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By Nicholas M. Short

Many a geologist or driller has wished he could somehow climb into a borehole to see for himself what fractures looked like. Or why recovery was poor. Or how the bit was actually lost. Now it is possible to do the next best thing to climbing into the hole. TV cameras are being used for a close-up look at borehole conditions. Ever since television was invented, geologists and others interested in subsurface conditions have wanted a TV camera that could be used in the narrow confines of a borehole. But development of such a camera was slow, mainly because of the need for compact size. Not until the late 1950's did the technology of electronic miniaturization develop to a point where a camera satisfactory for the purpose could be put together.

Jan 1, 1963

By A. W. Hann

THE importance, to geologists and metallurgists, of knowing the mineralogical forms in which the silver occurs in ores has increased during the past few years, and will continue to increase as long as working hypotheses are converted into proved theories and rule of thumb methods are supplanted by scientific data. The methods used for the determination of these silver minerals have been: (1) careful study of polished ore sections with the microscope, and more recently, (2) metallurgical separation of the ground ore by flotation, tabling and panning, supplemented by microscopic examination of these separated minerals, and chemical analyses. During the course of some experimental work carried on by the testing department of the International Smelting Co. and myself, it became important to determine, in a general way, the distribution of the silver values in the minerals, as they exist in Tintic Standard and North Lilly siliceous oxidized lead-silver ores. These mines are in the East Tintic Mining District, State of Utah. In this work the second method was used. Differential flotation tests were run, separating the sulfide from the oxidized minerals, and the products were assayed. Various concentrates were carefully panned and the separated products assayed; special samples of ore were selected and assayed. The microscope was used only for the purpose of determin; ing whether the individual minerals were in the so-called "free" state. Analysis of Tintic Ores These chemical and mineralogical determinations showed the silver to be present as native silver, argento jarosite, argentite, and combined or inherent in the tetrahedrite, chalcopyrite, galena, pyrite, cerussite, anglesite, mimetite, malachite, iron oxide and occluded in the quartz. Careful microscopic work would probably show other forms in small amounts, such as the halide silver minerals and some of the antimony sulfide combinations. The tabulation of the analyses of the various products (Table 1) shows no evidences of fixed ratios of silver to any particular base metal.

Jan 1, 1929

By A. H. Redfield

BITUMENS have been defined by Abraham1 as substances of variable color, hardness, and volatility; composed principally of 'saturated hydrocarbons, substantially free from oxygenated bodies, sometimes associated with mineral matter; the nonmineral constituents being fusible and largely soluble in carbon disulphide. The principal bituminous substances other than petroleums known to commerce are: (1) native asphaltites, such as gilsonite, grahamite, and glance pitch, distinguished by their hardness and relatively high fusing point; (2) native asphaltic pyrobitumens, such as wurtzilite, distinguished by their infusibility and comparative insolubility in carbon disulphide; (3) mineral waxes, such as ozokerite, distinguished by their high content of crystallizable paraffins; (4) native asphalts, containing varying amouqts of mineral matter, distinguished by the comparative absence of crystallizable paraffins; and (5) bituminous residues obtained from the distillation of petroleum. GILSONITE Gilsonite, a black native asphaltite 98 to 99.9 pct pure, characterized by a hardness of 2 (Mohs), a specific gravity of 1.01 to 1.10, and melting point of 230° to 400°F (K and S), is mined commercially only in northeastern Utah. It occurs in parallel, almost vertical veins, from a few inches to 18 ft wide and 8 to 30 miles long, that cut across the Tertiary limestone and shale of the broad Uinta Basin. The bitumen is believed to have been distilled by heat from oily material in the underlying Green River shale. At the Rainbow mine of the American Gilsonite CO.,† the gilsonite, formerly extracted in an opencut by a system of slopes and benches, is now mined by shafts and horizontal drifts. Little timbering is required. The mining methods of the Raven Mining Co., Chicago, and of the American Asphalt Association and the Utah Gilsonite Co., both of

Jan 1, 1949

By Walter S. Weeks

THE process of cooling air by allowing it to expand and do work in an engine is well known, but the theory of obtaining cold air by free expansion without the aid of an engine operating with cutoff has been little discussed. Case 1 If compressed air is allowed to expand to the atmospheric pressure through an orifice in an sir line that is supplied by a running compressor, no cooling results except the negligible one due to the Joule-Thompson effect, which will not be considered in this discussion. The effect of moisture will also be neglected. Symbols P1 Absolute pressure in pipe line, lb. per sq. ft. P3 Atmospheric pressure, lb. per sq. ft. V1 Volume occupied by 1 lb. air in pipe. V3 Volume occupied by 1 lb. air at P3. Cv Specific heat of air at constant volume, B.t.u. per lb. per deg. F. Cp Specific heat at constant pressure, B.t.u. per lb. per deg. F. T1 Absolute temperature of air in pipe, deg. F. T3 Absolute temperature of air outside after expansion and mixing and coming to rest. J Mechanical equivalent of heat (778 ft. lb.) R Gas constant for air, ft-lb. per deg. F. = 53.3. Formulas Consider 1 lb. of air moving out of a pipe. The air behind it does work on it to the extent of P1V1 ft-lb. This work is really done by the thrust of the piston of the compressor and does not come from any energy that exists in the air in the pipe. The pound of air contains

Jan 1, 1937

By Frank Foote, Willard L. Bruner, Eric R. Jette, Y. New york

The alloys of gold and iron were investigated in 1907 by Isaac and Tammann,l who determined the thermal diagram for the entire system by thermal analysis and microscopic examination. They also reviewed the previous literature. Since that time the present authors have been able to find only two additional references. Guertler and Schulze2 examined the electrical resistance of iron alloys containing up to 40 per cent by weight of gold between 0" and 200" C.; the alloys were in the form of wires. The main result of this work was to confirm the solid solubility limit found by Isaac and Tammann; namely, about 20 per cent Au. More recently, Shih3 has examined the magnetic properties of gold alloys containing up to 10 weight per cent iron and particularly the range below 5 per cent. The alloys in the lower range were found to be paramagnetic; the 10 per cent alloy was ferromagnetic. The present investigation was undertaken to determine the solid solubility limits at various temperatures, particularly below the a-y transformation point of iron, since these solubilities are of some importance in connection with the working of the alloys in the manufacture of certain "grey" and "blue" golds. Materials and Methods The gold was obtained from the U. S. Metals Refining Co. and contained 99.99+ per cent Au. The electrolytic iron had been annealed in hydrogen and contained impurities as follows: P, 0.035; Si, 0.001; S, C, Mn, Cu, each 0.01 per cent. Weighed quantities of the two metals were placed in small crucibles lined with pure sintered MgO; a saturated solution of magnesium nitrate

Jan 1, 1934

By Ralph Nichols

THE mines are near the town of Gilmore, in the Texas mining district. This district was organized in 1880. The present producing mines are near the terminus of the Gilmore & Pittsburg railroad. This railroad connects with the main line of the Oregon Short Line at Armstead, Mont. The distance from Gilmore to Armstead is 70 miles. The town of Gilmore is near the head of the Lemhi river at an elevation of 7,000 ft., while the mines are from 400 to 1,300 ft. higher. The range of mountains upon which the mines are situated forms the water shed for the Little Lost river on the west and the, Lemhi river on the east. The winters are severe and the snow fall is heavy, but the mines ship right through the year. There is an abundance of timber suitable for all mining purposes in the immediate vicinity. Water is piped into the camp from a lake about 2.5 miles distant. This lake is about 1,400 ft. above the town of Gilmore. The water is exceptionally good for boiler and domestic purposes. The mining companies now producing are. the Pittsburg Idaho Co., Ltd. ; the Latest Out Mining & Smelting Co:, Ltd. ; and the Gilmore Mining Co., Ltd. Besides the above properties, there are a number .of prospects in different stages of development. The producing mines of the district are fissures in limestone, with a general northeast-southwest course .and a dip to the west of from 40° to 70°. These fissures are at about right angles to the bedding of the limestones. The veins are regular and the ore shoots strong, both laterally and in depth, so far as developed. The ore shoots have a rake or pitch to the south. The character of the formation is shown in Fig. 1, a section of the Latest Out mine.

Jan 11, 1913

By Waldemar Lindgren

I. Character of the Deposits, 226: Principal Features, 226 (Form, 227; Posi tion, 227 ; Constituent Minerals, 227 ; Exceptions, 228) ; Literature, 228 ; Geo graphic Distribution, 230 ; (California, 230 ; Idaho, 231 ; Arizona, 233 ; British Columbia, 233; Northwest Territory, 234 ; Mexico, 234; Other Countries, 235). 11. Origin oF the Deposits, 236 : Contact-Metamorphism, 236; Caw of Contact Metamorphism, 237 ; Similar Deposits of Different Origin, 240; Genetic Classifi cation, 240 ; Relation of Pegmatite- Veins to Ore-Deposits, 242. I.—Character of the Deposits. 1. Principal Features. In many schemes of classification and description the term contact-deposit has been somewhat loosely applied to all accumu-

Jan 1, 1902

By Jamie Deuel

The a ad on Connection" For the purpose of this paper, we will concentrate on the ubquitous radon gas as the principle, low-level radiation effect from uranium tailings piles. Standards are also proposed for gamma radiations but, by most accounts, this is much less of a low level problem than is radon. I am also aware of some just completed research at Oak Ridge National Laboratories that suggest polonium may be a major concern in tailings, but those data are preliminary at this time. What is radon gas? In the first place it is not a gas in the accepted sense in that it has no driving pressure head. It might prove a more convenient description to call it radon vapor. Radon vapor, then, is 7-1/2 times heavier than air. Radiologically, it is an alpha emitter which means it spontaneously gives off high ionizing potential but low penetrating power particles. In fact, the alpha particle has such low penetrating power that this sheet of paper will completely shield a person. The problem, though, is breathing the radon decay products, called radon daughters. If radon daughter products are ingested into the lungs, their alpha emissions may cause cancer. The principle carcinoma associated with breathing radon, or more basically, associated with radiological effects is oat cell car- cinoma of the undifferentiated mall cell type. Radon has a 3.8 day half life which means in less than four days half of its initial radioactivity has decayed away. In less than a month it essentially becomes inert or non-radioactive. The Tailings Situation The NRC, in its April 1979 Generic Environmental Impact Statement

Jan 1, 1983

By O. K. Riegger, L. H. Van Vlack

The median angle of relatively few two-dimensional observations provides a satisfactory value for dihedral angle determinations. Those data that contain bimodal or non-equilibriated dihedral angle distributions are readily detected. THIS paper is concerned with a statistical simplification for determining dihedral angles in solids. Microstructures are partially controlled by relative energies of interphase boundaries and grain boundaries. smith1 has shown rather conclusively that such boundaries may be equilibrated to give a vectorial balance at grain and phase edges. Thus if an accurate measurement is made of the dihedral angle associated with grain and phase edges, an accurate calculation of the relative energies may also be made. The accurate measurement is difficult because the dihedral angle involves two planes in three dimensions, and only a two-dimensional cut through the dihedral angle is usually observed. Such a two-dimensional cut is statistically random provided there is no preselection or orientation. Harker and parker2 have shown that the mode of the frequency distribution of observed angles is within 5 deg of the true angle if the true dihedral angle is 120 deg. smith1 had calculations made to show that the same generalization could apply to dihedral angles of 30, 60, 90, and 150 deg. This procedure of requiring the determination of the statistical mode is time consuming because experience has shown that more than 200 angle observations are necessary before the mode is clearly indicated. It is possible to determine the dihedral angle with equal accuracy with only 25 angle observations if the median angle is used in place of the mode angle. Use is made of Harker and parker's2 basic equation tan =2 sin x cos

Jan 1, 1961

By Nathaniel Herz

The formula very frequently used for computing the economical size of pipe to transmit compressed air is that of D'Arey, as follows: D = cV w1l Where, D = the volume of compressed air delivered in cubic feet per minute, at the final pressure. c = an experimental coefficient determined for the various sizes of pipe, d = the diameter of the pipe in inches. 1 = the length of the pipe in feet. p, = the initial gauge-pressure in pounds per square inch, p2 = the final gauge-preesure in pounds per square inch. w1 = the density of the air, or the weight in pounds per cubic foot at the initial pressure, p1. The most common case is that in which the given quantities are: the quantity of air required, the length of the pipe, and the initial pressure. The method of solution is to assume a pressure-loss and to compute the remaining factor, cd5, thus giving the size of pipe corresponding to the assumed loss of pressure. It is always desirable to try two or more pressure-drops, in order to find the combination that is most satisfactory, since often a small change in the size of pipe will reduce or increase the loss of pressure several pounds. An alternative method is to assume a size of pipe and calculate the corresponding pressure-drop. Each method involves a series of tedious calculations to arrive at the most economical solution, and also requires the use of tables giving the constant, c, the density of the air, w1, and often, for convenience, a table giving the values of the expressions p1-p2 and c J I hare constructed a graphic chart, Fig. 1, for the solution of

Jan 1, 1913

ASIDE from the John Fritz Medal, in which the Institute partici¬pates through its representation on the John Fritz Medal Board, the Institute itself has four awards it may make annually, as fol¬ lows the Robert W Hunt Medal and Prize, the J E. Johnson, Jr , Award, the James Douglas Medal, and the William Lawrence Saun¬ders Medal ROBERT W HUNT MEDAL AND PRIZE The partners of Robert W Hunt established a fund which was, presented to the Institute at a fitting ceremony on May 27, 1920, to establish an annual medal and a sum of money to be awarded tinder the following rules¬ 1 The award shall consist of two prizes first of a gold medal, second of a sum of money, a certificate to accompany each prize The money prize shall not be awarded to a member' over 40 years of age, but under unusual circumstances, both prizes may be allotted to one per son provided that he is not over 40 years of age In general it will be understood that the Committee shall award the money prize to the younger men, rather than the medal 2 The awards shall be made not oftener than once a year to that person or persons contributing to the Institute the best original paper or papers on non and steel The scope of the term "iron and steel" shall be determined by the sub-committee consideing the awards In general, papers dealing with the practical side of the subject have preference over those dealing with the theoretical side in recognition of the fact that Captain Hunt's main con¬ti ibutions to the industry have been in the improvement of production and quality of material

Jan 1, 1923

By Gen-Hua Shi, William Boyle, Richard E. Goodman

This keynote paper calls attention to two critically important issues relating to selecting supports for excavations in hard rock. The first is the proportion of the ultimate sliding volume that needs to be stabilized by the support system. Some excavations can be imagined to liberate very large rock volumes, whose weight can not be assigned to supports without severe economic penalty. Using the keyblock principle, it is argued that only the most critically oriented and finite blocks right on the periphery of the opening have to be supported; if these are retained by the support system, or by self resistance due to friction on the sliding faces, then the blocks behind will remain in place. As all concepts, this one has bounds and limits. Since the keyblock analysis for rock engineering is very new, these limits are not yet understood ... The second issue is the degree to which possibly stabilizing forces associated with the in-situ stress field ought to be accepted as support for potential keyblocks. It is shown that the initial stress can be effective in stabilizing rock wedges whose faces are nearly perpendicular to the excavation surface. It is too early to decide this issue but important to consider it.

Jan 1, 1982

The authors have done a very thorough job in analyzing the factors affecting turndown sulfur performance at Inland's No. 4 B.O.F. While many of the results are not unexpected, it is helpful I am sure to have quantified many of the relationships that the operators rely upon daily. On the other hand, however, the results shown for ladle skimming are very surprising. I do not doubt the statistical relationship shown but I feel, based on our experience at Youngstown, that some other parameter has been ignored in the data on ladle skimming. It was our experience that by skimming our hot metal transfer ladle we could reduce our lime consumption by eleven percent while obtaining sulfur removal comparable to that shown by the authors. I would like the authors comment of similar adjustments on the lime charge that were made on skimmed heats at Inland. If not, it would seem that one could gain more desulfurization in the B.O.F. by raising the hot metal manganese than by installing a skimmer. The author's state that no comparisons are valid between the data sets for the two time periods involved because of the difference in the consumption of No. 2 Bundles. I feel this in fact is one of the important conclusions to be drawn from the paper, as there seems to be approximately a 10-20 percent difference in percent of heats that are under 0.020 percent sulfur for similar conditions, which is an extremely important difference with today's demands for low sulfur. I would like the author's comments on the difference in the amount of 82 bundles consumed. Along this same line I was quite surprised by the relatively low number of heats that had a first turn down of 0.020 percent sulfur or less. Also rather disconcerting are the conditions necessary to achieve a first turn of 0.020 percent sulfur, 50 - 60 percent of the time, as required by today's specifications. It is a problem which we are well aware of, but the numbers are still shocking.

Jan 1, 1972

By William White

History.—The making of iron and steel from the ores of northern Mexico was for years a favorite project of the late Don Patricio Milmo, upon whose estate large deposits of coal and iron were known to exist, and with whom Mr. Eugene Kelly, of New York, was associated. Several expert examinations of the property mere made for them; and when failing health forced Sr. Milmo to retire from active part in the matter, Mr. Kelly carried on the project and associated himself with Messrs. Vicente Ferrara, of Monterrey, Antonio Basagoiti and Leon Signoret, of the City of Mexico, and other leading citizens of Mexico, Monterrey and New York, who, in May, 1900, organized the " Compania Fundidora de Fierro y Acero de Monterrey," with a capital of $10,000,000. The main reason for locating the plant at Monterrey was, that a circle drawn with Monterrey as a center, and the distance from Monterrey to Laredo as a radius, will contain all the known Deposits of iron-ore of Bessemer quality, and the greater part of the available coal, in the Republic. Moreover, Monterrey is connected with all the Mexican trunk railwaylines, and thus with the Gulf of Mexico, and supplies, therefore, the conditions necessary for prosperous manufacturing, namely, cheapness in assembling raw materials and means for wide distribution of product. It also has a number of enterprising citizens, who have been successful in mining, smelting and manufacturing operations, and a sufficiently large population to supply the necessary labor. Iron-Ore.—The company's iron-mines are on the Carrizal mountain, on the Mexican National, and at Monclova, on the Mexican International railroad. At the former locality, two mines, Piedra Iman and the Anillo de Hierro, sufficiently large

Jan 1, 1902

By R. W. Raymond

By the death of Prof. Pettee the Institute has lost one of its earliest, most distinguished, most useful and most beloved members. Among those who survive him there are few who have rendered services of equal professional value or unselfish devotion. The warrant for this statement will be amply furnished in the present brief notice of his life and work. William Henry Pettee was born, January 13,1838, at Newton Upper Falls, Mass., where hie childhood and youth were spent. His father, Otis Pettee, a manufacturer of cotton cloth and of cotton-mill machinery, died in 1853. Up to that time, the son had been educated mainly in the district school; but, being inclined by temperament and constitution rather to books and study than to physical exertion, he had been wisely rest,rained in mental activity, and required, for a season, to work regularly in the foundry and machine-shop of his father. Unquestionably, this discipline not only benefited his health, but also constituted a valoable preparation for his subsequent professional career. In 1857, after suitable preliminary study at various New England academies, he entered Harvard College, where he took high rank in the classical course then required, was selected in his Junior gear to deliver a Latin oration; was elected a mem-

Jan 1, 1905

By Stanislaus Skowronski

THE melting of cathode copper, usually containing 99.98+ per cent. Cu, would appear to be a simple matter. Owing to the well known affinity of copper for sulphur, however, so much sulphur is absorbed by the copper during the operation that a long and expensive refining process is required to remove it, and the final product is inferior in purity and lower in electrical conductivity than the original cathode copper. The furnace operation, as now conducted, includes the following stages: 1. Charging the cathodes into the furnace. 2. Melting the cathodes. 3. Oxidizing period-saturating the copper with cuprous sub-oxide and bringing the metal to the condition known as "set copper;" this is now done by blowing air into the molten bath of metal. 4. Reduction period, otherwise known as "poling," whereby the oxygen previously added is removed by covering the molten bath completely with coke or charcoal and introducing large poles of green wood; this reduces the cuprous sub-oxide, bringing the copper to the "tough pitch" stage ready for casting. 5. Casting Period. Many experiments have been made to obviate the long periods of oxidation and subsequent reduction, with no success. While the copper first, cast will be good, as indicated by the set surface of the bars, it is impossible to hold it to the "tough pitch" condition, and long before the whole charge has been poured the copper will become "overpoled," entailing numerous difficulties. Sulphur has always been blamed by the furnace men as the reason why this refining process is necessary, yet the literature on the subject does not sufficiently emphasize how small a proportion of sulphur will ruin copper for practical purposes.

Jan 3, 1918

By J. L. Leland Myer

Some of the early experiments on the oxidation temperature of coal1 were undertaken in England in connection with a study of self-heating, or spontaneous combustion. It was then suspected that coals with low oxidation temperature were most likely to ignite by self-heating, but further experiments showed that many additional factors were involved. The oxidation temperature has importance as a physical property or characteristic of the coal. While only a few of the physical properties have been studied, they appear to have basic significance2 in the ultimate classification of all coals. When reliable data become available on the oxidation temperatures, as determined by standard and adequate methods, it should provide an additional basis for classification and comparative evaluation. Oxidation Temperature Defined For such a heterogeneous substance as coal is known to be, no simple definition of oxidation temperature can be established on a theoretical basis. If coals were homogeneous and of simpler structure, the accepted definition of "ignition temperature " as applied to simple gaseous mixtures might be adopted; that is, the temperature at which self-heating of the mixture sets in. But most coals self-heat slightly even at storage temperature, as evidenced by spontaneous combustion, and the definition for gases cannot be applied to coals with any exactness. By subjecting coals to suitable experimental conditions various oxidation characteristics can be obtained and examined for critical or significant stages of the oxidation process. Oxidation temperature itself must then be defined on the basis of such experimental results. Experimental Methods Attempts to determine critical points in the temperature functions of coal undergoing oxidation have resulted in the following experimental methods:

Jan 1, 1932

By J. B. Dilworth

In estimating the investment-value of a mining-property or plant, the value of which decreases with operation, it is often necessary to know the sum which must be set aside periodically from earnings either to renew the plant at the end of its life, or to return the capital involved when the earningpower of the investment has ceased. In such cases it is manifestly incorrect simply to divide the total amount to be retired by the 'number of periods (usually years) during which the investment shall be active, as the sums periodically withdrawn have a certain interest-earning power varying with the length of time they are held and with the opportunities afforded for their investment. But though the interest may be considered to accumulate regularly year by year, yet the rules and tables for compouiid interest do not apply, owing to the addition of a fixed amount of new money to the total at the beginning of each period. Briefly stated, the problem of sinking-funds is, to find the amount of money which must be periodically set aside at a certain rate of interest, regularly compounded, to yield a certain sum in a given length of time. In most practical cases the interest is compounded and the fresh amount added at the same time—usually once a year—and on this basis the problem may be solved as follows : Let S = total amount to be retired, Let T = interest rate : R = 1 + r, Let n = life of tlie sinking-fund or the amortization-period, Let L = the sum set aside at the end of each year. Then the amouilt of the sinking-fund at the end of first year is 2, which at the end of n years will have illcreased by compound interest to IRn-l. Similarly, another amount, x, will be set aside at the end of second year, which will in turn increase

Jan 1, 1911

By Roberto Fernandez

Want of knowledge on the part of experts from abroad respecting the amalgamation-system, known as the Mexican or patio process, has been the cause in this country of trouble to many foreign mining companies. This process has not been looked upon by their managers as a satisfactory method of treating silver-ores, and they prefer to employ others, which, although more modern, and often more profitable in other countries, have not proved to be so under the exceptional conditions of this country, where labor is cheap and paid in silver, while fuel is very dear. The cause of this error of judgment is probably the inexact information which has been furnished by several authors respecting the economical results of the patio process. This treatment is not suitable for silver-ores of every kind. Simple sulphides of silver are best adapted to it, and, next to these, the combinations of complex sulphides, viz., pyrargyrite, polybasite, stephanite, proustite, etc. Chlorides, bromides and iodides of silver are considered rebellious ; argentiferous galena, blende, bournonite, as also argentiferous arsenical pyrites of iron and copper, are absolutelg unsuited to this treatment. Experience has proved that high-grade ores do not give as satisfactory results as those of mediurn grades, as, for instance, carrying from 1 to 2 kilos of silver per metrical ton. The patio process, as actually practiced in this district, comprises the following operations: 1. The ore is crushed in a dry state in a roller-mill, reducing it to pea-size, from which uniform samples, and, in consequence, correct assays, can be obtained. 2. It is then thrown into the arrastra, and pulverized with water, so fine that it will pass through an 80-mesh screen.

Jan 1, 1900

By C. M. Warner

In both the Flat River district of southeast Missouri and the Joplin district of southwest Missouri the lead concentrates are of very high grade, free of arsenic, antimony and bismuth, and contain no gold and very little silver. The general practice in both districts is to smelt the concentrates containing 70 to 85 per cent lead on Scotch hearths, to recover 70 to 85 per cent of the lead, and then smelt in a blast furnace the slag formed in the Scotch hearths to bring the total recovery of lead from lead concentrates to over 97.5 per cent. At the lead smelter of the St. Joseph Lead Co. at Herculaneum, Mo., no Scotch hearths are used. In the other smelters in the district the blast furnace plays a minor role to the Scotch hearth . The concentrates produced from the Flat River district are either table concentrates or flotation concentrates containing: Both types of concentrates are received at Herculaneum in box cars after being sampled. Great care is taken in weighing and sampling of cars of concentrates and in the determination of moisture and lead contents. The concentrates are unloaded into bins by an adaptation of scoop grain unloader. Four men unload and sweep a 40 to 45-ton box car of concentrates in 30 minutes. The same grade of concentrates is received each day and no metal-bearing fluxes are available. The problem is to get as high a recovery as possible as cheaply as possible from the high-grade lead concentrates produced by the company's concentrating mills. Sintering The bulk of the sulphur is removed from the concentrates and the fine concentrate particles are agglomerated by double roasting on typical Dwight and Lloyd sintering machines.

Jan 1, 1937