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By Philip McKenna

WHEN a new material becomes available to industry, it is useful to describe its properties as a guide to its most effective application; and when the new material may be produced in compositions having a series of graded properties, tests to select the combination of properties best adapted for various uses are helpful. The class of materials to be con-sidered in this paper are hard tool materials produced by processes of powder metallurgy from hard carbide constituents and various matrices of iron, nickel or cobalt, or alloys of them with tungsten, or tungsten and carbon. The customary use of carbide hard alloys is for metal-cutting tools; although wire-drawing dies, lathe centers, follow rests, grinding rests, burnishers, rolls, extrusion dies, measuring gauges and micrometers, and a number of other tools are also made with these hard alloys as the essen-tial wear-resisting parts. The properties and tests to be considered are those affecting these uses. In the development of tool, materials since the industrial revolution we have had carbon tool steels, Mushet steel, high-speed steels, stellites, and now cemented carbide compositions. For an understanding of the latter category of materials their properties and uses relative to the older and more familiar tool materials will be considered.

Jan 1, 1938

By J. M. Morris

The point to be made most clear in this paper is the economic value of flotation in the Benguet mill flow sheet. It is rather a statement of effect with no attempt at a technical explanation of the cause. Certain well-known, easily understood reagents, mechanisms and principles have been adapted to the conditions at Benguet, and have proved to be more successful than was demonstrated in the laboratory. The mechanical and metallurgical development of this particular operation was arrived at by trial and error, with fortunately very little error. Changes were slow, of necessity, which in the end proved a blessing in that time was afforded for observation and analysis of the disturbing factors; and as a result each change was a definite step towards higher efficiency. Many of these steps were unpredictable from laboratory work because of the varied and differing characteristics of ores met with in daily operation of the mill, which were practically impossible to reproduce on a laboratory scale. The Benguet mill receives daily ores that differ as much as if they were delivered from three different properties. There is first the surface and upper-level zone, which produces an oxidized secondary ore containing considerable iron oxide, manganese oxide and some organic matter. Formerly, most of this ore consisted of very soft fill with some hard rock mixed in. It also contained an unusual amount of iron and aluminum sulfate, which formed hydrates upon entering the alkaline cyanide solution and caused excessive frothing. When flotation was introduced in the Benguet mill the general characteristics of this upper-level ore had changed considerably, in that it was practically all newly mined, fairly hard ore. It still contained many of the same disturbing elements, but was somewhat simpler to treat than formerly. The small proportion of fines is still troublesome in flotation, and plant practice probably does not show more than 80 per cent extraction on this small portion of the ore. No definite figure on this is available, as this particular ore is delivered at irregular intervals

Jan 1, 1939

By J. E. Clennell

It is a common observation that the improvements introduced in practice since the first announcement of the cyanide process have been almost entirely mechanical. Although .a good deal of study land research has been devoted to the chemical problems [involved, the results obtained appear trifling in comparison. Few of the suggested modifications in the chemical treatment have come into practical use and those only in limited fields. Nevertheless, if we study the recent history of the cyanogen compounds from a somewhat broader standpoint, we shall find that considerable additions have been made, not only to our knowledge of their chemical properties, but also to their applications for industrial purposes. The present review of these advances naturally falls into two divisions: (1) processes involved in the treatment of ores; (2) manufacture of cyanides and other related compounds. Part I. Advances in the Chemistry of Ore Treatment by Cyanide In the attempt to extend the scope of the process, various ores have been encountered which contain gold and silver in such forms that they will not yield satisfactorily to ordinary methods of cyanide treatment. In some cases the difficulty is due to the excessive action on the solution of base metals present in the ore; in others, to the occurrence of minerals such as dyscrasite (the native alloy of antimony and silver), or a supposed oxidized manganese compound containing silver, which are either altogether insoluble in or very slightly attacked by cyanide. A particularly troublesome case is that of the so-called "graphitic" ores, containing carbon in some form which has the property of precipitating gold and silver already dissolved. Other efforts have been directed to improving extraction by electrolysis of working solutions, and by addition of various chemicals with or without electrolysis; to the diminution of cyanide consumption by "re-

Jan 1, 1916

By F. L. Sizer

The mining regulations of British Columbia and Mexico present some features which might well be copied in the United States, if we are to have a complete revision of the laws governing mining titles. 1. First and foremost is the "squarc" location, which would mean the abolition of extralateral rights. This is a condition in both of the countries above named which has seemed to work no hardship upon any one, and certainly the limitation of underground rights by vertical planes through all lines makes a locator's rights clear. In view of the long and costly litigation which has involved so seriously many of our most important mining districts, it would seem to be the part of wisdom to avoid a repetition of similar trouble on titles of lode mining claims, by the enactment' of a law similar to that in force in British Columbia. Objections have been raised by .representatives of English companies to the investment of large amounts of money in mining operations in the United States, because of the insecurity of title under the 'present apex law; and the statement has been made to me personally by one of the largest English operators, that he would .never again consent to the purchase of mines in the United States, preferring Mexico with all its revolutionary troubles to the danger of encroachment upon his underground rights by an unscrupulous neighbor. Without going into further argument as to the desirability of the I(square location," it should be sufficient to say to those who are inclined to "let well enough alone" and still stick to the "law of the apex" that there have never been any serious objections raised to this feature of the square location in either British Columbia or Mexico. There are well founded and logical reasons for abandoning the doctrine of extra-lateral rights since it is so difficult of interpretation; the most natural substitute being a law similar to that of British Columbia, giving to each locator an area 1,500 ft. square. I would advocate the right to locate adjoining claims of equal extent on either side of the discovery claim, on the strike of the lode, subject to a seasonable requirement in the matter of work upon them; and in the case of a vein dipping flatter than 45' from the horizon, or in case of a

Jan 1, 1915

By P. A. Tucker, T. B. Rhinehammer, D. E. Etter, J. E. Selle

The Ce-Cu phase diagram was investigated by differential thermal analysis and rnetallography. Two congruent melting compounds, CeCu2 (817°C) and CeCua (938°C), and three incongruent cornpounds, CeCu (516°C), CeCu, (796°C), and CeCu, CERIUM and copper have been suggested as possible diluents in a liquid-plutonium fueled reactor. As part of the determination of the Ce-Cu-Pu ternary phase diagram, a review Of the Ce-Cu system (798°C), are present in this system. Eutectics exist at 28 at. pct Cu (424°C), 74 at. pct Cu (756°C), and 91 at. pct Cu (876°C). The purity of the cerium used has an important effect on the results obtained by differential thermal analysis. was considered necessary. Previous work by Hanaman was conducted with relatively impure metal: 96.7 pct Ce with 2.5 pct other rare earths and 0.5 pct Fe as major impurities. The metal had a melting point of 715°C as compared to the melting point for pure cerium of 804°C as reported by Spedding and Daane.2 Results presented in this work were obtained primarily by differential thermal analysis (DTA) and metallographic examination of slow-cooled or quenched samples.

Jan 1, 1964

By Ralph Hayden

PAGE I. IntRoduction........239 II. Definition of Anaconda SLime....240 III. The Source of Slime......240 Remodeled Flow Sheet......240 Old Plow Sheet,.......242 IV. ConStitution of Slimes......243 Chemical........243 Physical.........243 V. The Slime Problem.......247 VI. THe Experimental Slime Plant....248 VII. Slime Thickeners. ETc .......249 Slime Ponds........249 Tanks.........249 Comparative Efficiency of Open and Baffle Tanks .260 Callow Tanks........252 Kuchs-Laist Centrifugal Separator....253 Garred Filter........256 Dorr Continuous Thickener.....256 VIII. Concentrators........257 Round Table........558 Peck Centrifugal Concentrator....259 Competitive Tests.......260 Twenty-Deck Round Table..... 260 Slime Feed Distributor......261 IX. ConcluSion.........262 I. Introduction. In the wet concentration of ores there is always a certain amount of very fine material with which to contend. and which invariably carries such quantities of value that the treatment of it is worth while. commercially. This fine material usually contains that portion of the ore which hinders the separation of the mineral values: namely. the colloidal material resulting from the decomposition of certain constituents of the ore. The object of this paper is to show what efforts have been made to solve the slime problem as it occurs in the concentrator of the Washoe

Jan 1, 1914

By Robert B. Fulton

It is a pleasure to talk to you about the world economics of industrial minerals on this occasion of AIME's 100th anniversary. In order to fit this topic into the time and tenor of such a session as this where you are hearing subjects equally broad in scope one after the other, I will deal with the subject through the medium of eight minerals selected to illustrate import- ant economic factors. I must admit to some bias in the selection, since I picked personally familiar ones to elucidate facts of life in the industrial minerals business. It is a very interesting field, different in many respects from metals and certainly far different from petroleum. The minerals chosen are celestite, diamond, fluorspar, salt, sulfur, ilmenite, rutile and zircon. Celestite The market for celestite is mainly in the U. S. where it is consumed in the manufacture of strontium compounds for red-colored flares and other pyrotechnics, for the production of electrolytic zinc, for glass manufacture, and for the manufacture of ceramic ferrites. Smaller markets exist in Europe and Japan. Production comes from England, Mexico and Spain, and a new mining operation is being started in Nova Scotia. There is no significant production in the U. S. nor in the other principal consuming countries, except England; so it is mainly an international commodity. Celestite illustrates many of the factors important in the economics of industrial minerals. To have a marketable product, grade and freedom from deleterious elements are important for materials used by the chemical industry. In the celestite used to make strontium nitrate, calcium is the most objectionable of the commonly associated cations. Selling price is adversely affected because nitrate manufacturing costs are greatly increased if calcium is pre sent, hence less can be paid for the raw material. Meeting specifications can add significantly to the vendor's cost; hence a balance must be struck between the producer's capability and the consumer's requirements, permitting a reasonable profit for both. Sizing of industrial mineral products is often important to the consum-

Jan 1, 1971

By Waldemar Lindgren

THE purpose of this paper is to present certain facts relating to Cordilleran differentiation and metallization. Theoretical discussions concerning the exact modus operandi of differentiation, the causes that led up to it, and the original distribution of the magmas have been omitted because the author feels that his knowledge is deficient. These subjects have been adequately treated in the admirable works of Iddings, Daly, Harker, Tyrrell, Shand, and Wolff. The facts here set forth seem to indicate that differentiation and metallization form one continuous process during the eastward movement of the magmas, culminating in the alkaline province of the eastern border of the Cordilleran Ranges.

Jan 1, 1933

By Horace Knerr

The term. "high-yield-strength," used in the title of Dr. Gillett's paper (p. 40) is obviously relative. His discussion is limited to improved steels intended to compete with the low-cost, low-carbon, hot-rolled, sheet and plate steels of commerce made and used on a tonnage basis, without heat-treatment. In his list of about three dozen steels, only three have a yield strength of 70,000 lb. per sq. in., or over. Double such values are not uncommon in aircraft steels. Dr. Jeffries (p. 21) refers to "light-weight metals," obviously meaning strong alloys of low specific gravity; namely, aluminum alloys of the duralumin type and certain magnesium alloys. In a structural material, "lightness" is determined by two factors, strength and specific gravity. They must always be considered jointly. The basis of comparison is a strength-weight ratio, obtained by dividing the desired strength value, such as tensile strength, yield strength, or endurance limit, by weight per unit of volume, such as specific gravity or pounds per cubic inch1. For example, aluminum is a heavy metal, structurally, unless alloyed and heat-treated to give it high strength. When the strength of a structural metal is raised by heat-treatment or by cold-work, its specific gravity is not appreciably changed, but it is made lighter in direct proportion to the increase in strength because less of it will be required to carry the load. The lightness of the finished structure of adequate strength is the real point of interest. This structure must not only carry designed load, but "stand the gaff" of service, which includes the effects of accidental overload, fatigue, corrosion, loosening of joints, and so forth. Neither Dr. Gillett nor Dr. Jeffries mentions the true "lightest material of construction," which is alloy steel, tubular in form (Fig. 1), assembled by welding and heat-treated to a yield strength in excess of 150,000 lb. per sq. inch.

Jan 1, 1936

By Harrison Schmitt

During the past decade the writer has studied and mapped certain ore deposits and their structural associations in the states of Chihuahua, Durango, New Mexico and Arizona, and he believes that these deposits, with the exception of the manto-chimney, are representative of the principal types in the area of the states named. In this paper the deposits are described; then generalizations are drawn so far as seems appropriate. Hanover, New Mexico The Hanover, New Mexico, zinc deposits were briefly described by Lindgren and others,' Paige2 and recently in more detail by Schmitt. These, the kind ordinarily called contact metamorphic, border the southern end of an oval area of granodiorite intrusive ¾ mile wide and 2 miles long (Fig. I). The granodiorite has intruded, folded, and metamorphosed sedimentary and igneous rocks, which range in age from pre-Cambrian to Upper Cretaceous. About 90 per cent of the ore has replaced coarse, recrystallized, pure, fossiliferous, lower Mississippian, nonmagnesian limestone (Hanover limestone) 110 ft. thick;4 about 75 per cent of it occurs in the upper 50 ft. of this horizon just below an 18-ft. lower Pennsylvanian shale bed, which lies on a locally inconspicuous unconformity representing upper Mississippian time. The orebodies show five shapes or attitudes, each dependent on a special structural situation: 1. Most of the ore occurs as podlike, thick lenslike or other "three-dimensional" shoots extending from top to bottom of the Hanover limestone and lying adjacent to the outer contact of a silicate zone largely of andradite, which follows the intrusive contact (Figs. 1 and 2).

Jan 1, 1935

By Frederic P. Dewey

It is common to blame irregular assay results upon volatilization and much has been written upon the subject, but there is no real evidence that, in a properly conducted assay, the loss of either gold or silver by volatilization is sufficient to affect appreciably the result, even when arsenic or antimony may be present. Bulk assays of flue dust from assay muffles have been published, but the data given are totally insufficient to even approximate the volatilization from a single assay; and such figures as we have indicate the volatilization to be extremely small. Diligent search in the literature and wide inquiry among assayers and instructors have failed to produce a single case where the litharge volatilized in making an assay has been collected and assayed for gold and silver. Having attempted to do this, with most indifferent success, I am not surprised that this has not been done. While various textbooks give volatilization as a cause of loss in cupella-tion, it may safely be said that in the rare cases where this volatilization is sufficient to affect appreciably the result it is due to excessive temperature. Percy' says "The loss of silver by volatilization during cupellation is very slight (unless the temperature has been much too high), and may be disregarded." This statement is repeated by the Beringers2 and Smith,3 who includes gold with silver. Mitchell4 says the litharge fume rarely contains over one ten-thousandth of silver. Campredon5 ays that at a proper temperature no silver is lost by volatilization. Primarily, excessive temperature may be due to too high general temperature in the muffle; but it may often be due to temperature localized within the bead by oxidation of the metals and this may be influenced by other causes than the general temperature. I have shown an ex-

Jan 1, 1921

By D. J. Jr. McAdam

Fort the past five years, an investigation of the endurance properties of metals has been in progress at the U. S. Naval Engineering Experiment Station, Annapolis, Md. As a result of the investigations at this Station1-5 and other laboratories6-11 "endurance limits" of practically all kinds of carbon and alloy steels have been determined and have been correlated with other physical properties, especially with tensile strength. About a year and a half ago, the investigation at the Naval Experiment Station was shifted to non-ferrous metals. As a result, several papers discussing the endurance properties of numerous non-ferrous metals and alloys, especially the alloys of nickel and of copper12-16 have been published. In these papers, stress-cycle graphs illustrate. the endurance properties of each individual metal and alloy, and other graphs illustrate the effect of cold working, heat treatment, and chemical composition on endurance and other physical properties. Endurance tests of non-ferrous metals were made by the machines used in the endurance tests of ferrous metals. 1-4 The specimen for the rotating-cantilever tests, which has been described, 1,2,13 has a conical surface, with taper so adjusted that the stress is nearly uniform over a length of about 1 ½ in. Alternating torsion tests were made with the machine of the inertia types17 and usually by an accelerated-fatigue method.12 As the rotating-cantilever endurance limits of metals are about twice the alternating-torsion endurance limits, the former values are more generally useful in correlating the endurance properties of nonferrous metals. In several recent papers by the writer13-16 correlation of the endurance properties of a number of non-ferrous metals has been discussed.

Jan 10, 1925

By F. Julius Fohs

As an industry approaches stabilization, greater and greater stress must be laid on its technologic progress, which becomes a prime aid in improving its condition. The oil industry is tending toward this stage and hence its engineers must be pressed into greater service to prevent stabilization and stagnation from becoming synonymous, and to supply, either by improvements in processes or by new machinery, a means of obtaining savings in raw and finished products. Thus profits can be assured warranting continued investment. It may be repeated, technology must apply a slight improvement here, a change there, or a complete renovation, to eliminate inefficiencies and make each dollar invested yield greater results. The profits of ycstcrday were made of rich strikes, of monopolized patents or processes, of control of prices and of markets. Sixty-five years of growth, of large investment, of healthful competition, and of expanding markets, have put the oil industry in the foremost rank of world industries. .Just as the railroads passed a similar period of expansion and growth, and arc being stabilized with reasonable profits, so the oil industry must take advantage of the efforts of its engineers and experts to promote its healthful growth and a better service to the people. Herein is attempted a review of recent progress in which is presented the advances in exploration, production engineering, transportation, refining and greater efficiency in uses of petroleum, with a view not only to stressing important new processes and methods, but also the problems that press for solution. This review can only touch outstanding developments of recent years, but the several Petroleum Division symposiums of our program will present details worthy of attention. Exploration Geology offers directly little new in the technique of oil-finding— major stress being laid on improvement in subsurface correlation by means of foraminifera1 studies, additions to the knowledge of which are being made, slowly but surely, and by means of mineral, and especially heavy mineral, determinations in well samples. The general application

Jan 1, 1927

By Francis L. Sperry

Up to within a few years, the consumption of nickel has been more directly dependent upon the available supply than that of any of the other useful metals. The Gap mine, in Lancaster county, Pennsylvania,* has been, for the last quarter of a century, the only property in this country furnishing nickel in paying quantities. Its yearly output was about 300,000 pounds of metallic nickel, or nearly half the amount used annually in the United States. Foreign nickel from mines on the New Caledonia islands, in the South Pacific, found entrance into our markets as the production of the Gap mine fell off. The price of nickel was constantly maintained, and no special effort was made to extend its use. Over-production was cautiously guarded against, and all surplus metal was held by the banking-houses of the Rothschilds, who assumed the bonded indebtedness of the Sociètè le Nickel. The opening of the Ontario nickel-mines has, however, brought about a radical change; and nickel from the Sudbury district can be delivered in New York within four days, and in European markets within two weeks, as against two months consumed in transporting South Pacific ores. Former prices have been irretrievably smashed, and European trade-journals comment favorably on the influence which Canadian nickel has had in making lower prices, and breaking the backbone of the " nickel trust." Production and Costs. The quantity of nickel produced and the prices which it commanded may be briefly summarized as follows: The total production of the world from 1840 to 1860 was about 100 to 250 tons yearly of metallic nickel; from 1860 to

Jan 1, 1896

By W. A. Cole, E. L. Derby, J. F. Wolff

Exploration of Lake Superior iron ores is done principally by drilling. The soft iron ores are churn drilled and the harder ores are diamond drilled. The churn drill used is the Mesabi type and its operation should be described as "water jetting." The drill rods are washed down by the combination action of the water jetting from the bit at the lower end of the rods and the churning motion given the line of rods. The water, which is forced down through the rods, comes up between the wash rods and the casing, bringing the choppings to the surface. It is caught in three or more barrels, each of which has a stoppered hole 8-10 in. from the bottom. These barrels are successively filled, allowed to settle, and drained to the hole, until the desired depth is drilled. The sediment from each barrel is transferred to a settling tub in which it is allowed to settle; the water is then drawn off and the wet sample is collected and dried. The number of barrels used depends on the character of the ore. For example, when drilling sandy ores, all the wash water is caught and settled for the proper length of time without refilling any of the barrels. Thus, the sediment held below the stoppered hole in any one barrel is not disturbed. The casing is kept as near the bottom of the hole as practicable to prevent the caving of the hole from jeopardizing the sample. While the casing is being driven down and the hole is being washed clean after casing, the return water is not run into the sample barrels. In exploratory work in the harder formations, where the diamond drill is used, the sample comprises both core and cuttings. The care given in handling and preserving the core depends on the importance that may be attached to certain characteristic strata in different formations. The following instructions for the care of core samples are issued by the Ogle-bay Norton Co. for diamond drill work done for them on the Gogebic Range of Michigan:

Jan 1, 1925

By William E. Ford, Edward Salisbury Dana

IN the representation of crystals by figures it is customary to draw their edges as if they were projected upon some definite plane. Two sorts of projection are use8; the ah- graphic in which the lines of projection fell at right angles and the chirographic where they fall at oblique angles upon the plane of projection. The second of these projections is the more important, and must be tr2atcd here in some detail. Two points are to be noted in regard to it. In the first place, in the drawings of crystals the point of view is supposed to be at an infinite distance, and it follows from this that all lines which are parallel on the crystal appear parallel in the drawing. In the second place, in all ordinary cases, it is the complete ideal crystal which is represented, that is, the crystal with its full geometrical symmetry as explained on pp. 10 to 13 (cf. note on p. 13). In general, drawings of crystals are made, either by constructing the figure upon a projection of its crystal axes, using the intercepts of the different faces upon the axes in order to determine the directions of the edges or by constructing the figure from the gnomonic (or stereographic) projection of the crystal forms. Both of these methods have their advantages and disadvantages. By drawing the crystal figure by the aid of a projection of its crystal axes the symmetry of the crystal and the relations of its faces to the axes are emphasized. In many cases, however, drawing from a projection of the poles of the crystal faces is simpler and takes less time. The student should be able to use both methods and consequently both are described below.

Jan 1, 1922

By William Sharp

DISCOVERY of new ore in the Eureka district, Nevada, as a result of bold and persistent exploration based on a geologic interpretation of structure has recently aroused wide comment in mining circles. It may therefore be of interest to the profession to have a summary of the historical background and an account of the recent program of development. The mines of Eureka, discovered in the late 1860's, were the first important silverlead mines in the United States. They have a production record of more than fifty-one million dollars.1 After the ore bodies were apparently bottomed in the 1880's, repeated attempts to find new ore were unsuccessful until 1940, when a diamond-drill hole cut a 40-ft width of sulphide ore 1409 ft below the 841-ft level of the Locan shaft. The next hole cut 30 ft, of ore and three additional holes drilled in 1943 and 1944 showed the ore body to be continuous, Shaft sinking to reach and open up the ore body has been in progress since 1945. GEOLOGY Stratigraphy The ore in the Eureka district occurs in a series of Cambrian sediments which is exposed through a thickness of over 6000 ft. The stratigraphic column is as follows:2 [THICKNESS, FI ORDOVICIAN Pogonip limestone (upper part). Thin bedded limestone with some chert. UPPER CAMBRIAN: Pogonip limestone (lower part). Thin-bedded limestone (with shaly limestone and chert).... 425+ Dunderberg shale. Shale (clay and calcareous shale) and thin bedded limestone340+ Hamburg dolomite. Dolomite and limestonegoo+ MIDDLE CAMBRIAN: Secret Canyon shale. Shale and thin-bedded limestone1,035 Geddes limestone. Carbonaceous, flaggy limestone with some shale partings 335 MIDDLE (?) AND LOWER CAMBRIAN: Eldorado dolomite. Dolomite and limestone2,000 LOWER CAMBRIAN: Prospect Mountain quartzite. Quartzite with occasional inter calated conglomerate and shale 1,660+ The Prospect Mountain quartzite has been subdivided into two formations: Upper part, Pioche shale. Shale, quartzite with some intercalated limestone (Lower Cambrian fossils)-200 ft. Lower part, Prospect Mountain quart zite proper-I,460+ft. Total thickness6,695+] Much the most productive of these formations has been the Eldorado dolomite, which yielded more than $42,000,000 at Ruby Hill and an additional amount

Jan 1, 1947

By G. Sachs, G. Espey

Simple methods can be used for the determination of the residual stresses in thin walled tubing if the stresses consist of high tensile stresses at the one surface and high compressive stresses at the other surface. Such a stress distribution is approximated in sunk tubing and in deep-drawn shells. It is possible to cut sections from such articles in such a manner that a major part of the residual stress is relieved by a bending of the Part that is separated from the adjacent metal. The circumferential stress is evaluated from the change in diameter D, occurring on splitting a length of tubing (Fig. Ib) or from deflection resulting from the cutting out of a circumferential tongue (Fig. Ia) .6 The bending moment M released by such a flexure is. M - EI (I-I) = EI R1-R0 I - u2(R0-R1) I -V2 R0XR1 where E = modulus of elasticity, v = Poisson's ratio, I = moment of inertia of the section, R0 =. mean radius before splitting, R1 = mean radius after splitting. The release of this bending moment corresponds to the release of stresses, which, in a thin section, vary linearly from one surface to the other, and have the following value in a particular fiber a certain distance (x) from the surface: S = c d I - V2 x c x d 2 2 RI - R0____E (d ) R1 - R0 X R0 X R1 ~ i - u2 (2 x) Ro X R1 where C is the section modulus and d is the thickness of the section, the ratio M:C being d: 2 for a rectallgular section.* The maximum stress values at the surfaces are. Smax = +E X d X R1-R0 I — u2- 2 R0 X R1 For most purposes the simpler equations: EXd AD1 = ± I - u2 x dm2 and will be satisfactory, where D,, is the aver. age of the mean diameters of the tubing

Jan 1, 1942

By John W. Frey

[Minerals, generally of great geological age, are to a very large extent the material basis of what we know as modern civilization. In most of the so-called civilized world the use f minerals has become such a commonplace that it is easy to se sight of their importance. It was the use of minerals, obably more than anything else, that made it possible for e American people to expand from the Atlantic seaboard the Pacific in a little over one hundred years. As the 1 to use the natural wealth at hand constitutes a funda¬ental element in American life, there seems to be justification for the thought that American geography is largely mineral geography. Of all American environmental reactions, the most striking are those which have come about through the use of the metals and the power fuels. If we turn to the ancient industry of agriculture, we find very little that is unique in North America except those developments which have come about through the use of machinery and transportation, both of which are contingent upon the use of minerals. Practically every crop now grown n North America was grown in some part of Europe before merica was discovered. One can point out exceptions to statement but in general it is true. Analysis of the es of North American agriculture shows that the outstand¬ characteristics are: regional specialization (i.e., the Economic Geographer; Chief, Petroleum Section, Minerals Division, u of Foreign and Domestic Commerce.]

Jan 1, 1932

By W. L. Honnold

(San Francisco Meeting, September, 1915) OWING to a unique labor situation and other unusual circumstances, the mining methods of the Rand are hardly comparable with practice elsewhere. They are' of considerable interest, however, and their impor-tance is increased by the magnitude of the industry with which they are identified, gold of $166,186,000 value, say 40 per cent. of the world's production, having been recovered from 25,701,954 tons of ore milled in 1914. In the sketchy remarks to follow, attention will first be drawn to some influential factors of general bearing, after which certain features at two mines of the writer's group will be referred to. It is hoped that engineers associated with similar or different conditions and practice will contribute to broaden the discussion. Before proceeding, recognition is due the generous assistance of C. E. Knecht and F. A. Unger. GENERAL OBSERVATIONS The principal mines are situated along the northern limit of an irregularly shaped geological basin, and extend in almost unbroken continuity over a distance of about 60 miles. As the boundaries are defined by vertical planes there are both "outcrop" and "deep-level" properties, all differing in size and in technical features. So much has been written in regard to the geology of the Rand that only a few pertinent features need here be recalled. Briefly, the ore deposits are profitably enriched portions of certain conglomerate beds or "reefs," rarely more than three, which are interposed between quartzite, or quartzite and slate, and lie so closely together that where more than one are mined they are dealt with as a work-ing unit, although they may lie stoped separately. Their collective extension is locally referred to as "the Reef."

Jan 8, 1915