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By D. K. Deardorff, Haruo Kato

D. K. Deardorff and Haruo Kato (U. S. Bureau of Mines)—We wish to refute the 1875" 20°C value that Giessen, et al., report as the transformation temperature of hafnium. Although these authors state that their work along this line will be reported later, we can't leave their value undiscussed, for we believe it to be 125°C too high. Our value of 1750° 20°C, which the authors mention, has been substantiated in our laboratories by the use of three other methods. The first method of substantiation was by heating and cooling curves using a hafnium/tungsten thermocouple, the couple having first been calibrated against a t/Pt-10 pct Rh couple. The second method was by quenching and metallography of dilute Hf-Ta alloys. The third cussion, it may be pointed out that the observations of Rogers referred to large unidirectional strains where the internal cracks or voids appeared only after a strain of 32 pct or more. On the contrary the internal fissures observed, as a result of fatigue cycling, occurred for a total extension of some 5 pct and furthermore followed the directions of the slip zones. Finally, it is not our contention, as implied in Dr. Alden's last paragraph, that the tensile stress is an important factor in crack propagation. Indeed, in connection with the reference to the companion report, special note is made of the fact that "Deformation was apparently concentrated in grains which have a slip plane nearly perpendicular to the specimen axis and thus near the plane of maximum applied shear." This dependence of the growth of fissures on the orientation of the slip planes with respect to the direction of maximum applied shear is clearly shown in work on the torsional cycling of single crystals which has been submitted for publication. method was by heating and cooling curves with W/W-26 pct Re thermocouple. Counting the original resistometric method, four different methods have yielded 1750" 20°C as the transformation temperature of hafnium. All our work on determination of the hafnium transformation temperature has shown that the specimen under test must be quickly heated to and through the transformation temperature if the lowest possible transformation value is to be determined; otherwise a higher value not representative of pure hafnium will result. Speed was emphasized in all methods. In our resistometric work the corresponding voltage, amperage, and temperature readings were taken quickly and the transformation temperature was usually reached within 5 min total heating time. In the thermal analysis work involving Hf/W or W/W-26 pct Re thermocouples the transformation temperature was attained within three minutes total heating time, this time being less because the two variables were

Jan 1, 1963

Strain-Hardening Exponent of Cross-Rolled Beryllium Sheet by S. R. Maloff, Vol. 215, No. 5, page 872, was omitted from Table of Contents for the October issue. Stabilization Phenomena in Beta Phase Au-Cd Alloys by Howard Birnbaum, Vol. 215, No. 5, page 786. The figure denoted Fig. 1 should be Fig. 3, Fig. 3 should be Fig. 4 and Fig. 4 should be Fig. 1. The captions are in the proper sequence. Activity of Carbon in Liquid Iron Alloys by Tasuku Fuwa and John Chipman, Vol. 215, No. 4, page 708. First equation, right hand column, page 710 should read

Jan 1, 1960

By John D. Wiebmer

First, a definition of a small scale miner is in order. The US Bureau of Mines classifies him as one who produces 360 t/d (400 stpd) of ore or less. In Canada, he would be refered to as a "junior company." Mexico identifies the small scale miner as one whose gross income from operations is less than $880,000 per year. A small surface mine in India employs less than 400 people, and a small underground mine employs less than 150. Peru considers a small scale miner one who produces less than 54 000 t/y (60,000 stpy) of ore. Obviously, the term is relative. What may be a small mine in one country is a medium or large mine in another. This lack of agreement is understandable since small scale mining does not often cross national boundaries. Rather, its effects are felt at the regional and local levels within each nation. Its importance doesn't lie with any huge contribution to the GNP or balance of trade. Instead, its value is as a local employer and as a frontrunner in geologic exploration.

Jan 2, 1979

By JO. E. SHERID

THE Dawson coal-mines are owned and operated by the Stag Canon Fuel Co., of which Dr. James Douglas is President and E. L. Carpenter general manager. The property is situated in Colfax county, N. M., and the openings now in operation are in townships 28 and 29 N. R. 20 E., and township 28 N. R. 21 E., shown in Fig. 1. The mines are part of the southern end of the Raton coal-field, which extends north into Colorado and embraces many coal-camps of the Trinidad section. II. GEOLOGY. Geologically, the coal-measures, commonly known as the Laranmie series of the Cretaceous system, have a thickness of about 800 ft. in the vicinity of Dawson. The coal makes an excellent coke, and, according to some authorities, its coking properties are clue to the action of intruded sheets and sills of igneous rock, the sheets occasionally thickening into masses resembling laccoliths, at such places making nearer approach to the coal and sometimes producing small areas of natural coke. There are but few dikes through¬out the entire southern portion of the field and little or no faulting along the dikes. In some parts of this great coal-field the intrusive sheets are far removed in the green shales below the coal-measures, and are so much altered as to be difficult of identification. There is but little disturbance of the strata through¬out the Raton coal-field in as far as it extends into New Mexico. There are two workable seams in the coal-measures, and two or three smaller coal-seams, ranging from 1 to 2.5 ft. in thick-

Jun 1, 1909

By Frank W. Dickson, George Tunell

Five hot spring areas of the western United States show evidences of present day deposition of HgS; two also show evidences of accompanying Sb2S3 deposition. Sulfide minerals are depositing at or near the surface from hot waters that differ for each spring ai:ea in amount and kinds of dissolved matter. All the springs contain dissolved substances that act as buffering agents and that cause increased alkalinity with increasing temperature. Transport of Sb2S3 is possible in H2O and in boron and sulfide solutions. Increasing alkalinity and temperature enhance stibnite solubility. Quantitatively important transport of HgS appears restricted to alkaline sulfide solutions that contain HgS2=. Elemental mercury probably forms in deep hot waters because HgS breaks down into mercury and sulfur above 200°C, and free S is removed by reaction with water. Elemental mercury should accompany HgS2= in solutions that were at 200°C or higher. Cinnabar deposits from saturated alkaline sulfide solutions because of combinations of temperature decrease, dilution, oxidation, and reactions with wall rock: Amedee Hot Springs, Boiling Springs, and Coso Hot Springs are areas in which HgS is the only sulfide deposited. Hot waters at Amedee and Boiling Springs are supersaturated with HgS or transport colloidal HgS. Steamboat Springs waters deposit mainly silica and stibnite, but they have deposited HgS recently. Sulphur Bank waters deposit mostly stibnite and some HgS. The hot-spring waters of all springs represent highly modified deep water. Field and laboratory studies support the concept of transport of HgS in moderately alkaline sulfide solutions as HgS2=. Fluctuating deposition of stibnite and cinnabar reflects availability of sulfide or variations in deep-source HgS and Sb,S,. Silica and HgS dissolve mutually in alkaline sulfide solutions, and cinnabar and quartz would be expected to deposit simultaneously. Free mercury given off by hot-spring waters would impregnate country rocks.

Jan 1, 1968

Organization Place Date 1919 American Chemical Society Philadelphia, Pa. Sept. 2-6 National Assn. of Stationary Engineers Huntington, W. Va. Sept. 8 American Peat Society Minneapolis, Minn. Sept. 22-24 American Iron, Steel Electrical Engineers St. Louis, Mo. Sept. 22-26 American Institute of Min. and Met. Engineers. Chicago, Ill. Sept. 22-27 American Steel Treaters' Society, First Annual Convention Chicago, 111. Sept. 22-27 National Exposition of Chemical Industries.... Chicago, Ill. Sept. 22-27 National Safety Council Cleveland, O. Sept. 29-Oct: 2 American Foundrymen's Association Philadelphia, Pa. Sept. 29-Oct. 4

Jan 9, 1919

By S. F. Shaw

Tars paper is a review of the principal details of cyanide practice in several of the modern plants in America, mainly during the year 1908. Two of the mills, the Goldfield Consolidated and the Vets, Colorado, are not yet prepared to give data, the former having started about Jan. 1, 1909, and the latter not yet being completed. These two mills embody most of the latest methods and are therefore described as far as possible. I. CRUSHING. The principal methods of crushing ores for treatment by the cyanide process are with gyratory and jaw-crushers, stamps, Bryan and Huntington mills, and tube-mills. The first stage is usually done by gyratory or jaw-crushers, in a few cases sup-\

Jul 1, 1909

By Royal Preston Jarvis

minerals of different specific gravities. It is simple in construction, easily operated, capable of treating large quantities in a short time, and highly efficient under various conditions. The question, whether the material to be jigged has first been sized, determines the two principal methods of jigging. Jigging preceded by close sizing, generally known as the Continental or German system, involves a more or less elaborate series of screens or trommels, with attendant cost for installation, operation, and repairs. Jigging without sizing, known as the English system, is, according to Munroe,1 a development of the hand-jigging formerly employed in Cornwall . and introduced by English miners to this country." In its simplest form, the method consists in jigging an ore-mixture previously crushed to some maximum size (although, in some cases, even this preliminary is omitted) oil a relatively coarse sieve, and then jigging again on a filler sieve, the material passing through the first sieve and bedding. While many modifications have been necessary to adapt it for use in mills of large capacity, where hand-work was necessarily, replaced by machines, the principle remains the same; the fact that the English system has been successfully employed, both in this country and abroad, is well known; and arguments have been made for its efficiency and applicability in a wider sphere than it has occupied hitherto. II. REVIEW OF PREVIOUS INVESTIGATIONS. The fact that treating a mixture of minerals under jigging conditions increased the amount of mineral saved, or, as Professor Richards aptly terms it, 1 ?the extra jig-catch," has long been known. To account for this fact a number of theories have been proposed. The work of Rittinger2 in this field has, for many years, been a classic in the literature of ore-dressing. For the purposes of my present paper, however, the work of two American investigators, Prof. H. S. Munroe and Prof. R. H. Richards, is chiefly concerned. Professor Munroe has given the results of an elaborate series of experiments,3 and his deductions, based largely oil theoretical grounds, of this work. After reviewing briefly the two systems of jigging, followed by a discussion of Rittinger's formulas and

Sep 1, 1908

By A. T. Yu

The energy crisis and the resurgence of mining activities highlighted 1972-73. Added to the impetus for more effective materials handling systems has been the continued upward trend of inflation and labor costs. The need for addressing the fundamentals has led to the trend toward an overall systems approach to materials handling problems.1 The decision to move forward with large mining ventures such as the $150 million Hibbing taconite comple2 and the immense Carajas iron project must base themselves on indepth studies of a host of factors viewed in the context of an integral mine-transport-market system. What's important is that each ton of pellet or ore must be an economical commodity at the end users' furnace. The project can still be viaable even if certain components in the entire network appear to be individually costly.

Jan 2, 1974

By LEE H. CORNELL

Drilling activity in Kansas during 1945 continued at an accelerated pace to meet the demands of war; 1810 tests were drilled as compared with 1856 tests the previous year, 1771 tests in 1943, and 1516 tests in 1942. During the year 31 new oil pools and 10 new gas pools were discovered. Of a total of 364 wildcats drilled, 323 were dry; and of 1446 tests drilled in pools, 825 were oil wells, 197 gas wells, and 425 dry holes.

Jan 1, 1946

By P. H. Dudley

A Discussion of the Paper of Prof. Howe. (Bi-Monthly Bulletin, No. 14, March, 1907, pp. 169 to 274.) P. H. DUDLEY, New York, N. Y. (communication to the Secretary*) :-The characteristics of Prof. Howe's metallurgical papers are, that he is able, from the mass of confusing evidence on the subject, to make an analysis and present hypothetical and essential principles in concrete form for consideration and discussion. I can appreciate, from the practical side of the subject, the arduous labor of collecting and investigating the data that is essential to prepare the paper. Much of the data necessarily came from material of preceding years. of manufacture in which there was allowed time for chemical reactions of the recarburizer, and for the elimination of the oxidation-products before teeming the ingots. This condition gave a favorable tinge-element to free the metal from slag- and other impurities, but, in allowing the. ingot to cool before charging in the furnace, the time-element entered as a detrimental factor in the development of the pipe or shrinkage-cavities, which gave an ingot-structure deficient in soundness. The interpretations from such material must be made with due allowances for the methods of manufacture, and must be given proper weight, as general facts, in subsequent arguments. The difficulties under which investigators labor are not easily surmounted in differentiating between reliable and unreliable data incident to variables of methods of manufacture, chemical composition of the alloys of steel, mediocre practice and that of the highest state of the art. Modern practice and large outputs in Bessemer steel have reversed the effects of the time-element-by cutting short the chemical reactions of the recarburizer and the elimination of

Jan 5, 1908

By Herbert Clark Hoover, Lou Henry Hoover

SINCE the Sixth Book has described the iron tools, the vessels and the machines used in mink, this Book will describe the methods of assaying1 ores; because it is desirable to first test them in order that the material mined may be advantageously smelted, or that the dross may be purged away and the metal made pure. Although writers have mentioned such tests, yet none of them have set down the directions for performing them, wherefore it is no wonder that those who come later have written nothing on the subject. By tests of this kind miners can determine with certainty whether ores contain any metal in them or not ; or if it has already been indicated that the ore contains one or more metals, the tests show whether it is much or little ; the miners also ascertain by such tests the method by which the metal can be separated from that part of the ore devoid of it ; and further, by these tests, they determine that part in which there is much metal from that part in which there is little. Unless these tests have been carefully applied before the metals are melted out, the ore cannot be smelted without great loss to the owners, for the parts which do not easily melt in the fire carry the metals off with them or consume them. In the last case, they pass off with the fumes ; in the other case they are mixed with the slag and furnace accretions, and in such event the owners lose the labour which they have spent in preparing the furnaces and the crucibles, and further, it is necessary for them to incur fresh expenditure for fluxes and other things. Metals, when they have been melted out, are usually assayed in order that we may ascertain what pro- portion of silver is in a centumpondium of copper or lead, or what quantity of gold is in one libra of silver ; and, on the other hand, what proportion of copper or lead is contained in a centumpondium of silver, or what quantity of silver is contained in one libra of gold. And from this we can calculate whether it will be worth while to separate the precious metals from the base metals, or not. Further, a test of this kind shows whether coins are good or are debased ; and readily detects silver, if the coiners have mixed more than is lawful with the gold ; or copper, if the coiners have alloyed with the gold or silver more of it than is allowable. I will explain all these methods with the utmost care that I can.

Jan 1, 1950

By William R. Jones, Robert M. Hernon

This report on the Central mining district of New Mexico is the partial culmination of an intensive U.S. Geological Survey effort dating back some 30 years. Robert M. Hernon went to Silver City in 1948 to finish a detailed restudy of the district that had been started in the thirties by Samuel G. Lasky. He was joined by William R. Jones in 1951, and Jones took over as project chief when Hernon resigned to do consulting work in 1953; it was under Jones' guidance that most of the work was brought to completion or nearly so ( 17, 22-24, 26-30). Hernon returned to the Survey in 1958 to work in .the southern Appalachians. Early in 1965 Jones urged that Hernon be reassigned to the Silver City project to help complete the Professional Paper report on the ore deposits of the Santa Rita quadrangle as well as to take over preparation of the report on the Central district for the Graton-Sales volume. This reassignment was approved, and Hernon began work on the present report. By late June he had completed most of it in draft form, and on June 28 Jones and Hernon left Denver for a short trip to Silver City to fill in a few gaps and to reacquaint Hernon with activities in the district, which he had not visited for 12 years. Late in the afternoon of June 29, 1965, as Bob and Bill were 85 miles short of their destination, their jeep collided head-on with a truck that was attempting to pass another vehicle in a cloud of dust. They both died instantly. As the most recent surviving member of the Silver City project (1958-1962), I was given the honorable though rather sorrowful task of putting the Hernon-Jones report "in shape" for publication. Fortunately the manuscript was already in good shape, so that the task has consisted of little more than minor reorganization and editing, and of preparation of the illustrations, abstract, and bibliography. The sections on wall-rock alteration had been left for Jones to complete in the light of his recently intensified interest in alteration geochemistry (25), and it is in these sections only that. the report may fall short, for they have been filled in from a 1958 manuscript by Jones on the ore deposits of the Santa Rita quadrangle that he intended to revise considerably. The shortcomings, however, are largely in the interpretation, not in the field data. As a brief but accurate summary of what was known about the geology of the Central mining district in 1965, this report stands as a fitting testimonial to the scientific dedication of two exceptional men.

Jan 1, 1968

By AIME AIME

APOCRYPHAL, no doubt, but widely entertained is the proposition that top-flight mining geologists never agree with each other on anything. Being rugged individualists, they frequently seem intolerant of opinions that conflict with their own. However, one may suspect that controversy is often more apparent than real. For example, at last summer's meeting of the American Mining Congress, Ira B. Joralemon and Reno H. Sales, discussing "Mining Geology, Today and Tomorrow," seemed to be in serious disagreement over various phases of the subject; but much of this arises from the different angles of approach of the two distinguished and successful ore finders.

Jan 1, 1941

By J. J. Gilman

The dependence of ortho kink-band formation on crystal orientation, on temperature, and on the conditions at the ends of a specimen is described. Load-compression curves for crystals that kink are presented. The reversibility of ortho kinking is demonstrated, and motion of kink planes through crystals is shown. Finally, a phenomenological explanation of ortho kink-band formation is given. ORTHO compressive kink bands (Fig. la) were discovered for the case of metals by Orowan,1 and they have been discussed by Jillson2 and in some detail by Hess and Barrett." However, their history in nonmetallic crystals is considerably older. It is not known when they were first observed in mineral crystals, but descriptions of them may be found as early as 1885.* They were sometimes mistaken for twins.6 Mügge seems to have been first to realize their true nature and importance. He reviewed the knowledge of them for a wide variety of crystals: anhydrite, antimonite, kyanite, vivianite, gypsum, mica, graphite, molybdenite, barium bromide, cal-cite, sodium nitrate, and barite. Also, the "twins" observed by Bridgman7 in sapphire crystals resemble kink bands more than twins. The terms ortho and para kink bands have been coined in order to distinguish between two types of kink bands which seem to represent the same geometrical configurations, but which have different origins and sizes. Ortho kink bands are the usual type that form at low loads when zinc crystals are compressed parallel to the basal plane. Para kink bands form at much higher loads in highly deformed crystals. These terms refer to compression phenomena and are not to be confused with analogous tension phenomena such as tensile kink bands and deformation bands. Mügge described the geometry of ortho kink bands quite completely for kyanite crystals, Fig. lc. The geometry observed for cadmium by Orowan1 and for zinc by Hess and Barrett3 is very similar to that described by Mügge. (See Hess and Barrett for a complete discussion.) Mügge associated kinking with bending combined with basal slip. He pointed out that the kink angles

Jan 1, 1955

The following is a list of members who died in 1928. It is compiled from reports to the Secretary's office. Biographical sketches published in Mining and Metallurgy are indicated in the last two columns. Issue Containing Year or Date or Biography Election Name Death 1928 Page 1914 Adams. David T.................... July 22 October 471 1905 Aguilera. Pedro................... May 3 October 469 1902 Althouse, H. W.................... NOV. 3 December 559 1920 Averill: C. C...................... July 9 October 471 1915 Baldwin, C. Kemble............... Aug. 9 October 471 1926 Barquist, Walter C............... NOV. 14 June 298 Barron,* Clarence Walker......... Oct. 2 November 511 1917 Beasley, Fred E.................... Aug. 31 October 471 1901 Belden, S. B....................... May 15 July 333 1927 Binney, Edwin, Jr.................. Dec. 29 February 96 1915 Bonsall, James Malcolm............ Feb. 12 June 284 1917 Boyle, John....................... July 12 December 561 1913 BradEn, Eugene B............. Jan. 29 March 157 1889 Bulkley, Frank.................... Mar. 25 May 240 1896 Callaghan, J. T., Jr............... Apr. 1 1892 Chalmers, George.................. Feb. 4 April 197 1898 Clark, Josiah H.................. May 7 July 333 1887 Copeland, F. K............. Nov. 10 December 561 1915 Cunningham, B. L11............... Dec. 6 August 294 1888 Dana, R. T........................ Aug. 20 December 559 1907 Dennis, Clifford G............... Dec. 28 March 1 1920 DeVenny, Thomas................ Feb. 13 April 197 1882 d'Invillier-, Edward V........... Jan. 4 March 157 1884 Duncan, M. M..................... Dec. 17 February 96 1924 Dyrssen, WaldemaR ............... Aug. 4 October 471 1906 Edmondson. H. W................ Dec. 21 February 1884 Emmerton, F. A.................. Oct. 9 June 298 1911 Eu, S. H............................ July 20 February 1917 Farrand, Ira W.................... Sept. 6 October 469 1900 Fell, E. Nelson...........•......... Mar. 25 May 231 1918 Fenton, Clarence M.............. October Junet 298 1908 Ferraris, Erminio................. Sept. 22 June 298 1914 Galloway. A. D. R............... December April 215 1924 Grant, A. W., Jr................... .4pr. 5 June 285 1917 Grant, Clifford G............... Jan. 26 January? 37 1918 Grant, Frank E.............. Jan. 14 September 417 1921 Gunderoth, C. J.................. Feb. 15 1897 Harms, Ernest..................... Aug. 12 November 512 1891 Hartrick, J. S..................... Feb. 9 June 285 1925 Hochschild, Berthold.............. Jan. 24 April 197 1917 Hutton, L. W...................... NOV. 3 January 37 1894 Jenning", S. J...................... NOV. 17 December 560 1925 Jones, J. Ravenscroft............... Jan. 29 March 157 1880 Jones, J. T......................... May 4 June 284

Jan 1, 1929

By CHARLES R. KETES

I. INTRODUCTORY. INDUSTRIALLY, the most important service that geological science can now render to mining in the Upper Mississippi leadand zinc-fields is to devise some practical scheme whereby the productive ore-belts may be located with greater certainty than they have been in the past. Up to the present time there has been little service of this kind, and in spite of all that has been worked out concerning the geologic features of the region, and notwithstanding all that has been written about these ore-deposits, this particular phase of the subject has been, for some reason or other, the very one that has received the least consideration. The neglect by geologists in this respect has been all but complete. The following notes are suggestive of some practical solutions to the problems presented. As here suggested, the geologic relationships of the ore-bodies were surmised some years ago, though somewhat vaguely perhaps. No opportunity for securing critical data appeared until recent investigations of a private character were undertaken, which bad in view the extensive prospecting of undeveloped areas. Fresh from rather wide experiences of a decade in the principal mining-regions of four continents, and after a lenstrum's residence among the chief mining-camps of the West and of Mexico, under conditions which measured geologic hypotheses in meters and rigidly tested their values in, terms of dollars, the recent return to the Joplin field and a new survey of its ore-conditions were fraught with somewhat unexpected results. Aspects of the ore-deposition were presented of which previously there was no hint. Ten years' absence from the district had tended greatly to clarify former hazy impressions. It enabled many features, then only dimly outlined, to be considered more nearly in their true perspective and in their real relationships to their surroundings. It permitted a great mass of details collected a dozen years before in connection with the work of the Missouri Geological Survey to be viewed under new light and to

Feb 1, 1909

By William E. Ford, Edward Salisbury Dana

URANINITE. Cleveite. Broggerite. Nivenite. Pitchblende. Isometric. In octahedrons (o), also with dodecahedra1 faces (d) ; less often in cubes with o and d. Crystals rare. Usually massive and botryoidal; also in grains; structure sometimes columnar, or curved lamellar. Fracture conchoidal to uneven. Brittle. H. = 5'5. G. = 9'0 to 9'7 of crystals; of massive altered forms from 6'4 upwards. Luster submetallic, to greasy or pitch-like, and dull. Color grayish, greenish, brownish, velvet- black. Streak brownish black, grayish, olive-green, a little shining. Opaque. Comp. -A uranate of uranyl, lead, usually thorium (or zirconium), often the metals of the lanthanum and yttrium groups; also containing the gases nitrogen, helium and argon, in varying amounts up to 2'6 p. c. Calcium and water (essential?) are present in small quantities; iron also, but only as an impurity. The relation between the bases varies widely and no definite for- mula can be given. Radium was first discovered in this mineral and it has been shown that it and the helium present are products of the breaking down of the uranium.

Jan 1, 1922

By C. C. Harris

An analytical solution of the integro-differential equation of batch grinding is proposed as a first appoximation to the xYt surface. The size distribution equation (xY plane) is a three parameter equation previously suggested. Possible refinements are outlined. Comminution kinetics research is presently following several related courses. Some are equivalent, in that they represent different ways of viewing the same facet of the problem, though the entire endeavor cannot be described as being completely integrated. The purpose of this note is to propose and discuss a framework into which the various approaches might be fitted. This must clearly be founded upon an analysis of the xYt surface.' (See also Fig. 1 of Reference 26.) The investigations referred to above comprise mainly researches into the following: (1) The kinetics of the creation of the finer sizes during relatively small grinding times. This is the Fahrenwald-Arbiter-Bhrany 2-3 approach which leads to equations equivalent to a special case of the charles4 relationship. It emerges that initial production of fines follow essentially zero order* kinetics. (2) Disappearance kinetics of the coarser fractions. This appears to be a first order relationship.5-6 (3) Prediction of the xYt surface via the selection and breakage functions utilizing computer-programmed or approximate solutions of the integro-differential equation of batch grinding.5,8-17 A recent discussion by Mika et al.5 references the relevant literature up to about 1966. In addition to these main-stream researches there is some work on the minor topic of extremely long grinding time considered as a limiting case.18-19 The field is supported by investigations into the size distribution of fragments produced by breakage processes, some of this work being most valuably statistical-mechanical in nature.20-25 Better fitting equations, however, are obtained by statistical and curve-fitting methods.26 This

Jan 1, 1969

By H. H. Moss

OXYACETYLENE .cutting has experienced rapid development in the last few years and greater advances and expansion and broader application may be expected in the immediate future. Marked changes in cutting practice may be expected as a result of the advances in metallurgical science that have produced special alloy steels with properties requiring different cutting techniques than for ordinary low-carbon steels. Much current attention is being directed to those problems of modified cutting practices. Cutting has thus ceased to be merely a shaping problem. It is rapidly coming to have a predominantly metallurgical aspect. The problem is no longer how to cut a given shape, but how to cut a given steel. The answer

Jan 1, 1936