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By C. M. Romanowitz, H. A. Sawin

PLACER dredging as we know it today, especially gold dredging, is an industry about 40 years old, dating from the beginning of this century, when a few mining men in California saw the possibilities in adapting earlier dredging methods to California placer fields in and immediately adjacent to streams. At first it was thought that dredges must be operated in existing stream beds, but experience soon pointed the way to dredging alluvial deposits of old stream beds, operating on landlocked dredging ponds. Within the first five or six years of modern dredging, experience was gained so rapidly that dredges to dig 60 ft. below water level were designed and built. This depth was believed by many operators to be the maximum at which successful dredging could be carried on. Alluvial deposits of gold, suitable for dredging, were readily handled by equipment available and developed early in the industry's history. Much of the gravel was easily dug and if deposits were cemented, contained large boulders, or for some other reason could not be handled by a dredge, the ground was abandoned in favor of other deposits that could be handled easily. Many failures, adversely affecting the dredging industry, resulted from attempts at that time to extend the scope of placer dredging with equipment not suited to the formation being dredged. Dredging ground suited to early equipment was exhausted eventually, but many supposedly undredgeable alluvial fields containing gold in commercial quantities were found and became known to dredgemen. Improved equipment was needed to work deposits known to exist at great depths or associated with unusual obstructions. Operating companies looked to dredge manufacturers and metallurgists, particularly manganese-steel foundries, for improved designs and materials. Experience developed in California has spread throughout the world, and dredges of improved types have been adapted to the mining of platinum and tin as well as gold. Space will not permit a description of all the improvements in dredging since the early days, but a few of the recent developments are worthy of note, because they make possible the dredging of placer deposits of great depth, those having hard, irregular bedrock or containing large boulders in great quantities, and compacted or cemented gravel deposits. DEEP DREDGING At Hammonton, Calif., Yuba Consolidated Gold Fields has, within the past two years, built its dredge No. 20. The company has operated continuously in that field since 1904, digging successively at maximum depths of 60 ft., 80 ft., 112 ft., and now 124 ft. below water level. The first dredges were equipped with buckets of 6 and 7 1/2-cu. ft. capacity; six dredges operating in the field today have 18-cu. ft. buckets, digging now 65 to 124 ft. below water level. Some ground near Hammonton has been dug for the third time, owing to the devel-

Jan 1, 1941

By T. H. Courtney, G. W. Pearsall, J. Wulff

The mechanism, of the decrease in transition temperature of Nb3Sn was studied. Presintered Nb3Sn powder compacts were heated in a dynamic vacuum at elevated temperatures. Loss of tin resulted from these heat treatments and transition temperature as a function of tin loss was discontinuous at a critical value of tin loss. In general, decreases in transition temperature were correlated with deviations from AS a class, the A15 structure-type (also known as Cr3O or ß W) compounds have the highest superconducting transition temperatures.' In this class are stoichiometry and presence of vacancies in niobium sites. The effect of vacancy distribution on the physical properties of Nh3Sn is considered. It is concluded that the close-packed atomic A chain in the A3B A15 structure must be preserved both in coutinuity and direction if good superconducting properties are to he obtained. tempting to associate these high transition temperatures with the most unique crystallographic feature of the A3B structure: the three close-packed, orthogonal chains of A atoms.'0"' There are at least three principal mechanisms by which the perfection of these "A-atom chains" could be interrupted: changing stoichiometry, inducing disorder, or introducing vacancies. Departures from stoichiometry in either direction in V3Ga lower the transition temperature.7'8 In niobium-

Jan 1, 1965

By V. A. Zanadvoroff

THE mine and concentrator of the Howe Sound Co., Chelan Division, are at Holden, in a remote section of the Cascade Mountains of northwestern Washington. Holden is at an elevation of 3200 ft., in the narrow valley of Railroad Creek. This creek drains into Lake Chelan, at a point some 40 miles up the lake from the town of Chelan. The concentrator treats 2000 to 2500 tons of low-grade copper-gold-zinc ore per day. Concentration is achieved by the differential flotation process, with recovery of 94 per cent copper and 82 per cent gold in the copper concentrate, followed by the recovery of 65 to 70 per cent zinc in the zinc flotation circuit. The final flotation tailing is deslimed, and coarse sands, representing 60 to 70 per cent of the total, are cyanided. The tonnage of tailing material amounts to 1900 to 2370 tons per day. GENERAL CONSIDERATIONS The property is within the Chelan National Forest. Railroad Creek is a fishing stream, being stocked regularly with trout from State hatcheries. Consequently, in planning a milling operation, the Howe Sound Co. was obliged to avoid any pollution of the stream by tailing material, and also destruction of valuable stands of timber. Moreover, the selected tailing disposal sites should not mar the natural beauty of the valley. In addition to these requirements, the problem of tailing disposal at Holden was complicated by topography and climatic conditions. The valley is long and narrow, averaging 1200 to 1500 ft. in width. Its walls are flaring at a steep angle. There are no extensive flat areas suitable for deposition of tailing. All valleys tributary to Railroad Creek, also the well-marked paths of snowslides, must be avoided. Finally, the direction of prevailing winds and possible dust hazard arising therefrom dictated the necessity of selecting the tailing-disposal sites downstream from the mill building and two campsites. Heavy snowfall during the winter months of November to March, inclusive, impedes building of the retaining dike, making it necessary to prepare the needed storage space during the summer months. It is inadvisable, also, to do any dike building during the freezing weather, because the dike becomes unstable with the spring thaws, producing inevitable "sloughing" of the built-up borders. TAILING-DISPOSAL SITES The existing tailing-disposal areas are near the south wall of the valley. They were developed, and put to use in the following sequence: No. I. Area.-Covers approximately 10 acres. Built up to the height of 60 ft.

Jan 1, 1946

By J. E. Forciea, R. W. Salmi

Operating and research personnel at U.S. Steel's Pilotac concentrator have evolved specifications for magnetic separators suitable for use in beneficiation of Mesabi magnetic taconite. These specifications were developed as a result of investigations into the operating and metallurgical problems at the Pilotac concentrator over a period of some ten years. This paper discusses primary magnetic separator specifications, but much of the information is also pertinent to secondary and tertiary magnetic separators. Of particular significance is the proposal of a new basis for specifying the magnetic field which includes consideration of both field strength and field gradient. Other areas of discussion include flowsheet service, operating conditions such as drum speed and pulp level, tank configuration, magnet strength including field gradient, sleeve bearing design, designation of corrosion resistant materials and other details that result in a metallurgically efficient machine that has low repair and maintenance requirements. The mechanical and metallurgical design of magnetic separators at the Pilotac plant, Minnesota Ore Operations, United States Steel Corp. has progressed from the original single-stage, belt-type machines to the present multiple-stage, drum-type units, In ten years of operation, the plant operating and research personnel, in consultation with manufacturers, have made design changes to improve mechanical, electrical and magnetic features to meet process needs as flowsheet designs developed and to incorporate new permanent magnet materials as they became available. Separator specifications were an end result of this effort. The latest specifications which were developed for the Minnesota Ore Operations' plant were not all-inclusive listings; they covered only those points indicated by plant experience. For example, magnet pole piece design and dimensions were not stated. The manufacturers were given freedom to use any design as long as the field pattern was as specified. The selection of the items to be included in the specifications was undoubtedly influenced by particular conditions at Pilotac such as composition of plant water, concentration characteristics of the ore, repair and maintenance facilities available and the research programs that had been conducted. Only the developments leading to the specifications for a primary or "cobber" magnetic separator are presented in this paper. However, the same general concepts are used to specify secondary and tertiary separators. The areas of interest discussed include flowsheet service, tank configuration, magnet design, bearings, materials of construction, and some minor mechanical details. FLOWSHEET SERVICE The primary magnetic separators in the Pilotac Concentrator flowsheet are located after the first stage of grinding as shown in Fig. 1.

Jan 1, 1965

By A. J. Langhammer

Broadly speaking, it may be said that the engineer has two major responsibilities: One is to recommend the choosing of proper machinery and equipment; the other, to assist in the simplification of design, determination of method, and advise about the most suitable material to be used. The products of powder metallurgy enter broadly into both these fields. The oil-cushion, self-lubricating bearing surface on a machine part makes for better machinery and factory equipment, often proves a life-saver in curing difficulties where bearings are overloaded or inaccessible for lubrication, or on installations that with normal practice constitute a problem entailing frequent repairs. On the other hand, other parts may require low porosity approaching solidity. In the second field, powder metallurgy provides many possibilities for improved products, improved performance, solving of technical problems, saving of weight, quiet operation, higher factors of safety, greater flexibility, attractive economies, and so on. Parts We of the automotive industries are making many powdered-metal war-machine parts, both ferrous and nonferrous, including gears, external and internal; ratchets, both external and internal; levers; pillow blocks; sliding blocks; cams; gibs; hubs with external and internal splines, and similar units. Powdered metals play an important part in our war work, as they did in peacetime in the manufacturing of passenger cars and trucks. The art of powder metallurgy is not a panacea. Although on certain parts such operations as turning, boring, facing, reaming, counterboring, milling, countersinking. chamfering, broaching, hobbing, profiling. trepanning, gear cutting, grinding, etc., can be eliminated, there will always be the need for machine tools. Advantages of Powder Metallurgy Simple machining operations often are eliminated by using powdered metal, and also many other intricate operations, some of which are of the type impossible to perform on the most modern production equipment; for instance, an external spline on a flange hub, where the spline must continue to the flange face and at full depth. Another important feature is that some of the machine parts may require a self-lubricating surface at one or more points; for example, proper lubrication of a sliding splined spool, while ordinarily most digcuit, is accomplished automatically with a self-lubricating powdered-metal bearing. Frequently machine parts are made with physical, mechanical and technological advantages unobtainable from cast or forged metals of similar analysis. Thus powder metallurgy offers the designing engineer broader latitude. Similarly, the engineer may take advantage of powder metallurgy in his teamwork with other departments. Another important advantage in powder metallurgy for machine parts is the relatively short time required for tool-up.

Jan 1, 1945

By S. Stutz

COAL, like most other minerals, only exceptionally occurs in a sufficiently pure state to he directly available for general manufacturing purposes. And even where this is the case, the small coal or slack is usually more impure than the lump coal, as the slate, clay, etc., from the roof and bottom of the vein become mixed with it in the handling it undergoes. These impurities often exceed ten or more percent in addition to the impurities of the coal itself. The most common impurities of the coal are slate, or shale, clay, and sulphur. The latter occurs in different forms, but most frequently as bisulphide of iron, or iron pyrites, and as sulphate of lime, or gypsum. In both cases the impurities add greatly to the amount of ash, and where they are present in considerable quantities the raw coal, and still more the coke made from it, is unfit for the, manufacture of iron. Coke will contain on an average at least ;fifty per cent, more ash and sulphur than the raw coal from which it is, made. To the manufacturer of iron every additional per cent. of ash which his coal or .coke contains is a source of additional expense, seemingly small, and yet very important in the aggregate. In the blast-furnace, for instance, the ash must be heated up to the melting-point, and, since it is composed largely of refractory substances, the consumption of carbon in melting it will be equal to at least one-half of its weight ; that is, a certain part of the coke is consumed for the melting and fluxing of the ash and is lost. Besides this, it is well enough known to the-iron-master that coke containing less ash makes the slag or cinder more liquid and less inclined to stick to- the walls of the furnace. Fuel containing much sulphur produces generally a white iron, poor in carbon, while from the same ore and flux, with a pure fuel, a good foundry iron might be obtained. The work of separating slate, sulphur, etc:, from the coal 'has as yet only been succesafully accomplished by the washing process. This process depends for its success on the differences in the specific

Jan 1, 1881

By H. R. Reed

THE cost of hoisting with electricity in deep mines is a matter about which little information has been published. This paper makes a detailed study of such costs and presents the information in a series of curves. In particular the curves show the cost of hoisting ore from depths varying from 500 to 7000 ft. Vertical with the shaft at 70° incline for the double cylindroconical and double cylindrical drums, the hoists operating balanced, using Ward Leonard and Ilgner-Ward Leonard control, and designed for most economical operation from each depth. Operation with the double cylindrical drum is expanded to cover hoisting from 2000 to 5000 ft. using equipment designed for 5000 ft. and from 4000 to 7000 ft. using equipment designed for, 7000 ft. Additional curves are included to show the ratings of the necessary hoist motors, energy input per hoisting cycle and size of flywheel in tons for complete equalization when the Ilgner-Ward Leonard system is used, also hoisting efficiency. The duty imposed on a mine-hoist motor fluctuates between wide limits during a cycle of operation. The demand on the motor may vary from a large horsepower value' near the beginning of the cycle to a small or a negative demand near the end of the cycle. Such factors as tonnage to be raised per hour, depth of shaft, and balanced or unbalanced opera-tion have such a marked effect on the operating cycle and vary to such an extent for different mines that no set of rules can he formulated for quickly determining the size of the motor required. The duty cycle from which the motor rating is (derived must he determined for each case according to the conditions of the proposed hoisting operations. The motor torque required at the cardinal points of the duty cycle is determined from the moment or torque in pound-feet necessary to raise and lower the load and ropes, accelerate and retard the load, ropes, drum, etc. The torque diagram depends largely upon the type of drum. Two different types of drums, if used on exactly the same duty cycles, may have widely different peak demands and capacities of hoist motors. The essential feature in the design of hoisting drums and in determining

Jan 1, 1937

By William B. Stephenson

IN the pumping of sands, slurries and slimes, practices developed over the years are the real keystones of successful operation. These practices are necessarily based on modifications of familiar theories. Practical methods used in the solution of problems involving the pumping of materials are set forth in the following discussion. BASIC REQUIREMENTS To pump sands and slurries economically, a few basic requirements must be met by the pumping system as a whole. A pipe-line velocity must be established that will move the fluid mixture throughout the entire system without any possibility of the solids settling out. To accomplish this, the velocity of flow must be slightly in excess of the critical velocity of the mixture. The critical velocity of a mixture varies from 3 ft. per sec. to 18 ft. per sec., depending on the screen analysis, concentration, and specific gravity of the solids in the mixture. Most tailings are pumped at a minimum velocity of 4 ft. per sec. if they include slimes, whereas the pipe lines of sand and gravel dredges require velocities as high as 18 ft. per second. A number of articles have been written on the determination of the minimum velocities required to maintain solids in suspension. Studies have also been made on the friction and pumping heads developed when handling solids in suspension.1-4 Our experience so far has shown that, within the normal operating limits of a pumping system, the friction factor follows more nearly the basis described by Howard,1 who says, among his conclusions: " ... values of ƒ (friction factor) .. . will decrease with an increase in velocity." This conclusion is borne out by our actual experience. When the velocity in a pipe line is not sufficient to keep the solids in suspension, the total friction head is greater than when the velocity is increased to a point where the solids are in suspension. A slight increase in the volume of feed to the pump and a slight increase in the pump speed are usually all that is necessary to put the system in balance. MAINTAINING CONSTANT VOLUME Within reasonable limits, the volume of mixture to be handled through a pipe line should be held constant, so that the required velocity will be provided at all times. There are several ways in which this can be accomplished. The commonest is to provide a sump of sufficient capacity to take care of slight surges in the volume of mixture being fed to the pumping system. This sump, however, should not be as large as a settling chamber. The use of a float-controlled, fresh-water make-up valve in a sump will guarantee a constant volume. Where variations in volume are slight,

Jan 1, 1946

By William A. Johnson

IT was pointed out in an earlier paper1 that our understanding of the atomic mechanism by which diffusion occurs in metallic alloys is scarcely in an advanced state. This unsatisfactory condition is the result not of any lack of interest, but of the difficulty of designing experiments that will yield suitable data. The diffusion coefficient of an alloy, measured in the usual way, is simply a number specifying the rate of homogenization of a nonhomogeneous metal; this number, of itself, can furnish neither the rate at which the individual atoms move nor information as to the mechanism by which they move. It does not necessarily follow, however, that such information cannot he obtained, even if the path to be followed is still not clear. Much success has been attained in the study of diffusion in ionic crystals. A number of experiments, for which there are few counterparts in connection with metals, yields information often indicating a detailed mechanism by which diffusion probably occurs. From such work, quite acceptable theories of lattice imperfections have been developed by Wagner, Schottky, Frenkel, Jost and others.2 It is postulated that real crystals of stoichiometric composition contain, in equilibrium, certain imperfections of which the most important types are: (I) vacant cation sites, with an equal number of interstitial ions; (2) vacant anion sites, with an equal number of interstitial ions; (3) equal numbers of anions and cations in interstitial positions; (4) equal numbers of vacant anion and cation sites. The classification of a particular crystal according to this scheme then follows from studies of the variation of electrical conductivity with pressure of the electronegative component surrounding the crystal, with ion size, and with temperature; other physical phenomena, such as the Hall effect, have aided in establishing the classification. The relative mobility of the anion and cation may be determined by chemical analysis of the salt at the electrodes following electrolysis. With such information, and knowing that one ion never occupies the lattice site normally belonging to an ion of opposite sign, it is usually possible to ascertain the diffusion mechanism. It is clear that the same experiments are not applicable to metal crystals, and substitute experiments that yield as much information have not yet been devised. Much can be learned, however, about the mobilities of the two* kinds of atoms in alloys by the use of radioactive metals as indicators. Only one such experiment has been performed in the past. In 1933, Seith and Keil,3 in an effort to explain the great difference between the rate of diffusion of gold in lead and of lead in lead, measured the rate of diffusion of radioactive lead in a gold-lead

Jan 1, 1942

By D. K. Crampton, H. l. 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 conductivity 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 was 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 containing 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 Adrian C. Dorenfeld

Laboratory data form the basis for the design of flotation circuits. These data, obtained from testing samples of the ore, should show the optimum con- ditions for concentrating the ore and the effects of change in process vari- ables. Among the more important variables commonly met in flotation practice are: Liberation Size-This is the particle size at which substantially all of the valuable minerals are detached from the gangue minerals. Reagent Additions- Experimental data will show the reagents used and their quantity, quality, and point of addition. Pulp Density-This is an important variable in the design of the flotation circuit because it is one of the factors determining the size and number of flotation cells. Flotation Time-The time necessary to make the separation into concentrate and tailing depends on such factors as particle size and reagents used and must be known for determination of the size and number of flotation cells in the plant. Temperature of Pulp-Temperature affects flotation reactions. Water at approximately room temperature is satisfactory for most flotation separations, but some minerals such as fluorspar are best floated in hot water. Type of Circuit-Many types of circuits can be designed, as discussed in detail later. The laboratory tests should provide data for design of the plant circuit best suited to the ore. Water-Knowledge of the quality of the future plant's raw water is important because water quality may drastically affect flotation results. If possible, flotation tests should be made using samples of the water to be used in the plant. Flotation results may vary with seasonal temperatures and with circulation of reclaimed water. Experimentation can show whether it will be necessary to provide for heating, cooling, treating, or reclaiming the water. Uniformity of Ore-The extent of variation of the ore in hardness, grind- ability, mineral content, and floatability should be investigated so that the designer can ascertain methods to overcome problems caused by ore variations. Settling and Filtration Data-To design the plant flotation circuits, settling and filtration rates and ultimate percentage solids of the various products must be determined. Corrosion and Erosion-Corrosion and erosion tests should be made on the flotation pulps, particularly if the pulps are acid or at an elevated temperature, so that suitable materials of construction can then be chosen.

Jan 1, 1962

by their overdogmatic picture of geology and their resulting drastic oversimplification and idealization of geologic features. I am in hearty disagreement with the recommendation that geophysics should be done by cooperative work between a geologist and a geophysi-cist. That arrangement would be comparable to doing petrography by having a physicist at the microscope and a geologist sitting by his side. The interpretation of the geological significance of geophysical data can be done efficiently only by a physicist who has become also a good geologist or by a geologist who is also a good geophysicist. Less Well-trained Men The rank and file, composing perhaps two-thirds of the personnel of exploratory geophysics, is not, and should not be, composed of highly trained men. The routine, stereotyped character of the work and the impossibility of promotion of more than a few from these lower ranks even under the best circumstances justify companies in filling the bulk of these rank and file positions with men having only a bachelor's degree at the most. There can be a wide range of training for such positions, although certain lines of study are preferred for certain kinds of work, and different employers have different preferences. For work in gravitational and magnetic prospecting, first preference will be for men having geological training and second for men with civil engineering training. In seismic work, men with geological training are preferred by some employers for computers; physicists, electrical engineers and all whose technical education has covered radio circuits are preferred for the other technical positions. Collegiate training in geophysical prospecting brings no preference and by many employers is given a slightly inferior rating. One large company seldom hires men who have just graduated with a major in geophysical prospecting. This prejudice is based on the reasoning that much of what is learned in college is obsolete or obsolescent, that most of the techniques learned in college will have to be unlearned, because different from those used by the employing company, and that in the long run additional courses in basic physics, mathematics and geology are of more value to a man than the courses on geophysical prospecting. DISCUSSION [This discussion refers to the five papers beginning on page 23 and ending on page 74.1 L. W. Blau,* Houston, Texas.—I have had some rather sad experiences with forecasting. For example, I could not foresee 10 years ago my present occupation, and I do not profess to be able to look ahead 10 years and tell anyone what he will be doing then. Referring to the point raised in the discussion, I do not know, for example, what the price of oil will be 10 years from now. If an appreciable number of

Jan 1, 1940

by their overdogmatic picture of geology and their resulting drastic oversimplification and idealization of geologic features. I am in hearty disagreement with the recommendation that geophysics should be done by cooperative work between a geologist and a geophysi-cist. That arrangement would be comparable to doing petrography by having a physicist at the microscope and a geologist sitting by his side. The interpretation of the geological significance of geophysical data can be done efficiently only by a physicist who has become also a good geologist or by a geologist who is also a good geophysicist. Less Well-trained Men The rank and file, composing perhaps two-thirds of the personnel of exploratory geophysics, is not, and should not be, composed of highly trained men. The routine, stereotyped character of the work and the impossibility of promotion of more than a few from these lower ranks even under the best circumstances justify companies in filling the bulk of these rank and file positions with men having only a bachelor's degree at the most. There can be a wide range of training for such positions, although certain lines of study are preferred for certain kinds of work, and different employers have different preferences. For work in gravitational and magnetic prospecting, first preference will be for men having geological training and second for men with civil engineering training. In seismic work, men with geological training are preferred by some employers for computers; physicists, electrical engineers and all whose technical education has covered radio circuits are preferred for the other technical positions. Collegiate training in geophysical prospecting brings no preference and by many employers is given a slightly inferior rating. One large company seldom hires men who have just graduated with a major in geophysical prospecting. This prejudice is based on the reasoning that much of what is learned in college is obsolete or obsolescent, that most of the techniques learned in college will have to be unlearned, because different from those used by the employing company, and that in the long run additional courses in basic physics, mathematics and geology are of more value to a man than the courses on geophysical prospecting. DISCUSSION [This discussion refers to the five papers beginning on page 23 and ending on page 74.1 L. W. Blau,* Houston, Texas.—I have had some rather sad experiences with forecasting. For example, I could not foresee 10 years ago my present occupation, and I do not profess to be able to look ahead 10 years and tell anyone what he will be doing then. Referring to the point raised in the discussion, I do not know, for example, what the price of oil will be 10 years from now. If an appreciable number of

Jan 1, 1940

By W. G. Matteson

In 1915, the State of California passed a law of great scope and importance. This law has been in successful operation for a year and may be briefly described as an act " establishing and creating a department of the State Mining Bureau for the protection of the natural resources of petroleum and gas from waste and destrucbion through improper operations in production; providing for the inspection of petroleum and gas wells; requiring all persons operating petroleum and gas wells to make certain reports" and providing the necessary officers and assessments to carry out the provisions of the act. The statute provides for a separate department of the State Mining Bureau, under the general supervision of the State mineralogist, with a staff composed of a "state oil and gas supervisor" and four deputies. It rules that all petroleum and natural gas wells shall be drilled, operated or abandoned under the supervision of the State supervisor, who shall order such tests or remedial work as seems to him necessary to protect the interests of property owners and the general public. It also provides for a board of arbitration to consider orders given by the supervisor which are not acceptable to the well owner. Section 18 of the act, which is the provision that is directly related to this paper, requires ('the owner of any well referred to in this act to keep a careful and accurate log of the drilling of such well," and further requires that this log shall show the character and depth of the formations passed through or encountered in the drilling, particularly the location and depth of the water-bearing strata; the character of the water encountered (so far as ascertained); whether the water was shut off, and, if solat what point; that it shall show completely the amounts, kinds and size of casing used; the depth at which oil-bearing strata are encountered; the depth and character of the strata, and whether all water was successfully and permanently shut off so as to prevent percolation or penetration into the oil-bearing strata. This log is to be kept in the local office of the owner or operator, subject to the inspection of the supervisor or any of his deputies at any

Jan 1, 1917

By Frederick Prime

THE Great or Cumberland Valley, which (under a variety of names) extends from Canada, through Vermont, Massachusetts, Connecticut, New York, Pennsylvania, Maryland, Virginia, and East Tennessee, to Alabama, is composed in part of limestones lying immediately above the Potsdam sandstone. Geologically, they belong to the era between the Potsdam and Trenton, and are commonly termed Calciferous. A peculiarity of these limestones is their great richness in limonite or brown hematite ores, which form a large part of the charges of the many blast-furnaces situated on their outcrops. The mines from which the ores are obtained are (properly speaking) only pits or quarries, from which the ore is extracted by means of picks or shovels, powder being rarely employed. The ore does not occur casually at any point in the limestone, but forms regular lines, following apparently the 'outcrops of certain beds. In Lehigh County, Penn., where I have been engaged on the Geological Survey of' the State, during the past season, there are three or four of these lines. During the progress of the survey I was much struck by the fact that the two most important and promising lines of outcrop were, one at the base of the crystalline schists (forming the South or Lehigh Mountain), and overlying the Potsdam sandstone conformably; the other, near the line of junction of the calciferous limestone with the slates of the Cincinnati epoch. The mines along these two lines, following the topography of the country, were in place, richer and more permanent than those of the belts between, which were generally leaner. A peculiarity of these two lines of outcrop, and one to which I particularly desire to draw attention, is the occurrence of what I at first mistook for a highly altered slaty limestone, but which subsequent analysis proved to consist in great part of damourite (hydrated potash mica). The following are analyses of this damourite slate I. From Fogelsville, Lehigh County, within a few hundred feet of the contact of limestone and slate, by Dr. F. A. Genth. II. From Hensingerville, Lehigh County, within 300 feet of gneiss, by Mr. Sydney Castle, of the University of Pennsylvania. III. From Allentown, Lehigh County, within 150 feet of con-

Jan 1, 1875

By S. F. Radtke, J. A. Snyder, R. M. Scriver

An automatic, continuous casting arc furnace employing a nonconsum-able electrode and a direct current arc has been constructed and operated successfully for titanium. A comparison of the properties of arc and induction-melted titanium indicates that where high ductility, formability, and toughness are required, arc-melted metal is preferable. BECAUSE of the reactivity of titanium metal with all known refractories and the common atmospheric gases, melting of the metal presents numerous problems. It is necessary to provide an inert atmosphere in the furnace as well as a crucible material that will not react with the molten metal, if a ductile ingot is to be produced. Two special furnaces have been developed that meet the requirements and one, the induction heated graphite furnace, has been described in some detail.' Little information is available for sizable units wherein power is applied to the melt through an arc, and the dearth of technical information on such a furnace prompted this report. It has been demonstrated clearly that arc melting produces titanium metal with superior toughness, ductility, and formability. To produce titanium ingots with these properties, an automatic, continuous casting arc furnace has been developed and is described herein. The history of arc melting may be traced to 1800, when Sir Humphrey Davy2 first experimented with Volta's electric battery and found that light could be produced and an arc formed between two carbon points attached to the cell. The discovery of the arc was followed by the design and construction of an arc furnace by Napier," in 1845, for the reduction of metal oxides. In 1853, Pichou' described a similar furnace, although it was not until the discovery of the dynamo in 1867 that the arc furnace could achieve commercial significance. In 1878, Siemens- esigned the first arc furnace intended for the melting of metals and by 1882 had melted steel and platinum successfully. . This was followed by Moissan's" classical work with the arc furnace in 1892. W. von Bolton,' in 1905, found that the arc furnace was suited admirably for melting refractory metals. In his work with tantalum, no suitable refractories for retaining the molten metal were found to exist. Together with Otto Simpson, he developed an arc furnace with a water-cooled copper crucible in which tantalum could be melted without contamination. This technique proved eminently successful. In his paper on the preparation of ductile titanium, Krolle first described an application of the von Bolton furnace to the melting of this metal. The

Jan 1, 1952

By E. F. Kingsbury

ONE of the well-known and important uses of the noble or precious metals has been for electrical contacts. In fact, the elements of this group, comprising gold, silver and the six platinum metals, have been called "noble" because of their ability to resist heat and corrosion, properties which were early found to be of importance in good contacts. Of these, platinum and its iridium alloys, palladium, and silver, have been extensively used. In recent years the electrical industry has been responsible for about one-eighth of the total consumption of the platinum metals in the United States. Information is not available as to what part of this one-eighth has been used for contacts but it is certainly an important one. SUBSTITUTES FOR PLATINUM During the past 20 years a considerable number of contact alloys have been proposed in the patent literature largely with the aim of more or less replacing platinum by gold or silver, and some of these alloys are finding increasingly widespread application as the reliability of their performance becomes established. From even the partial data-at hand it appears that this substitution by the less precious metals has replaced at least one-half of the amount of platinum that the entire electrical industry would otherwise be consuming at the present time. While the subject is of considerable interest to the metallurgist it is , even more so to the electrical engineer and it is surprising that the literature records no systematic and comprehensive investigation along these lines. Practically all the scattered work on noble metal contacts has centered around platinum as a Standard and has had two more or less distinct aims. One of these has been the replacement of platinum by cheaper materials, and the other, the development of materials of superior electrical performance. The merit of a contact metal has been assumed to be dependent on its infusibility, and since the more precious metals have the higher melting points there has naturally been an association of the two qualities in the sense that the more precious were

Jan 1, 1928

By J. Walter Snavely

PRESENT-DAY processing in many industries, calcining, sintering, briquetting, beneficiation and nodulizing, increasingly calls for the handling of large volumes of hot bulk materials. Various types of conveyors have been employed. This discussion will cover the factors governing their selection. For temperature ranges up to 400°F, or approximately 200 °C, a wide range of conveyors is available. Special constructions of rubber conveyor belts, steel conveyor belts, vibrating and shaker conveyors, apron conveyors, and drag chain conveyors, all are used successfully. As temperatures go well above 400 2F, however, choice of conveyors is narrowly limited. This paper will consider the problem of handling bulk materials only where the temperatures exceed 400°F. The arbitrary selection of 400 °F as a dividing point undoubtedly can be challenged, as special conveyor belting constructions are available which are suitable for temperatures in excess of 400°F. However, when the relatively short life of such belts and the cost of their replacement, with the attendant down time, are balanced against the reliability and long service life of the properly designed steel constructed units to be discussed, there is little question in any operator's mind that the special belts are more expensive to use. Because the conveyors under study are for the handling of bulk materials, inevitably including a high proportion of fines, obviously wire mesh belts cannot be included for consideration. Even though this type of conveyor is widely used at high temperatures, i.e., for carrying glassware through a lehr, it is unsuited for the conveying of bulk materials, and therefore will be excluded from further discussion in this paper. Preliminary to the study of the conveyor itself is the determination as to whether the material is to be cooled while it is being handled, or whether the processing requires retention of all heat and the maintenance of a given temperature range. In the majority of cases cooling is incidental to or part of the handling process, when the handling, for example, follows completion of sintering, roasting, calcining, refining, or some other process. To meet such operating conditions successfully, the conveying medium used must have: 1—a construction capable of withstanding maximum initial temperatures of the material being handled. 2—a construction providing efficient heat transfer for cooling. 3—a construction providing dependable operation and long life with minimum service requirements, and 4—a construction providing controlled and efficient conveying. Under the usual conditions of cooling during the handling, the construction selected to withstand the initial maximum temperatures does not necessarily involve using alloys, as excellent results can be achieved with normal carbon steels and cast irons, when they are properly applied and proportioned. The earliest and simplest type of conveyor for handling very hot materials is the cast steel drag chain conveyor, still widely used for handling hot cement clinker, as illustrated by Figs. I and 2. Because of the rugged and generous proportions of the chain link design, low carbon steels are entirely suitable for the links. The pins, however, must be alloy steel. The simple, rugged construction of this type of conveyor makes it readily capable of withstanding high initial temperatures, even though the chain is operating buried in the material. The drag-chain type of conveyor has advantages and limitations. Although the efficiency of the heat transfer is relatively poor, the life of the conveyor is reasonably long, and because of its crude simplicity it does not require much servicing. However, as a conveyor, it is limited in capacity, and largely limited to horizontal runs. Furthermore, because of the crude design, heavy weight, and the chain operating at the temperature of the material, greatly reducing permissible operating chain pulls, this type of conveyor is limited to relatively short centers. Another type of conveyor that has been used for very hot materials is the cast pan conveyor. Because of its very generous proportions the cast pan, which is made of either cast iron or malleable iron, can withstand initial maximum temperatures. It also provides efficient heat transfer for cooling. Further, it is on efficient conveyor construction, which can be used for inclines. Because the chain employs rolling friction instead of sliding friction, and is not in the maximum temperature zone, much longer centers are possible. It is this type of conveyor that is frequently used in the casting of various metal pigs, pig iron, and aluminum; it is obvious, therefore, that very high initial temperatures are being handled. With this kind of conveyor the return run is frequently sprayed with water to accelerate heat transfer. The build-up of residual heat in the very heavy cast pans is thus overcome. The outboard roller steel pan conveyor is an improved pan conveyor' which provides high rates of heat transfer and substitutes formed steel pans for the heavy cast pans. It is a very efficient conveying medium. The details of this particular construction are clearly shown in Fig. 3. An early application of this type of conveyor is shown in Fig. 4. In this case the conveyor units are handling roasted phosphate rock at average temperatures of 1000" to 1500°F, and frequent maximum temperatures as high as 1900°F. Several widths are used. The capacity of the unit at a speed of 50 fpm is approximately 30 tph per inch of width at peak loadings, average capacity being about 1/3 of peak loading. The assembled conveyor is shown in Fig. 5, with views of both the top and the underside to show all the construction details. In particular, the following general design principles were carried out in this construction:

Jan 1, 1954

By C. J. P. Ball

Prior to 1939 the bulk of the magnesium metal produced outside of the united Stater was extracted directly from the ore and ifi the United States from magnesium chloride obtained as a by-product from the treatment of natural brines. A typical brine is one containing about 0.25 to 0.75 per cent bromine, 11 to 14 per cent sodium chloride, 9 to 11 per cent calcium chloride and 3 to 10 per cent magnesium chloride. The state of Nevada was known to possess large deposits of magnesite ore (MgCOs, the carbonate of magnesium), in Gabbs Valley, near Luning, approximately 350 miles north of Boulder Dam. Deposits mined in Europe were supplying magnesite giving 97 per cent MgCOs with about I per cent each of silica, lime and oxides of iron and aluminum. parts of the Luning de-posits Were almost equally rich, and the general average was of sufficiently high grade for production of magnesium. power to the amount of 200,000 kw. was available immediately from Boulder Dam, and water from Lake Mead, and it was this combination of available power, water, and ore that led to the initial proposal to erect a magnesium reduction plant in southern Nevada to reduce the magnesite ores from Gabbs. The extraction of magnesium metal from these magnesite deposits had been considered by the I. G. Farbenindustrie of Germany as far back as 1929. Mine and Oxide Plant The mine and oxide plant of Basic Magnesium Incorporated are perched upon the oride slope of the Paradise Range, at an altitude of 5000 ft., overlooking the 30 mile desert panorama of Gabbs Valley, Nevada. , Ore Occurrence The Gabbs magnesite ores occur in a thick series of flat, westerly dipping dolomites of Upper Triassic age. The mag-"esite bodies are exposed in steep canyon "areas encircling the north and east edges of a northerly projecting tongue of a roughly elliptical stock of granodiorite, which intrudes the dolomite. The magnesite mineralization is considered to be a a of calcium by magnesium through the agency of hydro-thermal solutions associated with the intrusion of the granodiorite. The ore bodies are of very irregular shape and distribution. Incomplete evidence points to deep pipelike replacement shapes that mushroom out erratically at various elevations. A wide latitude in the degree of magnesium replacement is reflected in a variance of quality from pure magnesite to magnesitic dolomite. The, ore is a massive crystalline mag-nesite. Though some differences in characteristics occur between ore bodies, in general the ore is a medium-grained carbonate varying in color from white, through all shades of gray, to black. Recrystallized dolomite, which encloses and occurs as

Jan 1, 1944

By John P. Bryant

Plant nutrients are obtained by plants from both the air and the soil. Carbon dioxide, a gaseous form of carbon and oxygen, supplies the carbon which usually makes up 50% or more of plant structure. Plants are capable of absorbing carbon dioxide directly from the air. Most of this nutrient comes from the air, although some carbon dioxide is absorbed by soil water and taken into the plant as liquid. Growing plants use more water than any other substance. Plant nutrients in the soil dissolve in soil water; soil water entering the plant carries nutrients into the plant structure. Water is then given off into the air as the plant breathes or transpires. The inorganic or mineral portion of the nutrients which plants require comes from the soil. Inorganic or mineral composition of plants is usually less than 5% of their weight, and this mineral requirement, usually lacking in the soil, must be provided by fertilizers. Proper fertilization of a soil to improve its mineral level and productivity is the basis for the fertilizer industry (Thomas, 1960). There are 13 essential plant nutrients which often must be added to soils or plants and are generally considered as fertilizer minerals. These nutrients are divided into the categories: primary minerals (nitrogen, phosphorus, potassium); secondary minerals (calcium, magnesium, sulfur); and micro or trace minerals (boron, iron, manganese, copper, zinc, molybdenum, chlorine). Further, cobalt is often added to fertilizers. Although it is not considered to be an essential plant nutrient, it is essential to animal health and is often applied to forages as a fertilizer constituent. One point of major significance to the fertilizer industry is that not all nutrient carriers supply that nutrient in a chemical form which will be available to the plant. Thus, a product which may be considered a fertilizer mineral may require substantial processing or treatment before it becomes useful as a nutrient carrier. Fertilizer Industry Scope Until about 1900 demands for higher crop yields were met simply by bringing new agricultural lands into cultivation. Since that time great progress has been made in increasing yields through fertilization and improved varieties and cultural practices. The importance of the fertilizer industry to the economy and welfare of the U.S. is widely recognized. [Fig. 1] illustrates the relationship of lime and fertilizers to crop yields. In terms of tons of fertilizer products, the growth of the industry has been phenomenal, particularly between 1950 and 1970. Table 1 shows the increase in fertilizer usage. Primary Plant Nutrients in Fertilizers Primary minerals (nitrogen, phosphorus, potassium) are designated as such because of their significance to plant growth. Practically all soils are deficient in both nitrogen and phosphorus, and most of them are also deficient in potassium. Consequently, these nutrients

Jan 1, 1975