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By John W. Gabelman

Uranium exploration technology historically has followed the economic cycle of demand, exploration spurt, and trailing supply; but with a greater lag. Greatest progress was made during the wane of demand as geological investigation caught up with the flood of new discoveries made during relatively short periods of peak demand. Updating brought technology to a new level based on the deposits which were discovered and not on the total range of deposit types which might exist. The technology was seldom able to predict new deposit types or new districts, which have consistently been surprises. Yet each new cycle of increased demand was at a new higher level, occasioned by a new use, which required the discovery of previously unrecognized larger types of deposits. Hindsight shows that data sufficient to have predicted most discoveries were available. The predicted growth of uranium demand far in excess of estimated resources is an incentive to examine current technology for data or promising techniques that might foster discovery by technical prediction rather than by systematic drilling. The world could well be reexamined systematically with new geophysical techniques including gamma spectrometry, radon emanometry, and magnetometry. Known occurrences could well be reevaluated in the light of new data on mineralization process and supergene leaching. Less-leachable extrinsic elements associated with uranium might he sought as clues to unleached uranium at depth. Uranium is increasingly being noted in environments containing coal and petroleum which might become targets. High-temperature replacement disseminations are increasingly reported and particularly attractive as exemplified by the Rossing district. The number of formations containing uranium occurrences is growing so that new, not necessarily fluvial, formations might be productive. Enough drilling has been done to indicate that uranium is selectively distributed regionally under some control yet to be determined. Exploration should address those environments and areas where uranium could occur rather than only those where it is already known.

Jan 1, 1976

By Gerard Matthes

WITHIN the last three years, aerial mapping has made wonderful progress. Its three sources of development in North America may be enumerated as follows: (1) The work of the U. S. Army Air. Service and Corps of Engineers at the McCook Experimental Field, Dayton, Ohio. This is generally regarded as the backbone of this class of endeavor in the United States. (2) In Canada, a great deal has been accomplished in a practical way by methods that have not even been tried out in the United States. Under the leadership of the late Doctor Deville, the Dominion Land Surveyors have turned out reconnaissance maps of large areas at very, small cost. (3) Private capital has contributed a great deal toward development of aerial mapping in a practical way in the United States. Prominent in this regard stands the Fairchild Aerial Surveys, Inc. which has spent large sums in research and development work, especially in the construction of aerial cameras. Its camera is, at present, the official camera of the U. S. Army and Navy Air Services, also, of the Canadian and Brazilian governments. Aerial photographic surveying is a flexible process and adapted to a variety of uses. To date, it has proved. of direct practical value for engineering projects such as reservoir and power transmission surveys, railroad location, drainage, harbor front studies; also, for many commercial purposes, tax assessment, city planning, forest surveys, and lawsuits. In a few instances, aerial photographs have been used successfully by geologists as base maps on which to record field observations, thereby dispensing with pacing and compass surveys. There is reason to believe that, eventually, the aerial map will find wide application in the work of geologists. The reason for advancing this opinion is that aerial maps have, in other fields, proved more complete as regards detail than maps made by standard processes of surveying and drafting, and often are more accurate than the latter. At the present time, five distinct uses are being made of aerial photographs: There is the "oblique" photograph taken at an angle with the horizon; it is used extensively for illustrations in newspapers, magazines, and advertisements. Also, for reconnaissance purposes, it has been found of great practical value. For illustrating reports of engineers and geologists, it offers many obvious advantages. In the Canadian Surveys, maps have been compiled from oblique photographs.

Jan 3, 1925

By D. K. Crampton, H. I. Burghoff, J. T. Stacy

The effect of cold-working upon electrical conductivity of copper and of copper alloys appears not to be generally known in detail. Although several papers on the subject have been presented, showing variable effects according to alloy composition, it is often assumed that the 2 to 3 per cent lowering of the conductivity of ordinary tough-pitch copper by severe cold-working is typical for copper alloys. Because of this situation it was decided to carry out the present work upon several types of copper, copper-zinc alloys over the commercial range of brasses, other binary alloys, and numerous age-hardening alloys in the quenched, and quenched and aged conditions. The large number of alloys investigated made it impossible to study every one in the detail it may have merited. Inasmuch as several interesting points that could not be satisfactorily explained came to light, further work is contemplated by the authors. It is usually considered that the normal effect of cold-work on ductile metals and unordered alloys is to decrease conductivity slightly. In alloys that are in the ordered state, as annealed or otherwise heat-treated, cold--working tends to disorder the structure, resulting in very marked lowering of conductivity. The random state of atomic arrangement produces lower con- ductivity than the ordered state for the same composition.1 Previous Work Previous work in the authors' laboratory has shown the electrical conductivity of several copper alloys to be decreased by greater amounts than might have been expected, in view of the general knowledge on the subject, when cold-worked. Guillet and Ballay2 investigated the influence of cold-work upon the resistivity of several metals and alloys, including copper and some copper alloys. The increase of resistivity due to severe working w is less than 4 per cent for all pure metals tested, while the increases for the alloys were generally higher. In the copper-zinc alloys, they found that the increase of resistance due to drawing increased with zinc content, and reported a 21.7 per cent increase of resistance for an alloy contaiiiing 67.9 per cent Cu as severely worked. Masima and Sachs3 studied the change in electrical resistance of three brass crystals when stretched in the tensile test, obtaining increases in resistance of the order of 3 per cent for 30 to 40 per cent reduction of area of the specimens. The resistance decreased again when the cold-worked crystals were subsequently annealed. Bardenheuer and Schmidt4 found that the conductivity of copper was decreased by 3 to 4 per cent when reduced 50 per cent by working. The conductivity of 72-28

Jan 1, 1941

By H. J. Hand

STATISTICAL methods are becoming increasingly important for interpreting routine reports, or for analyzing special test data in industrial plants, such as steel plants. They have already become practically a necessity to the plant metallurgist. A paper by Chancellor,' written in 1933, gives many examples of the benefits the plant metallurgist can derive from the use of these methods. The present paper discusses applications of importance to many others who must analyze reports in the steel plant, as well as other examples of interest to metallurgists. Statistical Methods Logically Suited to Plant Problems.-Statistical methods are not new as a branch of mathematics. Until comparatively recently, however, practical applications were confined mainly to actuarial science,, biology, and economics; fields in which an observed result is obviously influenced (and often determined) by a complicated set of variables more or less constantly tending to affect it. As pointed out by Daeves,2 a decade or more ago, problems in industry are basically similar to those in these other fields in that a given result is at least partly due to that chance combination of causes happening to be present at the time. When trying to do the same thing repeatedly, constant results are never attained; they vary about the desired result with more or less well defined mathematical regularity. Such a condition arises out of the great number of factors tending to affect the final result. If statistical methods are so valuable to the biologist or economist, why then should .they not also be of great value to plant managers and engineers, and to all who must interpret reports from various sources in the industrial plant? Within the last few years, industry has become conscious of this situation, and the use of these methods has been rapidly expanding in such plants. † Many Useful Statistical Devices Available.-Many statistical methods of attack are available for the analysis of plant data. It is the object of this paper to discuss applications of some of these methods to the solution

Jan 1, 1938

By R. E. Zimmerman, T. W. Guy

IN approaching the problems of sampling coal, a brief statement of certain facts that are more or less taken for granted may be helpful: 1. The coal-mine operator needs reliable data as to the physical and chemical characteristics of his coal in order to plan and control intelligently its mining, preparation, and marketing. The consumer needs such data in order to select the equipment and the coal best suited to meet his requirements, to check the quality of fuel delivered, and the efficiency of its use. Various government control agencies require such data as a basis for classifications and establishment of limits, for use in carrying out the requirements of federal, state or municipal laws. 2. All such data must be obtained by analyses, measurements, or tests made on samples, which are taken to represent the coal tested. It is now becoming generally recognized that, in accordance with statistical laws, test results from samples are not expected to represent the exact qualities of the lot or lots from which they are taken, except within statistical, or "expected" limits. Such limits are definitely specified by some present standards of the American Society for Testing Materials and the British Standards Institution. 3. Samples that give ash within satisfactory limits are usually assumed to be sufficiently accurate for other analyses, except under special conditions such as meeting close specifications for coals showing wide variability in sulphur, fusibility of ash, or other quality. 4. In modern coal sampling the increment is recognized as the basis for taking samples. For a given accuracy the number and weight of increments specified are increased with: (a) the expected ash, and (b) the top size designation of the lot to be sampled. 5. It is extremely important that every sampler recognize that: the specified number and weight of increments are minimums, and that the precautions to be used in order to take them properly are also minimums; that in the reduction of the gross sample the sizes specified for the coal after each stage of the crushing are maximum; that the quantities specified to be taken after each crushing stage are minimum; that any short cuts or failures to meet the requirements specified will reduce the statistical accuracy of the results, although it is possible that one or two checks on a few results may seem to show otherwise.

Jan 1, 1950

By E. M. MacKevett

The only source of uranium ore in Alaska that has been mined commercially is the Ross-Adams deposit, a gently inclined, fusiform orebody in alkali granite in which uranothorite and uranoan thoria-nit? ale the chief ore minerals. In mode of occurrence, apparent genetic association with the granite, and to a lesser extent in mineralogy, this type of deposit is uncommon. The mine is in the southern part of Prince of Wales Island (Fig. 1) at an altitude of about 950 ft on the southeast flank of Bokan Mountain. A steep unpaved road 1 3/4 miles long leads to the dock on the West Arm of Kendrick Bay, which can be reached by boat or seaplane from Ketchikan, some 35 miles to the northeast. The southern section of Prince of Wales Island is covered by dense forests interspersed with swampy tracts of muskeg. Most of the higher peaks support only sparse vegetation, and in areas underlain by alkali granite bare rocky slopes prevail to as low as 800 ft. Numerous fiord-like embayments penetrate this part of the island, and their shorelines provide near-continuous rock exposures. Rainfall is heavy, about 150 in. annually. Throughout the year the climate is relatively mild. History and Production: In May 1955 two members of a Ketchikan prospecting group, Don Ross and his wife, found the deposit while working with an airborne geiger counter. Later they confirmed their discovery by ground investigations. During the summer Climax Molybdenum acquired controlling interest in the property and started exploratory diamond drilling, resuming the drilling on a larger scale in the summer and fall of 1956. Climax began mining in July 1957, shipping the ore by barge and train to the Dawn Mining Co. mill at Ford, Wash. The open pit workings, about 370 ft long, between 25 and 75 ft wide. and 25 ft deep (shown in Fig. 2) were shut down in October 1957. As of September 1958 the pit was still inactive, although a small tonnage of known reserves remains in the southern part. The operators believe the 15,000 tons of uranium ore already produced will average 0.80 pct. GEOLOGY The Ross-Adams mine is within a small stock or boss of alkali granite, about 1000 ft from the southeast margin of the granite (Fig. 3). The area around the boss is underlain chiefly by plutonic rocks of intermediate composition and by metamorphosed sedimentary and volcanic rocks. The oldest rocks in the area probably are the metamorphosed volcanic rocks that are well exposed adjacent to the South Arm of Moira Sound. They are considered by Buddington and Chapin1 to be of Devonian age. These light gray to dark gray rocks mainly represent a layered volcanic sequence. They are commonly porphyritic with plagioclase pheno-crysts in an altered, fine-grained groundmass. The

Jan 1, 1960

By Gerald Edmunds, R. K. Waring, E. A. Anderson

Brass is liable to failure under the combined influence of stress, certain corrosion media, and time, a phenomenon commonly termed season cracking or stress-corrosion cracking. The consequences of this are serious in applications of brass generally, including the important field of cartridge cases. Cartridge cases (70 Cu: 30 Zn) that fail from this cause may allow the escape of gas from the gun breech, a hazard to the shooter, and may not eject, thus temporarily putting the gun out of action. In loaded cartridge cases, the stress present is partly residual from the, drawing and necking operations and partly applied by the insertion of the projectile. Ammonia, present as a decomposition product of smokeless powder, air and moisture constitute corrosive media. The prevalence of season cracking has been reduced considerably, but not eliminated, during the past quarter of a century by low-temperature annealing to relieve stresses residual from fabrication, a method suggested by Diegel 38 yr. ago(I).2

Jan 1, 1945

By E. N. Cameron

GRAPHITE has been included in U. S. lists of strategic minerals since the problem of mineral deficiencies was revealed during World War I. Since 1918 the domestic graphite industry has led a precarious existence, and there has been much uncertainty as to the amounts of usable graphite of various grades that would be available from domestic sources in time of emergency. In 1950-1951 therefore, the writer, assisted by Paul L. Weis, undertook a review of domestic graphite sources for the U. S. Geological Survey.' The conclusions of this study are presented here, with a discussion of some technologic and politico-economic factors bearing upon the problem. Uses of Graphite: Natural graphite as marketed exhibits a wide range of properties, which determine the uses to which it is put. The most essential uses are in the manufacture of crucibles and related refractory articles, in lubricants and packing materials, and in the manufacture of batteries, foundry facings, pencils, and carbon brushes. Numerous specifications covering the mineral in its various applications must be met by producers and processors of graphite. The problem of supply is therefore not simply one of procuring a sufficient total tonnage, but the more difficult problem of procuring enough of each different grade to meet foreseeable needs. The amount of graphite required by American industry is not large. Ordinarily only a few thousand tons of strategic grades are consumed annually, yet the elimination of this small tonnage would have serious effects in several industries. Strategic Graphite: Since World War I, 60 to 100 pct of the country's annual supply of graphite has been furnished from imports. At present, natural amorphous graphite for use in pencils and batteries is produced largely from American-owned mines in Mexico. Graphite for foundry facings is obtained from a number of sources. Neither grade is a serious problem. High purity graphite for carbon brushes and for pencil leads, however, is imported, largely from Ceylon, in the form of amorphous lump graphite. Most of the flake graphite used for crucibles and related refractory articles is likewise imported, largely from Madagascar, and much of the lubricant and packing grade graphite used by industry is obtained from the same source. The strateg'ic grades of graphite are therefore amorphous lump of the Ceylon type, crucible flake, and flake suitable for lubricants and packing. Ceylon lump and Madagascar flake have for many years been accepted as standard by domestic consumers of graphite, and various essential manufacturing processes are geared to the use of graphite from these sources. Ceylon graphite as marketed is classified into several grades based on particle size and purity. Processing methods are said to be simple, but the products marketed are carefully graded and are consistent in their characteristics, an important matter to the consumer. Nearly all the graphite produced in Ceylon is from veins. Resources are reported to be large, labor is cheap, production costs are low, and world competition is slight—factors accounting for the commercial success of the graphite mining industry in Ceylon. Madagascar is reported to have deposits of the Ceylon type, but its output consists almost entirely of flake. Madagascar graphite as received in the U. S. is further processed by importing organizations, and a large number of grades are produced to meet industry requirements, especially those for crucible flake and for lubricant and packing grade flake. Madagascar crucible flake as marketed is noted for coarseness, uniformity, toughness, clean-

Jan 1, 1957

By R. S. Wagner, C. E. Miller, H. Brown

A dc field was applied to liquid BI-Sx or Au-Ge alloys of eutectic composition. The liquid alloys were kept at a temperature slightly above the eutectic. The concentration changes due to electrodijfusion are large enough to cause nuclcation and growth of the primary phases at the respective electrodes. Nearly complete separation of Bi-Sn eutectic was obtained as well as substantial separation of Au-Ge eutectic. The effect of an electric field on the solute distrihn-tion was itluestignted itt tlirectiortally solidified rods of a dilute Bi-Sn (0.5 al. pc,t Bi) alloy. Field-freezing was carried out in small-diameter cupillay tubes to avoid cotuectice mixing -of the liquid. The relative sollcte corzcentratioi, Cs/Co , was rneusred by n radioac1il.e tracer netlod. Cs/Co can be made both largev than unity or srialler than the equilibiuwz distvibrrlion c.oejyicienl, k, , oiler a substattiul portion of the soliclifi&apos;erl rocls. A direct current, passed through a liquid-metal solution, can cause substantial concentration changes by electrodiffusion. The magnitude of the change depends on the difference in ionic mobilities of the atomic species in solution. Electrodiffusion has been studied in many binary and ternary liquid alloys.&apos;y2 It was found that the rate of material transport decreases with time for a constant applied field, as a concentration gradient is established in the solution. A steady-state concentration profile is achieved when electro-diffusion is compensated by chemical diffusion. This may seem to limit the use of electrodif fusion for metallurgical application. However, a way of utilizing the effect of electrodiffusion is to combine it with crystallization or controlled freezing. rakin was first to propose this as a new method of separating metal alloys of eutectic composition at temperatures slightly above the eutectic temperature. It was possible by this method to separate Bi-Sn and Bi-Cd eutectics into their component phases. Angus et al discussed the possibility that the effective distribution coefficient, keff, could be varied by proper application of an electric field during solidification. The combination of electrodiffusion and solidification, called field-freezing, was discussed in detail by Pfann and aner. It was shown that field-freezing can be used as a crystal-growth process, an efficient method for eutectic separation, and a new means of changing the effective distribution coefficient. k,ff, beyond the usual range of ko < k,ff < 1. The liquid layer adjacent to the solid-liquid interface can be either increased or depleted in solute due to

Jan 1, 1967

By J. S. Koehler, F. Seitz

THE dislocation theory of plastic flow originated in 1928, when Prandtl1 suggested that the internal damping of metals of plastic origin might arise from the motion of a crystalline imperfection. Following this, Dehlinger2 employed a similar imperfection in a theory of recrystallization. The first detailed theoretical discussions were those of E. Orowan3 and G. I. Taylor4 in 1934. The resulting theory was gen- eralized by J. M. Burgers5 in 1939. Mott and Nabarro, in England, and Seitz and Read,6 in the United States, started an extensive examination of the atomic theory of dislocations in the period between 1939 and 1941. However, this development was arrested by the mar and was not taken up again until after 1945. Since 1946, the field has been the object of very intense activity, particularly in the United States and England. Dislocations are beautiful and intricate imperfections; they are sufficiently complicated to account for the great variety of phenomena encountered in the field of plastic flow. Above all, the dislocation concept enables us to understand how a metal or other plastic solid can deform inelastically under very small stresses at temperatures far below the melting point. Suppose we attempt to shear a perfect crystal plastically. This can be done by sliding one entire atomic plane simultaneously through one atomic distance with&apos; respect to the near-

Jan 1, 1954

By R. B. Sosman

INTRODUCTION IT is well known that ferric. oxide, Fe.-,03, is paramagnetic, while magnetite, Fe304, is classed among the highly ferromagnetic substances. But magnetic data on oxides intermediate in composition between Fe-03 and Fe304 have been almost completely lacking. Fe203 and Fe304 form a solid-solution series, according to present evidence.&apos; In this series the properties change continuously from Fe203 toward Fe304, as the percentage of FeO increases from zero toward 31.03, which is the percentage in magnetite. It is possible that there is a break in the series near Fe304, but it has not yet been possible to establish the existence-of such a break experimentally. The occurrence of solid solution ill this series is shown by the dissociation pressure, or oxygen pressure in equilibrium with the oxides, which falls continuously over the range from Fe203 to Fe304. The oxygen-pressure curves at 1,100° and 1,200° are shown in Fig. 1. The existence of solid solution is also demonstrated by the continuous change in optical properties from Fe203 over to a composition containing about 18 per cent. FeO, at which point the opacity of the oxide becomes so great that it is im-possible to obtain measurements at higher percentages of ferrous iron. Natural oxides of iron intermediate in composition between Fe2O3 and Fe304 are much more common than is generally supposed. If a mineral oxide is not strongly attracted by a small hand magnet and if it gives a red streak, it is usually labeled "hematite." If it is strongly attracted by the hand magnet it is usually labeled "magnetite" without further tests. As we shall show later, oxides containing from 1 up to 31 per cent. FeO can be thus erroneously lumped together as "magnetite." It is a fact, nevertheless, that the great hulk of natural oxides of iron lie fairly near either Fe203 Or Fe304 in composition. The reason will be

Jan 6, 1917

By John L. Lamont, Walter Crafts

ADEQUATE hardenability has long been recognized as one of the first requirements for producing desired mechanical properties in a heat-treated steel. Since the introduction of the Jominy end-quench test1 and the development of correlative information to expand its use, industry has had an effective measure of hardenability. Prediction and control of the hardenability have been made possible by Grossmann&apos;s principle2 for calculating hardenability from chemical composition; and Field&apos;s conversion3 from depth of half-martensite hardening to Rockwell C hardness has made the relation more quantitative. These developments have facilitated the design of new steels and the control of standard grades to the extent that it has been possible to establish tentative hardenability bands for some of the more commonly used alloy steels.4 As the depth of hardening of the Jominy test specimen is usually measured by Rockwell C hardness, it was considered that it should be possible to predict the hardness by a more direct calculation. It has been found that this can be accomplished by the addition of Rockwell C units proportional to the carbon and alloy content, grain size, and position in the Jominy test specimen. The calculation has been found to be fairly accurate, and because of its additive character is relatively simple to use. In principle the method of calculation is somewhat similar to the expressions developed by Herty, McBride, and Hollenback,5 Burns, Moore, and Archer,6 and Burns and Riegel.7 The calculation is started from a base that includes the effects of carbon content and position in the Jominy test speimen. Rockwell C units are added to the base in proportion to the alloy content and grain size. This sum represents the Rockwell C hardness up to the level at which a disproportionate increase of hardness is caused by the formation of martensite, and above this level an increment for martensite hardening is added. The effects of alloys are directly proportional to the amounts present and are independent of each other, the carbon content, and the position in the specimen. Furthermore, the factors for determining the martensite increment are dependent only on carbon content and are independent of cooling rate and alloy content. It is this absence of interrelation between the different factors that makes it possible to calculate the hardness and makes the method of calculation consistent with the principle that the character of the hardening reaction is governed primarily by carbon and that alloys exert their effect chiefly through control of the critical cooling rate. The principle of the calculation, and the effects of alloys on the critical cooling rate,

Jan 1, 1945

By Jerry H. Service, F. L. Partlo

The following investigation was undertaken to develop a method for determining with reasonable accuracy the depth of overburdens of 100 ft. or less. Seismic methods seemed to offer good possibilities. The problem differed from that of the familiar salt-dome location in that the depth of overburden to be determined is much less than is encountered in oil prospecting. This means that a much shorter time interval must be measured with accuracy. Refraction methods seem at present to offer greater possibilities than reflection. The air sound persists for from 0.1 to 0.5 sec., because of echoes, and seismic reflections coming during this time are difficult to detect. A seismometer sensitive to vertical vibrations only offers possibilities and has been used here with some success. It is hoped that the application of this type of seismometer to reflection shooting in this region may be investigated still further. The apparatus used consisted of a carbon-button seismometer followed by a three-stage, transformer-coupled, vacuum-tube amplifier and a General Radio string oscillograph. Time marks are provided by a 1000-cycle, 600-r.p.m., synchronous motor provided with five spokes which intercept the light to the camera at 1/50 sec. intervals. This motor is driven by a two-stage vacuum-tube amplifier of 3 watt output, actuated by a tuning fork. The power supply for the seismometer amplifier is one 2-volt storage and one 45-volt B battery. The motor amplifier is powered by a 6-volt storage battery and 6 to 225-volt, 15-watt motor generator. The temperature-frequency characteristics of the tuning fork have been determined and for ordinary working temperatures the error in time that would be introduced is less than M millisecond for time intervals up to 100 milliseconds. The impact is produced by a sledge blow for surface distances less than 100 ft. and dynamite for greater distances. Two steel balls with wires attached form an electric circuit through a 1-ft. piece of railroad rail upon which they rest. When the rail is struck by the sledge the balls rebound, opening the circuit and indicating the time of impact by a break in the oscillograph record line as at A, Fig. 3. When dynamite

Jan 1, 1934

By W. C. Hagel, H. J. Beattie

Variations in the secondary phase reactions of six nickel-and cobalt-base alloys were determined as a function of solu-tioning from 1700" to 2200°F and aging at 1200" to 1800° F for times up to 1000 hr. Room-temperature impact energies and hardnesses were also measured. Precipitation hardening of these alloys results mainly from the grain-interior formation of ? &apos;; M23C6 appears principally as grazn-boundary cells which can be eliminated by intermediate high-temperature aging treatments. Cellular precipitation of ?&apos; occurs up to 1500°F in cobalt-nickel alloys devoid of chromium, where precipitation by this mode can be attributed to a large degree of lattice disvegistery. THE usefulness of nickel- and cobalt-base alloys is dependent on balancing the strength and ductility provided by the solid-solution matrix, dislocation-type subboundaries, grain-boundary phases and genera1 precipitation within individual grains. Since equilibrium relationships for complex austenitic alloys are not easily fixed, a satisfactory balance

Jan 1, 1960

By W. S. Landis

In brief, this is the story of an attempt to Americanize a process originally developed in Europe. The story will be recited in two sections, the first dealing with the process as developed by the European engineers; the second containing the improvements and modifications of American origin, together with some details of the operating results of the unit as finally assembled. Developments in other directions in this same field have not, up to the present, pointed out an economic future for the process, therefore our record here is largely a report of development progress. Whether some particularly favorable location will be found at some future time for a commercial installation cannot as yet be foretold. The project is now at a standstill. The peculiar tools of the electrometallurgist should be of great interest to the zinc smelter. The low thermal efficiency of the zinc retort, its comparatively small-scale unit and its intermittent cycle as it stood in 1925, should make this art a particularly fertile field for the electric furnace. Yet in spite of years of work recorded in volumes of literature, and an expenditure of large sums of money, there is not a single electrothermic zinc smelter operating anywhere in the world. In this industry the electric furnace plays only a secondary part today. Historical The first serious proposal to use the electric furnace for the smelting of zinc ores was made by the Cowles Brothers in 1885, but their experimental work did not advance the art to any extent. The next investigator of this field was Dr. Gustav DeLaval, a Swedish engineer well known to the industrial world through his development of the centrifugal and the steam turbine. The DeLaval cream separator is a familiar household appliance in most parts of the world. Although Dr. DeLaval commenced his experiments in the field of electric zinc smelting in 1893, it was not until 1898 that he had a practicable furnace, even then operating but intermittently. His work was done at Trollhättan, Sweden. He continued to improve this early fur-

Jan 1, 1937

By Dr. O’Neil Thomas J., Donald W. Gentry

"There is nothing so disastrous as a rational investment policy in an irrational world. " John Maynard Keynes INTRODUCTION The principles of time value of money concepts were discussed and illustrated in Chapter 3. The importance of time value of money and the role it plays in the discipline of engineering economy have been well established. Chapter 9 further illustrates that project evaluation criteria that fail to consider this aspect are seriously deficient in providing appropriate capital budgeting decisions. Obviously future project receipts and expenditures must be discounted to permit valid comparisons with current cash flows. Although the concept of discounting is widely accepted, the selection of the appropriate discount rate has been the source of considerable debate and much disagreement. This chapter, then, provides an overview of the theoretical and practical considerations for determining or calculating the appropriate rate for discounting, the corporate cost of capital. Note specifically that the assumption of constant business risk among the various investment alternatives is maintained throughout this chapter. THE INTUITIVE APPROACH The fact that interest exists suggests that all money has a cost associated with its use. The cost of this money may be the result of either explicit or implicit charges or some combination of the two. Any time an individual or a firm consumes less than the total earnings generated in a given time period that individual or corporation has either consciously or unconsciously decided to "invest" these excess funds in some type of activity. For instance, the individual or corporation may decide to invest the excess funds in tangible property, place the funds in a money market account, or simply keep these funds in cash. In any case, these funds have been invested in some type of activity which promises the investor some return on the invested capital. Remembering that the firm&apos;s primary objective should be the maximization of shareholder wealth, then intuitively it seems reasonable to suggest that the firm should not invest in any project where the anticipated return does not exceed the cost of funds (capital) committed to the project. Indeed, if the firm always invests in projects having returns in excess of the cost of capital committed to them, then the wealth of the firm (as measured by the price of common stock) should be in-

Jan 1, 1984

By Paul A. Bailly

2.1-1. The Exploration Function in the Mineral Industry. With regard to a new mine, exploration can be technologically defined as all the activities and evaluations necessary before an intelligent decision can be made establishing size, initial flowsheet, and annual output of the new extractive operation based on a certain mineral deposit. The activities that follow such a decision are called first development, then operation (90). Thus, in the U.S.A., exploration may continue in the technological sense after a mineral property has entered the "development stage" as defined for tax purposes. Regulations under Sections 1.615.1 and 1.616.1 of the U.S. Internal Revenue Code state that the "development stage" has been reached when "deposits of ore or other minerals are shown to exist in sufficient quantity and quality to reasonably justify commercial exploitation by the taxpayer" (95). There are, of course, many instances where additional later exploration discloses additional reserves which justify a plant much larger, more efficient and more profitable than the minimum feasible commercial operation. After a surface mine is put into operation, additional search generally will increase the reserves and thus warrant expansion of the rate of output and/or extend the life of the operation. The methods and techniques in such search are similar to those used in predevelopment exploration. This activity has produced a major part of new reserves for all mineral commodities but is not considered as exploration in the context of this chapter. The objective of exploration is, briefly stated, to find and acquire a maximum number of new economic mineral deposits with a minimum cost and in minimum time. The search must be so organized as to maximize the overall probability of discovering commercial mineral concentrations within a minimum time with the funds available. As shown by Celasun (27) these statements are neither adequate nor complete from a pragmatic point of view. Each actual exploration venture must define its objectives in terms of a minimum rate of return on investment for any deposit found

Jan 1, 1968

By Walter Mathesius

The use of high blast heats on furnaces melting Mesaba ores is still the exception, the average blast temperatures carried on Mesaba stacks seldom reaching 1,100" F. Some 15 years ago, when the use of fine Mesaba ores in larger proportions to the total burden first came into practice, it was found difficult to employ even those blast heats which it had been possible &apos; to carry with the Old Range ores. The furnaces refused to "take" high heats, and would persistently labor with irregular stock movement, which impaired the practice and increased the coke consumption. By lowering the blast temperature, the working of the furnace became smoother, and experience taught that with the softer and more easily reduced Mesaba ores, satisfactory practice could be obtained with comparatively low blast heats. Therefore a large number of Mesaba furnaces have ever since been operated on very low blast temperatures, ranging between 800" and 1,000" F. In the face of these difficulties, furnace men were slow to recognize that furnaces could be so designed as to permit a free movement of the charges in combination with the use of higher heats. Since higher blast temperatures did not seem to offer great advantages in the smelting of Mesaba ores, investments in hot-blast stoves were not as attractive to the furnace man as labor-saving devices and means of obtaining greater tonnages. The effect of this preference is keenly felt at the present time. It has brought about the peculiar situation, that the majority of our furnace plants (among them some of the most progressive) lack modern and efficient stove equipment. The result is that, even where the proper furnace lines have been adopted and conditions are now favorable to the successful employment of higher blast temperatures, the heats required for the greatest fuel economy are not available. In an endeavor to obtain results, even with inadequate equipment, we find that, at many plants, the stoves are worked far beyond their capacity. This leads, in many instances, to a situation in which the coke saving in the

Jan 1, 1915

By A. D. Hodges

The great mining region of Peru is a mountainous belt of country, running nearly the whole length of the republic, and comprising the two grand ranges of the Andes with the elevated table-lands between them. On the east of this belt are the extensive plains and fertile valleys of the Amazon and its tributaries. On the west is a narrow strip of coast 20 to 50 miles wide, for the most part a sandy desert, but producing abundant crops where irrigated ; and here are found petroleum (Department of Piura), salt (at Huacho and elsewhere), nitrate of soda in enormous amounts at the south, silver in a few localities (Province of Tarapaca), copper and other mineral products. The Western Cordillera, running nearly parallel with the shoreline, rises like a wall on the eastern side of the coast-belt, with passes from 15,000 to 18,000 feet high and peaks attaining 18,000 to 20,000 feet. Further east, at a varying distance, is the Eastern Cordillera, composed of broken mountain ranges which, considered as one group, have a general parallelism with the western chain, but individually vary greatly in direction, sometimes running nearly east and west, in places projecting out into the Amazonian lands, or here and there curving around to unite with the western ridge, and with this enclosing immense inter-alpine plains. These general features are indicated in Fig. 1. The surface of these plains is uneven and traversed by lower ranges of hills which surround large lakes, or rolling pampas, or fertile valleys; and through many of these last run rivers of considerable size. The whole country has a high altitude (averaging up to 15,000 or 16,000 feet), and slopes gradually north and east towards the Amazon, into which drain all its waters. Its bounding mountain chains are scored on all sides by narrow, picturesque and pre-

Jan 1, 1888

By George F. Weaton, Eugene P. Pfleider

13.4-1. History. During the past ten years the mining and production of iron ores has been through a revolution. From 1939 through 1948, which included World War II, 561,000,000 tons of iron ore was mined and shipped from Minnesota&apos;s Mesabi Range to the blast furnaces of the United States for the production of iron and steel products (20, 28, 29). The iron mining industry, anticipating the exhaustion of this highly productive source of raw material, instigated a worldwide search for new sources of iron ores. This search was highly successful, both as to quantity and quality. Venezuela (38), Canada (17, 28, 42), Peru (19, 23, 50, 52, 54, 56) Chile, (1, 66, 75), Brazil, and Liberia were among the countries where enormous deposits of high quality iron ores were discovered. The exploitation of these deposits took away the monopoly held by the Lake Superior region for so many years and created a highly competitive market for high quality natural iron ores. 13.4-2. Exploration and Development Practices. SPECIFIC TO IRON MIN- ING. American industries are motivated to continue exploration because new ore discoveries often lead to an improved competitive position with respect to raw material supply. Exploration techniques have advanced rapidly in recent years, to a degree that potentially important iron ore reserves, stratigically located, may now be detectable by application of a combination of refined and diversified geophysical exploration methods. Since the days of the dip needle, iron ore people have placed greatest reliance on the magnetometer. Its successive stages of development progressed from the balance and the torsion type to the fluxgate, and then to the "sophisticated" magnetometers-conceived and developed in th field of atomic physics. By far the greatest advancement in magnetometer prospecting was made when the self-orienting fluxgate magnetometer took to the air. This was not a new development, but it was a breakthrough in reconnaissance investi-

Jan 1, 1968