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Frank Firmstone, Easton, Pa. (communication to the Secretary*) : It may not be amiss to point out that the top-pressure in iron blast-furnaces is largely affected by variations in the temperature of the gas. I find in my note-books, cases in which the pressure was from 9.25 to 9.5 in. of water when the material in the furnace was low (after dinner-hour), which fell to from 8 to 8.5 in., when the furnace was again full, and the gas consequently cooled. The chief cause for this effect is, that, at the higher temperature, there is a decrease in the weight of the gas in the descending-leg of the siphon formed by the down-comer and the chimneys. It does not seem probable that there is any direct relation between top-pressure and quantity of flue-dirt. Top-pressure, at any given moment, measures the " head " necessary to discharge the gas then passing, against the resistances of pipes, valves, etc., in the gas-conduits between the top of the furnace and the mouths of the chimneys, and can be increased at will by closing, more or less, the valves, or dampers, at the stoves and the boilers. The question of relation between top-pressure and flue-dirt can be settled very easily by direct experiment, working alternately with gas-valves open, and partly closed, and noting the top-pressures and the respective quantities of fluedirt collected. The quantities of fine ore blown away, as shown by Mr. Grammer's tables, are astonishing to one who has had no actual experience with Mesabi ore and hard driving. Flue-dirt, in the sense in which he uses the term, was unknown at anthracite furnaces so long as the working was normal; when it did occur, it was always an incident of scaffolding and bad work, and was no doubt caused by an increase in the velocity

Jan 1, 1904

By R. M. Raymond

The Mining Section of The National Safety Council recently sent out a questionnaire to operators, regarding the class of rope used, specifications required or obtained, factors of safety observed, methods of fastening ropes, lubrication, inspection, and points observed when rope is to be discarded. The answers received from this questionnaire, largely from metal mines, give interesting information, from which recommendations for safety practice on hoisting ropes are drawn. Depth of Mine The depth in the majority of cases noted is from 1000 ft. to 1500 ft. (304 to 457 m.) and records come from a number hoisting from depths of 2000 to 3000 ft. Hoisting is generally done in balance, with a few companies using counterweights. Seldom, more than two shifts are occupied in hoisting. A number of large operators limit the shift for engineers to 6 hr. A few of the larger operators have separate hoists for men and supplies, with a higher class rope for men. The range of loads varies from 7 to 17 tons and greater in a few cases, with a balanced weight of 4 to 7 tons. Size or Drums and Sheaves The size of drums and size of sheaves are generally in accordance with recommendations of rope manufacturers. Only one-half of the operators use grooved drums; one, The Sulphide Corpn., New South Wales, uses wood-lagged drums. Very few operators have drums capable of holding all the rope in a single wrap. Cone drums or cone and cylinder drums, in the mines heard from, are very rare. A few mines of shallow depth use a small drum and large-sized sheave. While this may be allowed, and in some cases is all right, the size of drum and sheave should be fully equal to that recommended by the rope manufacturers and should be at least 60 to 100 times the diameter of the

Jan 1, 1923

By R. M. Raymond

The Mining Section of The National Safety Council recently sent out a questionnaire to operators, regarding the class of rope used, specifications required or obtained, factors of safety observed, methods of fastening ropes, lubrication, inspection, and points observed when rope is to be discarded. The answers received from this questionnaire, largely from metal mines, give interesting information, from which recommendations for safety practice on hoisting ropes are drawn. Depth of Mine The depth in the majority of cases noted is from 1000 ft. to 1500 ft. (304 to 457 m.) and records come from a number hoisting from depths of 2000 to 3000 ft. Hoisting is generally done in balance, with a few companies using counterweights. Seldom, more than two shifts are occupied in hoisting. A number of large operators limit the shift for engineers to 6 hr. A few of the larger operators have separate hoists for men and supplies, with a higher class rope for men. The range of loads varies from 7 to 17 tons and greater in a few cases, with a balanced weight of 4 to 7 tons. Size or Drums and Sheaves The size of drums and size of sheaves are generally in accordance with recommendations of rope manufacturers. Only one-half of the operators use grooved drums; one, The Sulphide Corpn., New South Wales, uses wood-lagged drums. Very few operators have drums capable of holding all the rope in a single wrap. Cone drums or cone and cylinder drums, in the mines heard from, are very rare. A few mines of shallow depth use a small drum and large-sized sheave. While this may be allowed, and in some cases is all right, the size of drum and sheave should be fully equal to that recommended by the rope manufacturers and should be at least 60 to 100 times the diameter of the

Jan 1, 1923

By Frank E. Hall

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

Jan 1, 1922

By Frank E. Hall

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

Jan 1, 1922

Discussion * of the paper of H. M. Chance, presented at the butte meeting, august, 1913, and printed in bulletin No. 79, July, 1913, pp. 1315 to 1341. George H. Ashley,+ Washington, d. C.:-Mr. Chance's long practical experience in reporting on coal lands admirably fits him for a discussion of the value of such lands. On behalf of the government geologists, I wish to express my appreciation of Mr. Chance's friendly, constructive criticism of the government method of valuing coal land in the first part of his paper and, at the same time, to reply to some queries he makes. All admit that coal has no " intrinsic "-monetary value, in the sense that a pound of coal of certain chemical and physical characters is worth " intrinsically " so many cents or fractions of a cent. The term has, however, been found very useful as including those natural factors of coal value, among which are its position and location in the earth, that affect its sale price in contrast with the other cost elements involved in the labor and capital necessary in mining, preparing, transporting, and selling the coal (extrinsic factors). Mr. Chance, while recognizing the " dual origin of value," does not offer any better terms. The survey agrees with Mr. Chance in his definition of coal conservation, that it means the fuller utilization of the heat contents of the coal, and the more complete recovery of the coal from the ground. Coal land withdrawals have not been made to keep such lands off the market, but to prevent their acquisition as non-coal lands before they could be classified so as to be disposed of under the proper law. Nor has the pricing of the more valuable coal lands above the minimum been to raise money for the reclamation fund, to which the money goes, but primarily to discourage the alienation, for holding or speculation, of coal lands not intended or needed for development, and, secondarily, to secure to the people the ?unearned increment," which they are certain in any case to be charged.

Jan 11, 1913

By John C. Nigro

The Bureau of Mines is investigating the use of pulverized coal as a fuel for iron ore pelletizing to determine its effectiveness as a substitute for natural gas and oil. Experimental data illustrates the application of both a gun-type suspension burner and a cyclonic-type slagging burner to a grate-kiln pelletizing unit. In addition, experimentation with a cyclonic fired external combustion chamber for possible adaptation to a shaft or straight grate pelletizing furnace is discussed. The tests were conducted in the Bureau of Mines Twin Cities Metallurgy Research Center's pilot plant with high rank bituminous coals from Kentucky and Colorado and low rank subbituminous coals and lignites from Montana, Wyoming and North Dakota. Although combustion was excellent with the suspension burner, the low ash fusibility temperature coals and lignites caused some kiln ringing and accretion buildup in the grate kiln transfer section which were not encountered when firing with the high ash fusibility temperature Kentucky coal. Pellet contamination by coal ash was not deemed substantial. Problems with the cyclonic burner and external refractory combustion chamber centered around (a) maintaining complete combustion of the coal within the burner, (b) molten slag attack on the lower refractory chamber resulting in erosion of the lining and increased slag viscosities, and (c) freeze-up of the slag tap hole.

Jan 1, 1977

R. F. McELVENNY.- The next item is: "Center and other methods, vs. side charging." That was all discussed in the Carson case, and I do not know but what many of the plants are still using center charging. Some are using side charging. Did I understand that where you use the wet charge it is all side charging on the wet ore? B.-G. C. HONEYMAN.- We were on center charging for about a year with wet ore. R. F. McELVENNY.- Then you went to side charging. Has anyone any remarks to make on side versus center charging? E. A. BARNARD.- We have one side and one center, both on deep bath. It is an experimental proposition so far, but the side charge looks very favorable.. R. F. McELVENNY.- This is with calcine? E. A. BARNARD.- This is with calcine on a floating charge proposition.. They are both water jacket. The charge acts very similar on both center and side charging. The calcine spreads much the same as it does on the center charge. It will run down 75 ft. on the furnace side as well as the center. The advantage is in taking care of secondaries and things of that nature. C. BARDWELL.- Do you get any side wall protection from it? E. A. BARNARD.- No. R. F. McKENZIE.- Do you not project the side wall up to protect the skewback? E. A. BARNARD.- There is a slot projection down around the top of the bath; but the repairs on the side wall have been practically the same; that is, they, have been practically the same as they have on the center charge. A. H. RICHARDS.- A point I would like to make is that if you have any doubt about the center charging, we feel that we get better tonnages and lower fuel ratios and better slags with center charging than we ever got with side. Different kinds of charges would, of course, vary, and I could readily see that if you had the same advantage with deep bath smelting that you mention you would probably get just as good a slag and as good fuel ratios. E. A. BARNARD.- In fact, I think the calcine charge spreads more on the side than on the center charge. A. H. RICHARDS.- If you maintain a deep bath. E. A. BARNARD.- That is one thing we have to be careful about, to hold the charge back.

Jan 1, 1930

By H. E. Kramm

(New York Meeting, February, 1919.) DURING the summer of 1911, I had the opportunity to study in detail the geological conditions of what is known in northern California as " Harrison gulch," in Shasta county. Though the district, as a whole, that is, the western part of Shasta and the eastern part of Trinity county, has contributed during the last 15 years a considerable share of the gold-production credited to Shasta county, very little is known of its geology, perhaps because the country is covered with a dense growth of brush which makes exploration and prospecting extremely difficult. Topographically the district presents a succession of ridges trending approximately N-S.; and alternating with deep narrow canyons. The drainage is partly into . the Sacramento, partly into the Trinity river. Climatic conditions in summer time are almost ideal. It is true, the thermometer may climb to 115°, but the air is dry and the heat is bearable, especially as the nights are always cool. It seldom rains during the summer months, and creeks and springs dry out towards the end of the summer. The winter is severe, lasting from November to April, and usually a thick layer of snow covers the mountains. By reason of the character of its gold-deposits, the region is known to miners as "the pocket country." It contains a series ?of eruptive rocks intruded into slates, cherts, limestones, and conglomerates. Dikes, laccoliths, and batholiths are frequent. In a day's ride it is possible to find all the common igneous rocks from the very acid to the very basic. Serpentines are especially abundant.. The sedimentary rocks are, as rule, broken and shattered as well as folded, and show the effects of intense metamorphism. ? Pocket-hunters " speak of the contact of diabase and slate as the ? pocket-contact." Some rich gold-pockets, however, have also been found in the diabase.

Jul 1, 1912

It is not often that a mining district is discovered, opened up, exploited and developed into a rich producer within the space of three or four years. Not until the year 1903 was the existence of the rich cobalt-nickel arsenides and silver of Northern Ontario even suspected by the mining public. But it is worthy of record that Dr. W. G. Miller, the man who has done so much to develop sanely and honestly the mineral resources of Ontario, pointed out [ ] the possibilities of this region at least two years before the first discovery was made. . Dr. Miller, then Professor of Geology at the School of Mining, Kingston, Ont., referred in these words to the district: "It will be seen from what has been stated on preceding pages that the district examined contains as great a variety of rocks as probably any part of the Province of equal area . . . Although few discoveries of economic minerals have been made in this territory, it may reasonably be expected that deposits of value will be found when

Jan 1, 1907

W ill the location of the world's largest reserve of rutile, a titanium oxide mineral, in Sierra Leone, Africa, put an end to the worldwide shortage of this important mineral? According to officials of the Pittsburgh Plate Glass Co. and the British Titan Products Co. Ltd., the answer is yes. These two firms have formed Sherbro Minerals Ltd., a new company that will recover and refine the relatively rare mineral near Africa's West Coast. PPG owns 80% of Sherbro, and British Titan 20%. The rutile reserves of Sierra Leone have been reported to be larger, on a comparable grade ore basis, than existing proven reserves throughout the world. The African operation is on a strip of coastal

Jan 8, 1964

By L. C. Uren, E. J. Bradshaw

This paper presents the results of a group effort by a number of University of California students and faculty members, and the authors attach their names primarily in the capacity of editors and interpreters of the data thus assembled. In addition to the writers, the following individuals have made substantial contributions in time and effort in the conduct of this research: Dr. A. J. Carlson, Associate Professor of Petroleum Engineering; J. E. Gosline, University Research Assistant; C. F. Bedford, G. W. Mikulasek and H. S. Conder, senior and graduate petroleum engineering students; H. Bachman, G. Spencer and G. W. Gard, mechanicians in the Department of Mining and Metallurgy. Acknowledgment is also due the Research Board of the University, the Department of Mining and Metallurgy, and Prof. F. H. Probert, Dean of the College of Mining, for continued cooperation in securing mechanical assistance and funds for the purchase and assembly of apparatus. Significance of the Pressure Gradient The expulsion of petroleum from its reservoir sand doubtless is due to expanding natural gas intimately associated with the oil, to the hydrostatic pressure of encroaching edge waters, and to gravitational influences. These forces may operate independently or collectively. In any case they subject the fluids stored within the reservoir sands to elevated pressures, thus causing movement of oil and gas through the productive formations toward the lower pressure of the well outlets. This movement is opposed by pore friction, capillarity and adhesion: resisting influences brought to bear by the reservoir sand on the moving fluids. The magnitude of the resisting force is influenced directly by the viscosity, surface tension and density of the oil, as well as by the properties of the gas. The more rapid the rate of flow, the greater will be the resistance offered, and the greater will be the energy consumed.

Jan 1, 1932

By Leason Adams

THE thermocouple as a device for the measurement of temperature is rivaled only by the platinum-resistance thermometer. Both instruments are capable of the highest precision, but the thermocouple, on account of its cheapness, ease of construction, and small cross-section, is finding a continually widening field of usefulness for industrial control as well as for laboratory measurements. Formerly, the thermocouple was subject to two disadvantages: errors due to lack of homogeneity of the metal and the labor involved in the interpolation between fixed points on the temperature scale. Former publications from the Geo-physical Laboratory have described the methods' for the selection and testing of thermocouple wire and have presented standard calibration curves2 for platinum-platinrhodiun and copper-constantan couples, so that the most important objections to the thermocouple as a precision thermometer have been removed. The calibration tables published in 1914 covered the range 0-1755° for the platinum-platinrhodium couple and 0-350° for copper-constantan. It has seemed desirable to extend the table for copper-constantan to -200 and also to include a table for the Hoskins thermocouple. Accordingly, in this paper, the new tables are presented, together with a brief explanation of their use; and, finally, certain diagrams and a paragraph on "cold-junction corrections" are given. Standard Calibration Tables.-In Fig. 1, which illustrates how the electromotive force (e.m.f.) of each of the three couples varies with the temperature, the temperatures of one junction are plotted as abscissas and the corresponding thermo-e.m.f.'s as ordinates. The second junction of the couple is supposed to be at 0°; the curves, therefore, pass through

Jan 9, 1919

By AIME AIME

A COMMITTEE, representing a number of the larger oil companies in California, met in San Francisco on Nov. 12, 1919, for the purpose of discussing the depletion deductions to be allowed in computing the Federal income taxes under the Internal Revenue Act of 1918. It was the general sense of the committee that a system based on sound engineering principles should be formulated for estimating the value of oil properties, so that better and more uniform results might be obtained by the various companies in filing their returns with the' Bureau of Internal Revenue. A subcommittee, consisting of five petroleum engineers, was thereupon appointed to collect information and draft a report. The committee consisted of G. C. Gester, Carl H. Beal, J. H. G. Wolf, E. G. Gaylord, and E. D. Nolan; this report is the work of that subcommittee.

Jan 1, 1920

By A. E. Schuetz, A. E. Roswell, W. R. Hibbard

THE drawn wire texture of body-centered cubic iron,' tungsten,' and molybdenum~ as been determined to be a [110] direction parallel to the wire axis. The purpose of this study is to extend the available information on body-centered cubic wire textures to other metals and alloys. Wires were produced using hand wire rolls and dies as given in Table I. In addition, attempts were unsuccessful to draw wires from chromium, vanadium (Vanadium Corp. of America), and tungsten (Cleveland Tungsten Inc.). Although it is known that wires can be made from these materials, suitable techniques were not readily adaptable. Where necessary, wires were polished and etched to form flat ribbons 0.005 to 0.007 in. thick, and transmission X-ray patterns were taken using molybdenum radiation with the specimen tilted 0 degrees from the perpendicular toward the beam to critically cover the wire axis. Analyses were made of (110), (002), and (112) reflection circles. In all cases reflection maxima indicated the texture to be a single [1101 deformation fiber, as illustrated by Fig. 1 for molybdenum. In the case of the hot-worked ß brass, a second texture, [loo], was also found, but this is believed to be the result of recrystallization since it has been reported for re-crystallized molybdenum wires' and it was not present in the cold-drawn ß brass. The difference in drawability between the 51.92 pct Cu ß brass and the 62.5 pct Cu ß brass (containing some grain boundary a due to incomplete quenching) is quite striking, since the latter could be cold worked readily while the former had to be hot worked to avoid cracking. Summary The deformation texture of drawn body-centered cubic wires of ß brass, iron, molybdenum, niobium, and tantalum is essentially a single [110] fiber as predicted by theory.' Acknowledgment The authors wish to thank the suppliers of the metals listed in the text, and the Grant-in-Aid from the Research Fund of the Society of the Sigma Xi and Scientific Research Society of America which made possible the purchase of X-ray equipment.

Jan 1, 1952

By P. Schwarzkopf, J. H. Brophy

A modification of the Mendenhall wedge blackbody1 has been used to determine solidus temperatures and to anneal alloys in the tantalum-rhenium binary system. The technique has proven to be simple and accurate with modest power requirements. For temperatures up to 2800° C a piece of 10-mil tantalum sheet was folded double and formed as shown in Fig. 1. The middle of the resulting ribbon filament was a cylindrical-shaped crucible with less than a 1/8-in. opening. After inserting a specimen in the cavity, the filament was clamped between molybdenum electrodes in a high vacuum chamber. A representative filament 2 in. long and % in. deep was heated to 2800°C with a current of 700 amp at 4 v. The specimen temperature was determined by sighting into the cavity with a Leeds and Northrup optical pyrometer. The twisted filament shape was necessary to avoid serious geometric changes during thermal expansion. For temperatures between 2800" and 3000°C a 4-mil tungsten filament was employed. To facilitate fabrication it was warm-folded, and a twisted segment of 10-mil tantalum was used to support one end to absorb thermal expansion. This element assembly required about 700 amp at 10 v to reach 3000°C. Two geometric modifications of the filament were helpful for solidus temperature determinations. A shallow chamber, with depth to opening ratio of 3 to 1, permitted direct observation of the specimen through the optical pyrometer. The fact that the specimen was visible permitted the melting point to be determined when sharp features on the specimen surface became rounded; it also indicated that blackbody conditions did not prevail. By standardizing against the melting point of molybdenum, the observed melting temperature was corrected by the following form of Wien's Law: in which T is the true temperature, To is the observed temperature, and K is a constant characteristic of the filament geometry and determined experimentally for the molybdenum standard. The resulting corrected melting point for each alloy served as a reference temperature for the second more precise filament geometry. With a 6 to 1 depth to opening ratio, the specimen was indistinguishable from the filament interior, indicating good blackbody conditions. Using this technique, a series of specimens was isothermally treated at temperatures above and below the corrected direct reading. Incipient melting was detected by visual or micrographic examination of the specimen after cooling. This procedure was checked with specimens of pure chromium, molybdenum, and tantalum. Table I represents the values obtained, together with the solidus temperatures in the tantalum-rhenium binary system determined by the same technique. The alloy specimens were approximately 1/8 in. in diam. They were pieces of 10-g buttons melted four times in a nonconsumable tungsten electrode arc furnace on a water cooled copper hearth in 2/3 atmos of titanium gettered helium. Several sources of error are possible in such temperature measurements. Within the accuracy of the pyrometer no gradients were detectable near the specimen, and element distortion was virtually eliminated by twisting the tantalum. Compensation was made for the 1/8-in. sight glass by inserting several identical thicknesses and extrapolating to zero thickness. As a result an additional 10°C correction was added to all observations in the temperature range of 2500" to 3000°C. The principal source of error was then in the operation of the

Jan 1, 1961

By Benjamin Petkof

The mineral mica, which has been known to man since ancient times, has played an impor¬tant role in the development of our modern industry. In the latter part of the 19th century sheet mica began finding use as a dielectric insulating material in the newly developing electrical industry. Later, when modern elec¬tronics began to develop, it became a vital insulating and dielectric material for use in electronic equipment. Both the electrical and electronic industries were greatly dependent on some form of natural mica. The manufacture of electric motors of varying sizes, electronic tubes, and other electronic items was dependent on an adequate supply of sheet mica. During World War II this material was so vital to national defense that special efforts were made to mine it in the United States as well as to obtain it from overseas mica-producing areas. However, advancing technology has successfully begun the progressive development of man-made mica-based and non-mica-based materials that can replace mica for many uses. In addition, developing technology has dictated changes that have made sheet mica unnecessary for some uses. As the demand for sheet mica declined, the demand for scrap and flake mica has continued to increase. In fact, today the domestic production and use of scrap and flake mica far outshadows the necessity for good¬quality sheet mica in this country. Historically the United States has always been dependent on foreign sources of material for good-quality sheet mica and imports practically its entire requirement. In the case of scrap and flake mica, the United States is the dominant world producer and consumer. End Uses Sheet mica (Chowdhury, 1941; Rajgarhia, 1951; Skow, 1962) is available in many com¬mercial forms, but these forms can be broadly classified into manufactured and unmanufac¬tured mica. Manufactured mica consists of mica that has been shaped, punched, or other¬wise processed into some form, suitable for a particular end use. Unmanufactured mica con¬sists of partially hand-trimmed or processed material that has not been prepared for any particular end use. Unmanufactured mica is broken into two commercial classes consisting of sheet mica and scrap and flake mica. These classes of mica differ greatly in their ultimate end uses and marketed forms. Sheet muscovite mica can be classified by color, degree of prep¬aration of the crude material, thickness, size, visual appearance, and electrical quality. In addition, phlogopite mica is also classified by its thermal stability. Scrap and flake mica consist of mine, trimming shop, and factory scrap that occurs as remnants from mining, processing, and manufacturing operations, and small particle size mica that is available from the beneficiation of pegmatites, clays, schists, or other mica-rich host rock. The end uses for sheet mica vary so greatly from those of scrap and flake mica that it is necessary to discuss them separately. Sheet Mica Sheet mica consists of relatively flat sheets of material which have been mined as naturally occurring books or runs of mica. These sheets are hand-trimmed to remove any imperfections and are punched or stamped into specified shapes for industrial use. Sheet mica can be further processed and is described or specified as block, film, or splittings based on thickness. Block mica is not less than 0.007 in. thick with a minimum usable cross-sectional area of 1 sq in. Film mica is split from the better quali¬ties of block mica to specified thickness groups ranging from 0.0012 to 0.004 in. Splittings are sheets of mica with a maximum thickness of 0.0012 in. and a minimum usable area of 0.75 in. Other small sized, lower quality block mica

Jan 1, 1975

By John A. E. M. Church

THE prospector's pan was the first implement used for saving gold, and its action is so effective that it has never been equalled for thorough work. Copper plates, blankets, sluices, and amalgamators of several patented designs have thrust it aside, but in spite of all the advances made there is no dispute among experienced men as to the comparative thoroughness of the work done by it and its rivals. When its rivals are doing their best, the pan can take their discarded refuse and prove their inefficiency by producing from it not only gold, but even the mercury which has been lost from the machines themselves. The trouble with the pan has always been that it was only a tool. Man was the machine that moved it. His work was high-priced, the quantity treated small, and it was impossible to use the pan for any but the richest sands. As a consequence the best gold-saving appliance known has been discarded for years and replaced by machines of inferior excellence, but which could more than make up for their limited ability in saving gold by their capacity for treating great quantities of ore. Mr. Peck is one of the old-time amalgamators of the Comstock district, and the first idea of the new machine came to him as he used to pan below the tailrace of his mill. No matter how fine the work of the mill was, the pan invariably proved that better could be done. The tailings always contained gold, silver, and mercury. This state of things is just as true to-day, after all the improvements that have been made, as it was then, and the much-vaunted method of the " Washoe process" consists in extracting 72 per cent. of the gold and silver by one operation, and then repeating this operation half a dozen times to get out about one-third of the remainder. With all the advances of twenty years in milling, there is nothing more crude in metallurgy than the treatment of tailings in many of the large mills of the West.

Jan 1, 1880

By J. R. Campbell

It is the purpose of this paper to review somewhat in detail the literature on the subject that is extant, which ought to provoke considerable beneficial discussion. The value of 1 per cent. ash in blast-furnace practice was brought to the attention of the writer when he was connected with the U. S. Steel Corpn. Various groups of blast furnaces in the Pittsburgh district compiled a statement in which the average saving was about 6 c. per ton on pig iron for every 1 per cent. of ash reduction. Later, the same groups of furnaces, when materials had reached a higher price, compiled a statement in which there was a 30-cent saving on pig iron for every 4 per cent. ash reduction in the Pittsburgh district, which was equivalent to 7½ c. for every 1 per cent. ash reduction. In the Chicago district, on long freight hauls of coal and coke from the Pocahontas district, the set-up was 30 c. per ton of pig iron for every 2 per cent. ash reduction, or 15 c. for every 1 per cent. Some years ago, Ralph H. Sweetser, of the American Rolling Mill Co., presented a paper which provoked considerable comment.' To get the matter again before this body a résumé of his computations is given below: Comparison of Pig Iron Costs Ash in Coal. Ash in CoKe, Fixed Carbon in Coke peR Ton OB PIG Iron peN Day, Per Cent. PeR CeNt. Coke. Per Cent. PIG IRon. Lb. Tons 6.00 8.70 89.80 1800 365.0 7.00 10.15 88.35 1860 353.2 Coke with 8.70 Per Cent. Ash Ore mixture, 4144 It). = 1.85 tons @ $5.50.............................. $10.17 Coke, 1800 lb. = 0.90 ton @ $6.50..................................... 5.85 Limestone, 1000 lb. = 0.50 ton @ $1.50................................. 0.75 Labor, $365 per day on 365 tons....................................... 1.00 Supplies and service, $250 per day...................................... 0.68 Overhead, $200 per day............................................... 0.55 Reserve for relining and depreciation................................... 1.00 Total............................................................. $20.00

Jan 1, 1931

By H. E. Nold

THIS paper is an effort to explain in a simple manner the fundamental principles involved in examining a clay deposit for both quantity and quality and in operating a clay mine, either open-pit or underground, SO that the best quality of finished material can be made from the raw material available. The writer is aware that what is recommended in this paper is everyday practice in many refractories plants and in some other heavy-clay products plants, but observations made while visiting practically every clay mine in Ohio have convinced him that the practices herein discussed are not as widely used as their importance warrants. It is true that the problem of mining for quality is more acute in refractories plants than in most heavy-clay products plants, yet some of the latter are finding it profitable to pay more than ordinary attention to the selection and blending of their raw materials. It is hoped that this short paper may prove helpful to some who are now finding it difficult to produce a uniform product of as high quality as their clay deposit seems to warrant. The coordination of the work of the clay mine or pit with the manufacturing plant, to the end that the best product possible be made from the raw material available, presupposes a rather intimate knowledge of the clay deposit. The knowledge must include not only information of the amount of clay available but also rather detailed information about both vertical and horizontal variations in quality of the clay. This information should cover three things: quality, quantity, and location. Sampling Undeveloped Deposits In the case of an undeveloped deposit with a shallow overburden, pitting may be the cheapest way of testing. For thick deposits or deposits with rather heavy overburden, the diamond drill, using a double core barrel, offers the best means of testing. When using the diamond drill in clay testing, it is doubtful whether it pays to take less than 2-in. cores; it is difficult to get complete cores with smaller drills, and the quantity of material obtained with smaller cores is not sufficient for the necessary tests.

Jan 1, 1929