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By John Griffen

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

Jan 1, 1943

By Thomas T. Read

THE benefits derived from stabilization of industry that might possibly be attained through some scheme of centralized economic planning have been much discussed of recent months, and opinions on the subject range from those who believe that some agency like the War Industries Board would be practicable to create and wholly beneficial in effects, to those who are equally convinced that none of the suggestions so far advanced are at all practicable, or likely to be productive of more of good than of evil. The discussion has been on the general topic, but-many of those who have written or spoken on it have introduced economic problems of the pinera1 industry; for example, Newton D. Baker, who referred to the coal industry in his address on economic planning at the Williamstown Institute of Politics on July 31, and then went on to say, "Industrial progress is made by the development of new things, but new things upset the equilibrium of any plan. Who could have planned the industrial effects of the development of the railroads, or the economic changes which you have seen attend the development of the internal combustion engine. Obviously, unless we are prepared to put world economics in a strait-jacket and, like the encyclopedists, write its full history on the theory that further progress is impossible, no such plan could be made for nations which are forging ahead as is entirely rational for nations which are still catching up."

Jan 1, 1931

By Alvin H. Lense

In the spring of 1967, after a careful study of existing geology along the Pacific Coast including Alaska, the USBM, in conjunction with the USGS, decided that the offshore area around Nome, Alaska, presented an unparalleled land-to-sea comparison site for the evaluation of marine core drilling techniques and sampling equipment. Considering the geological evidence available and the production history of the Nome Beaches (5-6 million oz. of gold recovered), it appeared likely that gold in commercial quantities could occur in the offshore area. A 180 sq mi area of Norton Sound, extending roughly 14 miles to the east and west of Nome and averaging 6 miles to the south, was tested by approximately 530 line-miles of sub-bottom profiling. A total of 4043 ft (56 holes) were drilled in unconsolidated sediments, yielding mixtures of gravel, sand, silt and clay. Of the total holes drilled, 16 went to bedrock and six were terminated short of their intended depths due to boulders which halted penetration, or rough seas which caused the ship to move as the anchors slipped over hard sea-floor surface. The rest of the holes were terminated when the penetrative capabilities of the drills were reached, or when the required amount of geological data were attained.

Jan 8, 1968

By E. D. Gardner

In 1954, the first year the award was conferred, Fred Searles, Jr., remarked, "The earlier years are the easiest." In this, the second year, it was easy to choose the outstanding mining engineer. Our conferee this year has been destined to mine. He comes from pioneer stock, and though a son of the American Revolution he is most proud that all four of his grandparents came to the Jordan River Valley of Utah the "first summer," which all Utahns will recognize as 1847. At the time of discovery of high-grade ore in Bingham, his grandfather, Archibald Gardner, had a crew of men getting out saw timber in the area. The first claim staked in Bingham Canyon was named the Jordan, and Bishop Gardner was the colocator of the claim as well as the man to record it.

Jan 4, 1955

Secretary Membership Committee Increase of Membership Papers and Publications Committee Library Committee Treasurer Report of the Secretary TO THE BOARDOF DIRECTORASN D THE MEMBEROS F THE AMERICANIN STITUTE OF MINING AND METALLURGICAENL GINEERS GENTLEME:N As will be shown by the special reports of the Finance, Membership, Library, Papers and Publications, Increase of Membership, and other standing Committees, together with that of the Treasurer, the year 1927 was one in which the Institute made very satisfactory progress in a number of directions. In total numbers the membership is no larger but in revenue from dues there has been a marked increase. This has been due to the promotion to full membership of Junior Associates of earlier years, to the larger proportion that come in originally as members rather than juniors, and to the keener interest in the work of the Institute reflected in prompter payment of dues. The latter is important, since experience shows that of those who fall behind a large number must ultimately be dropped for non-payment. Conditions in the mining industries have been healthy though not booming. It has been much easier for members to find employment and meet their financial obligations but there has not been that flow of young men into mining, and hence in part into the Institute, that characterized certain earlier years. Rather the tendency toward centralization and larger industrial units has restricted the number, though not the scope, of opportunities for technical men in the mineral industries. The Institute is constantly receiving resignations from members crowded out of mining into other lines of activity. On the other hand, those who remain in mining and metallurgy have a greatly increased necessity for i,dormation and contacts with technology. A few years ago many superintendents and most foremen were non-technical men. Today the reverse rule obtains and shift bosses and men who occupy even lower positions in industrial units are called upon to know and to apply such an amount of technical knowledge that graduate engineers are the rule rather than the exception. The curious situation has obtained that with a much smaller enrolment of students in the schools of mining and metallurgy there has been at times an actual shortage of young engineers for beginners' jobs. The young men retort that the conditions of employment and pay offered in mining are not equal to those in other lines and, while it is undoubtedly true that the young engineer beginning in mining is able to start under conditions markedly better as to pay, living, and responsibility than did the men who are now leaders, they are required to know much more and have usually spent more in time and money to qualify for their jobs. The whole matter is one which warrants much more attention than has been given to it. For the Institute it is important since the young men

Jan 1, 1928

By J. S. Owens, R. W. Marsden, J. W. Emanuelson, R. F. Werner, N. E. Walker

The iron ores of the Mesabi Range occur in a 340 to 750-foot thick, Precambrian cherty iron formation termed "taconite." For about 65 years, extensive natural iron ore bodies were mined, and the ores either shipped as a direct ore or processed by gravity methods to a shipping grade iron ore. Since 1956, magnetite taconite ores, occurring in magnetite-rich horizons in the Biwabik iron formation, have been commercially concentrated and agglomerated. The transition from natural ores to concentrating-grade ores is progressing rapidly so that, in the near future, a major percentage of the iron ore shipped from the Mesabi Range will be as iron ore pellets produced from taconite. Natural iron ores of the Mesabi Range occur in the Biwabik formation as trough ore bodies in elongated channels and as irregular and tabular deposits in fractured areas associated with faults and folds. Ore bodies range in size from a few thousand tons to hundreds of millions of tons and may occur in any part of the iron formation. In some areas of strong ore development, ore was formed from the hanging-wall argillite to the footwall quartzite. The natural ores and beneficiating-grade natural crude ores were formed by the oxidation of the iron minerals, magnetite, greenalite, stilpnomelane, minnesotaite, and siderite, to hematite and goethite and by the removal of much of the silica in the cherty quartz and in the associated silicates by leaching. The ores are believed to have formed by the oxidizing and leaching action of surface waters. Magnetite taconite ores occur as stratigraphic zones in the Biwabik formation where it contains sufficient magnetite to be concentrated profitably, by magnetic methods, to give a magnetite concentrate that is agglomerated into a high quality product. Unoxidized taconite has an extensive distribution away from and between channels of oxidation and leaching but only a part of the unoxidized taconite is of ore grade. Two general types of magnetite taconite ore occur: ( 1) magnetite taconite of the Main Mesabi Range, generally west of Mesaba, which is composed of magnetite associated with cherty quartz, greenalite, stilpnomelane, minnesotaite, and carbonates and (2) magnetite taconite of the Eastern Mesabi, generally east of Mesaba, composed of magnetite associated with quartz, cummingtonite, actinolite, ferrohypersthene, hedenbergite, fayalite, hornblende, pyroxene, garnet, and biotite. The Mesabi taconite is a metasediment derived from an iron- and silica-rich chemical sediment that has been regionally metamorphosed and, on the eastern end, additionally metamorphosed by the Duluth Gabbro Complex.

Jan 1, 1968

By Howard A. Meyerhoff

AS a source of mineral wealth, the larger islands of the West Indies have never had an enviable reputation. The Spaniards took possession of them in the sixteenth century hopeful that they would yield gold; but it was not long before they knew the rather rigid limitations of Antillean gold production and were seeking-and finding ---richer deposits of the precious metals in Mexico and on the west coast of South America. Although a great deal of wealth changed hands in the West Indian islands in subsequent years, the fact may be laid to the abundance of pirates and privateers and not to the richness of local ore bodies.

Jan 1, 1941

By R. Schumann

THE expression "unit process " comes up with increasing frequency in discussions among metallurgists and mineral engineers, especially among those concerned with training the next generation. The unit process approach characterizes a significant advance along the road from metallurgy as an empirical art to metallurgy as a branch of engineering. The purposes of this paper are to define and list the unit processes in specific terms, to indicate the scientific and engineering principles basic to all the unit processes, and finally to show how these ideas have been applied to a reorganization of instruction in chemical metallurgy. UNIT OPERATIONS AND UNIT PROCESSES Metals are extracted from ores and other raw materials by stepwise procedures. In general, each metallic element is extracted by a different procedure. For many of the metals there is a choice of several flowsheets. However, the procedures all have steps in common. In fact, the many different flowsheets are all made up of a relatively small number of steps which are combined in different groups and sequences. For example, crushing, screening, roasting, sintering, melting, and gaseous reduction are steps which each appear in the flowsheets for extracting the majority of the metals. The individual steps or flowsheet units can be designated as unit operations or unit processes. These terms are well established in the field of chemical engineering, as the American Institute of Chemical Engineers' definition of chemical engineering shows: " Chemical engineering is that branch of engineering concerned with the development and application of manufacturing processes in which chemical or certain physical changes of materials are involved. These processes may usually be resolved into a coordinated series of unit physical operations and unit chemical processes. The work of the chemical engineer is concerned primarily with the design, construction, and operation of equipment and plants in which these unit operations and processes are applied. Chemistry, physics, and mathematics are the underlying sciences of chemical engineering, and economics its guide in practice."1a In this definition, the distinction between unit operations and unit processes is that the unit operations are physical while the unit processes are chemical. Table I gives a list of the principal unit operations and unit processes of chemical engineering, taken from Shreve. lb Table 2 lists the principal unit operations and unit processes used for metal extraction. The division between unit operations and unit processes is similar to the chemical engineers' distinction and also corresponds approximately to the division of labor between mineral dressing and chemical metallurgy which has been customary in the past. Furthermore, it will be noted that in the proposed classification the unit processes primarily involve chemical reactions and/or changes in state of aggregation; the unit operations, primarily do not involve either bulk

Jan 1, 1948

By AIME AIME

FOR the development of a mine, a shaft of small cross-section is usually sunk, of no larger size than is absolutely necessary. After the mine has been developed and put on a production basis it is a common practice to sink a shaft of larger cross-section for hoisting and use the original shaft for the handling of men and material into the mine. While that ar¬rangement is usually expedient, the small size of the supply cages presents a problem in the handling of ma¬terial. Where a cage is, say, 4 by 4 ft., which is not an uncommon size, all lengthy and bulky material must be handled piece by piece several times from the supply department to the underground stations. Thus drill steel and timbers over 4 ft. long will be loaded on cars at the supply department and wheeled to the shaft, where each piece must be unloaded from the cars and stood up in the cage. They are then lowered to the shaft station, unloaded piece by piece and placed in cars, run to the supply station and again unloaded and stored until called for. In such a case handling becomes a major item in the cost of supplies.

Jan 1, 1930

By Frank A. Wardlaw

MY subject covers the effect that recent metallurgy has had on operations at the Utah-Delaware mine. This mine is the old Highland Boy mine of Bingham Canyon, Utah, one that has now been in operation for about 30 years. It was first operated by Messrs. Weir and Newhouse as a gold mine, under direction of the Highland Boy Gold Mining Co. The ore was oxidized gold ore and it was treated on the property in a cyanidation plant. During the process of development, sulfide ore was found assaying about 5 per cent copper. It proved to be the discovery of what is yet the largest sulfide copper orebody in the State. The first shipment was made in December, 1896. A smelter was built in Salt Lake Valley to treat this ore and not long after the property was sold to the Utah Consolidated Mining Co. From 1900 to 1924, the mine was a large producer of direct-smelting ore which averaged for many years 4.5 per cent. copper, then later dropped to 2 per cent. copper. During the years 1912 to 1920, direct-smelting lead ore was also mined. In 1918'and 1919 ore developments at depth showed a decided increase in silica content and a porphyry sill so closely associated with the ore that it was impossible to mine the ore clean and it was found necessary to build a copper flotation Eoncentrator at Tooele. The mill had a capacity of 1000 tons a day and made a recovery of 90 per cent., and would have been responsible for a continuance of profitable operations had it not been for a slump in the copper market and the necessary high cost of mining ore on the lower levels. RESULTS OF SELECTIVE FLOTATION In 1924 the mine was on the point of a shutdown which had all the earmarks of being permanent; it was being operated at a heavy loss and preparations were made to pull the pumps and salvage the machinery. The plant at Tooele was remodelled for selective flotation by the Inter- national Smelting Co. in order to treat custom ores, and incidentally to clean up a possible 10,000 tons of lead-zinc ore which it was thought possible to get in the Utah-Delaware before shutting the mine down. Results were so encouraging that an effort was made to develop more lead-

Jan 1, 1928

By Paul F. Kerr

The uranium-producing areas near Marysvale, Utah provide an unusual group of veins and replacement deposits associated with a Pliocene-Oligocene intrusive and extrusive igneous complex. Aside from several scattered occurrences in older volcanics, uranium-bearing veins occur in intrusive quartz monzonite or granite and in nearby rhyolite. The veins in general trend within a few degrees of N55-65°E, are more or less vertical, and are found along the western margins of a quartz monzonite intrusive. The replacement deposits are found in rhyolite intrusives and also in the lower portions of rhyolite flows close to places where veins forming solutions rising through quartz monzonite came into contact with the rhyolite. At least 14 veins have been mined since uranium mining operations began at Marysvale some 16 years ago, while ore has been extracted through about 10 miles of underground workings. The active mmmg area is approximately 3000 feet long and in the central portion 1500 feet wide. Ores have been found over a vertical spread of almost 2000 feet, between the highest occurrence on Jungfrau Hill ( ca. 7200 feet) and the deepest discovery of ore in a drill hole near the Prospector Mine (ca. 5200 feet). Under existing mining and marketing conditions, mining along the veins in the main area appears to have reached an economic limit at about 500-600 feet below the surface. However, orebodies in the rhyolite and in the upper portions of veins close to the rhyolite are subject to active mining. Isotopic dates indicate that the uraninitebearing veins and replacements are late Miocene or Pliocene (ca. 10-13 m.y.), the rhyolite is Miocene (avg. 17.5 m.y.), and the quartz monzonite and granite intrusives are late Oligocene (23.6 to 26.0 m.y.). The older Bullion Canyon Volcanic Series which encircles the area is Oligocene (28 to 31.1 m.y.). Two generations of alteration occur: ( 1) Earlier alunitic veins and replacement bodies are found in the Bullion Canyon Volcanic Series, none of which have produced uranium; (2) Later argillic alteration associated with the introduction of uranium is found along veins, replacing glassy rhyolite dikes and replacing phases of the rhyolite.

Jan 1, 1968

By Eugene Guccione

Evidence that the United States is gradually converting to the metric system of measurement can be perceived today even by housewives in a supermarket. The question is no longer whether but when the country will have completed the conversion. To the extent that any bickering about metrication still exists, the debate now centers on such issues as finding agreement on details of implementation, and whether federal legislation should speed up the metric-conversion process or allow it to proceed along its present evolutionary and voluntary course. Apparently, the voluntary or "make-haste-slowly" approach is gaining widespread support. According to The Research Institute of America, Inc., if and when federal legislation is enacted it will likely include the following national ground rules: (1) A National Metric Conversion Board will develop and submit to the President and Congress a comprehensive plan to achieve a coordinated, minimum-cost changeover. (2) The change- over will be completed 8 to 10 years after the board's plan goes into effect, and by that time the US will be predominantly, though not exclusively, metric. (3) Costs will "lie where they fall"; subsidies, special tax concessions, and antitrust exemptions will not be authorized by the legislation. (4) The changeover will be voluntary because of the recognition that while some firms can "go metric" in a matter of weeks, others may require 15 years or more, and a few might never convert. (5) In determining whether or not to convert, on an individual company basis, adherence will be to the "rule of reason-that is, ". . . do not convert unless the engineering, economic, or other benefits outweigh any metric-related disadvantages. No one is talking about rip- ping up our railroad tracks or rewiring our homes just to conform to the practice of metric nations in Europe." (6) Government is to be part of the solution, not part of the problem; in effect, says The Research Institute of America, the leverage of federal procurement will not be exerted to force-feed the metric changeover but will be coordinated with the sector-by-sector conversion of the economy.*

Jan 12, 1975

By C. M. Means

CONSIDERING the hazard involved in mining operations, statistics show, that a very small percentage of accidents is chargeable to electricity. These accidents do represent quite a large percentage of those that are preventable and they are the direct result of the introduction, for purely economical reasons, of a dangerous element. The introduction of electricity in mines should decrease the hazard, and in no case should electricity be applied to the mechanical operation of equipment if by so doing the dangers incidental to mining are increased. The greater number of accidents are the result of persons coming in contact with exposed conductors at potentials varying from 250 to 500 volts direct current. The use of alternating current at higher potentials than these is quite common in large mines, but it is very rare that an accident happens from this source. This is explained by the fact that where these high voltages are warranted, proper precautions are taken, and the installations are directed by those who fully appreciate the dangers incidental to the work. Direct current is in much more general use than alternating current because of its adaptability to haulage locomotives and the low cost of installation in small operations. We are, however, coming to a more extended application of alternating current for the operation of mechanical devices used in connection with mining. Our underground direct-current wiring system is an evolution from the surface trolley and feeder systems. This is probably due to the fact that our earlier successful applications were electric locomotives, which required the use of a trolley wire. The trolley current has been almost banished from industrial establishments on the surface because of the hazard involved, yet we use it indiscriminately underground, where the dangers from accidental contact or fire are infinitely greater. This does not mean that the underground trolley systems should be eliminated, but it does imply the proper safeguarding of such equipment as is necessarily a part of the trolley systems.

Jan 4, 1914

By Galen Clevenger

TELLURIUM has had the rare and unpleasant distinction of having fewer uses than any of the other common elements; indeed, it has had no regular or important uses. It is not only a useless and disagreeable element, but to the metallurgist it has been a nightmare. The interference of tellurium with the recovery of gold and silver from certain ores, as well as the difficulties it occasions in the electrolytic refining of copper, lead, and silver, are too well known to require enumeration here. In fact, the potential producers of the element have been quite willing to throw the crude products from which it might be recovered into the sewer. First isolated from a gold ore in 1782, although remaining a practically unknown element to the general public, it has long been a guiding star to the Western prospector in his quest for the "golden fleece." On the burning sands of the desert, in the frigid North, and in the mountain fastnesses of the more temperate regions of this and other continents, he has endured all manner of hardships in his search for tellurides; for where he found indications of tellurium, there he expected also to find rich deposits of gold and silver. This peculiar superstition, that tellurium, associates itself in nature with the precious metals, is not with-out reason, for witness the fabulously rich gold tellu-ride deposits of Cripple Creek and Western Australia. Selenium, the sister element of tellurium, which it resembles in many of its properties, was first isolated in 1817. It is found in small amounts in certain native sulfur deposits, and in many copper and silver ores from all parts of the world. Until a few years ago, selenium, like tellurium, was practically useless. The, unusual property of having its electrical conductivity influenced by light has long been known. Selenium cells, which for many years have been a scientific curios-ity, in the future may come to be of more commercial importance, but this use could scarcely absorb any large amount of the element.

Jan 1, 1923

By Percy Barbour

The town of Goldfield, Nevada, with the exception of six stone buildings, was burned to the ground to-day. One man is dead from causes attributed to the fire. A woman is missing and is believed to have perished and several persons were treated for burns as the result of the conflagration believed to have been of incendiary origin which started in the old Tenderloin District. The water supply was not sufficient and dynamite only scattered the frame structures and added kindling to the flames which were fanned by a forty-mile wind. Newspaper Dispatch, July 6. No former Goldfield resident could read that dispatch with unmixed feelings. About two o'clock one morning the crowded train from San Francisco landed me in Goldfield no more hours late than it habitually was. The desert air was clear and crisp and bracing but the pandemonium of cab and bus drivers did not drown out the sounds of music and merriment which floated from the blaze of light which was Goldfield about three-quarters of a mile from the station. As I stood in the ferry house, at the foot of Market Street, awaiting the Oakland Ferry, an old friend of mine, down to see who was departing for the greatest boom town of this generation, informed me that if I had made no reservation for quarters in Goldfield, I would be unable to obtain any, even chairs in the hotel lobbies were renting for $4 per night, and volun-teered the use of his room there for my convenience until his return. He described the house and location, which I identified without difficulty, but found no one to direct me to the room. I peered through a glass door into a room which seemed to be unoccupied and timorously entered and turned on the electric light., I found mail on the dresser addressed to my friend,

Jan 8, 1923

By Gilbert Doan

AN extensive program of investigation is being carried out at Lehigh University in the study of arcs and arc welds of high-purity iron1, spon-sored by the Engineering Foundation. The part of that program reported in the present paper deals with welds made of high-purity iron in an argon atmosphere and for comparison with them welds made of the same iron in ordinary air. Welds of commercial steel also were made in argon and in air. The primary purpose of the study is to discover the basic physical constants of iron welds when not contaminated either by impurities in the iron or by the action of oxygen and nitrogen of the air during welding. Upon these constants can be founded such future studies as will determine what effects the various impurities and alloy elements present in steel have upon its welding characteristics, and what influence is exerted by the action of oxygen and nitrogen. The welding of steel involves such a multitude of variables, both of composition and of procedure, that development in the fabrication of this most important metal has necessarily been slow, wasteful, and in many instances discouraging. In the present investigation, the simplest possible condition has been selected; namely, iron practically free from contamination and a nonparticipating atmosphere, the inert gas argon. This simplification reduces the number of variables to a point where more rigid control of the system is possible. Although this study is significant for the contributions it makes to the science of steel fabrication, yet it is hoped that it will not be without value also in increasing knowledge of the nature and behavior of iron and steel in general. From the standpoint of open-hearth practice, and to

Jan 1, 1936

By R. C. Ku, A. J. McEvily, T. L. Johnston

The microplastic response of a series ofas-quenched Fe-Ni-C martensites has been measured at 77°K. At strains less than JO'3 the flow stress is governed primarily by the transformation-induced dislocation structure of the martensite. Only at strains in excess of 10-3 is the influence of carbon manifested in the flow stress. At these macroscopic strains, typically 10-2, the solid-solution hardening is proportional to (wt pct C)1/3, and, in an alloy containing 0.39 wt pct C, amounts to 50 pct of the flow stress. THE technological significance of high-strength ferrous martensite has stimulated many investigations of its structure and properties. Although our knowledge of the characteristics of martensite has increased immensely, especially with the advent of high-resolution techniques, an understanding of the basic strengthening mechanism still remains elusive. The purpose of the present paper is to consider certain aspects of micro-plastic behavior of Fe-Ni-C martensite which we feel can help to resolve this important problem. Such alloys are particularly suitable for experimental investigation because their compositions can be adjusted to reduce the M, to a temperature low enough essentially to eliminate the diffusion of carbon in the freshly formed martensite.1 The mechanical properties in this condition are of interest inasmuch as they reflect a state that is free of the important but complicating influence of precipitation processes. In this virgin martensite the carbon is distributed as it was inherited from the parent austenite; i.e., it is present interstitially, and gives rise to tetragonality through strain-induced ordering.' In order to determine the source of strength of such alloys, Winchell and Cohen1 investigated the low-temperature macroscopic stress-strain behavior of a series of virgin martensites of increasing carbon content but of common M, temperature (-35°C). They found that the flow stress increased rapidly with carbon content up to 0.4 wt pct; beyond this point the flow stress increased at a much slower rate. It was concluded that martensite is inherently strong. To account quantitatively for the strength of virgin or as- quenched martensite in terms of the role of carbon, Winchell and cohen3 suggested that the carbon atoms, trapped in their original positions by the diffusionless martensite transformation, interfere with dislocation motion according to a model akin to that of Mott and Nabarro. 4 In this treatment, individual carbon atoms are considered to constitute centers of elastic strain and thereby generate an average stress resisting the motion of dislocations throughout the lattice. The additional stress necessary to move dislocations, over and above that necessary for motion in a carbon-free martensite, is given by where L is an effective length of dislocation capable of motion. L was assumed to be limited to the spacing between the twins that are an essential structural element of Fe-Ni-C martensites. They assumtd the spacing to be invariant and of the order of 100A. However, recent work5 has shown that L is variable and can be in excess of 1000Å, so that the assignment of an appropriate value of L is not straightforward. In contrast to the above conclusion that there is an intrinsically high resistance to plastic flow, it has been suggested by Polakowski6 that freshly quenched martensite is in fact "soft" in the sense that dislocations are initially free to move upon application of stress. The high indentation hardness and macroscopic yield stress of ferrous martensites are then a consequence of rapid strain hardening that depends upon carbon in solution. Consistent with this point of view are the results of Beau lieu and Dubé who measured the rate of recovery of internal friction as a function of aging (tempering) temperature in a freshly quenched steel containing 0.90 wt pct C, 0.37 wt pct Mn, 0.1 wt pct Cr, and 0.07 wt pct Ni. The kinetics were clearly consistent with the idea that many dislocations are unpinned in the as-quenched state and that during aging they become progressively pinned by carbon at a rate controlled by carbon diffusion in the body-centered martensite lattice. In order to provide a basis upon which to distinguish between the "hard" and "soft" interpretations indicated above, we have made studies of the initial stages of plastic deformation in Fe-Ni-C martensites similar to those'used by Winchell and Cohen. It will be shown that the results support the contention that dislocation segments in as-quenched material are indeed

Jan 1, 1967

By R. A. F. Penrose

I. INTRODUCTION. THE superficial alteration of ore-deposits is a recognized principle of geology, in the same way as is the superficial alteration of any of the common rocks. Its importance in some classes of ore-deposits is also well understood, as in many precious-metal deposits; while in other classes, its importance has been proved in individual cases, as in the Lake Superior iron-deposits. The causes and effects of superficial alteration in many classes of deposits, however, are not so generally understood; and it is the object of the present paper to show that such changes almost invariably give rise to exceedingly important chemical and physical phenomena, while in many deposits, the question as to whether they can or cannot be profitably worked depends largely on the extent and character of this alteration. The various treatises on ore-deposits published in the United States and Europe make frequent mention of superficial alteration, but have not treated the subject fully. As early as 1554, however, before which time but little accurate information was had on the geologic nature of ore-deposits, Prof. J. D. Whitney in his classic volume, The Metallic Wealth of the United States, describes the alteration-products, or gossans, in certain deposits and mentions others. On the more purely chemical side of the question, the work of Bischof, Daubrée, Roth, Rose, Hunt, Breithaupt, Blum, Julien, Deville, Debray, Volger, Moissan, Fremy, Lévy, Fouqué, and others has afforded much valuable information and many useful suggestions. The chemical principles brought out by these various authors have been applied, to a certain extent, to the solution of the phenomena of

Jan 1, 1913

By W. S. CAYPLESS, H. O. Hofman, E. E. HARRINGTON

1. INTRODUCTION. AT the Lake Superior meeting, September, 1904, Messrs. A. Gibb and R. C. Philp presented a paper entitled " The Constitution of Mattes Produced in Copper Smelting,)' in which they concluded that ferrous and cuprous sulphides formed the chemical compound, 5 Cu2S, fee. They arrived at this inference from the observed fact that a matte containing Cu2S, 90.4, and Fee, 9.6 per cent (or, in round figures, Cu2S, 90, and Fee, 10 per cent.), did not contain any metallic copper, while one with more than 10 per cent of FeS readily dissolved copper, and with less than this amount retained copper in mechanical suspension. Although they determined the melting-points of five mattes containing from 32.6 to 80.1 per cent of copper, they did not draw a freezing-point curve, as the necessary apparatus was not available. A microscopical examination of 11 polished samples, gave them a grayish-black field of very uniform appearance, except that 5 of the specimens showed the presence of metallic copper. The object of the present investigation was to supplement the above paper by drawing the freezing-point curve of the series ferrous sulphide cuprous sulphide, and to see how the constitution could be further, revealed by microscopical work. The results obtained lead to conclusions very different from those of Gibb and Philp. While their paper bears the date 1904, it was published only in 1906.2 In the meantime, Bolles3 had presented his paper, "The Concentration of Gold and Silver in Iron Bottoms." The raw material which formed the basis of the research was a matte containing Fe, 61.68, and Cu, 11.20

Jan 1, 1907

By WILLIAM BOWIE

THE development of the isostatic idea during the last century would make an interesting paper in itself. But the various steps in the development have been covered in a number of papers and books which are readily available. Therefore this short paper should not give space to. the historical phases of the subject. Isostasy is really an old idea, but it is only in the last few decades that it has taken on any great prominence or importance in the study of earth phenomena. It is really remarkable how closely Dutton' sensed the isostatic principle 40 years or more ago. His general principles of isostasy as outlined by him have stood the test of time and fit in closely with the general ideas held today. It would seem, however, that some of his views with regard to the application of isostasy to geological processes must be modified or abandoned.

Jan 1, 1930