in the surrounding region of what,is locally known as the "Pirin" field, developed by the Brown Brothers. It lies between Juliaca, a railway junction point and Lake Titicaca. No favorable results from the latest prospecting have been reported. During the past few months, an opinion has been expressed in various journals that it is doubtful if commercial production will be found in the high plains of the Lake Titicaca region. It is, however, due to the Peruvian oil industry to remember that the Pirin field, although covering but a small area, was a fair producer even under adverse circumstances. If the author's interpretation of the geology of the Titicaca section is correct, certain sections of the high plains will be found to be commercially productive, not-withstanding the unfortunate geographical position from the standpoint of transportation; or its elevation.

Jan 3, 1925

Wartime geological studies by the U. S. Geological Survey and subsequent drilling carried on by the Bureau of Mines disclosed new ore in the Illinois-Wisconsin zinc field. As a result, several companies are carrying on drilling programs to locate and define new ore bodies. The Vinegar Hill company, which operates a custom mill to handle ores from various sources, now employs about fifty men in production at their Andrews mine. The ore is usually found in a 200-ft horizon below the surface. Water problems are not serious. Commercial-grade ore ranges up to 8 and 9 per-cent zinc and the cut off is approximately 41/2 percent.

Jan 1, 1948

The Bureau of Mines extends. a cordial invitation to all members of the Institute to visit Pittsburgh, Sept. 29 to Oct. 1, to participate in the dedication of the Mines Experiment Station. Accompanying this will be a nation-wide participation in a First-aid and Mine Rescue Contest. The Pittsburgh Chamber of Commerce will cooperate. The Institute will be represented by a special delegate appointed by the President. MONDAY 8:30. A. M. Bureau Building open for inspection. 10:30 A. M. Dedicatory Ceremonies in rear of Main Building, .4800 Forbes St. 2:00 P. M.. Special Train and Automobiles to Experimental Mine near Bruceton, Pa. 3 to 6 P. M. Mine Explosion and Inspection of Experimental Mine . and of Explosives Testing Plant near Bruceton, Pa. 6:00. P. M. Return by Special Train and Automobiles to B. & 0. Station, Pittsburgh. 8:00 P. M. Informal Reception and Organ Recital Carnegie Music Hall. Arranged by Carnegie Institute of Technology.

Jan 9, 1919

There are no data available of shipments until 1858, and then estimated, when railroad service became available. By reason of the iron made in the county, and the large amounts of salt, the tonnage used locally was quite large, and until 1860 these are estimated from the probable salt and iron production. After 1859 the tonnages shipped by rail are partly estimated from the total shipments of the Allegheny Valley Railroad from four counties. It is believed that the totals are below, rather than above, what the actual production was. While considerably larger for the same years than figures given by the Secretary of Internal Affairs and census reports, these data were always too low in those days, partly because of lack of facilities for gathering them, but more largely because of the strong prejudice existing in those days against furnishing such data to any governmental agencies.

Jan 1, 1942

By Persifor Frazer

The accompanying diagrams represent a lamp provided with certain improvements which render it more serviceable for the use of the engineer or other mining official who is often compelled to visit several mines a day remote from each other, and may be called on to use the magnetic needle in any or all of them. These requirements demand that the material of which it is made should be copper, and that it should be capable of being closed oiltight, for emptying and refilling the lamp at each mine would be a less expeditious as well as a less cleanly process, and transporting a lamp of the ordinary kind over rough roads on horseback or in wagon, would result in spilling the greater part of its contents. The general form of the lamp, including the false back to keep

Jan 1, 1882

NEW MEMBERS. The following list comprises the names of those persons who became members during the month of March, 1913 BAECHTOLD, CHARLES A., Engr 9G Liberty St., New York, N. Y. BRANTLY, JOHN E., Instructor in Geology Tuscaloosa, Ala. CADDY, JAMES P., Net., ,Lake View & Star, Ltd Fimiston, West. Australia. LONERGAN, PHILIP J., JR., Prof. of Mining, Government University, Peking, China. MCKANNA, EDWIN A., Min. Engr P. 0. Box 834, Oklahoma City, Okla. MACDONALD, ANGUS W., Supt. Labor Dept., Dominion Coal Co., Ltd., 21 Queen St., Sydney, N. S., Canada. TSUBOI, Yoshio, Min. and Met. Engr., Kosaka Mine, Fujita Co., Akita-ken, Japan.

Jan 4, 1913

By E. D. Slone, F. L. Dillard

When a new mine is in the planning stages, one of the most important decisions to be made is the selection of' face haulage equipment and the interrelated transportation system to the surface. Equally important is the method of transporting personnel supplies and repair parts from the surface to the working places. When Bell & Zoller management elected to open the new Zeigler mine in the No. 9 seam near Madisonville, Ky., last year, various transportation systems were considered. It was agreed early that a slope mine would be preferred to a shaft mine, and that belt conveyors would be more economical than a rail system.

Jan 1, 1970

By Edward Skewes

In view of the importance of the Cripple Creek district, the large amount of the publications concerning it, and the circumstance that many members of the Institute reside in it, or are familiar with it through repeated visits, it is surprising that our Transactions should have remained so long without any contributions on the subject. The same observations may be made with regard to the Witwatersrand, in South Africa, the other great productive gold-field of recent development. And I suppose the explanation is the same in both cases, namely, that the members of the Institute persoilally acquainted with the

Jan 1, 1897

By E. S. Moffat

Members of the Institute who have visited the works of the Lackawanna Iron and Coal Company at Scranton, will remember the exposure of a large vein of anthracite coal in the rocky bank on the south side of Roaring Brook, near the blast-furnace. The vein is quite flat, and is exposed to view for several hundred yards along the banks of the brook, a few feet above the surface of the water. It is some ten feet in thickness, and is known as the Big Vein. At a point just opposite the blast-furnace, much of the coal from this vein was mined out many years since, the usual pillars being left to support the overlying rock and drift, which are here some twentyfive to thirty feet in thickness. Over thirty pears ago fire was communicated from an ore-roasting pile on the surface of the ground at this point, through an old shaft, down to the refuse and pillars which had been left in the mine

Jan 1, 1887

By Eugene McAuliffe

IT is not possible to include in this paper, limited as it is in scope, the many diverse steps toward the reduction of mine accidents that are taken in the mines that produce the nation's coal. Every coal-producing state has enacted laws covering proper mining practices, and the major portion of these are directly related to the safety of the mine employees. The United States Bureau of Mines, the American Institute of Mining and Metallurgical Engineers, The American Mining Congress, a number of national, regional and state organizations, as well as the coal technical press, have covered time and time again all of the "do" and "don't" phases of mine operation that bear on the important question of mine and employee safety. Within the past 15 years The Union Pacific Coal Co. has attempted to put into practice in its mines in southern Wyoming these many good recommendations, finding some value in all, and yet, to secure substantial results, the management found it necessary to resort in the end to what might be referred to as "extra-territorial" methods. It is the writer's purpose to show in this paper that marked and even extraordinary betterment can be brought about when employer and employee work together with due sincerity. In presenting our own experi-ence, one that has been duplicated in so far as results are concerned on numerous other properties, no theory of perfection of management exists; on the other hand, our organization feels that as long as our record of accidents remains as shown by even our latest and best performance we still have far to go. Safety work in some form has been carried on in and about the mining properties of The Union Pacific Coal Co. since the first mine was opened at the now long-abandoned town of Carbon, Wyo., in 1868. On June 30, 1903, an explosion and subsequent mine fire occurred in mine No. 1 at Hanna, taking 169 lives, and a second explosion occurred in tile same mine on March 28, 1908, in which 59 additional lives were lost. Looking back with impartiality on the causes leading up to these two unfortunate disasters, we can only conclude that shooting from the solid, the absence of adequate ventilation, rock dusting, the use of water at the face to allay

Jan 1, 1938

By F. W. von Batchelder

The principles of microradiography and their application practically coincided with the discovery of X-rays. These principles were first used in the metallurgy field by Heycock and Neville1 in a study of the dendrite structure of alloys of Au-Na, Au-A1, Cu-A1, and Ag-A1. The method was introduced in the USA by clark2 after a visit to France. Scores of papers have been written, and a very complete bibliography on this subject was compiled by the Eastman Kodak company. Although a number of papers have discussed X-ray

Jan 1, 1959

By John V. Beall

The mining industry of Japan is not very large, but it is very old. Some of the mines have 1000 years of history. At Nara, the capitol 1300 years ago, the great Buddha of bronze that was cast at that time was of metal mined from several localities in Japan including the Akenobe-Ikuno district, one of the present Mitsubishi properties. Methods of smelting copper and iron, it is believed, came from China via Korea. A characteristic of the Japanese mining industry today is one of buying abroad and treating at home, a variety of ores of different compositions. All in all, Japan's mineral deposits under its own flag are inadequate for its great industrial strengths.

Jan 5, 1969

The State Mining Experiment Station, Missouri School of Mines and Metallurgy, Rolla, Mo Charles H. Fulton, Director of the School of Mines Martin H. Thornberry, Director of the Mining Experiment Station. From the State Mining Experiment Station are issued all the general and technical bulletins of the School of Mines The latest bulletin containing a complete list of publications will be sent upon application to the Director of the Station Residents of the state may obtain bulletins as issued without charge, or may ask to be placed on the mailing list. Nonresidents should write to the Director for further information concerning specific bulletins. From the long list of bulletins the following have been care¬fully selected as being most likely to interest the geologist and the mining engineer. Vol 8, No. 1 (1916), Bibliography of concentrating ores by flotation, by J Cunningham, vol 1, No 3 (1912), Some apparatus and methods for demonstrating rock drilling and the loading of drill holes in tunneling, by L E Young, vol 2, No 1 (1915), Comparative tests of piston drill bits, by C R Forbes and L M Cummings; vol 2, No 3 (1916), Cupellation losses in assaying, by H. T Mann and C. Y Clayton; vol 4, No 1 (1917), The hydrometallurgy and electrolytic precipitation of zinc, by F D. James; vol 4, No 2 (1917), The effect of additional agents in flotation, pt 1, by M. H. Thornberry and H T. Mann, vol 5, No 1 (1919), The carbonization of Missouri cannel coals, by H L. Dunlap, K. K. Kershner and V. X Smiley. Vol 5, No. 4 (1921), Coal mining methods in Missouri, by W W Weigel, vol 6, No 1 (1921), The problem of the St Peter sand¬stone, by C L Dake, 50 cents, vol 6, No. 2 (1922), Bibliography on the electrothermic metallurgy of zinc, by B M. O'Harra, vol 6, No. 4 (1923), Experiments on the distillation of zinc from complex zinc-lead-silver ores, by B M. O'Harra and E S. Wheeler, vol 7, No 3 (1924), Underground loading devices, by C. E. van Barneveld, 81; vol 7, No. 4 (1924), Briquetting of zinc ores, by B. M. O'Harra; vol. 8, No 2 (1925), A treatise of Missouri clays, by M. H. Thornberry.

Jan 1, 1933

By T. A. Rickard

The notion prevails that writing is a knack, that the skilful use of the pen is a gift of nature. This is an error. Dogberry may be responsible for it; he said: "To be a well-informed man is the gift of fortune, but to write and read comes by nature". Because Dogberry said it, we may be sure that Shakespeare thought otherwise. Ability of any sort may be partly innate, but my own observation and experience lead me to conclude that most of the easy writers have become so by constant practice. As I recall the names of men successful with the pen, I remember that most of them have written a great deal and have taken particular pains to improve their style. The suggestion that proficiency in the difficult art is a happy accident provokes a sardonic smile. The larger part of the great writing in our literature is the result of persistent effort. An easy fluency has been the undoing of many; their flamboyant and fantastic scribbling has proved as perishable as froth. This criticism applies to technical writing also; in order that a technical description or discussion may hold the interest of the reader, at least long enough to cause him to read it to the end, the writing must be done carefully and systematically; otherwise it will fail in its purpose of conveying information. Clearness is absolutely essential. "It is not enough to use language that may be understood; it is necessary to use language that must be understood."* The purpose of writing, at least of that which is meant to be read by others, is not only to express ideas but to communicate them. Lack of perspicuity may prove as %ad as

Jan 1, 1931

By Wilford L. Stork

Certain influences of oxygen on iron have been known for many years and it has always been considered one of the worst enemies of the iron and steel founders. Nobody had a good word for it, hence little was done to make use of this oxygen. In all the fields of foundry practice, the desideratum was "melt without oxidation of the metal." In the consideration of the influence of oxygen on cast iron, we must not confuse this condition with oxidized iron caused by poor melting conditions, due to a high bed, heavy charges, low coke ratio, excessive melting rate, high blast, or poor charging. It is admitted that oxygen absorbed by iron melted under these conditions has a deleterious effect on the properties of the iron. The writer has had experience both in the melting under such poor conditions and in remedying these bad conditions and considers the product far inferior to iron melted under normal conditions. As stated by Dr. Richard Moldenke,l such iron has a higher melting point and high combined carbon, is sluggish, and contains slags and oxides in solution in the liquid, causing slag inclusions and gas occlusions, 'thus producing defective castings. This oxidized condition cannot be counteracted or removed by any of the known deoxidizers; it can be remedied only by proper melting conditions. Such iron is redly burned, whereas the iron considered in this paper was melted under normal conditions with moderate blast, correct bed height, light charges of iron, and low coke consumption and is not in this category at all. In 1914, the late J. E. Johnson, Jr., startled the metallurgists of the . world when he published his results on the advantages of oxygen on cast iron.2 His work is so convincing and so logical, in spite of the common and well-established notions on the subject, that nobody has been able to refute a single argument. Such an eminent authority on iron and steel metallurgy as Prof. H. M. Howe has accepted the work in all its details in his latest book.3 The work of J. E. Johnson, Jr., has revolutionized the metallurgy of cast iron and it seems apparent that all future work must include an oxygen determination just as we include silicon, sul-

Jan 1, 1920

By Arthur W. Sheafer

MR. ECKLEY B. COXE, in his able and interesting paper on " The Preparation of Small Sizes of Anthracite,"* read and discussed at the Glen Summit Meeting, October, 1891, refers to the reputed immense amount of coal contained in the culm-banks, which are the unsightly accompaniment of every mining operation in the anthracite coal-regions. Mr. Coxe thinks the available amount and value greatly exaggerated, giving among his reasons (1) the spoiling of the culm by mixing with other refuse; (2) its deterioration; (3) its destruction by fire ; and (4) frequent failures to realize expectations as to the size of the banks. These points are undoubtedly important factors in determining the advisability of working any individual bank, but they have a varying influence in the several regions, some prevailing more in one than in another. Although the amount of fuel lying waste in these banks is still an uncertain and undetermined quantity, yet no one can visit the Schuylkill region without being impressed with the fact that a considerable amount of culm, too valuable to be left merely to the mercy of the elements, surrounds and encumbers each site of an old or present colliery operation. The rapid increase in the number of washeries, and the demand for leases on old culm-banks, shows that, in the Schuylkill region at least, the question of deterioration doès not play an important part. The proportion of coal to refuse, the relative percentage of the sev-

Jan 1, 1895

By J. H. Westbrook

IT is always of interest to document the origin of real microstructures which closely approach various idealized morphologies. Such instances constitute excellent bases for experimental studies of the effect of microstructure on properties. Typical examples include the eutectoid steels (lamellae) used by many investigators and the two phase Cu-Cr alloys (spheres) recently employed by Hibbard and Hart The present note describes a structure with cylindrical particles. In a study of certain alloys in the Cr-C system, an alloy was arc melted whose composition was very close to the aCr-Cr,C, eutectic (3.2 wt pct C, according to the latest phase diagram published by Bloom and Grant2). The alloy was not analyzed but previous experience with the melting technique employed indicates good correspondence between intended and analyzed compositions with negligible tungsten contamination from the electrode. The phases present in the alloy were identified by X-ray powder patterns as a chromium and Cr,C,. Typical micrographs, presented in Fig. 1, show unmistakable evidence of the cylindrical geometry of the carbide phase. The eutectic grains are randomly oriented and, consequently, only a few show the true fibrous nature of the carbide particles, most being cut so as to show slightly elliptical cross sections. Within any particular grain, remarkable uniformity is to be observed with respect to the size, shape, spacing, and orientation of the carbide particles. Length to diameter ratios have been estimated from the micrographs to be at least 250:1, with diameters of about lp. This alloy may be of further interest from different viewpoints. On the one hand, it might be used to check the applicability of the equations derived by Fullman3 for computing true particle dimensions of cylindrical particles from opaque random sections. On the other hand, it might be possible to extract the carbide particles from this alloy and repack them in a ductile matrix to form a synthetic structure of the type discussed by Metcalfe et al.4 With the large l:d ratio and the small diameter of the carbide fibers, it is likely that the interdefect distance in each fiber is sufficiently great to permit realization of a large fraction of the presumed high strength of the carbide. References 1W. R. Hibbard, Jr. and E. W. Hart: Dispersion Hardening of Copper-Chromium Alloys. AIME Trans., 1955, vol. 203, p. 200; Joun-nal of Metals, January 1955. 2D. S. Bloom and N. J. Grant: The System Chromium-Carbon. AIME Trans.. 1950. vol. 188. p. 41; JouRnal of Metals, January 1950. aR. L. Fullman: Measurement of Approximately Cylindrical Particles in Ooaaue Samples. AIME Trans.. 1953, vol. 197, p. 1267; Journal of Metals. ~ebtember 1953 4 A. G. Metcalfe, C. H. Sump, and W. C. Troy: Fiber Metallurgy. Metal Progress, 1955, vol. 67, p. 81.

Jan 1, 1958

By J. D. Livingston, H. E. Cline

The lamellar-dendritic transition in Sn-Pb alloys near the eutectic composition has been studied at high growth rates. Lamellar structures were found over a substantial range of tin-rich compositions, and this range extended to increasingly tin-rich concentrations as growth rate increased. These results are discussed in terms of stability and competitive-growth arguments. Various experimental and structural limitations to the rate of directional solidification are discussed. The rate of heat removal at the heat sink is the major experimental limitation. ReCENT interet1,2 in the use of fine composite structures produced by directional solidification of eutectic alloys makes it important to determine the range of composition and growth conditions that yield such microstructures. Because increasing growth velocities produce increasingly finer microstructures, it is particularly significant to determine the factors limiting the rate of solidification. Mollard and Flemings3 have shown that composite structures, free of primary dendrites, can be obtained in Sn-Pb alloys of off-eutectic composition. The composition range of composite structures was found to increase with increasing values of G/V, where G is the temperature gradient and V is the growth velocity. These results are in good quantitative agreement with an analysis of the stability of a planar eutectic interface.4 This analysis specifically predicts that over a small range of compositions stable lamellar structures will be obtained even for G/V = 0, hence, even at very high growth rates. The lamellar-dendritic transition in Sn-Pb alloys has also been analyzed with a model based on competitive growth between dendrites and the composite structure.576 This treatment, based on earlier work on organic eutetics,7 predicts that the composition range yielding composite structures in Sn-Pb will increase rapidly at high growth rates. An increase in the composition range of composite structures at high growth rates was recently observed in Cu-Pb alloys near the monotectic composition.8 In view of these results, and the predictions of the stability and competitivegrowth analyses, it was decided to study the lamellar-dendritic transition in Sn-Pb alloys at high growth rates. EXPERIMENTAL Using 99.999 pct pure materials, a series of Sn-Pb alloys were prepared containing 16.8 at. pct to 27.6 at. pct lead. (Eutectic composition is 26.1 at. pct Pb.) Ingots were extruded to 0.175 in. rod, and some rod was drawn to 0.070-in. wire. Directional solidification was accomplished in two different ways, Fig. 1. For growth rates up to 2 x 10-1 cm per sec, a 0.175 in. diam sample was placed in a graphite crucible 5 in. long with 0.250 in. OD and 0.035 in. walls. Samples were melted under flowing argon in a vertical, platinum-wound furnace, and solidified by driving the crucible downwards through a \ in. hole in a water-cooled copper toroid, Fig. l(a). An insulated chromel-alumel thermocouple was imbedded in the center of a representative sample, and moved with the sample during solidification. The local temperature is plotted against the distance travelled by the sample in Fig. 2. As the growth rate increased, the solid-liquid interface moved closer to the water-cooled toroid and the temperature gradient increased. At growth rates above 10-1' cm per sec, heat was not removed fast enough and the sample moved into the toroid in the liquid state. The curve for V = 2 x 10-1 cm per sec shows a plateau caused by incomplete removal of latent heat from the interface, a problem which will be discussed later. To improve the heat removal, the toroid was cooled by nitrogen gas precooled in liquid nitrogen. This allowed successful solidification at rates up to 2 x 10-1cm per sec. Higher solidification rates required still more effective heat removal. Samples 0.070 in. in diam were placed in graphite tubes 0.125 in. in diam with 0.020 in. walls. Instead of cooling by sliding contact with a cooled toroid, these thinner samples were sprayed or directly immersed into water, Fig. l(b). After solidification, samples were stored in liquid nitrogen until they could be examined metallographic-ally. The surface was prepared with a diamond-knife microtome, followed by a light etch. The presence or absence of tin dendrites, Fig. 3, or lead dendrites, Fig. 4, was noted by optical microscopy, usually of a transverse section near the center of the sample. Replicas of the surface were prepared and examined in an electron microscope to resolve the fine lamellar structures, Fig. 5. The structures observed at various compositions and growth rates are summarized in Fig. 6. Composite structures were observed at increasingly cin-rich compositions as growth rate increased. This transition from dendritic to composite structure with increasing growth rate was also demonstrated by solidifying half a sample at a slow rate and then suddenly increasing the growth rate by lifting the furnace and quenching the sample with a water spray. A longitudinal section of this sample, Fig. 7, shows that the tin dendrites, which extended ahead of the slow-moving composite interface, were bypassed by the composite when the growth rate was increased. The range of composite structures at high growth rates was limited by the appearance of primary lead dendrites on the tin-rich side of the eutectic composition. Observation of representative longitudinal

Jan 1, 1970