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By J. D. Dixon

Procedures are given for calculating stresses in underground tunnel supports which accounts both for the structural behavior of the support and that of the adjacent rock mass. Stresses in the support are caused by service loads and rock reactions. Service loads are due to rock pressures, hydrostatic and hydraulic pressures, selfweight of the support, or other utilitarian-type loads. Rock reactions, equal and opposite those in the support, are due to the deformational interaction that results as service loads deform the tunnel support against the adjacent rock mass. The procedures developed for solving this problem are an application of matrix structural analysis. The principles involved in this method allow for the consideration of the deformable characteristics of most tunnel support systems and an iterative solution procedure is applied to determine the areas of support-rock interaction. Numerical results of example problems are given.

Jan 1, 1972

By W. E. Horst

During the past few years of operation at Kings Mountain, N. C., full-scale flotation has generally yielded poorer metallurgical results than those obtained in the laboratory or pilot plant. After 2 min in each size of Denver flotation machine in the spodumene rougher circuit, pilot recovery (41.7 pct) was almost three times that of the plant (13.6 pet) and about twice that of the laboratory (21.0 pet). Pilot and commercial plant data are based on continuous operation, and laboratory results on batch testing of rougher performance. The ore is a pegmatite containing spodumene, feldspar, quartz, mica, and amphibolite. Data were accumulated to evaluate the scale-up relationships between laboratory, pilot plant, and plant flotation cells. Flotation rate constants and dimensional analysis were used to define the relationship existing between flotation behavior and scale of operation.

Jan 11, 1958

By Oliver Bowles

When a new type of equipment revolutionizes methods of quarrying one kind of stone, producers of other kinds focus their attention on its potentialities in their particular fields. The purpose of this paper is to discuss the accomplishments of the wire saw in slate, to show its more limited attainments in other kinds of stone, and to point out the possibilities of much wider application. A wire saw consists of a 3/16-in. or ji-in. three-strand wire cable that runs as a belt and cuts the rock by abrasion. (Fig. 1. The teeth of the saw are sand grains carried in the grooves between the strands. Accomplishments in Slate† Initial experiments with wire saws by the U. S. Bureau of Mines in the Colonial Slate Quarry, Wind Gap, Pa., in 1926, attained success so immediate and pronounced that within two years in virtually every quarry in the neighborhood of Wind Gap, Pen Argyl and Bangor, the most productive slate area in the United States, wire saws were substituted for channeling machines. An 80-ft. cut in slate is shown in Fig. 2. The technique of operation has been described in several reports (references at the end of the paper). The present purpose is to summarize the accomplishments in a large, typical slate quarry after nine. years of experience. Parsons Bros. Slate Co., at Pen Argyl, Pa., substituted two wire saws for six channeling machines in 1927. The following comparisons are made between the present method with wire saws and the former channel-ing-machine method. Rate of Sawing.—The average rate of cutting with a wire saw in the early days of its operation, as determined by the Bureau of Mines', wits 14 to 17 sq. ft. per hour. Parsons Bros. Slate Co. estimates the present rate of cutting at about 25 sq. ft. an hour, whereas the channeling-rnarhirle

Jan 1, 1938

By Alan Morris

Impingement attack, as one of the types of corrosion suffered by condenser tubes, has been given a prominent place in corrosion literature of recent years. It has been reproduced and studied in carefully controlled laboratory tests. Much has been learned of its mechanism, and of the effects of variables such as temperature, amount of air, size of bubble and water velocity. Incidentally the technical public has been given comparisons between the behavior of some few metals under various conditions of impingement attack. The tests recorded here were undertaken in an effort to find at least some sort of qualitative answer to questions which arose occasionally as to the relative resistance of various alloys to impingement attack, and which could not be answered by reference to the literature. The final decision to start work on the problem was influenced in large measure by the nature of the water available in this particular place. The mill of the Bridgeport Brass Co. is located on the Pequonnock River at Bridgeport, Conn., within two miles of its mouth. The water is much like many other estuarine sources which are used in condensers, and which cause particularly severe corrosion. It seemed a most suitable water to use in such tests. As the work progressed an important seasonal variation was noted. The purpose of this note is to record this seasonal effect. The results of individual tests are given only incidentally. Impingement Tests Early in 1929 the apparatus was built. The samples were disks of 1-in. dia., cut from sheet metal. They were eleaned with fine emery cloth and set in holders, as shown in Fig. 1. A stream of water pumped directly from the river impinged on the surface of the sample. Compressed air was injected into the water stream through an air duct. Water pressure was maintained at about 35 Ib. per sq. in. and air was controlled by a needle valve. Velocity of

Jan 1, 1932

By James P. Kimball

THE object of the present memoir is to put on record some practical experiments by the writer in smelting a silicious native magnetite with no other flux than the silicates of its own gangue: This work was undertaken in the spring of 1878 for Messrs. Naylor & Co., of Boston, to whom I am indebted for the privilege of here communicating its results, these having hitherto only been simply announced.* So far as I am aware these are the first instances of the kind in this country that non-calcareous; or rather non-carbonated, magnetites have successfully been used strictly alone as self-fluxing ores in the blast furnace; that is, without the addition of calcareous flux in the form either of limestone, quicklime, calcareous ore, or basic (calcareous). slag. Previous to the spring of 1878, when the Chateaugay magnetic ore was first brought to my notice, its use had been limited to Catalan forges, after "separation" at the ore bed. The blooms and billets made from it in the several forges of Messrs. Weed & Williams, and of Mr. Williams, were well known in the trade as among the best in the market. The Chateaugay ore beds proving of great magnitude, and the ore exceptionally low in phosphoric acid, it commended itself for blast-furnace purposes to Messrs. Naylor & Co., who employed nee to blow-in the charcoal furnace at Pittsford, Vt., on this ore in the spring of 1878., a previous trial of this ore in the same furnace in the fall of 1877 having proved abortive. This was therefore the first time that Chateaugay ore was successfully smelted in a blast furnace, although since well known as a blast-furnace ore possessing superior and exceptional qualities. The Pittsford furnace, although rebuilt in 1844, and subsequently improved by the former owner, the late J. Prichard, is one of the few furnaces of the old type with open breast (Sumpfofen) still active in this country. Its improvements on furnaces of the period, * Bulletin American Iron and Steel Association, XII, 1878, 132, 156.

Jan 1, 1881

By Oliver Bowles

When a new type of equipment revolutionizes methods of quarrying one kind of stone, producers of other kinds focus their attention on its potentialities in their particular fields. The purpose of this paper is to discuss the accomplishments of the wire saw in slate, to show its more limited attainments in other kinds of stone, and to point out the possibilities of much wider application. A wire saw consists of a 3/16-in. or ji-in. three-strand wire cable that runs as a belt and cuts the rock by abrasion. (Fig. 1. The teeth of the saw are sand grains carried in the grooves between the strands. Accomplishments in Slate† Initial experiments with wire saws by the U. S. Bureau of Mines in the Colonial Slate Quarry, Wind Gap, Pa., in 1926, attained success so immediate and pronounced that within two years in virtually every quarry in the neighborhood of Wind Gap, Pen Argyl and Bangor, the most productive slate area in the United States, wire saws were substituted for channeling machines. An 80-ft. cut in slate is shown in Fig. 2. The technique of operation has been described in several reports (references at the end of the paper). The present purpose is to summarize the accomplishments in a large, typical slate quarry after nine. years of experience. Parsons Bros. Slate Co., at Pen Argyl, Pa., substituted two wire saws for six channeling machines in 1927. The following comparisons are made between the present method with wire saws and the former channel-ing-machine method. Rate of Sawing.—The average rate of cutting with a wire saw in the early days of its operation, as determined by the Bureau of Mines', wits 14 to 17 sq. ft. per hour. Parsons Bros. Slate Co. estimates the present rate of cutting at about 25 sq. ft. an hour, whereas the channeling-rnarhirle

Jan 1, 1938

By J. A. Bownocker

THE EXISTENCE of petroleum in the rocks of Ohio and Indiana seems to have been first shown by wells dug for salt. The fuel, however, was objectionable owing to its odor and inflammability. Not until the brake well was drilled in 1859 did the people appreciate the value of rock oil, and then they at once began plans to secure the coveted fuel.. The first successful well in these two states was near . Macksburg, in southeast .Ohio, where at a depth of 59 ft. (17 m.) :oil was found in commercial quantity (1860). A year later this fuel was secured on Cow Run, in the same county, and at about the same time in Noble, Morgan and perhaps other counties in that part of Ohio. The second great step in the production of oil in Ohio and Indiana was taken in 1884 when the reservoir of natural gas in the Trenton limestone of northwest Ohio was tapped, and where a year later oil was secured in the same formation. Petroleum in this limestone was obtained in Indiana in 1889.1 The third step in the production of oil' in Ohio and Indiana is associated with the Clinton sand of Ohio. Natural gas in large volume was discovered in that rock at Lancaster, in 1887, and the area has been extended until it has become the largest individual producer in the world. The presence of natural gas in such great volume all but demonstrated to the driller that-oil lay hidden near by. Soon the search for it was started but not until 1899 was petroleum in commercial quantity found in the Clinton sand, and a large pool was not located in it until 1907. The fourth step in the development of the industry was taken in 1913, when the pool in Sullivan County, in western Indiana, was opened. The producing rock is the Huron sandstone, which is the topmost member of the Mississippian system.2

Jan 2, 1920

By R. W. Mancantelli, J. R. Woodward

IN 1947 a large low grade deposit of uranium was located in the northwest corner of Saskatchewan, in the Beaverlodge property of Eldorado Mining & Refining Ltd. Most of the values occur as thin seams and as coatings on other minerals, and the ore, which is light and friable, is not amenable to the usual gravity methods of concentration. The acid leaching process developed to retreat the company's Port Radium tailings was also impractical, as the percentage of carbonates is high and the percentage of sulphides relatively low. Construction of the mill building and installation of equipment, both scheduled for 1952, awaited selection of a satisfactory ore dressing process on or before Oct. 1,1951. An extensive research program on dressing of ores from the Ace mine therefore was undertaken by the Mines Branch in Ottawa, a research team at the University of British Columbia, and an ore dressing group at the company's Port Hope refinery. Pilot plant operations were conducted at the Ottawa plant of Sherritt Gordon Mines Ltd. under the general direction of C. S. Parsons, consultant on metallurgy and ore dressing for Eldorado. In mid-September, having compared results of the several research programs, Dr. Parsons recommended a process employing a carbonate or basic leach. He reported that, while the chemistry of the process had been proved, engineering of the flowsheet was incomplete, and he suggested that under normal conditions further pilot plant work at the Ace mine might be profitable. However, since this would involve a delay of 12 to 18 months in bringing the property into operation, he recommended that design of the concentrator proceed immediately. Concentrator capacity was determined by two considerations: 1) the amount of ore then available and 2) the expectation that continued improvements would be made in the ore dressing process as a result of the intensive research being carried out by the Mines Branch of the Department of Mines and Technical Surveys. As these improvements could affect both the chemistry and the en-

Jan 1, 1956

By L. Massé, Th. Koulomzine

NOTE ON HAALCK'S FORMULA QUANTITATIVE interpretation of magnetic anomalies is admittedly a difficult process. Few authors have attempted a general approach to this problem. A [ ] number of publications can be found widely scattered through scientific periodicals, which present particular solutions obtained by the introduction of simplifying assumptions, such as the reduction to an equivalent magnet or pole, or the hypothesis of a very thin vein. The practical applications of these solutions are necessarily very restricted though they have given satisfactory results in isolated cases. Probably the most widely known equation of this type was given by Haalck.l His classic work contains curves calculated for typical conditions, and has now become a standard reference. However, a close scrutiny of Haalck's derivation reveals that, aside from the hypothesis of a thin vein, it rests on the

Jan 1, 1947

By Tracy C. Jarrett

The alloying of various elements with gold to produce different colors is an old art, but the effect of each element or combination of elements is not generally known. Investigations have been made in this field by F. E. Carter,' E. M. Wise,2 and L. Sterner-Rainer.3 It is the intent of this paper to present in schematic diagrams the effects of various elements upon the color and the melting point of gold alloys. In this investigation 2-oz. melts made in a high-frequency inductiorl furnace were used for all tests. The melting points were determined by the use of a calibrated chromel-alumel thermocouple sealed in a thin-walled alundum tube. The couple was then submerged in the molten metal and the freezing and melting points were determined by using a Leeds and Northrup potentiometer. By checking several melts using copper, zinc and gold, it was found that the accuracy of determining the melting point was within ± 5" F. To determine the differences in colors and to classify them, a wet tissue paper was placed over the polished samples and examined under a uniform white light. The 2 by 45 by 0.045-in. samples were cut from 50 per cent cold-worked strip. The original ingot was 3 by % by % in. This visual comparison, although not scientifically exact, served as a quite satisfactory means for determining and classifying these differences. The base alloys, or "hardeners," were first made up and analyzed, after which the gold and silver were added. This method of making up the alloys was chosen so that the same base alloy could be used for the gold alloys of different karats. The first series consisted of gold, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the "hardener" and the zinc and nickel replacing copper. The second scries consisted of gold, silver, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the hardener with the silver, nickel and zinc replacing copper. There was no particular reason for choosing these combinations, except that they gave a color range from red-pink to white.

Jan 1, 1940

By Rodney P. Smith

THE solubility of columbium nitride in ? iron has been determined for the temperature range 1191o to 1336°C from the nitrogen content and metallogra-phic examination of a series of Fe-Nb alloys.* (0.0 to 0.92 pct Nb) equilibrated with a purified gas mixture of 1 pct hydrogen in nitrogen. The method is the same as that used by Darken, Smith, and Filer' to determine the solubility of aluminum nitride in y iron. The variation in the furnace temperature during an equilibration period was about ± 2.0°C. Each sample was approximately 1/2 in. wide, 2 in. long, and 1/16 in. thick. A time series at 1200°C using samples of highest columbium content indicated that one day was sufficient for equilibrium; however, to be on the safe side all samples were left in the furnace for either two or three days. Afterequilibration, the samples were brought to room temperature by quenching in water. The experimental results are shown in Fig. 1. To be in accord with the values reported by Wriedt and Gonzalez2 and the temperature coefficient of our results at higher temperatures, the nitrogen content of iron at 1191oC is assumed to be slightly lower than our experimental value. Our data for the single-phase regions are not sufficiently accurate to establish an interaction coefficient for nitrogen in these alloys. However, the change in nitrogen content with change in alloy content for a number of systems (Fe-N-A1;3,1 Fe-N-Ni;372 Fe-N-Si.3949 Fe-N-V;3,5 Fe-N-Cr;3,6 Fe-N-Mo3,7) has practically the same value for the liquid alloy at a temperature near 1600°C as for the solid alloy at temperatures near 1200oC when the alloy content is below a few percent. On this basis the lines through the single-phase regions have been drawn with a slope corresponding to an increase in nitrogen of 0.0013 pct per 0.1 pct Nb.3 The straight lines through the two-phase regions were drawn with a slope corresponding to a one-to-one atom ratio of nitrogen to columbium in the nitride. The X-ray

Jan 1, 1962

By Joseph Jensen

When the legal holders of Government permits in the Middle dome of Kettleman Hills entered into an agreement on May 27, 1929, to suspend all drilling activities on five permits, covering portions of the Kettleman Hills Middle dome, until Jan. 1, 1931, and the owners of fee lands contiguous thereto assured Secretary Ray Lyman Wilbur, of the Department of the Interior, that they too would respect a drilling suspension for a period of a little more than 19 months, none of these interested parties realized that this was the first step in a chain of events that would culminate, more than four years later, in the formation of the Middle Dome Corporation for the development of the Middle dome area in a unit plan that would be the first unit plan to be approved by the California Regional Producers Committee and recommended to the President as a satisfactory unit plan, under Section 7 of Article III of the Oil Code, approved Aug. 17, 1933. Neither did they realize that more than two million dollars would be spent before oil or gas would be successfully and continuously produced from wells drilled on that Middle dome area. On Oct. 1, 1933, under the terms of the Middle Dome Agreement, the Middle Dome Corporation assumes control of activities and is responsible for the division of all product's produced from the Middle dome area to members of the Middle Dome Corporation. This Middle dome plan is the second successful unit plan developed in California in the past three years, the first being the Kettleman North Dome Associationll formed under the agreement, of Jan. 31, 1931, for the unified operation and development of more than 12,000 acres of land on the North dome of the Kettleman Hills. All other unit plans discussed in the past four years in the state have not yet been completed, for one reason or another, but under Section 7 of Article 111 of the new Oil Code numerous plans of development, some of which may be unit plans, will be forthcoming within the next few months. There is much

Jan 1, 1934

By Tracy Jarrett

THE alloying of various elements with gold to produce different colors is an old art, but the effect of each element or combination of elements is not generally known. Investigations have been made in this field by F. E. Carter,1 E. M. Wise,2 and L. Sterner-Rainer.3 It is the intent of this paper to present in schematic diagrams the effects of various ele¬ments upon the color and the melting point of gold alloys. In this investigation 2-oz. melts made in a high-frequency induction furnace were used for all tests. The melting points were determined by the use of a calibrated chromel-alumel thermocouple sealed in a thin-walled alundum tube. The couple was then submerged in the molten metal and the freezing and melting points were determined by using a Leeds and Northrup potentiometer. By checking several melts using copper, zinc and gold, it was found that the accuracy of determining the melting point was within ± 5° F. To determine the differences in colors and to classify them, a wet tissue paper was placed over the polished samples and examined under a uniform white light. The 2 by ½ by 0.045-in. samples were cut from 50 per cent cold-worked strip. The original ingot was 3 by ¼ by ¾ in. This visual comparison, although not scientifically exact, served as a quite satisfactory means for determining and classifying these differences. The base alloys, or "hardeners," were first made up and analyzed, after which the gold and silver were added. This method of making up the alloys was chosen so that the same base alloy could be used for the gold alloys of different karats. The first series consisted of gold, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the "hardener" and the zinc and nickel replacing copper. The second series consisted of gold, silver, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the hardener with the silver, nickel and zinc replacing copper. There was no particular reason for choosing these combinations, except that they gave a color range from red-pink to white.

Jan 1, 1939

Discussion of the paper of Woolsey McA. Johnson, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 79, July, 1913, pp. 1137 to 1145. F. L. GRAMMER, Leesburg, Va. (communication to the Secretary *):-Mr. Johnson's paper must interest by suggestion those connected with the " burning " of lime, the production of cement, and the smelting of iron. All iron men know how quickly the impalpable purple ore of wet origin reduces compared to finely ground red hematites of approximately identical composition obtained from Lake lump ores. Most housekeepers appreciate that the several forms of carbon-charcoal, coke, and anthracite, not to include graphite and diamond -have different temperatures of ignition. The temperature usually rises with the density and hardness. Some of the scientific bureaus of the government might appropriately conduct some tests along lines suggested by Mr. Johnson's article. We are unable to say whether the topic lies within the spheres of activity of the Bureau of Mines, the Bureau of Soils (Agricultural Department), the Geological Survey, or the Bureau of Standards. The calcining qualities of limestone is a topic too wide for individual effort and is of wide enough interest to merit government or State activity. It is of interest, as aforesaid, to burners of lime, cement manufacturers, and smelters. The chemical composition of a limestone does not tell all the story -if over 1-in. size lumps. The limestones of Annville and Myerstown, Pa., break at a tap; those on the Hudson above Poughkeepsie .act like "nigger heads." The manager of lime kilns near Lake Champlain told me his fuel consumption was high compared to that at other points. Yet the Hudson and Annville stones were both of greatest purity, being rivaled by only the marble at Rutland, Vt., or some stones near Martinsburg, W. Va. A local kiln operator says the conglomerate or pudding limestones of Loudoun county, Va., act very differently in the kiln from the more normal limestone deposits nearby. The tilted and twisted bedding in the anthracite region tells the story of hard coal origin. We might therefore expect that the limestones of greater geological age or depth or metamorphism

Jan 11, 1913

By Tracy C. Jarrett

The alloying of various elements with gold to produce different colors is an old art, but the effect of each element or combination of elements is not generally known. Investigations have been made in this field by F. E. Carter,' E. M. Wise,2 and L. Sterner-Rainer.3 It is the intent of this paper to present in schematic diagrams the effects of various elements upon the color and the melting point of gold alloys. In this investigation 2-oz. melts made in a high-frequency inductiorl furnace were used for all tests. The melting points were determined by the use of a calibrated chromel-alumel thermocouple sealed in a thin-walled alundum tube. The couple was then submerged in the molten metal and the freezing and melting points were determined by using a Leeds and Northrup potentiometer. By checking several melts using copper, zinc and gold, it was found that the accuracy of determining the melting point was within ± 5" F. To determine the differences in colors and to classify them, a wet tissue paper was placed over the polished samples and examined under a uniform white light. The 2 by 45 by 0.045-in. samples were cut from 50 per cent cold-worked strip. The original ingot was 3 by % by % in. This visual comparison, although not scientifically exact, served as a quite satisfactory means for determining and classifying these differences. The base alloys, or "hardeners," were first made up and analyzed, after which the gold and silver were added. This method of making up the alloys was chosen so that the same base alloy could be used for the gold alloys of different karats. The first series consisted of gold, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the "hardener" and the zinc and nickel replacing copper. The second scries consisted of gold, silver, copper, zinc and nickel, the copper comprising from 85 to 65 per cent of the content of the hardener with the silver, nickel and zinc replacing copper. There was no particular reason for choosing these combinations, except that they gave a color range from red-pink to white.

Jan 1, 1940

By F. V. Hicks

THE similarity of mining practices in bituminous coal fields through-out America is due to the fact that certain fundamental conditions are encountered in all fields. The problems of labor, housing and mining are somewhat similar whether the mine is in Pennsylvania, Illinois, Wyoming or the State of Washington. Each field has had its particular problems, resulting in advantages or disadvantages over a competing field. This might take the form of a wage differential, a better natural condition more favorable to cheap production, or proximity to a market that allows freight rate advantages, etc. In any event, no matter how favorably situated, the mining companies that have been slow to recog-nize and accept the advantage of mechanization, clinging too long to the old hand methods, have found themselves unable to meet competition. Throughout the Wyoming coal fields, production methods have so changed in the last decade as to be almost unrecognizable to an old-time coal miner who has had no connection with the industry during; that period. The old contract system, with its peculiar labor relationship between employer and employee, based upon the long-established custom that the miner's working place was his castle, and that it was his privilege to carry on operations within that place largely in his own way and to his own liking, is a condition that has passed away. The present-day, 100 per cent mechanized mine bears but little resemblance to the old. A change -in system has naturally altered the old-time labor relationship. Contract labor has been almost entirely eliminated and a straight day-wage basis established, with certain classes of work calling for different rates, which places the entire personnel of the underground operating force more directly under the direction and supervision of the mine foreman and his assistants. The transition from the old order to the new has gradually done away with the system of penalties, personal- rights and privileges existing under the contract system, which were so controversial in the past that the average mine management was constantly involved in labor disputes in fields where organized labor was employed.

Jan 1, 1936

By T. E. Harper, Gustave Reinberg

Electrolytic refining of all lead bullion produced at the Oroya smelter of the Cerro de Pasco Copper Corporation has been adopted as standard practice. A pilot refinery with a capacity of 25 metric tons daily has been in operation since June, 1934, and a new refining unit having an initial capacity of 100 tons per day is under construction. This program has been made possible by certain modifications of the usual Betts refining process1, developed at Oroya, which have the effect of making the purity of the lead produced, and the acid loss incurred in operating the process, entirely independent of the amount of impurities in the original bullion. The modified process, as developed and at present used, treats impure bullion direct, without presoftening or other prerefining step, except that if the bullion carries tin it is desirable to detin before casting into anodes, since tin carries over to some extent to the cathodes. The refining process developed differs from usual Betts practice in two essential particulars: the anodes are cast thinner and replaced at more frequent intervals, and anode slimes are washed by a system of counter-current dipping, prior to their removal from the surface of the anode scrap. Limiting the period of anode corrosion insures a cathode of high purity, since solution of impurities at the anode can occur only if the thickness of the anode slime blanket, and hence the voltage drop across it, becomes greater than a certain critical value. The dip washing system operates to prevent acid losses, by recovering the highly concentrated, nearly neutral lead fluosilicate solution present in the pores of the slime blanket on the corroded anode, and doing this in such a way that there is no opportunity for chemical decomposition to occur. The best illustration of the efficacy of these two expedients may be secured from records of more than a year's operation of the 25-ton pilot plant, during which period the acid losses were less than 2 Ib. of 100 per cent hydrofluosilic acid (H2SiF6) per ton of lead produced, and typical assays of bullion and refined lead were as shown in Table 1.

Jan 1, 1937

By D. G. Brubaker

IN the history of geophysical exploration by the electromagnetic method many procedures and types of equipment have been used. Source arrangements for surveying on the ground have included long wires grounded at both ends, large loops laid on the ground, small horizontal loops, and vertical loops of moderate to small sizes. Receivers have ranged from simple direction-finding coils to combinations of coils and a bridge circuit to measure quantities related to both amplitude and phase of the received signal. Primary considerations in choosing a survey method are effectiveness, speed, and economy. In work on the ground in which locating and outlining conducting bodies is the objective, methods using a vertical coil and a simple direction-finder have been found the most satisfactory. Mason1 and his associates applied such a method by setting up a vertical source loop, fed with low frequency alternating current by an engine-generator set. With a direction-finding receiver they surveyed lines along the ground in the plane of the loop, taking measurements at each station of the azimuth and inclination of the magnetic field direction. Deviations of this direction from the normal direction, that is, from horizontal and perpendicular to the traverse line, indicated a conducting body. Recent advances in design of light-weight generating equipment have encouraged using this and similar methods. In 1950 W. H. Westphal and the present writer developed a variation of this method and the apparatus for carrying it out. Their ideas were also based on experience with the Boliden Mining Co. method, which uses a small source coil and a vac- uum tube oscillator. The new procedure uses a small vertical source coil, powered by a vacuum tube oscillator, apd a direction-finding receiving coil. Source and receiver are kept a fixed distance apart and move as a unit along the survey lines. At each receiver station only the inclination of the magnetic field created by the source is measured. Source Unit: The source coil and a small vacuum tube oscillator together weigh about 45 lb. The source coil consists of about 60 turns of 10-gage

Jan 1, 1958

By H. Evans, L. A. Hunt

The raw materials used in the blast furnaces at the Geneva Works of U.S. Steel Corp. have a high degree of variability in size-consist and chemical content. To overcome the problems caused by the use of highly variable raw materials in the blast-furnace operation, large blending piles are used. An investigation of the blending system showed that variability was significantly reduced by the use of these blending piles. This paper describes the blending system, the method used to evaluate the effect of the blending system, and the results of the investigation. The remarkable improvement in blast-furnace performance since World War II has been in large measure due to the use of beneficiated burdens to reduce the variation of both chemical analysis and size consist. This practice allows the operator better control of his blast furnace, enabling him to operate more economically and to produce chemically uniform hot metal. Planning for uniformity usually begins during mining by extracting ore from several locations within a pit to produce a final product with a specified analysis. Another approach is to stockpile ores having widely varying analyses in individual piles and then drawing the required amounts from each stockpile to provide a blend with a predetermined analysis. A further improvement in blending procedures is to take ores from several sources, bedding them horizontally in layers and reclaiming by vertical slicing from the blended pile. The last procedure, when properly executed, is one of the best methods for achieving maximum uniformity with highly variable ores. U.S. Steel Corp.'s Geneva Works initially obtained iron ore for their blast furnaces from the Cedar City area of southern Utah. These ores were formed primarily by the replacement of limestone and siltstone formations with solutions containing iron and several other elements. The original iron content of the ores in the ground varied from a high of 70% to practically zero with a minimum acceptable iron content for shipping of 37%. Substantial amounts of silica, calcium, magnesium and alumina were found in the ores along with minor amounts of copper, lead, zinc, nickel, titanium, manganese, phosphorus and sulfur which were sometimes present in detrimental amounts. Iron-to-silica ratios varied considerably throughout

Jan 1, 1968

By Arthur V. Abbott

TO rightly use materials, two kinds of knowledge are essential: first, the actual strength of the substance; and secondly, the forces to which, in the structure, it may be subjected. Nearly all of the data which we have at the present time have been obtained from the experiments made on the materials used in Europe, and by foreign investigators. The materials commonly used in this country, es-

Jan 1, 1884