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By A. S. Keh, H. A. Wriedt

The Precipitation of nitrides in quenched Fe-N alloys, aged between 25° and 200°C, was studied by transmission electron microscopy. Different dislocation substructures were introduced into the materials by recrystallization, cold working, and by Phase transformation prior to the introduction of nitrogen. It was found that the precipitated nitrides, tentatively identified as Fe16N2, have (100) habit planes. Nucleation takes place Preferentially at dislocations and at subboundaries. It sometimes occurs in the matrix, probably on vacancy clusters, but rarely on high-angle boundaries. The process of nucleation on dislocations and subboundaries is very temperature dependent. At room temperature there is no particular orientation relationship between the dislocations involved and the (100) planes on which the nitride Particles formed. With increasing temperature, the nucleation sites tend to become restricted to those dislocation segments lying in (100) planes. The change of yield stress of the 0.022 and 0.043 pet N alloys during quench aging can be correlated semiquantitatively with the change in particle distribution. Strain aging in quenched alloys can be separated into two stages. The early stage is attributed to nitrogen segregation to dislocations and the later stage is associated with precipitation. When previously quench-aged specimens were strained and aged, no additional Precipitates could be seen, although a considerable amount of strain aging occurred. DURING the past two decades, the precipitation of nitrides from a iron has been extensively studied by various techniques. It has been established that two types of nitride exist. The stable nitride, Fe4N, forms at temperatures above 250oC and Fe16N2, the

Jan 1, 1962

Aase, Glenn D., (J'40) Jr. Met.. American Smelt. k Refin. Co., Selby, Calif. Abadie, Henry G., (J'43) Petr. Engr., Avenal, Calif. Abbott, Clarence E., (M'04) Civil Engr., V.P.. Tennessee Coal, Iron & R.R. Co., 1542 Brown Marx Bldg., Birmingham, Ala. Abel, Raymond L., (M'28) Chem. Engr., C.O., Pitts¬burgh Chem. Warfare Procurement Dist., American Bank Bldg., Pittsburgh. Pa. Abel, Walter D.. (M'32) Min. Engr., Supvr. Engr., R.F.C.Lee Angeles, Calif. Abele, Louis T., (M'31) Route No. 1, Adameville, Tenn. Abell, Leo M., (M'31) Mill Supt. & Met., Emperor Gold Min. Co. Ltd., Vatukoula, Fiji Is. Abernathy, G. E., (M'38) Geol., Kansas State Geol. Survey, Pittsburg, Kans. Abernathy, Jack H,, (M'40) Asst. Cenl. Supt. of Prod., Sunray Oil Co., 11th Floor, Philtower Bldg.. Tulsa 3. Okla. Abernethy, D. Carl, (M'44) Min. Engr. Rm. 3217, N. Int. Bldg., Washington, D. C.

Jan 1, 1944

William Clinton Brown, Brooklyn, N. Y.: The demand for an apparatus for cooling water for condensers, refrigeratingmachinery and air-compressors, as well as water-jacketed furnaces, has led manufacturers to put such an apparatus on the market, so that it is now possible to purchase a cooling-tower, properly designed and constructed, by simply stating the amount of water to be cooled and the temperatures of the hot and the cold water. The principle is similar to that described by Mr. Henrich, but wood is not used in the best apparatus. There are two great objections to wood: First, it cannot last long under the very trying conditions to which it is subjected; and second, it absorbs the organic matter with which water in constant use becomes impregnated, and the resulting odor is very disagreeable. A few days ago I saw a cooling-tower and condenser, built by the Henry R. Worthington Co., in operation at the Edison electric-lighting station in Brooklyn, N. Y., cooling the water for a 700 horse-power condenser. It consisted of a large stack of iron, about 15 feet in diameter by about 30 feet high. This stack was filled with tiling through which the water falls. A whirligig distributes the water evenly over the top, and a large fan, about 6 feet in diameter, driven by a 10 horse-power electric motor, blows air into the bottom, thus giving a positive circulation. The water, in running down the sides of the tiling, is met by the blast of air, and enough is evaporated to cool the rest. The vacuum-gauge on the condenser showed 26 inches; so the condenser was undoubtedly getting sufficient cool water.

Jan 1, 1896

By Edwin A. Rides

HISTORICAL ORIGIN OF THE EXPORT CREDIT AGENCIES Almost since the inception of international commerce sellers, having manufactured and/or sold and shipped goods to an overseas buyer, have been obliged to accept the risk that they will not be paid for one reason or another. There are many reasons why payment may not be forthcoming, for example, the goods may be lost at sea, or rejected by the buyer or the buyer nay simply not be creditworthy. These risks were brought into sharp relief as international trading became more sophisticated and the practice of giving credit to buyers gathered momentum. Inevitably enterprises sprang up which offered same mitigation of this exposure, accepting houses and later confirming houses and banks were prepared to assure acceptable credit risks an behalf of the seller, usually by discounting trade paper, and for many years the market ticked over reasonably satisfactorily. However, after the 1914-18 War international trade was at an extremely low ebb and its inherent risks were accentuated to a point where they were often commercially unacceptable. Yet a healthy and vigorous international market was indispensable to recovery of the world economy and a number of governments, led by the United Kingdom, perceived a need to offer their exporters a comprehensive form of insurance, particularly to facilitate the extension of credit to foreign buyers. In the United Kingdom the Export Credits Guarantee Department (ECGD) was set up to encourage trade through the provision of export credit insurance. Over the ensuing years others followed suit and now most of the developed trading nations and many developing nations have similar agencies. PRESENT DAY IDLE OF THE EXPORT CREDIT AGENCIES (ECAS ) Traditionally then the BA's role was to encourage trade through the provision to exporters of insurance against the risks of non-payment by overseas buyers of their goods and services. However, during the 1970's the manufacturing industries of most of the developed nations found themselves facing severe competition for business, particularly in the developing world. As a result the more aggressive ECA's began to introduce ancillary forms of cover designed to reduce exporters' risks outside of the credit field. For instance, most of the European agencies now have a form of cover against foreign exchange risks here contracts are denominated in currencies other than that of the exporter's country. Most of the agencies also provide cover to exporters against the risk of unfair calling of bid, advance payment, performance bonds etc and in certain countries, where high inflation rates were endemic, a form of cover against cost escalation. In certain circumstances it is also possible for an exporter to obtain cover against losses arising as a result of the involvency of a partner in a consortium or joint venture. These are all forms of insurance but, also during the 1970's, many of the national export credit programmes took a major step away from their original raison d'etre by facilitating the provision of preferential financing terns for the acquisition of capital equipment by an overseas buyer. This new line of business quickly became an important ingredient of major export financing packages and, as we shall see later, turned out to be extremely costly for the countries providing it.

Jan 1, 1985

By G. V. Smith, C. O. Tarr, R. F. Miller

Metallurgists have long recognized that the Fe3C type of carbide is not a stable phase in steel and that, given sufficient time, it will decompose with formation of graphite, at least at temperatures below about 205o°F.l This slow graphitization has never been of much concern to users of hypoeutectoid steels, for in such steels it occurs only during prolonged exposure at elevated temperature. In I935, Kinzel and Moore2 reported complete graphitization of the carbide of a 0. I5 per cent carbon steel that had been in service for about 26,000 hr. at a temperature of about IIOO° to 12oo°F. In discussing this paper, both Mathews and Sauveur reported graphitization of slightly hypereutectoid steels. In an extensive investigation of graphitization of high-purity iron-carbon alloys, Wells1 produced graphite at 7oo°C. (I29o°F.) in an alloy containing as little as 0.13 per cent carbon, and showed that graphite may precipitate either directly from austenite or from decomposition of Fe3C, also that the rate of graphitization tends to increase with increase of temperature, at least up to a certain point, and with the presence of graphite nuclei. Jenkins, Mellor and Jenkinson,3 studying the structural changes in carbon steels ranging from 0.17 to 1.14 per cent carbon during stress-rupture tests at elevated temperature, observed graphite in an aluminum-killed 0.40 per cent carbon steel after fracture in 4340 hr. under a stress of 17,900 lb. per sq. in. at 840°F. and in many of the steels after stress-rupture test at 12oo°F. Unstressed samples of 0.60, 0.86 and I.I4 per cent carbon steels graphitized almost completely in 360 hr. at I200°F., while samples of 0.90 and 1.10 per cent carbon steels were somewhat graphitized, and steels containing 0.24, 0.40 and 0.57 per cent carbon showed no sign of graphite. Their results indicate that graphite precipitates the more readily the higher the carbon content, though this tendency is influenced to some extent by deoxidation practice, and that graphitization is accelerated by plastic deformation. In a recent study of the graphitization of 0.4 and 0.6 per cent carbon steel strip, made by M. A. Hughes,4 it was found that at I2oo°F. graphite appeared after 72 hr. in aluminum-killed but not in silicon-killed steel, and that the rate of graphitization was increased by slow cooling from I6oo°F. and by cold-working prior to annealing. In creep tests of normalized 0.15 per cent carbon steel killed with 2.5 Ib. of aluminum per ton, at the U. S. Steel Corporation laboratory at Kearny, spheroidization and some graphitization were found after 3000 hr. at Iooo°F. under a stress as low as 1500 lb. per sq. inch. .

Jan 1, 1944

By C. O. Tarr, G. V. Smith, R. F. Miller

Metallurgists have long recognized that the Fe3C type of carbide is not a stable phase in steel and that, given sufficient time, it will decompose with formation of graphite, at least at temperatures below about 205o°F.l This slow graphitization has never been of much concern to users of hypoeutectoid steels, for in such steels it occurs only during prolonged exposure at elevated temperature. In I935, Kinzel and Moore2 reported complete graphitization of the carbide of a 0. I5 per cent carbon steel that had been in service for about 26,000 hr. at a temperature of about IIOO° to 12oo°F. In discussing this paper, both Mathews and Sauveur reported graphitization of slightly hypereutectoid steels. In an extensive investigation of graphitization of high-purity iron-carbon alloys, Wells1 produced graphite at 7oo°C. (I29o°F.) in an alloy containing as little as 0.13 per cent carbon, and showed that graphite may precipitate either directly from austenite or from decomposition of Fe3C, also that the rate of graphitization tends to increase with increase of temperature, at least up to a certain point, and with the presence of graphite nuclei. Jenkins, Mellor and Jenkinson,3 studying the structural changes in carbon steels ranging from 0.17 to 1.14 per cent carbon during stress-rupture tests at elevated temperature, observed graphite in an aluminum-killed 0.40 per cent carbon steel after fracture in 4340 hr. under a stress of 17,900 lb. per sq. in. at 840°F. and in many of the steels after stress-rupture test at 12oo°F. Unstressed samples of 0.60, 0.86 and I.I4 per cent carbon steels graphitized almost completely in 360 hr. at I200°F., while samples of 0.90 and 1.10 per cent carbon steels were somewhat graphitized, and steels containing 0.24, 0.40 and 0.57 per cent carbon showed no sign of graphite. Their results indicate that graphite precipitates the more readily the higher the carbon content, though this tendency is influenced to some extent by deoxidation practice, and that graphitization is accelerated by plastic deformation. In a recent study of the graphitization of 0.4 and 0.6 per cent carbon steel strip, made by M. A. Hughes,4 it was found that at I2oo°F. graphite appeared after 72 hr. in aluminum-killed but not in silicon-killed steel, and that the rate of graphitization was increased by slow cooling from I6oo°F. and by cold-working prior to annealing. In creep tests of normalized 0.15 per cent carbon steel killed with 2.5 Ib. of aluminum per ton, at the U. S. Steel Corporation laboratory at Kearny, spheroidization and some graphitization were found after 3000 hr. at Iooo°F. under a stress as low as 1500 lb. per sq. inch. .

Jan 1, 1944

By J. E. Lamar

THAT Illinois is an important mineral producing state is well known. A value of over $237,000,000 for the mineral products in 1926 indicates the magnitude of the industries. Coal mining is the largest mineral industry, and the value of its product was about 63 per cent of the total mineral production of the state. Oil and gas constituted about 8 per cent and the non-metallic minerals about 29 per cent. This 29 per cent represents the production of a varied group of mineral industries of wide geographic distribution through the state.

Jan 1, 1929

By S. Norton

GEORGE C. FOOTS, Port Henry, N. Y. (written discussion).-The paper by Mr. Norton and Mr. LeFevre will bear the most careful consideration by all interested in the iron business, particularly in the East. There is much information contained therein which should be emphasized. The idea of handling iron-bearing rock in quantities comparable to the porphyry coppers does seem at first blush to be beyond the pale of commercial possibility. Yet, today in the Adirondack region 25 per cent.

Jan 4, 1917

By Scott, Turner

MY whole life has been spent in the mining business, PO I naturally tend to address my remarks particularly to the newly-graduated mining and metallurgical engineers among you. To a certain extent, all forms of engineering principles are involved in the training of the mining engineer, and most sorts of engineering are certainly utilized by him, so every one of this graduatins class is concerned with the field I propose to discuss.

Jan 1, 1932

By J. J. Jakosky

A REVIEW of the progress in applied geophysics during the recent depression years reveals marked advances over the methods employed several years ago. Of late, geophysical work has been curtailed to a Con-siderable extent in the fields of oil and base-metal exploration, its especial domains a few years ago. Greater attention has been directed toward the use of geophysical technique in other engineering problems. Constantly maintained research programs have developed new instruments and per-fected better field, laboratory and interpretation techniques based on experience and skill acquired from years of application in the older geophysical field. During the past two years, geophysical methods have been employed in problems that required information on thickness of fill materials and subsurface bedrock contours. Considerable success has been attained, with subsequent drilling checking the predicted depths within one to five per cent. In general, these problems were similar as far as the fundamen-tal physical and geological conditions were concerned, but they have varied widely in specific detail and in engineering aspects. Character-istic of the different problems are: (1) yardage and bedrock profile in gold-placer mining; (2) water supply, involving underground drainage and storage conditions; (3) bedrock contours in dam-site and other structural investigations; (4) gravel and fill yardage, and other structural features along rights of way and in rock and gravel quarrying. Of particular interest, perhaps, to mining men are the problems of gold placer deposits and water supply. Geophysical work on gold placers is of especial interest because of the present expanded activity in all phases of gold mining. The development of a suitable water supply at an economical cost is often of prime importance in insuring a successful mining venture. Particularly is this true in the arid Southwest. How-ever, the use of geophysical work in water supply is not confined to the needs of mining development.

Jan 1, 1933

By R. A. Grange, H. M. Stewart

Man.; steel parts may crack if quenched directly into a bath near room temperature, but not if quenched at a temperature just above the range where martensite forms and then allowed to cool slowly to room temperature. This latter procedure, which is the basis for such modern hardening techniques as "martempering" and "isothermal quenching," may entail some sacrifice in depth of hardening but very little, if any, in intensity of hardening. In planning such treatments, it is necessary to know the upper limit of the martensite range, and often desirable to know the proportion of martensite that would form on cooling to any lower temperature; furthermore, the tendency of a particular steel to crack when quenched is unquestionably associated with the temperature range of martensite formation, and consequently knowledge of this range aids in selecting the optimum composition for a given application. Certain puzzling phenomena associated with the properties of quenched and tempered steel may be at least partly clarified as the manner in which martensite forms is more fully understood. Information on the temperature range of martensite formation, particularly with respect to how much martensite results from quenching to a given temperature, is lacking for most commercial types of carbon and low-alloy steel. These considerations led us to study martensite formation in 14 carbon and low-alloy steels. The resultant data may be directly used in the following ways: (I) for selecting the lowest quenching temperature at which no martensite will form; (2) for selecting the highest quenching temperature at which virtually all marten . site will form, thereby avoiding quenching to an unnecessarily lower temperature with attendant danger of cracking; and (3) in producing a mixture of tempered martensite and bainite, which in high-carbon steels has been found to possess somewhat better ductility than tempered martensite, yet does not require the full transformation time necessary for a completely bainitic (austempered) structure. PART I. OBSERVATIONS OF MARTENSITE FORMATION IN FOURTEEN CARBON AND LOW-ALLOY STEELS Transformation of austenite to pearlite or bainite can be conveniently studied by observing the change that occurs over a period of time at constant temperature; such studies are the basis of the isothermal transformation diagram (S-curve). This isothermal technique is not applicable to martensite formation, which occurs within a time interval too small to measure, at least by any ordinary means. For all practical purposes, therefore, martensite may be regarded as forming only during cooling and not during a period of time at constant temperature. As austenite is cooled below

Jan 1, 1947

By H. M. Stewart, R. A. Grange

Man.; steel parts may crack if quenched directly into a bath near room temperature, but not if quenched at a temperature just above the range where martensite forms and then allowed to cool slowly to room temperature. This latter procedure, which is the basis for such modern hardening techniques as "martempering" and "isothermal quenching," may entail some sacrifice in depth of hardening but very little, if any, in intensity of hardening. In planning such treatments, it is necessary to know the upper limit of the martensite range, and often desirable to know the proportion of martensite that would form on cooling to any lower temperature; furthermore, the tendency of a particular steel to crack when quenched is unquestionably associated with the temperature range of martensite formation, and consequently knowledge of this range aids in selecting the optimum composition for a given application. Certain puzzling phenomena associated with the properties of quenched and tempered steel may be at least partly clarified as the manner in which martensite forms is more fully understood. Information on the temperature range of martensite formation, particularly with respect to how much martensite results from quenching to a given temperature, is lacking for most commercial types of carbon and low-alloy steel. These considerations led us to study martensite formation in 14 carbon and low-alloy steels. The resultant data may be directly used in the following ways: (I) for selecting the lowest quenching temperature at which no martensite will form; (2) for selecting the highest quenching temperature at which virtually all marten . site will form, thereby avoiding quenching to an unnecessarily lower temperature with attendant danger of cracking; and (3) in producing a mixture of tempered martensite and bainite, which in high-carbon steels has been found to possess somewhat better ductility than tempered martensite, yet does not require the full transformation time necessary for a completely bainitic (austempered) structure. PART I. OBSERVATIONS OF MARTENSITE FORMATION IN FOURTEEN CARBON AND LOW-ALLOY STEELS Transformation of austenite to pearlite or bainite can be conveniently studied by observing the change that occurs over a period of time at constant temperature; such studies are the basis of the isothermal transformation diagram (S-curve). This isothermal technique is not applicable to martensite formation, which occurs within a time interval too small to measure, at least by any ordinary means. For all practical purposes, therefore, martensite may be regarded as forming only during cooling and not during a period of time at constant temperature. As austenite is cooled below

Jan 1, 1947

By H. J. Fraser

LIKE a runner catching his second wind, the mining geologist in 1944 has had some opportunity to appraise the result of three years of active and intense search for the metallic sinews of war and peace. The war period has been one of physical activity and accumulation of new data but has not so far resulted in the announcement of any profound or revolutionary theoretical concepts or techniques. Most technical publications during the year have been either descriptive or statistical. A review of accomplishments during the war years, although affording some measure of satisfaction in individual cases or regarding production of certain metals or' ores, is far from justifying any feeling of complacency regarding the growth of the profession either in fundamental knowledge or in application. During 1944 an abundant supply of all metals and minerals flowed steadily to smelters and fabricating plants. Also, during this and preceding years, adequate stock piles for war needs, in view of the improved foreign and domestic supply situation, were accumulated in many metals in such quantities that the mining industry has become concerned not with the problem of supply but with the effect these accumulated stocks, if maintained, might have on the postwar market. These considerations culminated in the enactment by Congress of the Surplus Disposal Act, which, admittedly a tempo-

Jan 1, 1945

By Herty, C. H.

One of the numerous requirements of many grades of present- day steel is that the steel shall be free from non-metallic inclusions. These inclusions may be composed of oxides, sulphides, complex oxy- sulphides, and nitrides, which enter the steel with the furnace charge, result from sulphur absorption from the furnace gases, or are formed in the steel during the deoxidation process. Although few' data are available which indicate in any quantitative manner the specific effects of inclusions in steel, there is a large mass of circumstantial evidence which points to the advisability of producing steel free from these impurities for many purposes. At the present time there is a growing feeling among metallurgists that non-metallic inclusions should be divided into two distinct types: (I) those readily visible under the microscope at ordinary magnifications; and (2) those in colloidal suspension or in solid solution. Both types are profoundly influenced by the character of the charge, the manipulation of the furnace slag, and the method of deoxidation. The work described in this bulletin deals primarily with inclusions visible under the microscope at ordinary magnifications, but the steels made by the various methods of deoxidation are being used LO study certain effects which may be ascribed to the second classification, named above. This latter work will be the subject of further bulletins on the effect of deoxidation practice on the physical properties of the steels involved.

Jan 1, 1957

Executive Committee, Board of Directors Augustus B Kinzel, Chairman, J L Glllson, Vice-Chairman, A W Thornton, Howard C Pyle, Grover J Holt Finance Committee, Board of Directors Andrew Fletcher, Chairman, J S Vanick, Gall F Moulton Investments Gail F Moulton, '60, Chairman, Henry Krumb, '59, J Loveloy, '61, C R Dodson, ex off as Treasurer, Andrew Fletcher, ex off as Chairman, Finance Com¬mittee Endowment Andrew Fletcher, Chairman, N G Alford, H DeWitt Smith, W J Coulter, J V N Dorr, R B Gilmore, J B Haffner, O H Johnson, D H McLaughlin, J R McMillan, L F Reinartz, C E Weed, Wilfred Sykes, J R Suman Honorary Memberships H DeWitt Smith, '59, Chairman, C E Reistle, Jr, '59, Grover J Holt, '59, L F Reinartz, '59, M L Haider, '60, D H McLaughlin, '61, John M Lovejoy, '62, Augustus B Kinzel, ex off as President

Jan 1, 1958

C. Le Neve FosteR, Llandudno, Wales: I regret that Prof. Clowes is not here, and also that I cannot produce one of his lamps for inspection. The lamp has but just passed the experimental stage, and is now on sale in England for the purpose of testing it in practice. The only complaint I have heard made against it is the high price. It costs six or seven guineas. Possibly that would not frighten you on this side of the water as much as it does us. R. W. RaymonD, Brooklyn, N. Y.: So far as my obsrvations and experience go, we have not yet reached a state of affairs in the coal-mines of this country which calls for the general use of safetylamps by common miners. Certainly such a practice is to be avoided if possible, on account of the recklessness of miners, which it seems almost impossible to control by warning or discipliue. It is much better, if practicable, to confine the use of safety-lamps to inspectors or " fire-bosses," and not to permit the miners to work or to go where naked lights cannot be carried. In a colliery near Pottsville, Pa., with which I was connected for five years, and which had the reputation of being highly "fiery " (jets of fire-damp bubbled continually through the puddles in the gangways, and a thin sheet of it lay along the roof), we managed to avoid all serious

Jan 1, 1894

By Zay Jeffries

Each generation accepts the developments of the preceding generations without full appreciation of the difficulties that had to be overcome or of the effect of any given development on society. Today, the production of pig iron is the yardstick with which general industrial health and progress are measured. So natural and logical does this seem to us, that it is difficult to picture conditions prior to the fourteenth century when pig iron was unknown. Not only was pig iron unknown but iron or steel could not be melted and poured into castings; all iron and steel articles were forged from sponge iron. All castings, as well as many worked articles, were made of non-ferrous metals or alloys. In many parts of the world, over long periods of time, not only was the annual exchange value of non-ferrous metals greater than that of iron and steel, but their combined tonnage was greater. At present, the value of the pig iron produced in a year is of the same order of magnitude as that of all non-ferrous metals combined; the tonnage of pig iron is, however, about twenty times that of all non-ferrous metals combined. Owing to lack of records, we will probably never know the relative importance of the various metals at all periods in historic times. A certain conclusion is that the iron and steel industry, since the discovery of pig iron and the cheap methods of converting it into steel, has grown at a much more rapid rate than the non-ferrous metal industries. Notwithstanding their fundamental fitness for man's needs, iron and steel owe their importance in no small degree to the low cost of production. The low cost was a result of increased knowledge of the production appliances and of the metallurgical processes. This increased knowledge is the key to our modern industrial civilization. It will remain for future generations to determine whether there is now going on a gradual change toward greater importance of the non-ferrous metals, as compared to iron and steel. The world's pig iron production in 1920 was slightly more than twice what it was in 1890, whereas the non-ferrous metals production in 1920 was about two and one-half times that in 1890. Every non-ferrous metal industry has shown marked growth during the last thirty years. During this period, the production of cop-

Jan 1, 1924

By Sherwin F. Kelly

THE geophysical scene shifts and alters, the emphasis changes, and new possibilities loom, but the tendency is always towards widening the field and deepening the analytical penetration. Seismic methods have had their heyday, the torsion balance is being displaced by the gravimeter, electrical methods are showing deeper penetration, soil analysis is the newest tool, and gamma-ray logging appears on the horizon. One of the striking features of re- cent geophysical work in the oil fields has been the marked decrease in the number of seismic crews employed. Although the percentage of company crews is believed to have increased appreciably. the sum total has fallen sharply, as shown by the figures for the Gulf Coast area. About two years ago probably over 100 seismic parties were operating there, whereas now there are only about 35. This decrease may be partly due to the low prices of petroleum with a consequent reluctance to spend money to increase crude-oil re- serves but more probably to the fact that reflection and refraction shooting have been carried on so extensively that they have been applied to a large pro- portion of the areas in which they may reasonably be expected to succeed. Some of the earlier enthusiasm, particularly over reflection prospecting, may have erred on the side of over- optimism; some of the present curtailment may be due to over pessimism; but in the opinion of various observers seismic work at the present rate seems to be at it- optimum. It nevertheless remains pre-eminent as a technique for detailing structures in areas where good reflections can be obtained and is the only method that will give accurate depth to definite beds. Results may be poor in certain areas but many regions still remain wherein it can be applied, so that plenty of structural mapping remains to be done by the reflection seismic method.

Jan 1, 1940

By AIME AIME

FEW mining schools possess an art gallery and certainly none can equal the collection of paintings depicting the mineral industries now hanging in the comparatively new building of the School of Mineral Industries at The Pennsylvania State College. Dean Steidle, who conceived the idea, early this spring boasted of 55 paintings in the collection, by 24 different artists, the gallery being appraised at $18,000. Since then, eleven additional paintings have been added. Opportunity will he presented for an inspection at the meeting of the Industrial Minerals Division, to be held at the College, Sept. 24-26.

Jan 1, 1936

By David P. Shoemaker, Clara B. Shoemaker

It has been shown for an important class of complex transition intermetallic compounds (a, P, R, 6, and p phases) characterized by "normal" coordination [CN12 (icosahedral), CN14, CN15, CN16/ that interatomic distances nay be calculated to a good approximation as the sum of characteristic atomic radii. Two radii, one for major ligands and one for minor ligmds, are specified for each atom, except in the case of CN12 where only a miaaor-ligand radius is specified. The same appears to be true of transition-metal phases of simpler struc-ture: Laves phases (CN12, CN16), and p-tungsten phases (CN12, CN14). In the case of known examples of the more complex phases, a simple rule is given which specifies these radii. However, only a fraction of the known examples of the simpler phases obey this rule closely. To include the latter phases the rule may be modified by considering the radii as linear functions of the weighted average of the Pauling CN12 radii of the two kinds of atonzs, with the radii weighted according to the over-all chemical composition of the alloy. With very few exceptions interatomic distances for both tlze complex and the simpler transition phases can b$ predicted with this modified rule to within 0.06A. ManY intermetallic compounds are known of composition A,By, in which A is a transition element to the left of the manganese column in the periodic table and B is a transition element in or to the right of it. Frequently the coordination numbers (CN) found in these compounds are CN12 (icosahedral), CN14, CN15, and CN16 (called "normal" coordinations by Frank and Kasperl). Well-known examples are the cubic and hexagonal Laves phases which have CN12 and CN16, and the 0-tungsten (CrsO) phases which have CN12 and CN14. In the more complicated (often ternary) phases, such as the a phase,2 the Beck phases p3 and R~, the 6 phase,5 and the p p atoms occur with CN12, CN14, CN15, and (except for a) CN16; in many cases several crystallographically independent atoms of one particular CN occur in the asymmetric unit. A large number of independent interatomic distances are found in these complicated phases, varying from 20 in the a phase to 94 in the 6 phase. These distances show a large spread; they vary, for example, from 2.358 to 3.278A in the 6 phase. In our analysis of these distances we found that in each of these compounds every atomic position can be characterized by either one or two radii. The CN12 positions are characterized by a single radius, The higher coordinated positions are characterized by two radii, namely: the CN14 positions by 4 in the direction of the twelve "5-coordinated" ligands3 (called 'minor" by Frank and Kasperl) and by r:, in the direction of the two "6-coordi-nated" ligands (called "major" by Frank and Kasper); the CN15 positions by r15 for the twelve minor and r:, for the three major ligands; the CN16 positions by rlE for the twelve minor and r:, for the four major ligands. We have expressed the experimentally determined interatomic distances in observational equations as the sums of the appropriate pairs of these characteristic radii and the value of these radii have been determined by the method of least Squares. Despite their wide range, the interatomic distances could then be predicted by the sums of these atomic radii with an average deviation in any one compound of 0.06A or less. The results are summarized in Table I. Inspection of the radii thus obtained shows that in the structures in Table I the radii (in A) are given to a first approximation by the simple relationship: Where CN is the coordination number (12, 14, 15, or 16), and A = 1 for major ligands and = 0 for minor ligands. The interaLomic distances can be predicted within about 0.1A by sums of these atomic radii. Another phase belonging in this group with CN12, 14, 15, and 16 is the y phase & B7, in which A is molybdenum or tungsten and B is iron or cobalt. Recently the M%C phase has been refinedE and the observed distances also agree well with those calculated with Eq. [I]. (In the original determination of the structure of W6FeV7 the F$(II)-W(II1) distance was erroneously given as 2.84A, but we have recalculated it fro? the published parameters and found it to b? 2.57i4, in good agreement with the value of 2.6A predicted with Eq. [I.].) Many binary transition alloys are known to crystallize with the simpler structures having "nor-

Jan 1, 1964