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By R. E. McNulty, R. D. Heidenreich, C. H. Gerould

TIIE electron microscope techniques and their application to magnesium alloys that are to be discussed in this paper are the result of research at The Dow Chemical Co. over the past three years. The view- point underlying the work is not wholly metallurgical, but has evolved through a variety of problems related to the physics and chemistry of surfaces. It can be said that the interest and stimulus were closely associated with a desire to employ effectively the electron microscope in research concerning the properties of solids as related to their physical structure. Only a portion of this work will be described here, and, consequently, many points of interest and debate are of necessity either only briefly recognized or are completely omitted. As has been pointed out by Desch,1 a great deal of the knowledge of the structure of metals has been obtained through microscopic studies of the surfaces of metallic specimens prepared in a particular manner. This information, when added to that obtained by means of thermal, electrical, X-ray, dilatometric and other methods, has been of great value both from a theoretical and a practical view- point. With the introduction of new instruments such as the electron diffraction camera and the electron microscope, it would be expected that still more information could be obtained. These two instruments have in many instances been very effective when directed toward the investigation of metallic surfaces, provided the proper methods of surface preparation were employed. Experience shows that the problems of surface preparation greatly limit the general application of these instruments to metallographic studies. It was found necessary to discard the standard metallographic procedures in applying the electron microscope to magnesium alloys and to work out new methods, which were required to satisfy certain conditions. These methods are unique to magnesium only in the specific chemical reactions occurring during etching. The presentation of the methods and results will be ordered as follows: I. Electron Microscopy of Surfaces. 2. Surface Preparation of Magnesium Alloys. 3. Discussion of Microstructures. a. Pure Magnesium and Single-crystal Studies. b. Types of Precipitation. c. Some Common Structures. d. Special Micrographs and Techniques. e. Structure of Mg-A1 Solid Solutions. 4. Correlation of "Fine Structure" with Corrosion Behavior of Magnesium Alloys.

Jan 1, 1946

By C. A. Herbert

WITHIN the past few years, considerable development has been made in the coal-mining industry in Illinois and Indiana and it is the purpose of the authors to record its most important phases. Perhaps the two most striking features are the entry into the producing fields of certain large consumers of coal and the magnitude of some of the new operations. Mines are now being equipped by the. Chicago & Northwestern R. R., the Chicago,. Burlington & Quincy R. R., the Standard Oil Co., of Indiana, and the Union Electric Light & Power Co. of St. Louis. Besides, the U. S. Steel Corpn. has increased its coal-mining activities by commencing operations on its large holdings northeast of Benton, Franklin Co., Ill. Until recent years, the supply of coal has commonly been adequate and prices have generally been favorable, especially to large consumers, as the magnitude of their purchases enabled them to obtain satisfactory quotations from producers. In fact, most consumers of coal have believed that they could buy their fuel more satisfactorily in the open market than they could produce it themselves. The entry of the United States into the war was accompanied by various disarrangements of industrial conditions, and a demand for coal in excess of the supply seemed likely to be experienced for an indefinite period. Under these circumstances it seemed that the greatest assurance of a supply of fuel was its production by the operation of mines. In the case of the Chicago & Northwestern R. R. and the U. S. Steel Corpn. the production of coal has been carried on for many years with satisfactory results, but the C. B. & Q. R. R., the Union Electric Light & Power Co. and the Standard Oil Co. of Indiana had not been producers of coal, at least in this district. Apparently the most impressive feature of the newest mines is their capacity, for in some cases it is planned that production shall be in the neighborhood of 1000 tons per hr. There are mine, now in this field having nearly that output, but these were not planned for such

Jan 9, 1919

The Sub-committee on Coal Mining, since its appointment, has been collecting data about subsidences in coal mines in this country, and thinks that almost all of the available data about occurrences of this sort in bituminous mines has been collected. Similar data is being compiled for the anthracite regions, which it is hoped will be ready for the 1927 meeting. As most of the bituminous seams are nearly level, the records obtained give the problem in its simplest form, without complications due to the pitch of the seam. Copies of the questionnaire, Appendix A, were mailed to all of the coal operators' associations, to most of the large operating companies and to many engineers, with the request that any data on the subject be returned to the committee, or that advice of any subsidences known be given: the replies to most of the questionnaires were general, although some specific cases were given. Many of the companies were unable to reply to all questions, as they lacked the necessary data, but in nearly every case where accuratc data was available, it was cheerfully furnished, and any additional information requested was secured. All specific cases of subsidence were followed up by correspondence, and in several cases by personal inspection. Figs. 1 to 31 were made from the information furnished. Table 1 gives measurements of elevations taken in one case at intervals from October, 1913, to May, 1918. With one exception, where the evidence cannot be released on account of a lawsuit, it is believed that the cases submitted with this report include practically all that have happened in bituminous coal mining in this country of which actual measurements were secured. Some of these have been published by Young and Stoek,l and some have been secured from other publications. In collecting these data, the subcommittee had the Engineering Societies Library extend its bibliography to date; this list is given in Appendix B. To assist in the study of the problem, all of the subsidence literature in English was examined for cases in which spccific measurements were given, and the essential data for each case are shown in Appendix C.

Jan 1, 1927

By S. D. Strauss

The marketing of nonferrous metals and of the ores and concentrates from which these metals are recovered is a fascinating trade, international in character, sensitive to every change in the economic tide, and complex in its organization. Each individual metal has its own marketing mechanism; no two are exactly alike. The differences sometimes are a matter of tradition rather than of necessity, but usually they have developed because of the very nature of the problems of producing or consuming the individual metal. This description, because of limitations of space, can do no more than indicate the major aspects of the trade and touch lightly on the marketing structure of each metal. The dictionary states that a market is a "meeting of people for selling and buying." In the case of nonferrous metals this meeting may occur on a half-dozen different occasions between the time the ore has been first mined and the time the refined metal is available for use by industry; or it may not occur at all until after the metal itself has been rolled, drawn, stamped, cast, or forged into a useful semifabricated shape. To illustrate: A Chilean miner may sell his small ore production to a custom mill, which produces concentrates that are sold to an ore dealer, who finances the shipments of the concentrates to a United States custom smelter, which buys these' concentrates for conversion into blister, which is subsequently refined into electrolytic copper and sold. Conversely, much of the production of aluminum is in the hands of integrated concerns that mine bauxite, convert bauxite to alumina, smelt the alumina to produce aluminum, and then fabricate the aluminum into semifinished or even finished products before title to the material changes hands for the first time. Some nonferrous ores are not converted into metal at all but are sold by the miners or dealers directly b the ultimate consumers. A good example would be chrome ores used by the chemical industry. And of course a substantial part of the commerce in nonferrous metals is in scrap, which is the reconversion into useful form of metals that have long since been mined and smelted. Thus, one-third of all the lead used in the United

Jan 1, 1959

By R. M. Keeney

Before the outbreak of the war in 1914, the only electric-furnace smelting plant operating on a commercial basis west of the Mississippi River was an electric pig-iron plant in California; rare metal ores were not smelted, concentrates of molybdenum, tungsten, uranium, and vanadium ores being shipped East for reduction. Practically no chrome ore was being mined, and only comparatively small amounts of manganese ore. Today there are two electric smelting plants in California, one in Washington, one in lowa, and four in Colorado; two plants are under construction in California, and one in Montana. Ores of manganese, chromium, molybdenum and tungsten are now smelted in the West, and although uranium and vanadium concentrates are still shipped to the East, they will probably be treated in western plants in a short time. The four electric-furnace plants in Colorado are listed in Table 1. Table 1.—Electric Smelting Plants in Colorado Capacity. Company Location KilowattB PRoductS Tungsten Products Co........... Boulder 800 Ferrotungsten, ferromo- lybdenum. Boulder Tungsten Production Co .. Boulder 400 Ferrotungsten. Ferro Alloy Co.................. Utah Junction 1200 Ferrochrome, ferrotung- sten. Iron Mountain Alloy Co......... Utah Junction 3000 Ferromanganese. Power for all of these plants is supplied by the Colorado Power Co. The plant of the Ferro Alloy Co., at Utah Junction, contains one 750-kw., three-phase furnace, to which power is supplied by three 250-lrw. transformers, connected /Y to give 129 volts on the furnace cables, the transformer ratio being 13,200 to 75 volts. The furnace operates with an actual voltage of 120 volts, and produces about 3 tons of ferrochrome per 24 hr. from 40-per cent. Cr2O3 ore. The furnace consists of a steel shell of circular cross-section, 8 ft. (2.43 m.) in diameter by 7 ft. (2.13 m.) deep, lined with magnesite, and having three vertical carbon electrodes 12 in. (30.48 cm.) in diameter. A 450-kw. furnace, of the same size as the 750-kw. furnace, is also operated on chrome ore. This furnace is three-phase in appearance, but operates electrically as a single-phase furnace. There are three vertical

Jan 1, 1920

By Sir Robert Hadfield

Introduction.-I esteem it a great honor to be asked by this Institute to give them an address chiefly devoted to metallurgy. While it is with great regret that I find myself unable to be present to deliver this in person, I take this opportunity of wishing your society every success in its continued career of usefulness to the metallurgists of the great Republic. To be elected, eight years ago, along with Dr. J. E. Stead, F. R. S., as one of your Honorary Members, was a privilege which I greatly esteemed, for I consider that no society in America has done so much as ours for the advancement of metallurgy. Those who have Served our Society.-Where many have served so well, it is difficult, without appearing to make unavoidable distinctions, to select names from those of your members who have done so much for the cause we have at heart-the advance and progress of metallurgy. As typical, however, and not in any way meant as a complete list, there are among others the following names which in the past and to-day stand out prominently in this science of ferrous metallurgy. With most of those now mentioned I have personally come in contact, or by correspondence in some few cases, and have exchanged views, since I first came over to America 30 years ago. Holley; Jones; Weeks; Andrew Carnegie; Thomas Carnegie; Fritz; Sterry Hunt;. Egleston; Maunsel White and Taylor, who did so much for high-speed tool steel, and helped to revolutionize machine-shop practice; W. J. Taylor; Robert Hunt; Alfred Hunt of Pittsburg, who did so much in the early history of aluminum, and, alas! did. not live to see the wonderful progress which has been made in that particular branch of metallurgical industry; James Douglas; C. B. Dudley; Birkinbine; Howe; Metcalf; Barus; Langley; Raymond; P. H. Dudley; H. H. Campbell; W. R. Webster; E. D. Campbell; Talbot; Spilsbury; Gayley; Dinkey, under whose supervision and responsibility modern armor has been so successfully produced in this country, which the writer can testify from personal knowledge of , test results possesses very high Figure of Merit; Schwab; Kennedy; Wellman; Garrison; Wood; Moldenke; Webster; Swank; Unger; Richards; Sauveur; Strat-

Jan 5, 1914

By A. M. Gaudin

The study that is presented here was undertaken in order to condense information concerning comminution, and covering a great variety of conditions, into one or several rules which would be of use in the development of a systematic theory as well as in many directly practical ways. As the result of this work, the following conclusions appear justified: 1. Rocks may be classified, from the point of view of comminution, into two general classes which are (a) structurally homogeneous, and (b) structurally heterogenous. Structurally homogeneous rocks are those in which fracture takes place through grains and grain boundaries alike; heterogeneous rocks are those in which fracture passes in preference through grain boundaries. 2. If a sized product composed of structurally homogeneous rock grains is crushed, a product results in which the relation between the percentage weight of grains of various sizes and these sizes themselves follows a definite law. This is not true of structurally heterogeneous rocks. 3. Ball milling with structurally homogeneous rocks, and under certain conditions, presents exceptions to this rule. 4. In ball milling with structurally homogeneous rocks, there exists a critical ratio of size of feed to size of balls, above which the machine operates essentially by surface wear, and below which it operates essentially by breaking across the body of the particle. 5. In ball milling, with structurally homogeneous rocks, and when the size of feed grains exceeds the critical size, the particles worn off are of a substantially definite size which depends upon the ball size. 6. In the case of a typical heterogeneous rock, such as Manhattan schist, particles are crushed in such a way that there is a greater proportion of grains of the size that is the average grain-size of the rock than there would be in that range of size with a structurally homogeneous rock. This has been found to be true with all the crushers tested. 7. Different methods of crushing produce grains of different shapes. 8. The importance of sizing the — 200-mesh portion of a crushed product, in crushing-efficiency investigations, has been greatly under-

Jan 1, 1926

By W. H. Bassett

ALTHOUGH brasses and bronzes have been made for ages, a systematic study of their physical properties has been carried out only during the years of the present century. Among these properties may be included those which are to be detected by means of microscopic examination; in other words by the science of metallography. The earlier workers in this field, both in this country and abroad, gave their attention to steel. When the senior author explored the situation in 1902, there was little encouragement to be found in undertaking the study of the non-ferrous alloys. A start was made, and the metallography of the brasses and bronzes, as well as of the copper-nickel- zinc alloys developed materially under his direction. Annealing experiments were begun in 1902, and in the succeeding years the effect of temperature, and the influence of previous working, on the grain size of brass were studied. The conclusions so well known and widely published today were largely reached during those earlier years. In 1905 the first complete annealing series were made. By this it is meant that brass and copper sheet, 5 B & S Nos. hard, was machined into tensile test specimens, then annealed under accurate control for 30 min. at temperatures up to the melting point of the material. Various determinations were made, including tensile strength and elongation in 2 in. There rapidly followed similar series on all of the copper-zinc alloys from 100 to 60 per cent. copper, on the bronzes, cupronickels, and on copper-zinc-nickel alloys. At this point there was published by Grard, in October, 1909,1 the very comprehensive and complete work on the tensile properties of cartridge brass, 90-10 copper-zinc, and electrolytic copper. The excellent photomicrographs in that paper illustrated the changes in structure produced by cold rolling as well as by annealing at different temperatures, but where Grard's work was confined to copper and to two alloys, the investigations in this laboratory have been over the entire fields of the commercial copper-zinc alloys, copper-tin alloys, representative copper-nickel and copper-nickel-zinc alloys as well as aluminum bronzes and others of a more special nature.

Jan 1, 1927

By J. Ellzey Hayden

THE Cliffs Shaft mine of the Cleveland Cliffs Iron Co., located in the city of Ishpeming, Mich., is the largest producer of hard hematite ore on the Marquette iron range. The two shafts, A and B, lying 820 ft. (250 m.) apart on the east-west trend of the ore formation, were sunk in the early eighties, and, except for four years, have been steady producers of iron ore. Their location, on a hill overlooking the general offices of the company on the one side and the city of Ishpeming on the other, has made the shaft houses landmarks. In the spring of 1919, as the old wooden shaft houses had become shaky and out of line, and would soon be unsafe, it was necessary to replace them with the least possible delay. Three plans of construction were, therefore, considered: To replace the old shaft houses by somewhat similar structures made of wood; to use steel and radically change the design; or to build reinforced-concrete shaft houses outside of the wooden structures, completely enclosing them. The first plan was disapproved, because it is anticipated that the mine will have a long life and the proximity of other buildings makes the danger from fire rather great. Delay in receiving material, and the necessity for closing the shafts during erection, were other factors in the situation. The second plan was disapproved on account of the high cost of steel, slow delivery, and interference with hoisting during the period of erection. The presence near one of the shafts of a large bed of hard gravel suitable for concrete made, the cost of the third plan considerably less than the second, and little, if any, delay in hoisting was expected. Our expectations in this regard' were fully realized. Furthermore, the work could be done by unskilled labor, which was plentiful, and the erection could be quickly started. When the proposition was submitted to Mr. W. G. Mather, president of the company, he recommended that, on account of the prominence of the buildings due to their location, an effort should be made to combine in the design as far as practicable something of architectural beauty. Following his recommendation, the original plans were submitted to the

Jan 8, 1920

By Henry F. Hebley

In preparing this paper it has been the aim of the writer to keep the problems of both producers and consumers in mind. Until now, no attempt has been made to familiarize each group with the other's practice and limitations. This paper is an effort to acquaint the readers with some of the factors pertaining to the problem and cost of mining and preparing steam coal, and also to the economics of producing steam with such coal. In recent years all lines of endeavor have turned to intensive mechanization in order to lower the unit cost of production. The average fuel consumption in steam electric generating stations has dropped in 20 years from 4.0 lb. to 1.4 lb. per kilowatt-hour; while the modern power station can generate 1 kw-hr. on a fraction under 1 lb., or 13,000 B.t.u. coal. Also, the amount produced per man has in that same period risen from 3.8 to 8.2 tons, owing to the use of modernized equipment below ground for coal cutting, drilling, shooting, loading, hauling and hoisting. Unfortunately, the rapid speed of 5 tons per minute of operation at which the coal is loaded mechanically precludes any appreciable removal of impurities at the coal face, so that the raw coal is hoisted containing a markedly higher percentage of impurities than the hand-loaded coal, which was subjected to the scrutiny of the miner during loading. Also, during the past 20 years, certain seams of coal lying close to the surface have been made economically available by the improved design of electrically operated shovels and draglines for the removal of overburden running as high as 56 ft. This strip coal frequently contains so much ash in the raw state (Table 1) that it would have no sales value. Therefore, coal preparation must be adopted to beneficiate the raw product. Some seams in the United States have a decreasing ash content with decreasing size, owing, in all probability, to the fact that the coal is friable while the impurities are hard, causing a concentration of the low-ash material in the fine sizes. Illinois No. 6 coal being rather hard, naturally the reverse is true.

Jan 1, 1938

By Henry F. Hebley

In preparing this paper it has been the aim of the writer to keep the problems of both producers and consumers in mind. Until now, no attempt has been made to familiarize each group with the other's practice and limitations. This paper is an effort to acquaint the readers with some of the factors pertaining to the problem and cost of mining and preparing steam coal, and also to the economics of producing steam with such coal. In recent years all lines of endeavor have turned to intensive mechanization in order to lower the unit cost of production. The average fuel consumption in steam electric generating stations has dropped in 20 years from 4.0 lb. to 1.4 lb. per kilowatt-hour; while the modern power station can generate 1 kw-hr. on a fraction under 1 lb., or 13,000 B.t.u. coal. Also, the amount produced per man has in that same period risen from 3.8 to 8.2 tons, owing to the use of modernized equipment below ground for coal cutting, drilling, shooting, loading, hauling and hoisting. Unfortunately, the rapid speed of 5 tons per minute of operation at which the coal is loaded mechanically precludes any appreciable removal of impurities at the coal face, so that the raw coal is hoisted containing a markedly higher percentage of impurities than the hand-loaded coal, which was subjected to the scrutiny of the miner during loading. Also, during the past 20 years, certain seams of coal lying close to the surface have been made economically available by the improved design of electrically operated shovels and draglines for the removal of overburden running as high as 56 ft. This strip coal frequently contains so much ash in the raw state (Table 1) that it would have no sales value. Therefore, coal preparation must be adopted to beneficiate the raw product. Some seams in the United States have a decreasing ash content with decreasing size, owing, in all probability, to the fact that the coal is friable while the impurities are hard, causing a concentration of the low-ash material in the fine sizes. Illinois No. 6 coal being rather hard, naturally the reverse is true.

Jan 1, 1938

By H. S. Bell

It seems unnecessary to dwell upon the advantages of the modern pipe still as compared with the older type of distillation equipment used by oil refiners. The relatively low installation cost, coupled with remark-able operating efficiencies of pipe stills, precludes the consideration of other types except in rare instances where some peculiarity of product or plant may have an influence. The question of the actual heat required to distil petroleum is quite involved. We have extensive data on the latent heats of the various hydrocarbons under different conditions of pressure. We also have information regarding the specific heats of various oils and the effect of temperature thereon. Because of the complexity of petroleum and of each fraction, it seems impossible to analyze theoretically the partisl-pressure effect of the great number of hydrocarbons upon one another during distillation. If a distillation curve and percentage analysis of any crude or product are available, it is possible to construct a curve with ordinates representing per cent. distilled and B. t. u. per pound or per gallon, or other desired unit. To do so the crude is split into fractions, of 5 or 10 per cent. The boiling point and gravity of each fraction being determined, it is possible to evaluate the heat required. As each fraction is removed, the residue must be raised to a higher temperature and latent heat supplied for the successive fraction. As the calculations progress, the latent heats decrease while the specific heats increase. Such a curve is illustrated by Fig. 1 for a typical 39.9° Be. North Texas crude. The chart is illustrative of batch distillation. Theoretically, if the oil were heated by a single flash in a pipe still, the partial-pressure effect of the light products would result in the removal of the same amount of vapors at a lower temperature. Practically, we find that because of the necessarily extensive fractionating equipment required when separating many products all in vapor phase, the oil has to enter the separator at temperatures corresponding to or even above those required in the batch still. Furthermore, in single-flash distillation the vapors evolved in the heater must be superheated to the outlet temperature. Very little is

Jan 1, 1928

By John B. Dilwoth

This paper treats primarily of the valuation of developed coal properties by the method of capitalizing their estimated average future earnings. However, reference is also made to valuations of undeveloped coal lands and to various methods of appraisal other than by future earnings. Fundamental Valuation Principles Before discussing in detail coal property valuations, a few statements bearing on the general subject will be made to present certain of the writer's views on the question as a whole. 1. A certain property at a given time has but one true value. This is not universally admitted. The appraiser rather frequently finds that a coal owner has in mind three valuations for his holdings; one, the figure at which he feels they should be appraised for taxation purposes; another, the much higher one that should be used if a loan is to be negotiated on the property; and a third, intermediate between the other two, the price for which he would be willing to dispose of his holdings were they for sale. The last is usually nearest to the true value, and because this is so the statement is generally accepted that the fair value of such a property is the price arrived at by negotiation between a willing seller and a willing buyer who are otherwise disinterested. 2. Notwithstanding the foregoing, it is only very generally and approximately true that the proper measure of the value of a given developed' coal acreage is the unit or per-acre price for which one or more bodies of similar coal in the same district have been sold recently. To give a few reasons why such a measure of value can not be strictly applied, it may be noted: a. That sales are often forced by circumstances at times when the coal business is depressed and buyers can be found only for properties that are offered at figures far below their true value. b. That conversely, during periods of unusual prosperity, abnormally high prices are paid. Such conditions obtained several years ago when coal brokers, with very profitable contracts but no sure source of supply, were bidding against inexperienced or shortsighted operators for proper-

Jan 1, 1928

By J. Moore Samuel

INTRODUCTORY BEFORE the year 1909, no measurements of dust losses and flue gases had been made at the Copper Queen Reduction Works, at Douglas, Ariz. At that time the "unaccounted" loss of the smelter had reached a figure, that drew attention to the possibility of large stack losses. The measurement of dust losses had not been studied much at that time, and estimates of dust losses, with a few exceptions, were the results of tests by what has been termed "chemical methods," that is, the aspiration and filtration through cotton, wool or some similar medium of a few liters of gas, the dust being weighed on a chemical balance, and the volume of gas computed from the volume of aspirator water. The possible error of this method is enormous, and the probable error much too large for reliable results. Since the object of these tests was to discover not only the extent of the dust losses, but also the possibility of profitably reducing the same, it was decided that the method adopted must have the following characteristics: 1. The sample of gas taken for filtration must be representative of the whole volume of gas, that is to say, it must have the same dust content. This condition will be fulfilled in all cases if the gas sample is drawn off without change of rate of flow. Then it will contain the same proportion of entrained or suspended particles of dust as the original gas. In the case of flue gases which contain only fume, at a temperature above or near the sublimation point, this condition need not be adhered to since the fume will not behave as entrained particles, but more nearly as a true gas. Consequently the gas sample in this case only may be drawn off at any rate of flow. 2. The gas sample taken must be large enough (a) to yield sufficient dust to permit of accurate chemical and physical examination; (b) so that the ratio of the total volume of gas passing through the flue to the volume of gas sample taken shall not be too large.

Jan 6, 1916

By E. F. Kern, W. W. Loo

A review of the literature on the reduction of cassiterite showed that scarcely any progressive changes were made in the methods of reducing cassiterite until within the last two decades, and that during that period many improvements in the metallurgy of tin have taken place. Since 1914 the world's consumption of tin has increased considerably, resulting in the exploitation of primary tin deposits such as the Bolivian lode, which has become an important source of tin. On account of the low tin content of Bolivian ore, and the presence of objectionable impurities of the reduced tin, the smelting of this ore and the refining of the tin has changed considerably from the methods formerly used. A comparative study of the methods of smelting cassiterite concentrates suggested that an investigation be planned so as to determine what factors effect the extraction of tin from its ores by reduction with carbon. The first part of the experimental work was the determination of whether roasted cassiterite concentrates can be reduced by carbon without the use of flux, and the reduced pellets of tin be collected into a single mass separate from the dry gangue residue. The second part of the experimental work was a comparison of the effect of variations of the different factors on the smelting of roasted cassiterite concentrates: first, the effect of varying the composition of the slag; second, the effect of varying the amount of reducing agent; third, the effect of varying the relative amount of the resulting slag; and fourth, the effect of different kinds of reducing agents. Review of Literature Experiments on the smelting of Bolivian tin concentrates were made by James P. Gill in 1920 in the metallurgical laboratory of the School of Mines, and submitted as a graduate thesis. The results of these tests are fully reported as they are preliminary to the experimental part of this paper, and also because they have not been published. The variables investigated by Mr. Gill were: (a) the effect of temperature on the rate of reduction of cassiterite concentrates; (b) the time required for

Jan 1, 1928

By R. Y. Williams

IN the United States, fully 98 per cent. of the anthracite and bituminous coal tonnage obtained from underground operations is mined by the room-and-pillar system. Under this system, the total cost of the coal f. o. b. railroad cars contains as its greatest single item the money paid for "labor." Each labor dollar in an. average bituminous mine may be subdivided into 85 c. paid for work done inbye the gathering turnouts (including all work at the face), and 15 c. outbye that point (including all work in and under the tipple). In an average anthracite mine, the corresponding figures are 70 c. and 30 c., the larger breaker force accounting mainly for the difference between these and the bituminous figures. The next largest single item after "labor" is usually "supplies and power;" and a division of this item inbye and outbye the gathering turnouts shows somewhat the same relative proportions as has been noted under the case of "labor". During the past 10 years, the chief advances made in the coal industry have been to obtain economies through complete mechanization covering that portion of the work which lies outbye the gathering turnouts. These results have been accomplished by applying scientific principles to railroad yard layout, to cleaning and sizing machinery, to dumping facilities, to roller-bearing haulage equipment, and to heavy-rail, well-ballasted trackage. But these improvements, while gratifying in their resulting economies, apply only to 15 to 30 per cent. of the important cost items. Obviously, then, the big problem before the engineers of the coal industry today has to do with the methods of mining and the layout inbye the gathering turnouts. Four years ago, Weston Dodson & Co., Inc., determined to have an exhaustive study made of the conditions which must be met in order to gain complete face mechanization, and in order that such a mining layout would be based on, correct underlying principles. The result of that study, which was made by the writer, led to the adoption of a method of longwall mining wherein the. roof is worked on the caving system and is supported as an overhang along the face by steel jacks.

Jan 1, 1928

By W. H. Bassett, C. Davis

Although brasses and bronzes have been made for ages, a systematic study of their physical properties has been carried out only during the years of the present century. Among these properties may be included those which are to be detected by means of microscopic examination; in other words by the science of metallography. The earlier workers in this field, both in this country and abroad, gave their attention to steel. When the senior author explored the situation in 1902, there was little encouragement to be found in undertaking the study of the non-ferrous alloys. A start was made, and the metallography of the brasses and bronzes, as well as of the copper-nickel-zinc alloys developed materially under his direction. Annealing experiments were begun in 1902, and in the succeeding years the effect of temperature, and the influence of previous working, on the grain size of brass were studied. The conclusions so well known and widely published today were largely reached during those earlier years. In 1905 the first complete annealing series were made. By this it is meant that brass and copper sheet, 5 B & S Nos. hard, was machined into tensile test specimens, then annealed under accurate control for 30 min. at temperatures up to the melting point of the material. Various determinations were made, including tensile strength and elongation in 2 in. There rapidly followed similar series on all of the copper-zinc alloys from 100 to 60 per cent, copper, on the bronzes, cupronickels, and on copper-zinc-nickel alloys. At this point there was published by Grard, in October, 1909,' the very comprehensive and complete work on the tensile properties of cartridge brass, 90-10 copper-zinc, and electrolytic copper. The excellent photomicrographs in that paper illustrated the changes in structure produced by cold rolling as well as by annealing at different temperatures, but where Grard's work was confined to copper and to two alloys, the investigations in this laboratory have been over the entire fields of the commercial copper-zinc alloys, copper-tin alloys, representative copper-nickel and copper-nickel-zinc alloys as well as aluminum bronzes and others of a more special nature.

By Albert Hayes

FOUR mines at Wabana, on Bell Island in Concep-tion Bay, Newfoundland, produced 1,209,777 tons of ore in 1927, and it is expected that the produc-tion will be larger in 1928. The ore is a stratified oolitic hematite of sedimentary origin. Three workable beds and many thin beds occur in a thickness of 400 ft. of interbedded sandstones and shales. It is not profitable under present conditions to mine extensively in ore beds less than 4 ft. thick. The iron ore beds outcrop on the small island and are inclined northward more steeply, than the slope of the ocean bottom. The mine work-ings follow the bedded ore below the sea bottom, No. 3 Mine extending about 2 miles north of the island. At this point there is a cover of 1500 ft. of rock and 600 ft. of ocean water. It is impracticable to operate drills in the ocean to prove the extent of the submarine orebody in advance, and diamond drilling from the mine workings is the only method of exploration. Bell Island has been settled for a long time and a monument at Cupids, near Brigus at the head of Conception Bay, commemor-ates the tercentenary of a settlement there in 1611 by Captain Guy of England. was one of the chief ports of Newfoundland for deep sea fishing and doubtless many a captain wondered about the red rocks as he sailed past. The famous geologist, J. B. Jukes, records seeing a bright red sandstone 8 ft. thick on the northwest side of Bell Island during a visit in 1842, but he evident ly did not try to land on that rocky coast to get a sample. The iron ore is plainly visible in the high cliffs along the coast of the island, as bright brown layers interbedded with gray and white sandstones and dark shales. The heavy red rock was used by the fisher-men as anchor weights for fish nets and small boats, but its real value, so the story goes, was discovered by a merchant in Saint John,

Jan 8, 1928

By F. W. Gordon

The Whitwell firebrick hot-blast stove, for furnace use, may be seen in its three main stages of development in the accompnying drawings. Fig. 1 is the stove of 1869, the year in which it was thoroughly tested at the Consett furnaces, England; Fig. 2, the stove of 1876 and 1877, in which it was intended to reduce the cost by increasing the height; Fig. 3, the stove of 1880. Many modifications were made from time to time, generally in the direction of improvement, but the drawings illustrake the main features of progress. In the stove of 1869 the plan was to introduce the gas at A, and pass it up and down between each alternate wall, the air in the reverse direction, passing in at B. The friction in this stove was so great, owing to the restricted area of the passages and the many revervals of the gaseous current, that it was deemed imprudent to build the stoves higher than 28' 6". Another reason mas that the great importance of cleaning was carefully kept in view, and it was very difficult to operate any hand scraper even to this depth. For these reasons the 22' X 28½' stove held the field for several yearn. A slight change made from this was to the 18' X 40' stove, where the height was increased, but the dumber of walls diminished. In this stove the friction was somewhat reduced, but so was the heating surface, and although it cost a little lea it was not any better. The next important change, seen in Fig. 2, was by increasing the height to GO feet and keeping the full number of walls in the stove. The heating surface and mass were much increased in proportion to the cost, and the friction decremed by alterllating over and under two or more walls, instead of one, as formerly. This stove gave admirable satisfactiou, but, although the proper doors were provided, it was very difticult to clean, owing to the long (distance the scrapers lid to traverse. Stove No. 3 is a modification of No. 2. The great question was how to decrease the cost mithotlt impairing in any yaw the

Jan 1, 1881

By F. W. Gordon

THE Whitwell firebrick hot-blast stove, for furnace use, may be seen in its three, main stages of development in the accompanying drawings. Fig. 1 is the stove of 1869, the, year in which it was thoroughly tested at the Consett furnaces, England; Fig. 2, the stove of 1876 and 1877, in which it was intended to reduce the-cost by increasing the height; Fig. 3, the stove of 1880. Many modifications were made from time to time, generally in the direction of improvement, but the drawings illustrate the main features of progress. In the stove of 1869 the plan was to introduce the gas at A, and pass it up and down. between each alternate wall, the air in the reverse direction, passing in at B. The friction in this stove was so great, owing to the. restricted area of the passages and the many reversals of the gaseous current, that it was deemed imprudent to build the stoves higher than 28' 6'". Another reason was that the great importance of cleaning was carefully kept in view, and it was very difficult to operate any hand scraper even to this depth. For these reasons the 22' X 28 1/2' stove held the field for several years. A slight change made from this was to the 18' X 40' stove, where the height was increased, but the number of walls diminished. In this stove the friction was somewhat reduced, but so was the heating surface, and although it cost a little less it was not any better. The next important change, seen in Fig. 2, was by increasing the height to 60 feet and keeping the full number of walls in the stove. The heating surface and mass were much increased in proportion to the cost, and the friction decreased by alternating over and under two or more walls, instead of one, as formerly. This stove gave admirable satisfaction, but; although the proper doors were provided, it was very difficult to clean, owing to the long distance the scrapers had to traverse. Stove No. 3 is a modification of No. 2. The great question was how to decrease the cost without impairing in any yaw the

Jan 1, 1881