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By C. W. Davis

Two general schemes have been used for the determination of gold and silver in material containing considerable quantities of copper ; one is known as the " all fire " method , and the other as the , " combination " , or " wet and dry" method . The all fire crucible method , using an excess charge of litharge , has been found satisfactory when the copper content of an ore is under 6 per cent , ( Loevy , J. , Zur Edelmetallbestimmung in hochprozentigen Kupfererzen : Chem. Ztg . Jarhrg . 35 , 1911 , p . 278 ) , or where the precious metal value is so great that a small sample can be used . In the latter case , silica is added until the copper ratio is sufficiently low . If there is more than 6 per cent of copper in an ore , the lead button obtained from a crucible fusion will require repeated scorification before . it can be cupelled successfully . Rescorification is not only tedious , but also causes a slag loss of precious metals . In combination methods , the copper is dissolved , and the gold and silver in the residue . is determined by fire assay Although some combination methods have given satisfactory results for gold and silver , they are not applicable when an estimation of the platinum metals is required . Since substances containing platinum are frequently high in copper , a study of methods which might be used for the estimation of small quantities of gold , silver , and the platinum metals in such material was considered worth while . The estimation of platinum in ores by fire assay methods has been described in Technical Paper 270 of the bureau; ( Davis , C.W. , The detection and estimation of platinum in ores : U. S. Bureau of Mines Tech . Paper 270 , 1921. ) the present paper , which is supplementary to that report , deals chiefly with the application of combination methods , taking them up to the point where the fire assay is to be applied .

Mar 1, 1921

By Dorsey A. Lyon

"The ceramic industry of the United States has a total yearly manufactured product of nearly half a billion dollars, despite large foreign importation.After careful investigation of the industry by the Bureau of Mines, it is the belief of those in charge that the usefulness of the industry can be greatly enlarged and the importations greatly lessened through the development of processes that will lead to a greater and better development of the ceramic resources of the United States. This will result in a greater industry with more men employed than ever before, and perhaps a world's supremacy in ceramic trade matters.Investigations in behalf of the ceramic industry are being made at the Bureau of Mines experiment ceramic station at Columbus, Ohio, under the supervision of R. T. Stall, superintendent, who reports a number of instances of practical, beneficial cooperation between the industry and the station during the last fiscal year.Graphite to Crucibles:Prior to 1914, practically all graphite crucibles manufactured in the United States were made from Ceylon graphite bonded with German Klingenberg clay. It was the general belief among graphite crucible manufacturers and users that good crucibles could not be made from American bond clays and graphites.Graphite crucibles were essential for melting certain alloys and special steels urgently needed for the manufacture of war materials. The demand for such metals was so great that it created an unprecedented demand for graphite crucibles.After the European war began no Klingenberg clay could be shipped out of Germany. However, it was fortunate for the cyucibly makers that they had large stocks of Klingenberg clay on hand. When the stock of Klingenberg clay became exhausted, it was necessary for the credible makers to turn their attention to American clays. There were no data or other information available to guide the crucible makers in the selection of good bond clays for their crucibles. It was necessary for them to select their clays more or less by ""guess"", which resulted in the period of service or life of graphite crucibles being shortened 15 to as much as 60 per cent."

Feb 1, 1921

By R. J. Wensley

THE use of small substations for the supplying of 275-volt energy to the locomotive and cutting machines in coal mines is a well-established practice. A few years ago, when labor costs were lower, these substations were located as near to the load as possible, and an operator was provided for each station. This practice has now become so expensive that substations are being located with reference to other mining machinery, such as hoists or pumps, so that one operator can look after both. Some-times the substation is operated by one whose duties make him traverse quite a large area. In such cases the interruption of alternating-current supply may produce a long interruption in the direct current, as the station cannot resume service until this man reaches it. Such interruptions interfere seriously with production and may easily counterbalance the supposed saving gained by such operating methods. The grouping of substations for convenience in operating may also result in excessive copper loss and consequently poor trolley voltage, with its attendant evils of low locomotive speeds and increased locomotive motor maintenance. The speed of the coal-cutting machines will also be reduced. By relieving the substation of its, burden of the operating labor cost, the most economical location, from an electrical standpoint, may be chosen. The matter of machine insurance should also be considered. If an attendant is caring for several kinds of equipment, he cannot watch the machine continually for signs of trouble; therefore, continued overload, phase failure, low alternating-current voltage, bearing trouble, etc. may result. Some partly automatic equipments have been installed; these have protection against low voltage, reverse current, and bearing trouble and are provided with automatic reclosing circuit breakers. This is a step in the right direction but it does not go far enough to give first-class machine insurance.

Jan 9, 1921

By John Griffen

THE modern anthracite breaker or washery uses almost completely a wet method of preparation, which requires, roughly, 1 gal. of water per minute per ton of production per day. The entire anthracite industry uses about 320,000 gal. per min. of water for this purpose or 800,000 tons of water per day. As this water leaves the breakers, it contains fine solids-coal, slate, pyrite, and clay-and is then called silt or slush; as slush is the term most commonly used, it will be employed throughout this paper. The solid content of the slush will be referred to as solids. In the earlier days of anthracite mining, little coal was washed, less crushing was employed, and virgin coal was mined exclusively. As a result, the slush problem was not acute because of the relatively small quantity and the coarseness of the solids. Such slush as was produced could usually be easily impounded and retained or could be discharged into streams without any appreciable pollution being apparent. The character of the fine waste from the breakers, changed materially as its quantity increased until now about 40,000 tons of slush solids are produced daily. Second mining and robbing operations materially increased the quantity of fine solids delivered to the breaker in the mine car. The demand for chestnut, stove and egg sizes, to the exclusion of grate, steamboat, and lump sizes, require finer crushing of the mine-run coal with a consequent increase of fine solids in slush. The use of rice and barley sizes removed a considerable tonnage of coarser solids from the slush but left great quantities of fine solids difficult to retain completely and store and long considered of no possible fuel value. Despite the efforts of the coal operators, the slush solids have found their way into the streams causing, in some cases, serious pollution. The Water Supply Commission of Pennsylvania published, in 1916, a report on Culm in the Streams of the Anthracite Region,1 from which the following is taken: About 40,000,000,000 gal. of water carrying 10,000,000 tons of fine culm are discharged into the water-courses direct, flushed into the mines, or disposed of by various means on the surface. The extent to which the very small sizes of anthracite

Jan 9, 1921

By Dever Ashmead

ANTHRACITE was first mined in the Wyoming Valley and sold as an article of commerce in 1808. As some preparation has always been necessary to make it ready to burn, the preparation of anthracite must date back over a hundred years. Two vital factors have determined to a large extent the degree and method of anthracite preparation. These are, first, the character of the beds worked and the methods by which they were mined and, second, the equipment used and practices followed in the burning of the coal. It is not the intention here to go deeply into these phases of preparation as a paper of no mean length could be prepared on the history of either. Rather, the intention here is to point out the main considerations and to show the influence they have exerted on the preparation of anthracite. MINING METHODS AND THEIR RELATION TO PREPARATION In the beginning f the nineteenth century, the coal beds were virgin with the possible exception of some outcroppings that had been worked, to a slight extent, by the Indians. It is known that the American aborigines had a knowledge of the use of this fuel, because when the Wyoming Valley was purchased from them, in 1754, they mentioned the fact that, by selling the land, they would lose their coal.

Jan 9, 1921

By Herbert Kynor

BY THE term mechanical mining is meant that operation, or series of operations, that replace the hand methods of mining. The first undercutting machine to operate in anthracite was placed in the Butler mine of the Hillside Coal & Iron Co., Dec. 23, 1910, by the Sullivan Machinery Co. The first Jackhamer used in the anthracite field was installed at the Wadesville colliery of the Philadelphia & Reading Coal & Iron Co. in Oct., 1912, by the Ingersoll-Rand Co. The first longwall conveyor was installed at the Dodge mines of the Delaware, Lackawanna, & Western Coal Co. in March, 1912. The first mechanical scraper equipment was installed in the Seneca mines of the Lehigh Valley Coal Co. in January, 1914. The amount of anthracite mechanically mined since the first mining machine was installed in 1910a is as follows: PENNA. COAL Co. D. L. & W., SCRANTON TEMPLE HUDSON YEAR AND HILL- TONS COAL Co., COAL CO., COAL CO., TOTAL. SIDE COAL TONS TONS TONS TONS AND IRON, TONS 1920 372,737b 367,000d 322,892 74,127 371,878 1,508,634 1919 950,786 no record 306,616 81,575 319,356 1,658,333c 1918 917,778 744,966 24,880 44,756 288,781 2,021,161 1917 757,940 838,800 5,050 57,279 164,180 1,823,249 1916 286,780 860,663 13,960 114,173 101,475 1,377,051 1915 428,819 592,169 8,253 1,029,241 1914 219,188 153,896 373,084 1913 171,505 171,505 1912 124,267 124,267 1911 40,319 40,319 1910 1,184 1,184 a. A slightly greater production than shown was obtained as the tonnage from individual operations is not shown. b. Decrease due to strike conditions in 1920. c. Does not include tonnage of D., L., & W. d. D., L., & W. decrease in 1920 due to having less mining machines in operation. There are about 150 undercutters in use in the anthracite region, 80 mechanical loaders, and 10 longwall conveyors.

Jan 9, 1921

By Donald Markle

ANTHRACOAL is a mixture of small particles of anthracite coal and a matrix of practically pure carbon, formed from the distillation of coal-tar pitch or other suitable bitumen. It is a hard, dense, homogeneous mass, with a silvery luster and in color varies from silvery to grayish black. When pushed from the oven, it develops only partly the fingerlike structure of coke; but, unlike coke, it has a tendency to remain in blocky masses. When struck with a hammer or passed through crushing rolls, it breaks with an irregular fracture, similar to anthracite, but with very little fines. Due to its density, anthracoal is harder, tougher, and stronger than coke. The results of a test made by the blast-furnace department, of the Bethlehem Steel Co., on two barrels of anthracoal are given in Table 1. TABLE I.-Results of Shatter Tests on Anthracoal and Coke Anthracoal Test Good Blast-furnace Coke First Second Barrel Barrel Moisture, per cent 0.77 0.76 Under 5, variation not over 3 points Sieve test Through 2-in. screen, per cent 7.71 7.29 Under 40 Through 1-in. screen, per cent 1.37 1.56 Through ½ -in. screen, percent 0.93 1.08 Under 8 Over 2-in. screen, per cent 92.29 92.71 Over 60 Shatter test Through 2-in. screen, per cent 10.06 ' 12.40 1 Under 16 Through 1-in. screen, per cent 2.66 2.06 Through ½ -in. screen, per cent 1.80 1.26 Over 2-in. screen, per cent Hardness number 86.40 86.10 Over 81 Analysis Ash, percent 16.64 16.48 Under 11 Sulfur, per cent 1.17 1.10 Under 0.95 Volatile matter, per cent 0.77 0.27 Fixed carbon, percent 82.59 83.25 Over 87

Jan 8, 1921

By John Dilworth

THE word "development," as used in connection with .mining, is a rather general term and in most instances must be qualified or explained before the exact thought in the mind of the user is made clear. For instance, by the development of a mining district is often meant its entire facilities of mineral production, such as railroads, towns, mine plants, etc. In speaking of the development of a property its prospecting by test pits or diamond drill borings may be referred to; or it may be the mines, strip pits or quarries from which the coal, ore or rock is won. But, as a rule, when the development of an individual mine is spoken of the idea in mind is the system of underground workings by means of which the mineral is recovered and transported to the surface. It is this character f development that is considered in this paper. The discussion will be confined to the ordinary room-and-pillar, system of mining. practically horizontal coal seams that is used in most bituminous coal mines in this country, and to only two phases of this subject; viz., what is properly included under the head of "Development"' as it appears on the books of a coal company or the inventories of an examining engineer, and how its "value" should be determined -by the accountant or engineer. No absolute rule or definite agreement covers these points, yet these questions are far more than academic. Development is often an important part of a mining company's assets, affecting the amount of its invested capital (and hence its rate of taxation under present Federal income tax laws) as well as the value of its total assets and the amounts chargeable to cost of coal and to depreciation.

Jan 7, 1921

By J. Moore Samuel

THE prospective change in ore receipts at the Copper Queen reduction works necessitated a careful study of conditions to determine the most economical method of smelting. The first step, calculating the known, probable, and possible results, showed the economy of a unimetallurgical flow sheet f which the three pyrometallurgical stages would be roasting, reverberatory smelting, and converting. The past and future ore receipts (not including converter flux) are as follows: AVERAGE MONTHLY FUTURE MONTHLY RECEIPTS, 1918 RECEIPTS TONS PER PER CENT. OF TONS PER PER CENT. OF MONTH TOTAL RECEIPTS MONTH TOTAL RECEIPTS Ore 84,553 82.3 43,000 44.0 Gravity concentrates 16,375 15.9 25,500 26.0 Flotation concentrates 1,883 1.8 29,400 30.0 Total 102,811 100.0 97,900 100.0 Of the 102,811 tons per month received in 1918, only 28,945, or 28 per cent., was treated in the roasters and an average f 14.1 roasters out of 20 were in operation; the remaining ore was treated in the blast furnaces. The change to "all reverb." practice, therefore, called for considerable additional roaster capacity, which could be obtained either by building additional units, or by remodelling the present units so as to give increased unit capacity. In view of the progress in roasting practice since the construction of the Copper Queen roaster plant and the heavy investment in that roaster plant, the second plan seemed to be the more desirable. The Copper Queen roaster plant consisted of twenty six-hearth, McDougall roasters, 18 ft. in diameter, equipped with cast-iron arms that originally were water cooled but now are air cooled. They have no top dry hearth and the feed is discharged through the top arch, near its periphery, by plunger feeders from two bins at opposite sides of the roaster.

Jan 7, 1921

By Benjamin Tillson

To MOST mine operators, it seems evident that there is a drill-steel problem, although under certain conditions the amount f drill-steel breakage does not appear serious. What is at fault? It may be one or a combination of circumstances. The development of rock drills to the hammer-drill type in place of the old reciprocating piston drill, probably is one important cause for the greater steel breakage. Perhaps the manufacturers of drill steel have failed to realize what alloys are needed for this new service or have overlooked the changes in the art of rock drilling. Although suitable alloys are provided, they may not be so handled in the manufacturing process as to be in the best condition to withstand the demands of rock drilling. The mine operator may be at fault in desiring to use the smallest possible drill-steel section in order that the gage of the drill bits may be correspondingly small and the amount of footage drilled per unit of labor may be greater; or the black-smithshop practice at the mines may need improvement. The miner who uses the drill steel may also require more intensive supervision and education. Again, the manufacturer of rock drills may have failed to study the types of blows the steel alloys will withstand satisfactorily and which their tools are delivering and so he may not know whether or not a different design of rock drill would equal or excel their present drilling speeds without treating the drill steel so severely. All of these hypotheses probably have their supporters. On the other hand, perhaps we are seeking too much service from drill steel and we need a fuller realization of the fatigue strains developed and should prepare to relieve these by a periodic heat treatment of the steels. However, we do not find any proof that any of these suppositions may be held responsible for the drill-steel breakage attendant to mining. The proposed investigation of this matter by the U. S. Bureau f Mines is fully warranted in the promotion of the conservation of labor and material, and the safety of the workmen. The great range of field conditions, as well as the scope of the research, requires the energetic cooperative support of many interests. Various manufacturers of steel,

Jan 5, 1921

Sykes, W. P.-Effect of Temperature, Deformation, Grain Size, and Rate of Loading on Mechanical Properties of Metals. Discussed by Zay Jeffries, W. H. Bassett, F. E. Carter 3 Evans, Geo. Watkin.-Alaskan Coal Fields. Discussed by P. N. Moore, H. H. Stoek, G. S. Rice, H. Emerson 4 Eavenson, Howard N.-Run-off and Mine Drainage. Discussed by J. R. Campbell, Andrew B. Crichton, J. B. Warriner, R. V. Norris, H. G. Moulton, H. B. Wright 7 Andrews, Allen, and Garcia, John A.-Skip Hoisting for Coal Mines. Discussed by R. V. Norris, Geo. S. Rice, H. N. Eavenson, E. A. Holbrook, Robert Obert, Andrews Allen, T. M. Chance 12 Rice, Geo. S.-Coal-pillar Drawing Methods in Europe. Discussed by Carl Scholz, D. Harrington; H. 1. Smith 16 Knapp, Arthur.-Modified Oil .well Depletion Curves. Discussed by Roswell H. Johnson 21 Alvey, Glenn H., and Alden W. Foster.-Barrel-day Values. Discussed by Roswell H. Johnson 22 Matteson, W. G.-Secondary Intrusive Origin of Gulf Coastal Plain Salt Domes. Discussed by Eugene Coste, E. W. Shaw, Joseph E. Pogue, F. G. Clapp, E. DeGoIyer, W. G. Matteson, H. W. Hixon, R. Van A. Mills 23 Reger, David B,-Carbon Ratio of Coals in West Virginia Oil Fields. Discussed by J. T. Singewald, Jr 33

Jan 5, 1921

By Euzebio De Oliveira

ONE of a recent batch of samples from the Serra da Baliza, in the state of Parana, Brazil, contained asphalt and a dark heavy oil; and workmen on the railway from Porto União to Uruguay discovered asphalt, coming from eruptives that outcrop along the Rio de Peixe. The occurrence f asphalt in the triassic eruptives of southern Brazil, however, has been known a long time, according to Dr. Gonzaga de Campos. It is generally believed that the Botacatú sandstone is always a hard vitrified rock, from the metamorphic action f. the overflowing eruptive contacts. In this region, however, the contact metamorphism is almost nil; the sandstone is slightly hardened in a narrow zone about 20 to 30 cm. wide. In many places, the sandstone is so friable as to be easily reduced to sand, which is used-.in, mortar for building in Guara-puava and Palmas. South and west from Porto União,. this bench of sandstone is about. 50 m. thick, and is capped by a heavy bed. f basic eruptives, many of which are amygdaloids. Dr. Geo: P. Merrill, after studying the triassic eruptives collected by the Coal Commission, reached the conclusion that. "All these rocks are of typical basalt-diabases, not in any essential different other than in structure. An interesting mineralogical phase is its paucity in olivine, which in many cases is completely lacking. Professor Hussak, who carefully studied these rocks and their accessory minerals, decided that in the dikes they are granular (diabase) and, that in the lava sheets, porphyritic (augite-porphyrite or melaphyre), and that the latter pass evidently to normal diabases and are always typical of effusive rocks. The examination f many slides from dikes and sheets leads us to adopt the opinion of Professor Hussak; the rocks of the dikes are of ophitic structure, while that of the sheets show a great variety f structure and may vary from almost granular to basaltic. The great paucity in olivine had been noted by Hussak, who classes as melaphyres, the porphyritic triassic rocks in Brazil which contain olivine.

Jan 4, 1921

By Enrique Touceda

FOR a number of years prior to the world war, the firm of Geo. H. Thacher & Co., of Albany, N. Y., was engaged in the manufacture of marine and other gray-iron castings. At -the outbreak of the war the firm decided to specialize in the manufacture f propeller wheels. It attacked the problem, therefore, from a foundry point of view, seeking to produce a casting that would be so accurate that no subsequent machining would be required on the blades, also from the point of view of the ship builder. There were two general methods f manufacture, the shortcomings of which have been freely acknowledged. In the sweep method, the nowel, or bottom half-mold, for each blade is swept up by a spindle beam and pitch race, while the top half-mold for each blade is built up individually. In the pattern method one individual blade, with the hub or hub portion, is mounted on a spindle and the individual -blade mold formed, the pattern is then rotated on the spindle to the position- for the next blade, etc. In rare cases wheels were made from a solid pattern. Owing to the cost of the pattern, its failure in many instances to be correctly made, and (when made of wood) its early and sure distortion the disadvantage of this practice is obvious, while metal patterns in most instances were prohibitive in cost. In these methods both green-sand and loam molding was practiced. The casting produced by either method can be considered only as a blank from which the propeller must be machined. The back surface f each blade must be chipped too the templet and through this procedure chipped to such accuracy, as will be required for a static balance. Inasmuch as the' work done by the machine tool is confined to the driving face of the blades, not only is perfection most difficult, but corrosion will be greater because of the removal of the dense skin f the casting and the local strains set up by the pneumatic tool in chipping. To produce a finished 9-ft. propeller for a Navy destroyer required from 8 to 21 days f foundry work and about the same length of, time for the machining. Through the use f the Thacher process, only as many hours are required, besides it is possible to produce a finished casting in perfect conformity, with any particular propeller-wheel design,

Jan 4, 1921

By David Reger

THE value of carbon ratios in determining the boundaries of possible oil deposits appears to have passed the hypothetical stage. The theory that the ratio of fixed carbon in pure coals is an, invariable index of incipient metamorphism in both, surface and underground rocks and that it may be applied in defining the limits of petroleum, advanced by David White,1 has been received with keen interest by many petroleum geologists. Detailed isocarb maps have been prepared of the Pennsylvanian area of North Texas and Eastern Oklahoma by M. L. Fuller.2 A similar map of the coal-bearing area of West Virginia is given here. An isocarb3 is a line showing an equal fixed-carbon percentage, pure coal basis; the term has been proposed by David White to supersede a less expressive nomenclature. The term carbon ratio is applied to the percentage of carbon in pure coal after water and ash have been eliminated. As a comparatively small number of analyses have been made on this basis, it is usually necessary to compute the ratio by dividing the fixed carbon of the proximate analysis by the sum of the fixed carbon and volatile matter of the same analysis. Many thousands of proximate analyses have been made by the West Virginia Geological Survey, covering nearly every county in which coal is found. Numerous others have been made by the. U.S. Geological Survey and the U. S. Bureau of Mines, but as uniformity of results is

Jan 2, 1921

By A. J. Lanea

INDUSTRIAL MEDICINE bids fair to become one of the most important and highly developed branches of medical science. Mining companies, even in remote districts, have developed large and efficient medical organizations that comprise the best types of physicians and surgeons. Not infrequently, however, company medical departments have been influenced too much by local conditions-including the compensation laws, which differ widely in the various states. The possibilities of industrial medicine are just beginning to be generally understood, and the variations in the organization and aims of medical departments of mining companies are no more pronounced than in industry as a whole. The industrial physician should be as much a part of the organization as any other official and he should know intimately the various types and phases of work in the plant and should look at his work from the viewpoint of the needs and requirements of his particular industry and company. He should not-be on the outside looking in, but on the inside, working hand in hand with the superintendent, manager, foremen, employment director, safety director, and anybody else with whom in his work he might associate. In any industry it is essential that the doctor be-familiar with working conditions. The mine doctor who never goes underground must remain ignorant of the factors causing many of the disorders he treats as well as miss the best opportunity of gaining the respect and cooperation of the men he. serves. If the mine doctor remains unfamiliar with underground working conditions he bars himself from valuable preventive medical work. It is estimated that the time lost by industrial workers, as a whole, because of illness is about four times as great as that lost because of accidents. While the effort to determine the responsibility of working conditions for illness is often futile, there is a wide field, both for study and practice, in the lessening of sickness among industrial workers. The first step in this direction must be a knowledge of the factors involved.

Jan 2, 1921

By John Mathews

IT is twenty years since the writer made his first molybdenum steels and others were making them commercially five years earlier but the prevailing opinion seems to be that molybdenum steels are new; from time to time the daily press speaks of important discoveries in Europe and intimates that American steel makers have much to learn in regard to alloy steels. The earlier experiments were largely confined to the use of relatively high percentages of molybdenum in tool steels and permanent magnet steels. Recent developments deal with the types of alloy structural steels used for airplane, automobile, and other engineering requirements; in these, the molybdenum content is usually less than 1 per cent. The earlier types generally have been unsuccessful commercially, but the newer types of steels are becoming of increasing importance. The war showed our dependence on foreign sources for alloying metals; molybdenum alone is widely distributed in the United States and seemingly abundant. Many deposits are not now of commercial interest, owing to location and relatively small amount of ore available, but other deposits are being developed and a stable source of supply seems well assured. In tool and magnet steels, it was early found that 1 part of molybdenum was equivalent to from 2 to 2.5 parts of tungsten. The permanent magnet steels investigated by Madame Curie,1 in 1898, contained from 3.36 to 4.05 per cent. molybdenum; in 1902, Dr. E. L. French and the writer thoroughly tested steels containing from 2:0 to 4.0 per cent. These steels gave satisfactory tests for permanence, but were low in residual density and much more sensitive to hardening than the corresponding tungsten products. We discontinued work with them, therefore, and have no advice that such steels have been used commercially here or abroad.

Jan 2, 1921

By Thomas Fraser

About 24 per cent of our total production of bituminous coal is used in industrial power plants. As regards fuel conservation, therefore, the recovery of unburned fuel from furnace refuse presents interesting possibilities. Considerable attention has been given to this problem in the past, but because of the comparatively low initial cost of power plant fuel in the pre-war period little progress, has been made in this direction in the United States. Because of the higher price of coal in Europe more attention has there been given to the problem. In Germany a process has been developed for separating unburned coal in refuse by using an electromagnetic separator In the United States the use of mechanical stokers enabled low-priced screenings of high ash content to be used, so that even with relatively high percentages of combustible material remaining in the refuse, the loss in money is not excessive. If the price of screenings returns to the pre-war level around $1.00 per ton the process proposed here will probably not be especially interesting, except where the freight charges are very high. However, if the price of delivered coal continues high, such a process should result in considerable saving. The cost of continuous operation of such a refuse treating plant should not exceed 75 cents per ton of fuel recovered.

Jan 1, 1921

By W. P. Sykes

THIS investigation was undertaken primarily to establish the relations existing between temperature and mechanical properties in molybdenum, nickel, and an aluminum-copper alloy. Molybdenum (m.p. 2500° C.) was chosen because it is partly similar to tungsten and partly similar to the common ductile metals. Also it is known to furnish, by proper treatment, a desirable material to use in studying relation of grain size and physical properties. The molybdenum used was of the quality that is drawn into wire 0.003 in. in diameter for use as filament supports in incandescent lamps; chemical analysis shows less than 0.1 per cent. of impurities. Nickel belongs to the same class as iron. Its melting point is 1450° C. and an allotropic change at about 370° C. results in a loss of magnetism above that temperature. This feature made nickel doubly valuable for the purposes of these tests. The nickel used was obtained from the Driver-Harris Co. as 0.090 in. (2.3-mm.) wire, annealed; analysis showed 99.8 per cent. nickel and 0.150 per cent. iron. Aluminum is one of the low melting-point metals. Some tensile tests at elevated temperatures have been reported by Bengough but the possibility of learning more with the low temperature and sensitive apparatus available recommended this metal. The samples marked Al are an aluminum-copper alloy; they contained 3 per cent. copper, 0.42 per cent. iron, and 0.21 per cent. silicon. The presence of the copper somewhat complicates the analysis of the results; but the action of copper in aluminum has been studied so that its influence might have been foretold, in part at least. The material and analyses were furnished by the Aluminum Castings Co. The nickel wire, which was deformed at 400° C., was drawn under a bath of molten lead and through a die, which also was immersed in the bath. A thermocouple was suspended in the molten metal to indicate

Jan 1, 1921

By N. A. C. Smith

[The beau of Mines made its first survey of motor gasolines sold throughout the United States in 1915, a second in 1917, and a third in April. 1919. These surveys shored that motor gasoline had become notably less volatile during each two-year interval. In order to ascertain whether this change was continuing, it was planned to institute semi-annual surveys, the first of which teas made in January, 1920. Contrary to expectations based on the previous surveys, the average volatility of the gasoline tested at this time was practically identical with that of the average volatility of the gasoline from the same districts in 1919. The next survey, made in July, 1920, showed a very marked decrease in volatility but as it has long been recognized that the volatility of motor gasoline manufactured for sale during the summer months is loss tan that of gasoline made and sold during the winter, part at least of the change was attributed to this factor. The average boiling point of the samples collected in the present survey is 263 degrees Fahrenheit, as compared with 264 a year ago. This shows that the average gasoline marketed at the present time is fully as volatile as that marketed a year ago. There has been, however, a noticeable change in the character of the product: the initial boiling point and 20 per cant point are lower than a year ago, whereas the 90 per cent and end-points are higher, which indicates a greater proportion of gasolines made by blending casing-head, or natural gas-gasoline, and naphtha.]

Jan 1, 1921

By A. G. McGregor

IN THE Southwest a number of large steel chimneys discharge the gases from the copper smelting furnaces. Some of these chimneys show no deterioration after twenty years, others show serious deterioration after tour years service. A steel stack 20 ft. 7 ½ in. (6.3 m.) in diameter by 279 ft. (85 m.) high, Fig. 1, used for roaster gases only at the Calumet & Arizona Mining Co.'s plant at Douglas, Ariz., was lined to the top of the bell, 40 ft. (12 m.) from the base, with common brick placed on end, lime and cement mortar being used. Above the bell, the stack was lined with 4 by 4 by 8 in. (10 by 10 by 20 cm.) building tile, placed on end, making a lining 4 in. thick. The tiles were supported on angle-iron rings, riveted to the inside of the chimney shell about 15 ft. apart. The chimney was put into use in the latter part of 1913. Four years later, considerable of the tile lining had fallen out of place and mixed with the flue dust at the bottom of the chimney. About a year later, several . flattened and distorted sheets were noticed about 70 ft. below the top. An investigation showed that the thickness of these distorted sheets, which was originally ¼ in., had been reduced one half. One year later, or six years after the chimney went into use, several holes, a square foot and smaller in area, appeared near the flat spots mentioned. Soon afterwards, when the chimney was shut down for repairs, it was found that most of the tile lining for 125 ft. from the top had fallen out and that the steel shell was badly corroded; but where the lining remained in place the shell was undamaged. Many of the tile which had fallen out of place had become soft or flaky and crumbling, others were as hard as when placed. An analysis of the hard and soft tile is shown on p. 2. These tile were of a fireclay mixture, and were used instead of common brick on account of lower cost. The steel forming the upper 125 ft. (38 m.) was replaced, and a 4 ¼ -in. (11-cm.) lining of firebrick was laid from the bell to the top of the chimney. The brick were placed on end, wedges and keys being used. After each 8-in. course was set, keyed, and wedged tight, thin mortar -water, sodium silicate, and finely ground silica-was worked into the joints. The brick are supported on angle-iron rings, every 15 ft., in the same way as the tile.

Jan 1, 1921