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The Library of the above-named Societies is open from 9 A.M. to 10 P.M. on all week-days, except holidays, from September 1 to June 30, and from 9 A.M. to 6 P.M. during July and August. The Library contains about 55,000 volumes, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library can render valuable service through correspondence; letters requesting information will receive special attention. The Library is prepared to furnish references and copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information as to the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not, include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape. The members of the Institute can be of service to the Library by forwarding copies of mining reports, maps privately issued, and similar material, which will be classified, indexed, and made available to other members. Suggestions for additions to the Library, either by purchase or personal solicitation as gifts, will be welcomed. It is hoped that members while in the city will use the Library freely, and assurance is given that most careful service will be rendered to them.

Jan 9, 1915

By D. G. Brubaker

IN the history of geophysical exploration by the electromagnetic method many procedures and types of equipment have been used. Source arrangements for surveying on the ground have included long wires grounded at both ends, large loops laid on the ground, small horizontal loops, and vertical loops of moderate to small sizes. Receivers have ranged from simple direction-finding coils to combinations of coils and a bridge circuit to measure quantities related to both amplitude and phase of the received signal. Primary considerations in choosing a survey method are effectiveness, speed, and economy. In work on the ground in which locating and out- lining conducting bodies is the objective, methods using a vertical coil and a simple direction-finder have been found the most satisfactory. Mason1 and his associates applied such a method by setting up a vertical source loop, fed with low frequency alternating current by an engine-generator set. With a direction-finding receiver they surveyed lines along the ground in the plane of the loop, taking measurements at each station of the azimuth and inclination of the magnetic field direction. Deviations of this direction from the normal direction, that is, from horizontal and perpendicular to the traverse line, indicated a conducting body. Recent advances in design of light-weight generating equipment have encouraged using this and similar methods.

Jan 7, 1957

By H. A. Schwartz

By analyzing cementite separated electrolytically from white cast iron of known composition and history, the distribution of silicon between austenite and cementite during and after freezing has been followed. The results constitute a contribution to our knowledge of equilibria in the ternary (metastable) system iron-carbon-silicon. Incidental information was obtained, also, with respect to the distribution of manganese, silicon, and phosphorus, when only relatively small amounts of each are present. The major conclusion of the paper is that during solidification, equilibrium is attained when the silicon is all rejected to the liquid phase, permitting silicon-free austenite to separate. OF THE outstanding investigators of the system iron-carbon-silicon, Gontermann,1 Charpy and Cornu-Thenard,2 and Honda,3 only the first touched on the chemical composition of the solid and liquid phases in equilibrium with one another. He concluded that his data did not permit a decision as to which of an indefinitely large number of pairs of compositions of liquid and solid would be found in any given case. If through the three dimensional equilibrium diagram of the iron-carbon-silicon system an isothermal plane is passed in the region of partial solidification, two lines of intersection with the liquidus and solidus, respectively, are obtained, also a point marking the alloys' composition. If, in this, plane, a straight line is drawn through the point, and intersecting both the liquidus and solidus isothermals, the two intersections mark a liquid and a solid alloy that may be chemically in equilibrium at the chosen temperature. From thermal data alone, Gontermann could not assign any particular direction to the line and, hence, could not determine which pair of conjugate points to choose.

Jan 7, 1924

By W. Scott Dunbar

INTRODUCTION Methods of linking boundary integral (BI) solutions with finite element (FE) solutions have been well described theoretically in other publications (e.g., Zienkiewicz, et al., 1977). The purpose of this paper is to point out some practical aspects of implementing these linkage algorithms for rock mechanics applications and to describe an alternative linkage algorithm. A not so obvious motivation for using FE-BI linkages is illustrated in Figure 1. The cost of modeling the excavation of the crusher station by the BI method can equal or exceed the cost of an equivalent FE model. This is due to the large surface area which must be modeled by the BI method. In such cases, a more economical approach might be to model the region immediately adjacent to the crusher station by finite elements and link the solution at the periphery of the FE model with a solution for the exterior region. Further economies can be realized if some flexibility in the type of exterior solution is possible. For example, it would be desirable to use a coarse discretization of the FE-BI interface for a BI solution, which would be less demanding of computer storage and time, or to use an analytical solution for the exterior region. The alternative linkage algorithm to be discussed allows such flexibility. BOUNDARY INTEGRAL METHODS There are basically two formulations of BI methods: the direct and the indirect. FE-BI linkage algorithms depend on which formulation is used. The purpose of this section is to briefly describe each method.

Jan 1, 1982

By I. Iwasaki

In the flotation of iron ores and nonmetallic ores desliming is the key to a successful operation; the technology of flotation of well-deslimed ores has become fairly well established. When finely disseminated ores are ground to liberation, however, conventional desliming of the fully dispersed pulp results in an excessive loss of valuable constituents. Selective flocculation of iron oxides followed by removal of dispersed siliceous slimes is a new development and is one of the most promising approaches to the treatment of finely disseminated, oxidized iron ores, available in vast quantities both here and abroad (1,2,3). To apply selective flocculation to the variety of refractory iron ores or to cope with the fluctuations in an individual ore and the make-up water, the factors governing this technique must be clearly formulated. For the removal of siliceous and clayey slimes from oxidized iron ores by selective flocculation, the optimum conditions are extremely sensitive to the mineralogical characteristics of the ore, the type and the amount of soluble salts in pulp solutions, and the mesh-of-grind. Certain starches appear to function better than others (4, 5). Selection of the proper reagents and their judicious use is important not only for their efficient utilization but also for minimizing the adverse effects they might exert on the flocculation and flotation steps, and the pollution the effluents might cause when discharged, either intentionally or accidentally, into lakes and streams. In the present article some of the major factors that influence the selective flocculation of iron ores are summarized.

Jan 1, 1979

The War Department is appealing to skilled workmen and scientifically or technically trained men to enlist in any one of a large number of engineering troops needed for immediate action in France. Any registrant under the selective service law, who has not actually been called to service, may be immediately inducted into an engineer organization at his own request. Application for induction should be made to the Chief of Engineers, giving a complete statement of the applicant's qualifications. Any man who is physically qualified, between the ages of 18 and 21, or between 31 and 40, may voluntarily enlist for an engineer organization, provided he proves to the recruiting officer that he is experienced or skilled in any engineering trade, or is a handy main who is' especially suited for engineering work. There are about 600 recruiting stations in the United States, and an officer at any one of these will enlist a candidate for an engineer organization if he is suitable. Enlistment is in the grade of private. Subsequent promotion to the rank of non-commissioned officer is secured by merit. It is intended to fill many of the vacancies which will occur from time to time among the commissioned officers by selection from the ranks. A few of the special services, of most interest to mining and metallurgical workmen, urgently needed by the army, are as follows: Crane Operating and Maintenance Regiments; Depot Detachments; Electrical and Mechanical Regiments; General Construction Battalions; Mining Regiments; Quarry Regiments; Battalions for the construction, maintenance, and operation of railways; Road Building Battalions; Sapper Regiments; Supply and Shop Battalions; Surveying, Ranging and Map Reproduction Regiments; Water Supply Companies; and many others. All of these organizations will be assigned to such duties as competent

Jan 4, 1918

By Heinrich Ries

The manufacture of fire-brick represents one of the oldest branches of the clay-working industry in New Jersey, and is of more importance than is commonly imagined. The New Jersey clays were first used for fire-brick after the war of 1812, and one of the earliest records, according to Professor Cook, shows that clay was taken from Woodbridge to Boston in 1816, arid used for that purpose. The value of the clays of the Woodbridge district does not seem to have been well and widely recognized for some years, however, although in 1855 the statistics, given in the Geological Report, show that clay for making 50,000,000 fire-bricks was then taken annually from the pits at Woodbridge, Perth Amboy and South Amboy. Perhaps the oldest works in the State was that known as the Salamander works (no longer in existence), where brick were made as early as 1825. A little later, in 1836, John R. Watson established a factory at Perth Amboy, and in 1858 Sayre & Fisher began the manufacture of fire-brick at Washington. The works of W. H. Berry at Woodbridge began operations in 1845, and have continued up to the present clay, although in 1896 the name was changed to J. E. Berry. The works of Henry Maurer & Son were established in 1856, and those of M. D. Valentine & Brother in 1865. These latter were started for making bath brick; later, sewer-pipe, and, finally, fire-brick and other refractory shapes were produced. A branch-works, located at Valentine on the Central railroad of New Jersey, was started in 1887. Even in the last two years several works have begun the manufacture of fire-brick. These include factories erected by

Jan 1, 1904

By Fred P. Dewey

Early last March Mr. Jerome Coldren, an old miner add prospector, undertook a prospecting tour through the western part of Kansas, and discovered a very peculiar bed of rock, which yielded a white metal on fusion with soda. Mr. W. D. Church, city chemist at Topeka, examined the metal and found it to contain nickel. This discovery created much excitement, and was at first doubted. Many samples of the material, from a range of twenty miles, were sent to the Smithsonian Institution for examination ; and in every instance a qualitative test showed the presence of nickel, although the amount appeared to vary greatly. The ore is quite different from any other nickel-ore. It consists of a quartzose conglomerate from bean-size down, with much decomposed material between the pebbles, and the whole cemented by a more or less manganiferous limonite. In the qualitative tests, the nickel appeared to vary with the manganese. In all the tests, simple treatment with HCI dissolved a great deal of AI2O3. The principal deposit is near the top of a small hill on the divide between Smoky Hill river and Butte creek. The surface-rock is the conglomerate, and, at varying distances, stains of the limonite appear and gradually increase ; so that the ore is simply the lower portion of a bed of conglomerate which has been heavily charged with the manganiferous limonite. Below the conglomerate is a layer of selenite; below this, a soft sandstone, containing well-preserved fossils, and below the sandstone, a shale. From 2 to 6 per cent. of nickel in selected samples has been reported by different chemists; but the following two analyses on large samples show the average composition of the material:

Jan 1, 1889

By H. H. Campbell

In the extending employment of open-hearth steel for structural purposes, it is a matter of prime importance that the test-piece shall represent with practical accuracy the characteristics of every portion of the heat from which it comes. In ordinary practice this homogeneity is assumed; but inasmuch as leading exponents of the revolving-hearth system have claimed that a reasonable uniformity could be obtained by their method alone, it may be pertinent to offer a few facts on the subject. The following heats made by the Pennsylvania Steel Company, for bridge-work, were tested by casting two four-inch ingots, one being taken during the first third and the other during the last third of the cast. Test-pieces obtained from these small ingots usually give results inferior to those obtained from larger sizes; but for purposes of cornparison they are equally conclusive. Many of the tests were made for experimental purposes within a few hours of the time of rolling, and before sufficient time had elapsed for the usual molecular redistribution necessary for the best results. All the tests were made on 3/4-inch rounds just as they left the rolls and without annealing; the results, therefore, are subject to the errors caused by variations in the diameter, and in the temperature at which the bar was finished. The tests from any one heat, however, were always nude as nearly as possible under the same conditions; and inasmuch as these data include the results of every heat so tested, and inasmuch as the errors could not by any chance always support any single theory, we may be certain that the unanimons testimony of the experiments indicates a valid conclusion.

Jan 1, 1886

By Robert Glass Cleland

THE CLOSING years of the nineteenth century witnessed a rapid expansion in Phelps Dodge activities in Arizona and other parts of the Southwest and a corresponding decline in its exporting and importing interests in New York. Before the close of another decade, this process had gone so far that the company was committed lock, stock, and barrel to its western undertakings. By 1910 the evolution that began with the tentative investments at Bisbee and Morenci was complete. An enormous increase in the domestic production of iron and copper, which made it increasingly difficult to find markets for imported cargoes of those metals from English mills, accounted in part for this radical shift in Phelps Dodge activities and interests. In the case of tin plate, the change was even more spectacular. In 1890 a seventh of the world's supply of pig tin passed through the hands of Phelps Dodge agents. In 1906, thanks chiefly to the McKinley Tariff of 1890 which imposed a duty of over two cents a pound on tin plate imported into the United States, the company received its last shipment of tin from England, and thus ended a form of

Jan 1, 1952

By Nobuhiro Takahashi

PROLOGUE The Yaguki mine, which is located near the southern end of the Tohoku region, Japan, near the coast of the Pacific Ocean, had had a long history as a copper mine, but had not been operated since 1925. About 30 years later it was reopened by Nittetsu Mining Company, and in 1958 a small flotation and magnetic separation plant, a so-called test plant, started production. The ball mill the author first met, a 8x4x4x7 ft tricone mill, called No.1 mill, had started running at that time. With his experience in initial, running of this mill he realized that the ball mill was not simply a preparatory process to flotation, but a determinant factor for flotation performance, an energy-consuming and costly process, and that its operation control was an important task in the plant (1). The working part of an operating ball mill is the ball load inside, whose properties govern the grinding performance. Its size distribution affects the efficiency greatly and the capacity is nearly proportional to its weight. When a ball mill operates for a long period of time with a constant and consistent addition of renewal balls, wear and renewal of balls are balanced, and an equilibrium ball load is formed. A stable equilibrium load is the primary requirement for a stable ball mill operation. However, renewal ball size would be the most influential factor affecting efficiency and capacity of operating ball mills. To improve efficiency, to increase capacity, or to get finer product, attempts to find out the optimum size assortment of renewal balls should be made. When re-

Jan 1, 1976

By Kermit Allen

Historically, major natural gas transmission companies have been faced with the problem of meeting peak demands when the source of natural gas is located hundreds of miles away from the marketing area. Transcontinental Gas Pipe Line Corp.'s position was further complicated when offshore gas supply wells were shut-in during hurricane alerts. Transco's solution to this problem was the construction of salt storage wells adjacent to their pipeline near Eminence, Miss. Storage caverns were constructed using conventional solution mining methods. Two 13 3/8-in.-diam cased wells were completed and a 1,000,000-bbl cavern was leached at an interval of 5700 to 6700 ft at the base of each well. The two caverns have a usable storage volume of 2.0 billion cu f t and each well has a deliverability rate of 375 million standard cfd. The caverns are unique in that brine is not used for product displacement-all brine has been removed from the caverns. Natural gas is stored at a maximum pressure of 4000 psia. During withdrawal the cavern pressure drops to a minimum of 1225 Asia-the volume of gas between these two pressures becomes "usuable or top gas." The Eminence storage terminal is located on the Eminence salt dome about 30 miles north of Hattiesburg, Miss. Construction began in July 1968 and was completed in October 1970.

Jan 1, 1972

The Institute makes liberal provision for inclusion of engineering students through individual Student Associate membership. Such members pay $2 per year, receive MINING AND METALLURGY, may purchase Technical Publications at reduced rates, have the privilege of attending all meetings and are furnished a distinctive badge in the form of a watch fob. Provision is also made for the affiliation of organized student societies in recognized schools of engineering chemistry, geology and related sciences. In order to qualify for affiliation it is not necessary that all members of the society become Student Associates since the individual members of the society are not listed as members of the Institute However, a large majority of the members of many of the societies are also Student Associate Members of the Institute. Among the things that the Institute does for the affiliated societies are the following: (a) A copy of each issue of MINING AND METALLURGY is furnished to the society; (b) Reports of the meetings and activities of the society are reported in MINING AND METALLURGY; (c) Assistance is given by the Institute in obtaining speakers for the meetings of the society; (d) The name of the society and of its officers is listed in the annual Directory and other publications of the Institute; and (e) Members of the society are given the use of the Engineering Societies Employment Service. Student organizations, desiring to be recognized as affiliated student societies of the Institute, should make application to the Secretary, giving particulars as to the nature of their organization, of their membership, and their officers. The accom¬panying list on page 24 gives the names of the affiliated student societies, their presi¬dents and their secretaries, as of April 17, 1931.

Jan 1, 1923

By Frank Hall

THE needs of the World War showed the necessity of a metal stronger than cast iron which would supplement the supply of steel. So patriotic metallurgists were spurred to new efforts to improve the status of that half-breed of the metal world that had been, more or less erroneously, christened semisteel. As a result, it was developed that for certain purposes semisteel was superior to steel in the manufacture of shells. Steel, because of its greater strength and toughness, is able to carry a greater charge of explosive, weight for weight; consequently, a steel shell can be expected to cause greater destruction when used against fortifications or other inanimate objects, while semisteel, because of its comparative brittleness and its resulting greater fragmentation, is capable of inflicting more serious loss of life when used against opposing forces of men. Therefore, each has its proper place in the economy of war. For the present purpose, steel may be defined as a comparatively pure iron whose physical nature is modified by small amounts of carbon, silicon, sulfur, phosphorus, manganese, and possibly other rarer elements; while cast iron generally is limited to approximately 93 per cent. of iron, the remainder consisting of larger percentages of carbon, silicon, sulfur, phosphorus, and manganese. Semisteel may be defined as cast iron in which the carbon and silicon have been reduced to as low a point as is consistent with maintaining the nature of gray iron, and in which the remaining elements are manipulated so as to give the greatest strength.

Jan 1, 1920

By Walter Miller

Developments in oil refining were so varied during 1938 that a refiner had to be alert or be left behind. The long-talked-of conversion of oil refining into a true chemical industry using petroleum as a raw material was hastened, particularly in the realm of motor-fuel manufacture, by the increased understanding and use of catalytic processes. The petroleum refiner's vocabulary has been extended to include alkylation, cyclization, aromatization, and isomerization. There are other devel: opments of a similar nature, but these are now considered commercially feasible under proper conditions. New Equipment Less expensive equipment and processes encouraged new construction and replacement. Estimates of money spent in the United States on building new plants and remodeling existing installations during 1938 place the sum at not less than $200,000,000, a noteworthy amount in a year marked by a business recession. The commercial application of small-scale catalytic polymerization of refinery gases made one of the latest advances available to the smaller operators, who usually are faced with unit installation and production costs higher than the large refinery enjoys. Competition was thereby fostered. Outstanding in this respect was the construction of two or more polymerization plants in small refineries at extremely low installation costs, with amortization measured in months instead of years. Houdry Processes Bursting like a bombshell late in the year was the disclosure of the extent of the development of the Houdry processes of catalytic cracking, viscosity breaking, gasoline treatment, desulphurization, and polymerization, said to be applicable to almost any raw petroleum stock and yielding gasoline of exceptionally high octane number. This process is claimed to be particularly adapted to once-through cracking of aliphatic hydrocarbons, and when combined with any of the conventional thermal

Jan 1, 1939

By K. G. Black, B. P. Faulkner

Laboratory batch flotation rests are used for comparison of the floatability of ores and for comparison of the effect of various treatments on ore floatability. Although it is difficult to predict exact recoveries for continuous flotation on the basis of batch tests, considerable quantitative information can be obtained through their use. A simple method is presented which provides a convenient means of quantitatively evaluating results from laboratory batch tests. The information obtained is in the form of a discrete flotation rate distribution, which, if desired, can be used directly in a simulation of continuous flotation. Equation of Batch Flotation The validity for batch flotation of the first-order kinetic equation is accepted: [ ] where k is flotation rate of a class of articles and W (t) is weight of particles of the class in cell at time t. Thus, at time t, the fraction of the original amount of the class of particles still remaining in the cell is [ ] where W (0) is weight of class of particles in cell at time zero. If there are several classes of particles in the cell, each with its own flotation rate, k4, the fraction of the particles remaining is [ ] where W (t) is now the total weight of n classes, a, being the original fraction of W (0) belonging to the ith class. Accordingly, [ ] [Fig. 1] shows the result of a typical batch test. Such result can be characterized by a set of particle classes, each set described by a flotation rate, [ki,] and a corresponding fractional magnitude, [ai.] [ ] Multiple Regression Equation Eqs. 3 and 4 may be combined to give

Jan 1, 1973

W. R. Ingalls, since 1905 editor of the Engineering and Mining Journal, retires from that position with the issue of Mar. 22, to open offices in New York City as a consulting engineer. The severing of this connection .will not be complete, however, as Mr. Ingalls will continue as consulting editor, and will handle the metal-market quotations in the Journal which are now the accepted authority for the government settlements of ore importations and the basis of practically all the ore settlements between miners and smelters throughout' the country. No greater compliment can be paid to Mr. Ingalls than this, unless it is the recognized fact that these quotations have been made what they are by his ability and his integrity, which secured for him channels of information vital to the accurate estimating of the market, but denied to anyone else. The Journal, under the. strong hand of Mr. Ingalls, has always been the acme of ethics in technical journalism, and the best wish that can he given to his successor, not yet announced, is that the Journal may long continue to live up to the standards not originated, but so consistently maintained and strengthened by Mr. Ingalls. His spelter statistics are accepted as authoritative wherever the English language is read and zinc ore is mined. He has found time during his very arduous years on the Journal to he the author of several works on the resources and metallurgy of zinc, lead, cadmium, etc.; for 5 years was the editor of Mineral Industry; and was consulting engineer for the Bureau of Mines and joint author of their voluminous and authoritative work on mine safety rules. His retirement from the Journal is a distinct loss to every one of the Journal's readers individually and to the profession as a whole. Universal good wishes go with Mr. Ingalls to his new field, which has for a long time been offering him professional attractions that his confining editorial work has not permitted him to accept.

Jan 4, 1919

By F. A. Forward, A. H. Ross, J. Halpern

IN treating carnotite ores by carbonate leaching it is often necessary to subject the ore to a prior roast. Among the advantages that may result from roasting are: 1) improvement in settling and filtering characteristics of the ore; 2) destruction of carbonaceous impurities that would otherwise contaminate the leach solution and consume carbonate reagent; and 3) substantial increase in extraction of vanadium, which is usually low when the un- roasted ore is leached. Recovery of vanadium may be an important factor in processing carnotite ores, and the fact that vanadium is usually recovered in good yield by acid leaching has often been an economic advantage over results obtained with carbonate leaching. It has been found that response of an ore to carbonate leaching, following roasting, depends primarily on its composition and on the conditions of the prior roast treatment, particularly with regard to the roasting temperature, the atmosphere maintained above the charge during roasting and cooling, and the presence of certain reagents. These factors, especially the last, virtually determine the extractions of uranium and vanadium attainable by carbonate leaching, as well as the reagent consumption on leaching, whereas adjustment of the leaching conditions has only a limited influence.

Jan 10, 1957

THE second award of the Saunders Gold Medal for "distinguished achievement in mining," of which the first was awarded last year to the late D. W. Brunton, has been made to Herbert Hoover. The main events of Mr. Hoover's life are so familiar to all through the numerous journal articles about him and his work, and the interesting biography written by Vernon Kellogg, that no attempt will be made here to touch on anything other than his achievements as a professional mining engineer, for which the award was made. He graduated in mining from Leland Stanford, Jr., University in 1895, but had served as an assistant to Dr. Branner on the Arkansas Geological Survey in 1893 and had also worked two sum-mers as an assistant to H. W. Turner and Waldemar Lind-gren on U. S. Geological Sur-vey work in the Sierra Nevada around Lake Tahoe, and on the American River. Immediately after graduation he got "a job" underground at Grass Valley, and soon rose to be night shift-boss. He then secured employment with the late Louis Janin and made such a good record as office and field assistant that he was soon placed in charge of a small mine at Carlisle, N. M. In 1897, Mr. Janin recom-mended him to Bewick, More-ing & Co., who were looking for an examining engineer for their staff in Australia. Two years were spent in hard work there which was done so creditably that his princi-pals held him and his judg-ment in the highest regard, and he came to the head of their local organization. Among the properties which he acquired for them was the Sons of Gwalia.

Jan 2, 1928

By R. B. Sosman

INTRODUCTION WE have shown in the preceding paper that practically all natural oxides of iron contain a determinable percentage of ferrous iron, and in many cases the percentage approaches that in magnetite itself. Some of these oxides are true homogeneous solid solutions. Others are not homogeneous, and can be separated magnetically into fractions. The nature and cause of this inhomogeneity in certain special cases form the subject of the present paper. MAGNETIC FRACTIONATION OF OXIDES OF IRON The magnetic fractionation of a sample of oxide can be conveniently carried out by powdering the material very fine, and exposing it at various distances from the poles of an electromagnet. The magnet that we used was specially designed 1 to give a strong field together with a steep gradient outside of the poles. It is set in a frame, with the pole pieces directed downward. A glass plate can be adjusted at various distances beneath the poles. If the fine iron oxide powder is placed just beneath the glass plate, successive portions of the powder are picked up by the magnetic attraction and are caught against the glass plate, the most magnetic portions being taken up at the greatest distance from the poles. Some natural oxides can thus be separated into several-fractious of different magnetic susceptibilities. Among other natural iron oxides, we examined the powder obtained by crushing some crystals of hematite from Elba.2 We found that

Jan 6, 1917