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By J. C. Fisher

Nucleation theory is applied to martensite nucleation in substitutional iron alloys. Composition fluctuations are neglected, and a steady rate of nucleation is predicted for any composition and temperature. The maximum rate of nucleation (as a function of temperature) is shown to be measurable only for on extremely narrow composition range, being too great or too small outside this range. A number of experimental observations, including completely isothermal transformation in some alloys and composition-dependence of M. temperature in others, are compared with the calculated behavior. IN a previous report,¹ nucleation theory was applied to the formation of isothermal martensite in an Fe-Ni-Mn alloy. The experimental observations of Cech and Hollomon² were accounted for quantitatively. It now is of interest to examine the predictions of nucleation theory with respect to martensite transformation in substitutional iron alloys of other compositions. Since Fe-Ni alloys have received considerable attention, both as to their transformation kinetics and their free energies, they will be treated in detail, although the results apply with equal validity to other substitutional alloys. In substitutional alloys, where composition fluctuations can be neglected in volumes of critical nuclear size, the rate of nucleation of martensite in subcooled austenite is¹ n - Nv exp (—W*/kT) [I] where the free energy of formation of the critical size nucleus is W* = 8192 p (?² s³) [2] In the expressions for n and W*, the symbols have the following meanings: N is the number of atoms per unit volume; v, the atomic vibration frequency; 8, a function of the elastic constants of austenite and the shear angle of martensite; , the austenite/mar-tensite inter facial free energy; and ?fc is the free energy change per unit volume accompanying the transformation. Jones and Pumphrey² have determined the austenite to martensite free energy change as a function of nickel content and temperature for Fe-Ni alloys. Their expression is ?F = 2500 C + 1.25 (1 —C)?FFc cal per mol [3] where C is the atom fraction of nickel, and ?Ffe is the free energy change per unit volume for pure iron as tabulated by Zener4 (or, equivalently, Fisher"). From Eqs. 1 to 3, it is possible to calculate isothermal nucleation rates as a function of temperature and composition for Fe-Ni alloys. The only unknown parameter is (?² s³). The best value of this parameter for Fe-Ni alloys, determined from M. temperatures in a manner to be described shortly, is (?² s³)= 9.92 (10)21 cgs units [4] Taking this value of (?² s³), C-curves for isothermal nucleation were calculated for Fe-Ni alloys of several compositions, and are plotted in Fig. 1. It is evident from Fig. 1 that completely isothermal nucleation of martensite in Fe-Ni alloys can be observed experimentally for only a very narrow range of compositions. Cech and Hollomon find that a nucleation rate of about 10' nuclei per cc per sec is as fast as they can follow dilatometrically, and a rate of about 10-1 nucleus per cc per sec is about the slowest that can be measured conveniently. If the nucleation rate is to lie between the limits 10-1 10 the nickel content of an Fe-Ni alloy must fall in the atomic fraction range 0.299 5 C 5 0.302. Nickel contents lower than 0.299 correspond to nucleation rates too great to follow, and those higher than 0.302 to nucleation rates too slow to measure in a reasonable time.* In view of the narrow corn- position range in which successful isothermal measurements can be made, it is not surprising that only one substitutional alloy has been described' that comes close to being in the proper range.

Jan 1, 1954

By J. T. Ryan

SAFETY practice or the elimination of accidents in our coal mines is specifically a problem of management. It cannot be delegated to any governmental agency except that the various coal-producing states do and should have some minimum safety standard laws. However, the legislative method of attempting to control mine accidents is ineffective because of the delay between the necessity and the action. It will always be impossible to keep our various state mining laws up to date; and when the law says you must do a certain thin there is a tendency to do this and no more. Unless the scheme for setting up state regulations is so flexible that when a new hazard develops it can be immediately and adequately covered and the whole responsibility for accident elimination placed undivided on the

Jan 1, 1937

By H. M. Howe

A Discussion of the paper of Professor Howe, presented at the London Meeting, July, 1906, and printed in Bi-Monthly Bulletin, No. 14, March, 1907, pp. 169 to 274. SECRETARY'S NOTE.-M. Beutter's introductory remarks, being simply a resume of Prof. Howe's paper, with a disclaimer of the intention to criticise it, have been omitted, and the remainder of this contribution has been somewhat condensed, without omitting any essential statements. M. BEUTTER, St. Etienne* (communication to the Secretary-+):-Professor Howe observes in paragraph 47 of his paper that the fluid-compression of steel. diminishes piping by forcing the liquid and viscous metal, while the pipe is forming, or after it has formed, into the space so produced, and proceeds to study the different systems of compression, alluding to the four principal ones: Whitworth, Illingworth, Williams, and Harmet. Having now for many years had in use the last-named process, that of M. Henri Harmet, I shall attempt to explain the difference between it and the three other processes named. The Harmet process does not diminish or close the pipe after it has formed, but prevents it from forming; and I may add that it is the only one of the four which produces this result. It is true that the Whitworth process diminishes the interior hollow by localizing it around the central axis of the ingot, which is afterwards removed by trepanning the hollow forgings for which this process has been, I believe, always exclusively used. The Illingworth and Williams processes, which, in my opinion, are applicable only to small ingots, of necessity allow the pipe to form, or (to use the expression of Professor Howe) they allow the surface of the lake of liquid steel to sink into the interior of the ingot, since they involve waiting a certain time before compression, so that (in the case of the Williams process) the ingot-mold can be opened without dan¬ger, or (in the case of the Illingworth process) so as to avoid the risk that the steel may enter the grooves produced by the removal of the distance-bars. During the time required for

Jul 1, 1907

By Peter Allen, John R. Stuermer

COUNTRY RISK ANALYSIS A company operating in a foreign country assumes all the risks that it would at home. However, beyond these, it assumes risks that arise from the unique political economic, financial conditions of the foreign country which it operates. These risks are known as "country risks". The importance of these risks has grown appreciably in the recent past (particularly in the aftermath of Iran's revolution in the late 1970s and Mexico's debt rescheduling of 1982-83), and as a result, country risk analysis has become an increasingly useful management tool. Country risk analysis seeks to assess the probability that countries will service their aggregate foreign liabilities on time, as well as the probability that country conditions could inhibit the debt service capability of private sector debtors. This involves assessment of both the ability and the willingness of countries to meet their external liabilities in a timely fashion. "Ability" is linked economic and financial variables: principally, a country's economic structure, foreign exchange generating capacity and debt service burden. On the other hand, "willingness" is tied to political factors: mainly the economic/financial orientation of government policy and the stability of economic decision making. Ability: Economic, Financial Conditions and Prospects Judgement of a country's ability to meet foreign financial obligations begins with a detailed study of a country's external balance sheet which compares the country's foreign liabilities and assets. Table 1 below presents country balance sheets for Mexico, Korea and Indonesia. [TABLE 1 The External Balance 3-,-et 1983 (billions of dollars; Indonesia Mexico Korea Foreign Liabilities 31.1 67.6 40.5 By Source: Bank 13.1 75.5 26.3 Non-bank 18.0 12.114.2 Foreign Reserves 9.3 4.7 7.0] The large magnitude of Mexico's external debt (nearly $90 billion), compared to foreign assets of approximately $5 billion, illustrates the weakness of this country's external payments position, and the main reason that it has been unable to meet interest and principal payments and been forced to reschedule its foreign debt. On the other hand, the relationship between Korea's external liabilities and assets ($50.5 billion and $7 billion, respectively), is more favorable and helps explain why Korea has been able to meet debt service payments and maintain its access to the international capital markets. Indonesia has even a more favorable relationship between its foreign assets and liabilities, $31 billion and $9 billion, respectively, and its debt is mostly lower interest rate, non-bank debt, making for a less onerous debt service burden. After the balance sheet, the analysis turns to a comparison of the country's foreign exchange earning capacity and its prospective financing requirements, that is, the country's future earnings stream

Jan 1, 1985

By J. F. Haseman, J. E. Davenport

IN the brown rock phosphate fields of Tennessee there are large deposits of phosphate matrix in which quartz is a major constituent of the gangue, and which cannot be beneficiated by the conventional washing process to yield a concentrate of suitable grade for use in the electric furnace. A huge tonnage of high-grade phosphate concentrate is produced in the Florida pebble district from low-grade siliceous feed. However, the characteristics of the low-grade siliceous Tennessee ore are such that flotation under the conditions employed in treating the Florida ore1-2 results in inadequate beneficiation. INVESTIGATION OF FLOTATION METHODS Flotation has been used in Tennessee primarily to produce a concentrate of premium grade by moderate enrichment of a marketable grade of phosphate.3,4 A secondary use was to increase the recovery of phosphate from the fines (down to approximately 200 mesh) from medium-grade ores with a concomitant moderate increase in over-all grade.3,5 It was considered desirable to investigate methods of improving the grade of washed products from low-grade siliceous Tennessee ore when these products were substantially below the requirements for use in the electric furnace. The present paper describes the results of a laboratory-scale study of factors that affect the beneficiation of such siliceous phosphate ore by flotation. The primary objective of the investigation was to ascertain the conditions under which the ore could be made to yield a concentrate suitable for reduction in the electric furnace. It was assumed that a phosphate concentrate for electrothermal reduction should contain at least 26 pct P205 and should have a weight ratio of silica to lime of not more than 0.80. Since a concentrate of moderate grade can be used in the electric furnace, and since, as Grissom4 has shown in detail, the ore will not bear the cost of expensive treatment, the study of collectors was limited to the relatively inexpensive fatty acids. A secondary objective was to determine whether a portion of the phosphate could be recovered in a grade suitable for treatment with phosphoric acid to produce 45 pct superphosphate. The ore consisted of variably cemented sand interlayered with clay. The sand layers were composed of grains of quartz, phosphate, and clay embedded in a matrix of clay and phosphate. Some clay was finely disseminated in the phosphate grains. Little massive high-grade phosphate was present. The material used in the flotation tests was a washed sand that had been separated from the ore in a bowl classifier at the TVA phosphate-washing plant. The percentage composition of the sand was as follows: P205, 20; Si02, 40; CaO, 29; Fe203, 2; A1203, 3; F, 2.3. The particle-

Jan 1, 1947

By AIME AIME

THE 140th meeting of the Institute will be held in the Engineering societies Building, 'New York, Feb.: 16-19, and one of the most important features, one which cannot be reduced to text in the TRANSACTIONS, will be the opportunity to renew old friendships and make new friends, to talk things over -to orient one's self in these troublous .times. There will be daily get-together luncheons for all, luncheons and dinners for specialized groups, an informal dance, the annual reception and banquet, and a smoker. And such a smoker! It starts with dinner at .dinnertime, shows signs of cabaret, turns smoker, and then goes entertainment-all for the price of one. This year one can stay long after 11 o'clock-there will be time and opportunity to amble around and meet everyone present. The formal program is rapidly rounding into shape. The annual business meeting will -be held on Tuesday morning and the banquet will be at the Commodore. The four Divisions and the various, Technical Committees are arranging their sessions. and scheduling for these a long list of significant papers. A .feature of the meeting will be a number of round tables on timely subjects.

Jan 1, 1931

By AIME AIME

BERYLLIUM is one of the most interesting of the minor metals and distinctly a modern development, for until the last two decades it had practically no commercial importance whatever. Then it was discovered that when small quantities of it were alloyed with copper, a copper alloy of unusual and valuable qualities resulted. This is by far its major use-in the manufacture of strong, heat-treated copper-base alloys in which the beryllium content varies from about 0.3 to 2.5 per cent. Its second most important use, though much smaller, is in the form of oxide or other nonmetallic products in the fluorescent lamp, X-ray, cathode ray, and television industries. Certain beryllium salts have the quality, in common with several other materials, of transforming short-wave radiation and cathode rays to visible radiation. Such materials are commonly known as phosphors, and the beryllium salts are the most important phosphors now in use. The third largest use for beryllium is for ceramics, including refractories. Beryllium is also used in small quantities in the form of the metal itself.

Jan 1, 1943

By JOHN R. SUMAN

OVERWHELMING proof of the importance of oil in a modern national economy is afforded by the present European War. Treat¬ies and national boundaries have been cynically violated to secure greater supplies of the precious fuel. Petroleum substitutes have been desperately, and far from successfully, sought. The whole German military theory of the drang nach Osten, the drive to the East, is directed at cutting the British supply of oil and securing a supply for Germany. This is a war of machines, and the machines of war feed hungrily on oil. In view of this fact, it is surely comforting to know that we are living today in a nation which has surpassed all the rest of the world not merely in unearthing the raw supplies of petroleum which lie beneath its surface but also in every phase of the industry in mining, refining, processing, production, and distribution.

Jan 1, 1941

By J. Burns Read, S. Tour

It is the purpose of this paper to summarize, as far as possible, the metallurgical information and experience gained by the Ordnancc Department, during the war, in the manufacture of artillery cartridge cases, to describe the tests to which artillery cartridge cases were put, and to summarize the knowledge and experience gained in this testing. The authors wish to acknowledge the aid given by manufacturers, army officers, and civilian employees of the Department in obtaining data. Artillery cartridge cases are cold drawn from circular disks punched from strips of rolled brass. The rnanufacture involves from 25 to 30 main operations, which are done almost entirely on a punch press. Descriptions of the operations have appeared in various periodical:: and, therefore, will not he given here. After each cupping, or drawing, operation, except the last, the cases are annealed at from 540" to 650" C. (1000" to 1200°F.), to remove all the hardening stresses set up in the metal and to allow complete recrystallization. After each annealing, the cases are pickled in niter cake or sulfuric-acid solution and then washed in water to remove all traces of acid. In some instances, the cases arc then immersed in a cyanide-salt solution, and afterwards rinsed in water, to remove the thin layer of copper that forms on the surface of the cases during the acid pickle. The last cold-drawing operation is followcd by the heading operation which, by flattening the head of the case on the outside, causes the metal to flow on the inside to approximately the proper finished dimensions. The mouth, or open end, is then annealed at 430" to 450" ('. 1800" to 900" F.) by immersion in a salt bath or by gas flames. After being washed, the eases are tapered, when they arc ready for machining, inspection, and testing. Cartridge-case Disks Good disks of proper composition and physical properties are essential to the production of good cartridge cases. The Ordnance Department

Jan 1, 1923

By J. Burns Read, S. Tour

It is the purpose of this paper to summarize, as far as possible, the metallurgical information and experience gained by the Ordnancc Department, during the war, in the manufacture of artillery cartridge cases, to describe the tests to which artillery cartridge cases were put, and to summarize the knowledge and experience gained in this testing. The authors wish to acknowledge the aid given by manufacturers, army officers, and civilian employees of the Department in obtaining data. Artillery cartridge cases are cold drawn from circular disks punched from strips of rolled brass. The rnanufacture involves from 25 to 30 main operations, which are done almost entirely on a punch press. Descriptions of the operations have appeared in various periodical:: and, therefore, will not he given here. After each cupping, or drawing, operation, except the last, the cases are annealed at from 540" to 650" C. (1000" to 1200°F.), to remove all the hardening stresses set up in the metal and to allow complete recrystallization. After each annealing, the cases are pickled in niter cake or sulfuric-acid solution and then washed in water to remove all traces of acid. In some instances, the cases arc then immersed in a cyanide-salt solution, and afterwards rinsed in water, to remove the thin layer of copper that forms on the surface of the cases during the acid pickle. The last cold-drawing operation is followcd by the heading operation which, by flattening the head of the case on the outside, causes the metal to flow on the inside to approximately the proper finished dimensions. The mouth, or open end, is then annealed at 430" to 450" ('. 1800" to 900" F.) by immersion in a salt bath or by gas flames. After being washed, the eases are tapered, when they arc ready for machining, inspection, and testing. Cartridge-case Disks Good disks of proper composition and physical properties are essential to the production of good cartridge cases. The Ordnance Department

Jan 1, 1923

By Frances Hurd, Clark

Iv 1897, Roberts-Austen(l)$ found an arrest in the thermal curves of alloys of 60 per cent. copper and 40 per cent. zinc. This break occurred from 450° to 470° C. Shepherd, (2) working in 1904, was unable to detect any change in the direction of the thermal curve. In 1911, Carpenter and Edwards(3) confirmed the work of Roberts-Austen and called this a eutectoid transformation of beta to alpha plus gamma. Hudson') in 1914, showed that the beta constituent could be produced synthetically at temperatures below the transformation point. He believed the change in the beta was polymorphic in nature rather than a eutectoid. The work of Matsuda(32) in 1922 demonstrated this break by thermal analysis, microscopic investigations, dilatation, electrical resistance measurements, and a thermoelectric study. He believed the transformation to be continuous from 300° to 480° C., and comparable to the A 2 transformation in iron. Later, in 1924, Andrew and Hay, with electrical resistance measurements, confirmed Matsuda's work. Imai(28) showed the transformation to be progressive and therefore a function of the temperature rather than the time. He stated that it was neither a eutectoid nor an allotropic change of phase. Atomistically expressed, it was a change, not of atomic configuration, but of atomic energy of some kind; and again it was compared to the A 2 transformation in iron. Imai believed that his analyses by X-rays led to the same conclusion. In order to study this change, at 470'C., in homogeneous 60:40 brass, Homerberg and Williams «0> and Homerberg and Shaw(41) quenched their material in iced brine to obtain the beta solid solution and reheated at various temperatures. At 200° C., a change in the microstructure and physical properties occurred. A fine-grained structure, which they termed alpha and which had the appearance of a sorbitic steel, appeared, with an increase in the tensile strength to 82,750 lb. per sq. in., and a Brinell ball hardness of 240 with 3000 kg. load. At 470° C., the alpha

Jan 1, 1927

By John R. Lotz

DEVELOPMENTS in Iran currently arousing interest in a considerable portion of the world, particularly on the part. of that country's immediate neighbor on the North and in our own country, an inseparably related to and largely dependent upon the government's attempts to strengthen its economy and improve the standard of living of its people. These efforts are encompassed by provisions of the Seven-Year Development Plan recently enacted and not, in the process of implementation. It is a fine example of what one financially sound but extremely backward and poorly equipped country has undertaken to do on its own account and with its own resources. This Seven-Year Plnil was formally authoriztld by an act of the Iranian Parliament in February 1948. Its stated objects are to carry out such plans for the development of the country and its economy as ail1 raise the standard of livinc: and standard of education of the people, and re- duce the cost of living. A seven-yrar program for carrying out the work within the limits of appropriations was assigned under the law. The total amount to be expended during the seven- year period was fixed at the equivalent of $670 millioil at current rates of exchange.

Jan 1, 1950

By F. Keller

SOME PHRASEMAKER has aptly said that nature made aluminum light but research made it strong. Research has been a vital element in the past progress of the aluminum industry and its future growth likewise depends upon the application of the results of research. The role of aluminum products in World War II is well known and this metal will certainly be increasingly important in the postwar world. Some of the principal developments in the war years were in the field of high-strength aluminum alloys. New and stronger alloys were developed which enabled designers to get increased speed and performance in our fighter planes and bombers. The aircraft industry will continue to use these new materials for peacetime passenger and cargo airplanes. High-strength alloys will also find structural applications in trucks, buses, trains, ships, and bridges.

Jan 1, 1946

By Frank T. Sisco

SHORTAGES of metals and minerals and substitution of less critical materials for those in which a virtual famine exists received detailed and frank discussion at a recent conference in Washington called by Robert E. McConnell, director of the Conservation Section, Office of Production Management. Representatives of the large engineering societies in the United States and O.P.M. department heads participated in the discussion. To open the session Mr. McConnell called upon Zay Jeffries, chairman of the O.P.M. Advisory Committee on Metal Conservation and Substitution, to summarize the present situation. Dr. Jeffries touched briefly on the status of metal shortages, which has already received considerable attention in the popular press, and said that much of the present difficulty was caused by the too-hasty substitution-without sufficient con¬sideration of the immediate conse¬quences-of metals having ordinarily a small yearly consumption, for those having a much larger annual consumption. As a result, all the alloying metals used in alloy-steel manufacture have become scarce, with the exception of molybdenum; further¬more, despite a reserve of 11,000 tons of molybdenum in this country and despite a normal consumption of only about 3500 tons and a prospective annual production rate of 21,000 tons by October, a shortage of molybdenum is possible before this war is over.

Jan 1, 1941

By AIME AIME

DATA in this report enable comparisons to be made within the bituminous coal industry and comparison as well with copper and steel in respect to capacity and overdevelopment. The conclusions reached from the data will tend to correct numerous current misconceptions. The data have been prepared by various members of the Coal and Coke Committee of the A.I.M.E., from the most authentic sources avail¬able, and cover the period 1913-1924 wherever possible. CAPACITY AND OVERDEVELOPMENT Table 1 shows statistics for the industry, mainly from the U. S. Geological Survey sources, but partly from the U. S. Coal Commission reports. The mine capacity with equipment and labor as of given date is calculated for each state by obtaining the total man days worked as reported by the operators, and dividing this figure into the total production, getting the production per man day; this figure times the number of men employed times 308 (a theoretical full working year) equals estimated full-time capacity. Two major objections are made to this method-one that the total number of men employed is used instead of the number actually working, and the other that the number of days used only deducts Sundays and five holidays. Covering the first, the same number of men is used in estimating capacity as is used in actual production, and this condition exists at all times. Regarding the second, the opinion is general among coal men that 280 days is as great a figure as should be used, as it is practically impossible to keep any mine working full time at the same daily rate as when it is working part time. The capacity, as estimated on this basis, is much more nearly the true capacity, although even with present railroad efficiency this amount of coal could not be moved.

Jan 1, 1926

By J. B. DILWORTA

Ix estimating the investment-value of a mining-property or plant, the value of which decreases with operation, it is often necessary to know the sum which must be set aside periodically from earnings either to renew the plant at the end off its life, or to return the capital involved when the earning-power of the investment has ceased. In such cases it is manifestly incorrect simply to divide the total amount to be retired by the number of periods (usually years) during which the investment shall be active, as the sums periodically withdrawn have a certain interest-earning power varying with the length of time they are held and with the opportunities afforded for their investment. But though the interest may be considered to accumulate regularly year by year, yet the rules and tables for compound interest do not apply, owing to the addition of a fixed amount of new money to the total at the beginning of each period. Briefly stated, the problem of sinking-funds is, to find the amount of money which must be periodically set aside at a certain rate of interest, regularly compounded, to yield a certain sum in a given, length of time. In most practical cases the interest is compounded and the fresh amount added at the same time-usually once a year-and on this basis the problem may be solved as follows

Nov 1, 1909

By Sheldon P. Wimpfen, Ralph H. Sweefser

FOR centuries the pumping of water has been one of the chief problems to be overcome by the persistent men who win the mineral wealth of the world. Profitable operations have often been forced to suspend activities as the mine penetrated well below the water table or when sudden rushes of water were encountered. To operate below the local water level requires continuous pumping equal in volume to the amount of water flow¬ing into the mine workings. Often the water to be removed exceeds the tonnage of valuable material produced. To be above local water level is a valuable asset. Modern mining practice permits nothing short of the extraction of the last pound of profitable ore from a mineral deposit. In the days before the development of mechanical and electrical power as we know it today. water in any quantity was a major

Jan 1, 1948

JOHN B. HASTINGS, Los Angeles, Cal. (written discussion *).-This, paper is so admirable for its brevity that one hesitates to enter into discussion. The cycle of eruptives makes one wonder, "Where's the basalt?" and the youthfulness of the Idaho flows suggests they may yet come. Veins and Dikes.-Veins and dikes seem to be closely aligned in the minds of some authors, while to me they appear quite distinct, the first representing quiet, long-continued action, typified by metasomatic replacement, far removed from volcanic action; the latter, sudden and cyclonic, emanating from the heart of vulcanism. The rock openings occupied by both types were formed by kindred forces, but in the one they were closed for indefinite periods before invasion by the solfataric solutions, and in the other their formation and occupation were simultaneous. Open Fissures.-I do not believe in the existence of open spaces of discission that may be occupied by veins. Occasionally they occur; I found one with. a machine drill 350 ft. below surface, fortunately in an adit; the water spouted for 12 ft. in a 6-in stream for nearly 24 hr. It was only a flattish fissure, 6 in. wide, crossing the perpendicular vein, and indicating how tabular veins of ore might be formed. The practical absence of open fissures should be a joy to miners. We all know the misgivings with which we feel about for an old winze having only 30 ft. of water in it, in an unsurveyed and inaccessible part of a mine. It is said that veins are sometimes formed in open spaces left by Protuberances of the walls, which meet after having been displaced; but I believe that in such circumstances there would be sufficient attrition and brecciated material to fill the fissure, though perhaps loosely. Parts of veins may possibly have been formed in originally open spaces, but if so, the spaces were made by solution shortly preceding the deposition of the veins. That total solution of rock adjacent to a fissure may occur under favorable conditions is proved by the existence of large bodies of sulphide which contain only a few per cent. of silica; while on the same level, and in other levels above and below, all being within the same ore shoot, assays may show as much as 50 to 60 per cent. of silica, although the gold, silver and copper assays may be almost identical in all the

Jan 1, 1918

Aaby, Alton O , (S'47) Univ of Minnesota, Mimeapolis, Minn Aaby, Waldo S , (S?48) Univ of Minnesota, Minneapolis Minn Aalde, Kaare, (S'48) Univ of Nevada, Reno, Nev Aaring, Floyd D , (S'48) Univ of Oklahoma, Nor man, Oka Aaronson, Hubert I , (S'47) Carnegie Inst of Technology, Pittsburgh, Pa Abbott, Peyton Osborn, (S'46) 1502 Westover, Austin 21, Texas Abel, Malcolm D , (S'47) Univ of Texas, Austin, Texas Aberg, Richard S , (S'47) Univ of Minnesota, Minneipolis, Minn Abrahamson, Guy C , (S'43) 420 W Dennis St , Wilmington, Calif Abrahao, Benjamin, (S'46) Escola Politeenica da Unnersidade, de Sin Piulo, Braizil Achter, Meyer R , (S'46) Carnegie Inst of Tech , Pittsburgh, Pa

Jan 1, 1952

Jan 1, 1884