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For the year ending February, 1917 PRESIDENT L. D. RICKETTS,1 NEW YORK, N. Y. PAST PRESIDENTS BENJAMIN B. THAYER,1 NEW YORK, N. Y. WILLIAM L. SAUNDERS,2 NEW YORK, N. Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 NEW YORK, N. Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK, N. Y. SECRETARY . BRADLEY STOUGHTON NEW YORK, N. Y.

Jan 5, 1916

For the year ending February, 1917 PRESIDENT ................... L. D. RICKETTS,' NEW YORK, N. Y. . PAST PRESIDENTS BENJAMIN B. THAYER 1 NEW YORK, N. Y. ................. WILLIAM L. SAUNDER2, NEW YORK, N. Y. FIRST VICE-PRESIDENT ................ SIDNEY-J. JENNINGS,1 NEW YORK, N. Y. TREASURER ................ GEORGE C. STONE,l. NEW YORK, N. Y. . SECRETARY EMERITUS ................ ROSSITER W. RAYMOND, NEW YORK, N. Y . SECRETARY ............... BRADLEY STOUGHTON, NEW YORK, N. Y.

Jan 8, 1916

For the year ending February, 1917 PRESIDENT L. D. RICKETTS,1. NEW YORK, N. Y. PAST PRESIDENTS BENJAMIN B. THAYER,1 NEW YORK, N. Y. WILLIAM L. SAUNDERS,2 : NEW YORK, N.Y. FIRST VICE-PRESIDENT SIDNEY J. JENNINGS,1 NEW YORK, N. Y. TREASURER GEORGE C. STONE,1 . NEW YORK, N.Y. SECRETARY EMERITUS ROSSITER W. RAYMOND, NEW YORK,. N. Y. SECRETARY BRADLEY STOUGHTON NEW YORK, N.Y.

Jan 1, 1917

By C. D. Tedmon, D. P. Ferriss

THE yield stress, o of low-carbon steel has been shown to vary with the average grain diameter, d, according to the relation1-3 where o is taken to be the lower yield-point stress Of is the friction stress on an unlocked dislocation, and ky is a constant. The interpretation2,4 of ky in terms of dislocation theory relates this constant to the stress to unlock a source across a grain boundary. cottrel14 predicted that ky would increase with decreasing temperature. This was observed to be the case by Adams and coworkers5 in their investigation of niobium (columbium). However, petch6 and Backofen: both working with low-carbon steel, found ky insensitive to temperature. In his work with high-purity niobium, Johnson' found ky equal to zero. Evansg showed that k, was essentially zero for niobium containing nitrogen in an appreciable concentration range. The present experiments were designed to check this apparent anomaly in the value of ky in another Group V metal. Yield points were determined as a function of grain size at several temperatures for tantalum and a tantalum-tungsten alloy. The material used was double are-melted tantalum and a double are-melted alloy of 90 pct Ta and 10 pct tungsten (by weight), both obtained as unannealed, swaged rod. The impurity content of the materials is given in Table I. The tantalum was annealed at 1325"C. in a vacuum resistance furnace using a tantalum boat. The alloy was similarly annealed at 1660°C. Annealing times varied from 15 min to 2 hr, depending on the desired grain size. Nominal pressure in the furnace was 3 X 10~4 mm of Kg. Metallographic examination showed that the annealing treatment produced grain sizes ranging frorn 0.021 to 0.200 mm in the tantalum, and 0.060 to 0.160 mm in the alloy. Tensile bars were made by centerless grinding the annealed specimen;, and then electropolishing to remove all grinding marks. The specimens were than pulled :it 2 1/2 pct per rnin in an Instron testing machine. The tantalum specimens were tested at 77", 195", and 300°K. The alloy was tested at 300°K only. All specimens exhibited a yield-point phenomenon at all temperatures. Typical load-elongation curves at the three test temperatures are shown in Fig. 1. The lower yield stress is plotted as a function of (grain size) in Figs. 2 and 3 for tantalum and the 90 pct Ta-10 pct W alloy, respectfully. The position and slope of the curves was determined by least-

Jan 1, 1962

By Leon Orlowski

THE oil-bearing districts of Poland are found on the slopes of the Carpathian Mountains. The oil belt extends from Gorlice southeast to Stanislawow. It is approximately 250 miles long and 30 miles wide, and comprises four geological districts: the western, or Gorlice district; next, to the east, the Krosno district; the Boryslaw district; and, in the extreme southeast, the Stanislawow district. The amount of petroleum produced in Poland from the beginning of the oil industry scarcely totals 26,000,000 metric tons, or 15 per cent. of the estimated supply. Of this amount, 18,000,000 tons have been taken from the fields of Boryslaw within 25 years; and only about 8,000,000 tons from all other fields within a period twice as long, although some of these other fields represent just as good possibilities as did Boryslaw at the beginning of its development. The Polish oil industry was severely stricken by the war. The retreating Russian armies, in 1915, destroyed a large number, of the existing oil wells, nor was the post-war period favorable for the development of this industry;; the money and credit stringency interfered with the expansion of drilling. But since 1921 there has. been a slow steady increase in production and there is now every reason to believe that conditions in the industry will improve. In fact, an increase in new drillings has been reported for the current year. The production of crude oil in Poland, in 1913, amounted to 1,113,668 metric tons. In 1914, the production declined- to 655,600 metric tons. In 1921, the production was 705,596 tons; in 1922, 712,428 tons, and in 1923, 737,182 tons; or more than 5,000,000 bbl. But the fields have a much greater potential output, which could be realized were the capital available for prospecting and new drilling. The principal producing, and at present most exploited, fields are around Boryslaw and Schodnica. These fields were developed rapidly for in the first year of their modern exploitation the wells were gushers of moderate depth. However, as a result of heavy drilling, the shallow folds have been exhausted and oil can be reached now only by deep drilling. Wells of almost 5600 ft. have been drilled in Boryslaw. Because of these drilling conditions, a large number of engineers and workmen specially skilled in deep drilling are to be found in this field.

Jan 3, 1925

By Sidney H. Loram

As the work carried on by this Company, of which the writer has been in charge for the past two years, is somewhat unique, the following account of it may be of interest, and, on that account, is offered to the Institute without any attempt to claim this practice as the best. Mines. The mines supplying ore to the Company arc situated in three groups: the Guanaco field,.about 80 miles N.E. of the port of Taltal (lat. 25" S., long. 70" 30' W. of Greenwich); the Sierra Overa, about 63 miles S.W. of Taltal; and Paranao, about 42 miles due N. of Taltal (12 miles N. of the small town of Paposo, once famous for its copper-output). Guanaco. This field lies in the center of an absolutely waterless mountainous desert, where not a sign of vegetation can be found for miles. The dryness is such that ivory and horn crack and open, while raw-hide must be used in place of leather, which -would become worthless in a very short time. Water is brought about 21 miles by piping from the Cordillera, but only in small quantities, and costs in the Guanaco $7 (= $1.78 gold) per cubic meter. All supplies and food are sent from the port of Taltal, which in turn draws its supplies from the south of Chile, the

Jan 1, 1900

By A. F. Melcher

THE present paper is a progress report. on an investigation of the physical factors of oil and gas and especially of their sands, I such as-pore space, size of pores or permeability, retentivity, viscosity of the oil, temperature, pressure, thickness and area of the pay sand, water relations, and capillarity. The purpose is to determine as many of these physical factors as possible, and to ascertain the relations existing, directly or indirectly, between these physical factors and the production of oil and gas. As yet only pore space2 and size of grains of pay sands have, been investigated, although an apparatus has been designed to determine the permeability of a sand to oil, water, or gas under definite drops of pressure between the entrance face and exit face of the sample. Messrs. E. W. Shaw, R. Van A. Mills, D. Dale Condit, G. B. Richardson, G. C. Matson, and C. H. Wegemann collected the samples upon which the physical determinations were made. Acknowledgment is made to my colleagues of the United States Geological Survey for many suggestions and criticisms; to Mr. Mills for the production data given of the oil wells from which some of the samples were collected; to Mr. A. W. McCoy of the Empire Gas and Fuel Co., Bartlesville, Okla., for many ideas.

Jan 4, 1920

THE first session of the Institute was held at the Smithsonian Institution, on Tuesday evening, February 22d. The members were welcomed to Washington and to the Smithsonian by Prof. Joseph Henry. President Holley responded to the cordial welcome of Professor Henry, and then read an introductory address on the subject of Technical Education. Following the discussion on President Holley's address the following persons, duly proposed and indorsed by the Council, were elected members and associates of the Institute : MEMBERS. Emile R. Abadie, - St. Louis, Ma. R. J. Anderson, - Pittsburgh, Pa. Commander L. A. Beardslee, - Washington, D. C. Charles Bender, - New York City. Channing M. Bolton, - Richmond, Va. Thomas E. Bowman, - Silverton, Colorado. Calvin E. Brodhead, - Bethlehem, Pa. M. L. Brosius, - Lewistown, Pa. Harvey H. Brown, - Cleveland, Ohio. James A. Burden, - Troy, N. Y. J. P. Clemes, - Sonora, Mexico. N. H. Cone, - Nederland, Colorado. W. F. Durfee, - New York City. Robert Frazer, Jr., - Ashland, Pa. Joseph E. Galigher, - Bingham, Utah. William Golding, - Steel Works P. O., Pa. Samuel E. Griscom, - Pottsville, Pa. Gen. E. Burd Grubb, - Beverly, N. J. Arthur R. Guerard, - Charleston, S. C. Edward Hart, - Easton, Pa. Prof. Lewis M. Haupt, - Philadelphia. . R. S. Hawley, - Buffalo, N.Y. John W. Hoffman, - Philadelphia. Nelson P. Hulst, - Milwaukee, Wis. H. C. Humphrey, - Philadelphia. Ed. P. Jennings, - Ithaca, N. Y. B. F. Jones, - Pittsburgh, Pa.

Jan 1, 1876

The John Fritz Medal is awarded from time to time for notable scientific or industrial achievement by a board composed of representatives from the four engineering Societies. The members of the Board of Award for 1917 are: A. S. C. E. A. S. M. E. George F. Swain Ambrose Swasey, Charles Warren hunt, John, A. Brashear, Charles D. Marx, Frederick R. Hutton, Clemens Herschel. John R. Freeman. A. I. M. E. A. I. E. E. Gybbon Spilsbury, C. 0. Mailloux, Charles F. Rand , Paul M. Lincoln, Christopher R. Corning, John J. Carty, Benjamin B. Thayer. Harold W. Buck. The John Fritz Medal was awarded in January, 1917, to Dr. Henry Marion Howe, for his "investigations in metallurgy, especially in the metallography of Iron and Steel." The presentation ceremonies were held in the Auditorium of the United Engineering Societies' Building, New York, on Thursday evening, May 10. Mr. Ambrose Swasey, Chairman of the John Fritz Medal Board of Award, presided, and addresses were delivered by Dr. Rossiter W. Raymond, Secretary Emeritus of the American Institute of Mining Engineers, and Dr. Ira N. Hollis, President of the American Society of Mechanical Engineers. Professor Albert Sauveur, Chairman of the Board at the time the award was made, presented the medal, and the ceremonies concluded with the response of Dr. Howe.

Jan 7, 1917

By E. B. Branson

Introduction to Geology, by E. B. Branson, W. A. Tarr, and W. D. Keller, revised-by Carl C. Branson. McGraw-Hill, 1952. $5.50.-Dealing with physical and historical geology, the book has been revised from an earlier edition. An attempt has been made to eliminate unnecessary detail in discussing processes and history. Revisions bring technical and statistical data up-to-date, and follow suggestions by teachers who used earlier editions. The book carries an eye witness account of the severe earthquake in Assam, India, in 1950 and the story of Paricutin and other major examples of volcanism. Charts summarize chemical weathering, and the results of metamorphisms. The book also contains many new illustrations, including aerial photographs. A History of Phelps Dodge 1834-1950, by Robert Glass Cleland. Alfred A. Knopf, 1952. $4.00.-The book traces the growth of Phelps Dodge from the day Anson Greene Phelps opened a small saddle shop in Hartford, Conn., to the present day. As the country grew, so did Phelps Dodge. The company took part in large affairs from its very beginning. It bought and sold, exported and imported, built factories and railroads, and widened its scope of operations economically and geographically. Entrance of Phelps Dodge into copper mining and the gradual giving up of other interests in favor of the new venture is traced.

Jan 1, 1952

The following is am incomplete list of members and guests who called at Institute headquarters during the period May 10, 1918 to June 10, 1918. Arthur K. Adams, Potrerillos, Chile. J. M. Mahoney, Wilkinsburg, Pa. John Carter Anderson, Tucson, Ariz. Benjamin L. Miller, South Bethlehem, Pa. George S. Blair, Camp Cordon, Ga. Wilbur A. Nelson, Nashville, Tenn. W. A. Deane, Summitville, N. Y. Miles G. Nixon, Chicago, Ill. Charles H. Fulton, Cleveland, Ohio. Walter G. Perkins, San Francisco, Cal. Rudolf Gahl, Inspiration, Ariz. G. M. Ponton, Ottawa, Canada. C. C. Griggs, Eureka, Utah. D. A. Powell, Columbus, Ohio. J. F. Hanst, Potrerillos, Chile. H. W. Reed, Salt Lake City, Utah. Stanley C. Herold, Pittsburgh, Pa. J. C. L. J. Seelig, Padong, East. Indies. Floyd D. James, Boston, Mass. Oberlin Smith, Bridgeton, N. J. Charles Janin, San Francisco, Cal. Harrison Souder, Cornwall, Pa. E. Horton Jones, Copper Cliff, Ont. Stanley A. Spellmeyer, Camp Meade, Md. William Kelly, Vulcan, Mich. Roger S. Sperry, Waterbury, Conn. Ichiro Kitsunezaki, Tokyo, Japan. D. R. Thomas, Toronto, Canada. P. K. Lucke, San Antonio, Tex. Thor Warner, Phoenix, Ariz. E. Francis McCrossin, Birmingham, Ala. L. Douglass Anderson, formerly superintendent of the United States Smelting Co., Midvale, Utah, is now manager of smelters, Intermountain District, United States Smelting, Refining & Mining Co., Salt Lake City, Utah.

Jan 7, 1918

The Raymond Memorial Volume, which the Members of the In-stitute have been so anxiously awaiting since the beloved man's death, is nearly ready for publication. It will contain about 45,000 words and some illustrations and a frontispiece portrait. This book promises to fill every expectation of the contributors to the volume and the host of admirers of the genius who so long guided the destiny of the Institute. It will contain one of Doctor Raymond's best stories, entitled "James and Jim;" his famous article on "Job on Mining;" and one of his poems entitled "The Grand Canyon." A biography of Doctor Raymond has been written by his daughter, who is the wife of a member of the Institute. The memorial addresses delivered by Dr. Henry F. Drinker and T. A. Rickard at the annual meeting in New York in 1919 will be included. There will also be very interesting reminiscences by H. M. Howe, A. S. Dwight, C. W. Goodale, R. W. Hunt, Lyman Abbott, J. F. hemp, T. A. Rickard. The volume has been edited by T. A. Rickard, which promises all that can be wished for the volume from a literary standpoint. The edition will he limited so that it is very desirable that orders for this volume be sent in to the Institute as promptly as possible. The price will be $5.00.

Jan 12, 1919

By E. P. Shea

The Anaconda Co.'s Geological Department at Butte, Mont., was started early in the Company's history because of litigation involving vein ownership and extralateral rights. The problems, some of which were resolved in courts, were many because of the large number of veins and lode locations. Defensive action was required to prove ownership and protect against illegal exploitation of the downward and extra-lateral extensions of the ore bodies. In many cases it was necessary to define the outcrop of the vein and to show that its apex was within the boundaries of the lode claim. Exhibits illustrating geology were needed to present the cases clearly, and these could be made only after careful inspection and mapping of the underground workings by competent geologists. Also, The Anaconda Co. was one of the first companies to recognize the worth of skilled mining geologists and the value of accurate records in the search for new ore. The department was organized in 1900 by H. V. Winchell who, with D. W. Brunton, worked out the methods. Reno Sales was Chief Geologist from 1906 until 1948 when he was succeeded by V. D. Perry, the present Chief Geologist. Under their direction, F. A. Linforth, M. H. Gidel, C. H. Steele, E. P. Shea, C. C. Goddard, Jr., and W. A. O'Brien enlarged the scope of the work and improved the technique.

Jan 3, 1961

By John Griffen

THEORY HYDRAULIC classification as explained by Rittinger and others was largely restricted to conditions wherein the free-falling velocities of the particles were conceived as governing the separations effected (see chapter 9). The laws governing classification under free-falling conditions have been summarized by Chapman and Mott as fo1lows:l Nomenclature r represents, in a particle of irregular shape, the round-hole screen through which the particle would pass, or some other linear dimension of the particle equivalent to d, the diameter of a sphere. s, the specific gravity of the particle. 1, the specific gravity of the water used as a medium. K, a constant. W, the velocity of the water. In an Upward Current of water 1. A particle will move upward if [V > K dr(s - 1)] and, by suit- ably regulating the speed of the water current, the larger and heavier particles may be made to fall downward against the current, leaving the smaller, lighter particles in suspension in the current. 2. Particles such that [- = -] cannot be separated in an upward- current classifier with any one velocity of current. Coal particles having a specific gravity of 1.35 cannot be separated from refuse particles of [2.5 - 1 2.5 sp. gr.] unless the ratio of diameters is less than [ 4.3 to 1, 1.35 – 1] and the raw coal must be screened to size limits within this ratio if they are to be separated. Cone-shaped vessels or vessels of other shapes that allow the use of different velocities of current at different points in the flow are used to modify this limitation.

Jan 1, 1943

By A. N. Mitinsky

Discussion of the paper of A. N. MITINSKY, presented at the San Francisco meeting, September, 1915, and at the New York meeting, February, 1916, and printed in Bulletin No. 104, August, 1915, pp. 1697 to 1705. ALBERT SAUVEUR, Cambridge, Mass.-The author expresses the belief that steel will not fail under fatigue when subjected to ultimate stresses unless the stresses exceed the elastic limit or the limit of proportionality. I think this statement is contrary to the evidence. It is conceivable, however, that a stress ever so small does produce a permanent set, although so slight that we cannot detect it with the instruments at our disposal. Nevertheless the repetition of this small stress a great many times will finally break the piece and the nearer, we approach what we call the elastic limit, the quicker will the piece break under fatigue. J. W. RICHARDS, So. Bethlehem, Pa.-I would like to ask Professor Sauveur whether there is a similar indefiniteness about the limit of .proportionality as there is about the elastic limit. ALBERT SAUVEUR.-Yes; I believe it also depends upon the delicacy of our instruments. J. W. RICHARDS.-If that is so then we are as badly off by adopting the limit of proportionality as a criterion as we are by adopting the elastic limit.

Jan 5, 1916

THE Institute assembled in the Hall of the Boston Natural History Society on Tuesday evening. Dr. T. Sterry Hunt, of the Boston Institute of Technology, after a brief address of welcome to the Institute, read an introductory paper on the Geognostical History of the Metals. President Raymond responded to the welcome of Dr. Hunt. The following names were then presented to the Institute, with the recommendation of the Council, for election: Adams, J. M., . . . . . . Silver City, Idaho. Daggett, Ellsworth,. . . . . Salt Lake City, Utah. Geist, Alfred W., . . . . . Boston, Mass. Hays, Dr. S. Dana, . . . . . Boston, Mass. Heinrich, Oswald J., . . . . Midlothian, Va. Johnson, J., . . . . . . Braidwood, Ill. Leckie, Robert G., . . . . . Actonvale, Canada. Lyman, Edward, . . . . ' . Troy, N. Y. Maltby, William, . . . . . Braidwood, Ill. Nichols, Lyman, Jr., . . . . Bbton, Mass. Ordway, Prof. J. M., . . . . Boston, Muss. Rand, Theodore D , . . . . . Philadelphia, Pa. Richards, Prof. Robert H., . . . Boston, Mass. Roclrwell, Prof. Alfred P., . . . Boston, Mass. Roepper, Charles W ., . . . . Bethlehem, Pa. Schulz, A. von, . . . . . Central City, Colorado. Singer, William F., . . . . Pittsburgh, Pa. Spillsbury, E. G., . . . . . New York. Wells, Calvin, . . . . . . Pittsburgh, Pa. The session concluded with the reading and discussion of a paper, by Henry Engelmann, On the Mines and Ores of the Little Cottonwood Canyon, Utah. The second session was held on Wednesday morning, when the following papers were presented : On the Midlothian Coal Mines, by Oswald J. Heinrich. On the Probable Existence of Microscopic Diamonds in California, by Prof. Benjamin Silliman.

The first session of the Institute was held at the Smithsonian Institution, on Tuesday evening, February 22d. The members were welcomed to Washington and to the Smithsonian by Prof. Joseph Henry. President Holley responded to the cordial welcome of Professor Henry, and then read an introductory address on the subject of Technical Education. Following the discussion on President Holley's address the following persons, duly proposed and indorsed by the Council, were elected members and associates of the Institute : MEMBERS. Emile R. Abadie,. .. .. St. Louis, Mo. R. J. Anderson,.....Pittsburgh, Pa. Commander L. A. Beardslee,. .. Washington, D. O, Charles Bender,. .. .. New York City. Charming M. Bolton,. .. . Richmond, Va. Thomas E. Bowman,. .. . Silverton, Colorado. Calvin E. Brodhead,. .. . Bethlehem, Pa. M. L. Brosius,. .. .. . Lewistown, Pa. Harvey H. Brown,. .. .. Cleveland, Ohio. James A. Burden,.. .. . Troy, N. Y. J. P. Clemes,. .. .. . Sonora, Mexico. N. H. Cone,. .. .. . Nederland, Colorado. W. F. Durfee,.. .. . New York City. Robert Frazer, Jr.,. .. . Ashland, Pa, Joseph E. Galigher,.. .. . Bingham, Utah. William Golding,.. .. . Steel Works P. O, Pa. Samuel E. Griscom,.. .. . Pottsville, Pa. Gen. E. Burd Grubb,.. .. Beverly, N. J, Arthur R. Guerard,. .. .. Charleston, S. C. Edward Hart,.. .. .. Easton, Pa. Prof. Lewis M. Haupt,. .. . Philadelphia. E. S. Hawley,.....Buffalo, N. Y. John W. Hoffman,.. .. .. Philadelphia. Nelson P. Hulst,.. .. . Milwaukee, Wis. H. C. Humphrey,.. .. . Philadelphia. Ed. P. Jennings,.. .. .Ithaca, N. Y. B. F. Jones,......Pittsburgh, Pa.

By E. P. Abrahamson II

The effect of transition element binary solid-solution additions upon the recrystallization temperature of vanadium has been investigated. Cr, Fe, Co, Ni, Mo, Ru, Rh, Os, and IY lower the recrystallization temperature, while Ti, Mn, Zr, Cb, Pd, Hf, Ta, W, Re, and Pt raise it. The majority of elements have their greatest effect in less than 0.15 at. pet. Both the rate of change of recrystallization temperature with atomic percent solute and the limit of initial linearity are found to Correlate with the free atom grozdnd state outer electron configuration of the sollte element. THE work of Abrahamson and Grant1 and Abraham-son and Blakeney2 has shown that the solute's elec- tron configuration appears to be a prime determinant of both brittle-to-ductile transition and recrystallization temperature in dilute binary alloys. It has also been shown by Abrahamson3 that the limit of linearity, i.e., the limit of initial linear change of recrystallization temperature with atomic percent solute, is also a function of the electron configuration of the solute in iron base alloys. Because of the systematic nature of the solute electron configuration correlation, it is to be expected that some systematic variation might be observed upon changing the solvent. Thus, this study of recrystallization in vanadium base alloys is the first of a series aimed at defining the role played by the electron configuration of solute in determining the recrystallization characteristics of dilute transitional alloys. PROCEDURE All alloys were made using 99.8 pct V containing 0.011 C, 0.024 N, 0.08 0, 0.006 H, 0.035 Ta, and

Jan 1, 1962

By E. H. Burdick

The difficulties inherent in table concentration operations as applied to gold, silver, lead and zinc ores, are accentuated in the scheelite mill, which has a flowsheet that is similar in general principles. The narrow "spread" in the specific gravity between scheelite and the usual gangue in which it occurs often makes its clean separation extremely difficult and in some cases impracticable. The problem is further complicated by the extreme friability of the mineral and its inordinate tendency to "slime," particularly where fine grinding is necessary and wet grinding methods are employed. The physical aspect of the occurrence of scheelite in the ores, the kind and character of the rock in which the mineral is present, its hardness, friability and the specific gravity of its constituents, as well as like characteristics of the associated minerals— pyrite, pyrrhotite, sphalerite, and others, all have a bearing on the successful milling of crude ores and the production of a concentrate that is marketable with minimum price penalty or none at all. Most tungsten deposits are considered low grade when the limiting factor of low percentage recovery by gravity methods is borne in mind. The great majority of deposits developed or in process of development carry from 0.4 to 1.0 per cent tungstic oxide. Ore carrying I per cent is considered good grade; 0.7 to 0.8 per cent, fair, and below that figure, low grade. Steady mill feed averaging upward of I .o per cent WO3 is exceptional. Inasmuch as buying specifications demand a 60 per cent W03 content, the mineral content of the ores as mined must be concentrated to at least that degree. A few companies have constructed chemical plants for the treatment of their complex concentrates and low-grade flotation product, but the smaller operator must rely on table concentration, borrowing the tools and to a large extent the methods of his predecessors in the gold, silver, lead and zinc mills. Whether these are the best tools and methods that can be devised is an open question. Except in rare instances, table concentration, however carefully conducted, does not yield a satisfactory final recovery of the mineral content in headings as indicated by chemical determinations of tungstic oxide content. A saving of 60 to 65 per cent is considered fair, and an average 80 per cent recovery, exceptional. Each scheelite ore body is a separate problem. Details of handling that give best results in one case may not be successfully operative at a property on the same contact zone and but a short distance removed. Supplementary treatment of tailings by flotation may be successful in producing a low-grade concentrate of around 15 per cent W03, which is adapted to further treatment chemically at a given property and entirely unsuccessful at another. This problem constitutes another of the unanswered questions. The following paragraphs relate solely to the beneficiation of scheelite ores by table concentration and supplementary methods.

Jan 1, 1943

By E. H. Burdick

The difficulties inherent in table concentration operations as applied to gold, silver, lead and zinc ores, are accentuated in the scheelite mill, which has a flowsheet that is similar in general principles. The narrow "spread" in the specific gravity between scheelite and the usual gangue in which it occurs often makes its clean separation extremely difficult and in some cases impracticable. The problem is further complicated by the extreme friability of the mineral and its inordinate tendency to "slime," particularly where fine grinding is necessary and wet grinding methods are employed. The physical aspect of the occurrence of scheelite in the ores, the kind and character of the rock in which the mineral is present, its hardness, friability and the specific gravity of its constituents, as well as like characteristics of the associated minerals— pyrite, pyrrhotite, sphalerite, and others, all have a bearing on the successful milling of crude ores and the production of a concentrate that is marketable with minimum price penalty or none at all. Most tungsten deposits are considered low grade when the limiting factor of low percentage recovery by gravity methods is borne in mind. The great majority of deposits developed or in process of development carry from 0.4 to 1.0 per cent tungstic oxide. Ore carrying I per cent is considered good grade; 0.7 to 0.8 per cent, fair, and below that figure, low grade. Steady mill feed averaging upward of I .o per cent WO3 is exceptional. Inasmuch as buying specifications demand a 60 per cent W03 content, the mineral content of the ores as mined must be concentrated to at least that degree. A few companies have constructed chemical plants for the treatment of their complex concentrates and low-grade flotation product, but the smaller operator must rely on table concentration, borrowing the tools and to a large extent the methods of his predecessors in the gold, silver, lead and zinc mills. Whether these are the best tools and methods that can be devised is an open question. Except in rare instances, table concentration, however carefully conducted, does not yield a satisfactory final recovery of the mineral content in headings as indicated by chemical determinations of tungstic oxide content. A saving of 60 to 65 per cent is considered fair, and an average 80 per cent recovery, exceptional. Each scheelite ore body is a separate problem. Details of handling that give best results in one case may not be successfully operative at a property on the same contact zone and but a short distance removed. Supplementary treatment of tailings by flotation may be successful in producing a low-grade concentrate of around 15 per cent W03, which is adapted to further treatment chemically at a given property and entirely unsuccessful at another. This problem constitutes another of the unanswered questions. The following paragraphs relate solely to the beneficiation of scheelite ores by table concentration and supplementary methods.

Jan 1, 1943