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By O. W. Bilharz

Acid mine-water drainage is a serious problem with many mines in the Tri-State zinc and lead mining district. Particularly is this true when large volumes must be considercd in unwatering old mines that have refilled with water which has dissolved the products of oxidation and has become chalybeate in character. The experiences discussed in this paper have to do specifically with the unwatering of a comparatively small area west of the town of Baxter Springs, Kans., where the pumping job was complicated by water of this type and where the extremely high sulphate content particularly effected that phase of mine drainage having to do with stream pollution. Location, Geology and History The Baxter Springs area of the Tri-State mining field is situated just west of the town of Baxter Springs and is a northeasterly extension of the main mineralized zones of the Oklahoma part of the district (Fig I). The mining area is traversed with well defined shear zones which provide easy circulation of ground waters and the ore bodies are found along these shear zones as localized enrichments wherever the structural conditions are favorable (Fig 2). The ore-bearing strata is Mississippian with an overlain capping of shale of Penn- sylvanian age. This shale strata carries much pyrite and marcasite at its base and undoubtedly was a contributing factor to the subsequent high iron content of the water. The area originally contained a sulphide water which discharged as an artesian flow in springs within the town and gave Baxter Springs its name. These springs were famed for many years for their mineral water. This original sulphide water was first removed about 1917 and active mining was carried on west of the town during subsequent high metal price periods. Many small mines were opened, with each localized enrichment becoming a separate mine. During the depression mining ceased and all mines in the west Baxter area were allowed to flood. No serious effort was made to again unwater until higher prices caused from the demand for metal for World War II once more focused attention 011 this part of the field. Original Mining Results in Oxidation As plans for unwatering progressed, it soon developed that the mine-water pools had become strongly acid in character and carried large amounts of sulphates in solution. This occurred in the following way. When the original sulphide water was removed, shafts sunk, and mining carried on over a number of years, ferrous sulphate was formed by the spontaneous oxidation of the pyrite beds in contact with air admitted through churn-drill holes and mine openillgs. These products of oxidation can be seen today in the old mines of the district as crusts of crystalline sulphates

Jan 1, 1949

By H. Kenworthy

This report concerns cooperative milling investigations of the Central mill of the Eagle-Picher Mining &. Smelting Co, The work carried on at the Central mill and the Rolla, Station shows that: It is possible to reduce the Central mill heavy-medium plant tailings by 0.05 to .15 percent zinc; the 3/16-inch to 10-mesh fraction of the jig feed can be treated by sink-float to obtain a tailing containing only half as much zinc as the jig tailing; Humphreys spiral concentration of the flotation tailing does not recover enough zinc to be economically attractive; and crushing and wet grinding of ferrosilicon for heavy medium are commercially feasible. The Eagle-Picher Co. operates extensive mines in the Tri-State area of Missouri, Kansas, and Oklahoma. The ore is milled at its Central hill, which also accepts custom ores. During the recent war the mill handled about 12,-000 tong- of low-grade ore per day. The company milled about 50 percent of the district tonnage and purchased nearly 90 percent of the custom ore. About 50 percent of the mill feed was from company mines. Zinc is the chief value in the Tri-State ores,-with Varying quantities of lead and cadmium minerals, as well as small amounts of germanium and gallium.

Jan 1, 1949

THE compiler, or author, of the Probierbücblein is not known, and the date of its first printing is uncertain. It was obviously not written by an assayer who wished to give a coherent description of his craft for the instruction of others; this was left for Biringuccio first to do. It is easy to believe that originally the Probierbücblein was a random collection from various sources of information useful to an assayer, probably gathered by one of the profession for his own use. It must remain a matter of speculation whether this was shown to a printer, who recognized the opportunity to turn an honest penny and made an inept attempt to give the manuscript the appearance of a coherent account by writing a preface and arranging the various items in somewhat logical sequence, or whether the assayer him- self started this job and was prevented from finishing it. That some sections of the book, especially near the be ginning, present an almost continuous story, while others are chaotic in their arrangement; that several paragraphs are printed more than once in different places; that there are paragraph headings, for which the text was never written, or lost, followed by irrelevant information-all this seems evidence of a job unfinished and points to a publisher's offering for the public's quick money. The demand must have been brisk, for metal working was a profitable profession, and the jeweler who was working with metals but did not care to become completely trained in assay methods would jump at the chance of acquiring easy knowledge. Even the great Agricola has whole sections obviously plagiarized from the Probierbücblein. Neither Biringuccio nor Ercker shows any direct influence, though they and all subsequent metallurgists will in some degree be affected by

Jan 1, 1949

By J. S. Bryner

In the study of metallographic specimens in the electron microscope, there is need for a method of locating the same field in both the light microscope and the electron microscope. This need arises chiefly from the fact that in the electron microscope the magnification and degree of resolution are so much higher, and the field so much smaller than in the light rnicroscope that it is often difficult, if not impossible, to identify positively what is being observed. The difficulty is increased by the fact that, because a transparent film replica of the metal surface must be used in the electron microscope, micro-constituents can be identified not by their color but only by their texture and contours. For these reasons it is desirable to obtain a series of photographs showing the same field in both microscopes in order that the appearance of common microstructures and micro-constituents in the electron microscope may be identified and catalogued for future reference. The need for a method of locating the same field in both microscopes arises also when it becomes desirable to enlarge in the electron microscope for more detailed study a particular interesting structure observed in the light microscope. Using the standard polystyrene-silicalJ replica technique, in which the silica film replica is fished from the ethyl bromide on a 1/8 in. diam zoo-mesh specimen screen, the possibilities of locating a particular area on the film in the electron microscope are rather remote. The desired structure may be obscured by the wires of the specimen screen or unrecognizable at the high magnification. A solution to the problem would be provided if a specially designed specimen screen, containing an opening which could be absolutely identified and quickly located in the electron microscope, could be fastened to the silica film replica in such a position that the desired field on the specimen would be located at the identifiable opening in the specimen screen. The design for such a specimen screen, a method for producing it, and a technique for fastening it to the silica film replica are described below. Description OF Method The Specimen Screen A simple design for a specimen screen containing an opening easy to identify and locate in the electron microscope is one with two lines of openings at right angles in the form of a cross. Such a screen is shown in Fig I. The opening at the center of the cross is identified easily and can be located quickly in the light microscope and in the objective image of the electron microscope. The specially designed specimen screens for this work were produced in quantity by electroforming. On both sides of a polished strip of copper I X 3 X 1/8 in., twenty patterns of the cross of openings were punched with a diamond point micro-hardness tester, using a load of magnitude

Jan 1, 1949

By Soule&apos, John H.

Although known since 1902, the Capitan iron deposits have not been tined, mainly because of the low grade of the ore. Only a small amount of exploratory work has been done since the discovery. C. H. Johnson, district engineer of the Bureau of Mines in New Mexico in 1942-4, visited the property; as a result, preliminary sampling of the property was done in 1943.2/ Owing to the results of this preliminary work, an extensive development program by wagon drilling was planned and executed early in 1944. Equipment available at that time was limited in the depths that could be reached; and as geologic studies indicated the possibility that other limestone beds below the surface might have been replaced by iron minerals, a supplementary development program by churn drilling to reach greater depths was prosecuted in late 1947 and early 1948, with the author as project engineer.

Jan 1, 1949

By F. W. Horton

Investigation of an extensive deposit of chromite-bearing actinolite-talc schist situated on the summit of Casper Mountain, 10 miles south of Casper, Wyo., was one of the first projects Undertaken by the Bureau of Mines under the Strategic Materials Act (Public 117, 76th Cong., Ch. 190, 1st sess.), for which an appropriation became available August 9, 1939. During the previous summer; the Geological Survey? made? a magnetometrical survey of the area in which the schist occurred. It was exposed in several small lenses and two larger ones aggregating about 19?acres in area. Although the occurrence of chromite here had been known for many years, the only work done on the deposit was the digging of? a few shallow pits on some of the more promising outcrops. From August 23 to December 3, 1939, the Bureau of Mines investigated the larger of the two main schist bodies. Twenty-four trenches having a total length of 8,073 feet were dug across the deposit, and its subsurface extension was explored by 3,623 feet of diamond drilling. Over 32 tons of samples were shipped to the Metallurgical Division of the Bureau of Mines at Reno, Nev., for reduction, analysis, and ore testing. In all, there were 853 individual samples. Geological maps, based upon examination of outcrops, trenches, and drill cores, as well as a contour map of the area were made by the Geological Survey.

Jan 1, 1949

By G. A. Apell

Completion of 18 churn-drill holes totaling 2,218 feet and 3 diamond-drill holes aggregating 421.5 feet of drilling in the M.C. mine area, near Truman, Wis., provided information indicating the existence and trend of a zone of zinc mineralization extending for 1,000 feet west of the old M. C. shaft.

Jan 1, 1949

By A. S. Dawson

Introduction The purpose of this paper is to discuss, in a general way, the application of geological principles in the exploration for, and development of, deposits of industrial minerals. Mention of geological factors pertaining co specific minerals will be by way of illustration only. Since many prospectors are little acquainted with the geological setting and mode of occurrence of deposits of these minerals, some prospecting possibilities in the field will be pointed out. Geology is a tried and proven tool in the search for and exploitation of metalliferous deposits and of oil and gas fields, but, so far at least as Canada is concerned, only very rarely has a directed, intensive search been made for deposits of industrial minerals. Examples might be cited, however, where, in other countries, such investigations have yielded rich rewards. Thus, development of the vitally important potash deposits of New Mexico was the result of a deliberately planned programme of geological investigation, first by United States Government agencies, and later by private interests. War or the threat of war, or peace-time industrial expansion, can render concentrated exploration for specific minerals desirable or even essential. Such exploration is, primarily, a geological problem. Admittedly, there is in general less scope for the application of geology in the search for, and development of, deposits of industrial minerals than of metalliferous minerals, oil, etc. Where the latter are concerned; the objective of exploration is to find a material that is valuable, within broad limits, no matter where it is located or how it occurs. The unit value of the material is limited only by the amount of the valuable constituent in the formation- its possible upper limit is tremendously high. On the other hand, many industrial minerals constitute in themselves 90 per cent or more of the formation- their amount cannot increase and their unit value is commonly low. Moreover, for commercial exploitation, the deposit must, in general, be reasonably close to markets or to plant or other facilities for processing the raw material, since, owing to its low value, this cannot be transported any great distance. As a consequence, intensive geological search for and investigation of such deposits has been restricted to industrialized areas. Obviously, however, it is good insurance for any operator to understand the geological background of his deposit, particularly in the case of new developments.

Jan 1, 1949

By R. I. Jaffee, J. G. Dunleavy, W. Hodge, H. R. Ogden

Jan 1, 1949

By Welton J. Wenger

Apparatus for the analytical distillation of crude oils under an artificial pressure of 760 mm. of mercury has been designed and constructed. This apparatus enables laboratories at high altitudes to make Bureau of Mines routine analyses of crude oils with results similar to those obtained by laboratories at sea level. This is especially important for laboratories in the Rocky Mountain region, where barometric pressures of approximately 600 mm of mercury are encountered. During the past 30 years, the ?Bureau of Mines has made several thousand analyses of crude oils from various parts of the United States and from foreign countries. The first part (stage 1) of the distillation for the analysis is made at atmospheric pressure, and as most petroleum laboratories are near sea level, comparable results are obtained ordinarily. However, the increased use of the method by .laboratories at high altitudes has caused difficulty, as the analyses cannot be accurately compared with analyses from laboratories at sea level. For instance, laboratories at 7,200 feet generally report 2 to' 4 percent (based upon the crude oil) more gasoline than sea level laboratories. The use of the pressurized apparatus developed by the writers makes it possible for these high-altitude laboratories to duplicate analyses made at sea level.

Jan 1, 1949

By F. S. Wartman

This paper gives an account of the production of ductile-grade titanium powder in 100-pound batches by reduction of purified titanic Chloride with magnesium, grinding, leaching, and magnetic-separation of the reaction product. Apparatus, technique, and methods of controlling product quality are described and some data on operating costs are given.

Jan 1, 1949

By R. E. Zimmerman

The separation of fine sizes of coal from its impurities by means of various flotation methods has become of increasing importance in the coal industry. This, no doubt, will be even more so in the future as the quantity of high grade coal is depleted, particularly that used for metallurgical purposes. The purpose of this paper is to describe and report the results of research work done under the auspices of the Pittsburgh Coal Co. to determine the amenability of their bituminous fine sizes of coal to flotation, to investigate the value of various reagents and factors affecting their use, and compare the results between froth flotation and bulk oil flotation. Compared with the preferential flotation of complex minerals, or ores, the flotation of coal is comparatively easy. However, this statement should not lull one into the feeling that there are no special problems involved. For instance, the separation of coal from pyrite in high sulphur coals is still far from being 100 pet successful. Size consist has considerable effect on reagent consumption and recovery. Other factors will be described and finally it must be remembered that in the flotation of coal a low priced material is being treated and thus economic considerations govern more closely its application than is generally the case in treating other minerals. As a result of the research work done by the Pittsburgh Coal Co. on the flotation of coal, it was concluded that it was practical to clean the —48-mesh coal commercially by froth flotation and after several different types of flotation units and circuits were investigated by means of pilot plants, large scale units were installed at their Champion Nos. 1, 4 and 5 Preparation Plants for the cleaning of —48-mesh slurries. These large scale operations have been recently described by D. H. Davis.' C. P. Proctor and C. B. Carlson2 in their chapter on Froth Flotation of Coal in the AIME Seeley W. Mudd series book on Coal Preparation describe some of the practical applications of our Pittsburgh Coal Co. laboratory work in actual plant practice as well as summarizing part of the investiga-tional work. The author presents this paper, however, as a supplement to their reports, and records the basic research accomplished in the laboratory investiga-tional work as well as the results of experiments using bulk oil flotation. In presenting this work the author wishes to state much more work must be done in applying the principles of flotation to cleaning coal, especially in view of recent studies and practices in other mineral beneficiation fields. Methods of Conducting Laboratory Tests The bulk of the research work was conducted in the laboratory of the Champion No. I Preparation Plant. This plant has elaborate facilities for sampling and analyzing coal and proved to be an admirable location for the investigational work. Four types of laboratory flotation ma-

Jan 1, 1949

By W. J. Blackstock

Introduction To The great majority of people, the term 'strip coal' has little or no meaning, or if it has any significance it is thought to refer to a poor grade of coal that had to be accepted during the war because no other fuel was available. Few people in the Province of Alberta realize the magnitude of our coal stripping industry, and fewer realize that strip coal has been available to domestic consumers for at least forty years. Among the first in the field of strip coal mining in Alberta were the Tofield Coal Company, Ltd., and Sterling Collieries Company Ltd. It was not until the advent of World War II, with its huge drain on industrial and domestic coal sup? plies produced by the underground mines, that some other source of coal was seriously sought. The tremendous shortage of manpower du ring this period of National emergency made it imperative that any increase in the coal production must be procured on a high tonnage per man-hour basis. It was therefore natural that the highly mechanized strip mine should be eagerly encouraged and subsidized by the Governmental agency - the Emergency Coal Production Board - under the very able direction of Mr. G. A. Vissac.

Jan 1, 1949

By L. E. Djingheuzian

Introduction Cylindrical grinding mills have been used for a long time, but during many years of testing no methods were established that gave consistent results. The work by both scientific investigators and operators led very often to contradictory conclusions, and each millman was very much 'on his own' when trying to find the limits for working of his ball-mills. Fred C. Bond, in the introduction to his paper on Wear and Size Distribution of Grinding Balls, freely states that the mathematical immaturity of the grinding process "is the cause of many inefficient designs and installations as well as of much poorly oriented experimental work", and evidently he sees the solution of all our grinding problems in the discovery of the fundamental laws "which can change the empirical art into a mathematically exact science". While the writer is in complete agreement with Mr. Bond that grinding is governed by fundamental laws which can be expressed by mathematical formulae, there are so many variables in grinding, all interwoven with each other and mutually influencing each other, that the coalescing and merging of all these variables into a harmonious mathematical whole appears to be a homeric job. However, a light appeared on the horizon when it was proposed that power be used as an index of the grinding operation. It is pertinent to quote Gow, Guggenheim, Campbell, and Coghill from their paper on Ball Milling, in which they say: "Much of the past literature devoted to the subject has been concerned with the Kick-Rittinger dispute over evaluating grinding, or with dissertations on ball paths and the closely allied impact versus attrition hypotheses or with the exclusive consideration of certain specific variables, such as mill speed or circulating load, irrespectve of the other factors in operation. Such subjects may be dismissed with but little discussion in what may be called, by comparison a new philosophy in the stud of ball milling. Briefly this 'new philosophy' consists ' of using power as an index of the mill operation, and investigating grinding from the standpoint of set and induced variables with emphasis on the latter". But it is safe to assume that it was the work by E.W. Davis, H. E. T. Haultain, F. C. Dyer, A: M. Gaudin, J. Gross, S. R. Zimmerley, and others, that cleared the path for the authors of Ball Milling and induced them and A. W. Fahrenwald to look farther afield and thus to establish a far-reaching relationship between the power and capacity and the diameter of the ball-mills.

Jan 1, 1949

By W. D. Steele, S. D. Brady

The Pittsburgh coal seam in West Virginia contains the largest coal reserves of any coal seam in that State and is, therefore, one of the most important seams, and attains minable thickness and purity throughout that part of the seam extending from the Northern Panhandle to Monon-galia Co. thence south and southwest across the state to Wayne Co. near Hunt-ington. The Pittsburgh coal is also minable in the Upper Potomac region but is now practically exhausted there. The total minable areas of this coal amount to 2,165 sq miles and are estimated, by the West Virginia Geological Survey, to contain 13¼ billion net tons. The largest body of Pittsburgh coal outcrops on the western edge of West Virginia, along the Ohio River as far south as Moundsville, West Va., going under the river at that point and extending at various depths down the river as far as Wetzel Co. line where it thins out to such an extent that it has little practical value, and on the eastern edge this large body outcrops along the Monongahela River. The territory to be covered by this paper is the area known as the Northern West Virginia District comprising Wetzel, Mon-ongalia, Marion, Preston, Harrison, Dodd-ridge, Taylor, Barbour, Upshur, Lewis, Gilmer, Braxton and Calhoun Counties, and is also known as Dist. 3 under the Bituminous Coal Act. This region was originally opened for commercial mining along and adjacent to the Monongahela River around 1852 when the Baltimore and Ohio Railroad was constructed to Fairmont. It has been extensively developed, first, in 1880 (when the Monongahela River Railroad, now B. & 0. R. R., was constructed) between Fairmont and Clarksburg, and later, in 1916, between Morgan-town and Fairmont when the Monongahela Railway was constructed and placed in operation, this area furnishing the major portion of the production over the past years. With the mining out of a great deal of this territory adjacent to the Mononga-hela River considerable interest has been developed in the back acreage; and within the past few years a number of diamond core drill holes have been made in the back areas of Monongalia and Marion Counties. In this back area the oil and gas well drilling showed that the Pittsburgh coal seam was of minable thickness and ranged in depth from 350 to 1,000 ft below the surface of the stream valleys but this drilling did not furnish any definite data as to its thickness and quality. Economic Importance The Pittsburgh seam in Northern West Virginia is of primary importance as a coal resource not only because of its large reserves but because of its contributing a very large part of the coal used in this country for general steam uses. The Pittsburgh seam is a consistently thick seam, averaging 8 ft in thickness, with very easy grades underground, so it has always been

Jan 1, 1949

By Robert Thomson

"The Cobalt camp is by far the most productive camp of the Temiskaming silver-cobalt area. The date of discovery, 1903, is an important one in the history of Canadian mining; from then on prospecting and mining grew rapidly to take the prominent places they now hold in Canadian life.At Cobalt, prospectors and operators, who were to play prominent parts in other Canadian camps, received their initial training. The exploration campaigns leading to the discovery of several new camps were organized at Cobalt, and a considerable part, indeed, of the funds for these campaigns were profits from mining at Cobalt.The discovery of the Cobalt camp was purely accidental, not the result of any purposeful search. Fred LaRose, a blacksmith employed in the construction of the Temiskaming and Northern Ontario Railway, discovered mineral, afterwards determined to be valuable, within a few feet of the right-of-way. This discovery became part of the very productive LaRose mine. The publicity given this discovery, particularly by Willet G. Miller, later Provincial Geologist of Ontario, led to the rapid development of the camp.ProductionCobalt is a great camp by virtue of its silver production; cobalt is also important, although clearly subordinate. Copper, nickel, arsenic, and bismuth are by-products of mining for silver and cobalt and have not been of great importance to date.The following table gives the metal content of ores, concentrates, etc. from the Cobalt camp for the years 1904 to 1954 inclusive, as reported by the mines (l):"

Jan 1, 1949

By A. L. Engel

The Stayton Mining District in San Benito County, Calif., near Hollister, includes several square miles with many occurrences of antimony ore. The sample submitted for the test described in this paper came from a vein said to have been traced and sampled for 5,000 feet on the surface, 1,500 feet carrying 2-1/2 to 3 percent antimony and the remainder 1/2 to 2 percent. Thirty thousand tons 'With a content of 3 percent antimony are said to be blocked out. A drift of 200 feet on the vein has shown ore containing 4.2 percent antimony. The present sample assayed 3.8 percent. Previous flotation investigation of this are resulted in a recovery of only 71.6 percent in concentrates containing 56.8 percent Sb. It was desired to develop a method of treatment that would give better results. The antimony in the sample occurred as the mineral stibnite, Sb2S3, antimony sulfide.

Jan 1, 1949

By W. E. Uren

The Dominion Coal Board was created by Statute passed on July 17th, 1947, and was brought into effect by proclamation on October 21st, 1947. It is, consequently, a comparatively young body, having been in existence for only eighteen months. Before dealing with the constitution and duties of the Board, it may be well to answer the unspoken question of why it has been considered necessary to single out coal as one specific mineral requiring the continuous attention of a specially created permanent Board. In Canada, coal has been the neglected sister of the more spectacular minerals and it comes as a surprise co many to note that in 1948 the value of the coal produced in Canada was higher than that of any other mineral with the one exception of gold. Coal touches upon our daily lives in many different places of which the public are not generally conscious. As household fuel, it is a necessity of life in this northern climate; as a source of steam, it provides the heat for most of our industries; it is the food of the 'iron horse' chat shuttles our persons and our goods across the land; it is the source of power in many parts of the country; it is the chemical reducing agent chat, in our furnaces, transmutes the metallic oxides to the virgin metal. Coal is, in fact, the indispensable mineral chat forms the corner-stone of our present structure of industrial civilization. Is it, then, such an odd thing that the provision of an adequate supply of coal should be a matter of national interest or that measures should have been taken by government co provide for a constant watch, by a permanent Board, on the supply of co al? ? The Board is the result of the recommendations of the Royal Commission on coal which made a long and detailed study of the Canadian coal problem. It is composed of a permanent Chairman and six part-time members, most of whom have had intimate contact with various phases of the industry.

Jan 1, 1949

By Bert Taylor

"The Mining concessions of Quemont Mining Corporation, Limited, are located at 48°16'N latitude, 79°00'W longitude, in Rouyn township, northwestern Quebec. Six hundred and forty acres in area, they lie directly north of, and contiguous to, the Horne mine of Noranda Mines Limited. The north arm of Osisko Lake covers a large area of the southern part of the property. The orebodies lie below the Jake with one body extending through to the bedrock surface.The property was staked in 1922, and was originally known as the Murray Claims. The group attracted interest from numerous exploration companies because of the proximity of the Noranda orebodies.The United Verde Extension Company, of Arizona, optioned the claims in 1926. They sank a shaft to a depth of 235 feet, at a short distance from the Noranda boundary. From a level established at a depth of 215 feet they completed 3000 feet of exploratory driving from which 6000 feet of diamond drilling was done. Only a small body of siliceous gold ore was found before they dropped their ·option.In 1928, The Mining Corporation of Canada purchased a 90 per cent interest in the property. An operating company, later named Quemont Mining Corporation, was formed. An electrical survey was carried out on a portion of the property, followed by deepening of the shaft to 922 feet. Levels were established at 500 and 900 feet, and 4,800 feet of driving and more than 3000 feet of diamond drilling were carried out from them.Geological knowledge at that time recognized that a major break, the Horne Creek fault, lay not far inside the south boundary. Striking north 80 degrees east, the fault dipped south at 85 degrees. The rock on the north side of the fault was massive rhyolite; to the south, meta-diabase and a little rhyolite. A left-handed movement was indicated by a 600-foot offset on a north striking diabase dyke. The small body of siliceous gold ore, referred to previously, was confined to the 215 level."

Jan 1, 1949

By G. L. Oldright

The first Report of Investigations of the present series (No. 4562) was on the fundamental properties of lead compounds, and the manner in which they set limits to the richness of lead products treated in the usual sintering-blast furnace units. These properties of the compounds were emphasized, as' it was desired, also, to learn the limitations of smelting the same compounds in present ore hearth practice; the hearth has a competitor in these "usual" units, even with the rich lead feeds best adapted for the hearths. Operating conditions that were followed in older metallurgical processes, when rich products, were treated, were outlined. The second report of the series (R. I. 4563) was on the development of the ore hearths of the types now used in the Tri-State from the viewpoint of the features, functions, and dimensions of the earlier hearths that had been most changed. Experimental data, for both well and poorly desulfurized charges being considered, were given to show the relative changes in the sizes and compositions of the charges after they were added to the ore (Scotch) hearths. A general picture was given of the charge column and of the conditions prevailing there when the operation was satisfactory. In this third paper, the composition of the gases prevailing in the charge column at various elevations will be correlated with what has been learned of the nature of the charge column in order to trace the steps of operation by which lead sulfide is converted into metallic lead. The metallurgical factors that govern operation and the lines along which improvements may be made will be noted.

Jan 1, 1949