Search Documents

By G. E. McElroy

[The purpose of this paper is to present type: of charts adapted to aid in the graphic solution of fan-performance problems of selection and operation, and to urge the adoption of similar charts by the National Association of Fan Manufactures as standard forms for presenting fan-performance data. As matters now stand, it is difficult for the average engineer to solve such problems because a large number of variables are involved, and performance data are not presented in a manner that permits their direct application to many problems encountered in practice. The performance of any centrifugal machine is determined not only by the machine itself but also by the fluid-flow system on which it operates. Actual performance of centrifugal fans is therefore a matter of the type, size, and speed of fan, on the one hand, anti of the relation of pressure to quantity of flow, as determined by the physical condition of the airway s: stem, on the other.]

Jan 1, 1936

By R. E. Lamborn

A summary of oil and gas development in Ohio for 1935 must necessarily be brief. As attention of the state government to the oil and gas industry has never included the collection and compilation of statistics on production, either by producing sands, by counties, by fields, or for the state as a whole, such information as requested in Table 1 of this symposium is impossible to secure for this state. In the absence of production data chief attention must be directed to drilling activity for the year. Information such as can be compiled from various sources, including weekly drilling reports to operating companies and trade journals, is given in the following paragraphs with the realization that the data may not be complete in all its details. Drilling Activity by Fields Drilling activity during 1935 was similar to the preceding year in , that the major operating companies were generally content to drill lease-requirement and offset wells and in that comparatively little effort was made to discover new pools. A compilation of completions recorded in weekly reports to drilling companies and in trade journals show 1022 tests completed for the year in 53 counties of the state. Of this total number, 653 wells were commercial producers and 369 were classed as dry holes. Production was secured in 40 counties from formations ranging in depth to 5700 ft. and ranging in age from Middle Ordovician to upper Pennsyl-vanian. From the standpoint of new production for the year, the most important sands are the Clinton of Silurian age, the Berea of Mississippian age and the Shallow sands of Mississippian above the Berea and of Pennsylvanian age. Trenton Sand Field Production in the field of Trenton sand, which originally included parts of 15 counties in northwestern Ohio, is now on the decline. Seventy-three completions were reported in this field during 1935, of which 33.8 per cent were dry holes. Activity centered in Allen County with 12 completions, two of which were dry holes; in Hardin County with 11 producers; and in Wyandot County with 12 producers and 2 dry holes.

Jan 1, 1936

This consolidated index covers all publications of the Institute for the years 1926 through 1935. The following list indicates subjects of volumes and gives numbers or abbreviations used to designate them. TRANSACTIONS VOLUME *G26. Petroleum Development and Technology in 1925 (Published in 1926). *G26. Petroleum Development and Technology in 1926. *E27. Institute of Metals Proceedings. 73. Nonferrous Metallurgy, Milling and Concentration, Nonmetallic Minerals, Institute of Metals and Iron and Steel. [ ]

Jan 1, 1936

By Alden B. Greninger

Twinned metal crystals are usually designated as either deformation twins or annealing twins. If twins are to be classified according to the treatment the metal has undergone just prior to the observation of the twins, there are two other possible groups: (1) solidification twins,† when observed in the as-solidified or as-cast condition, and (2) transformation twins,† when observed in a metal which has been cooled from above an allotropic transformation temperature. McKeehan has demonstrated that ferrite does, occasionally at least, contain twinned structures2. The twins, which he studied by optical methods, were obtained during the preparation of iron single crystals by very slow cooling through A3. He proved that the twin relation was actually that which previous investigators had predicted; namely, twinning along three planes of the form (112). Since McKeehan's discovery, little or no attention has been given to this transformation twinning of alpha iron, or to the possibility that it might occur at all speeds of cooling from above A3 instead of merely during the preparation of single crystals. McKeehan's twins were evidently regarded as interesting only in proving that a body-centered cubic metal could form twinned structures—at least under certain conditions. It is generally believed that iron seldom if ever forms annealing twins. Certainly the straight-line banding which is so abundant in annealed face-centered cubic metals is characteristically absent in iron annealed below A3. However, O'Neil13 has studied "twin-like" crystals in annealed alpha iron and concludes that the specimen he studied actually contailled a few annealing twins. Tamura4 as reported "twin-like" crystals both in wrought iron and mild steel; specimens of the latter were annealed above and below A3 and showed "twin-like" crystals after both kinds of treatments.

Jan 1, 1936

By E. C. Harder

BRITISH Guiana, Great Britain's only South American colony, may be reached by very comfortable steamers, both from North America and Europe. The trip from North American Atlantic ports requires about 12 to 14 days; that from Europe about 18 to 20 days. A number of steamship lines, including Canadian, American, and Dutch, have regular sailings between North America and British Guiana, with calls en route at various interesting ports in the West Indies and northern South America. Moreover, several lines, including British, German, and French, have steamships operating regularly between Europe and the West Indies. Indeed, so popular have the West Indian voyages become in recent years that, during the winter months, special cruises in considerable number are organized for many vessels that ply in the trans-Atlantic service in the summer. A trip to British Guiana, therefore, has become a delightful experience. After visits at the various attractive Leeward and Windward islands and Trinidad, the approach to the low, flat, British Guiana coast, with its muddy coastal waters extending for many miles offshore, is somewhat of a contrast. Arrival in Guiana waters is signalled by the appearance of the modern high-power Demerara Light, located "on a shoal about twelve miles from the mouth of Demerara river. From this point, if the tide is right, a pilot takes the steamer across the bar, eight to ten miles offshore, and into Georgetown harbour. At high tide, the water above the bar ranges from 15 to 18 feet in depth, depending on whether it is neap tide or spring tide; at low tide, the corresponding depths are 9 to 11 feet. As the bar is of soft mud, however, it is usually possible for vessels to pass over it with a draught of about two feet in excess of that indicated by the tide tables. Upon nearing the shore, one sees first the Georgetown wireless towers, then the light-house and the tall chimneys of sugar mills and of various factories in Georgetown, and finally the palms and other tropical trees and the houses of Georgetown itself along the sea shore and the east bank of Demerara river. Extensive wharves operated by various exporting and importing companies stretch along the river bank and activity prevails in Georgetown harbour. The principal exports are sugar, rice, gold, diamonds, bauxite, balata, lumber, fruit and other tropical products. The imports are food-stuffs, wearing apparel, and manufactured materials of many kinds.

Jan 1, 1936

By J. J. Rutledge

FULLY 60 per cent of the serious and fatal accidents in Maryland coal mines are due to falls of roof and side. Usually, the victim of the fall sustains a broken back, sometimes not only the vertebrae being fractured but the spinal cord also being severed. When the spinal cord has not been severed and yet the vertebrae have been broken or injured, it is often possible to rehabilitate the victim of the broken back. - Such accidents are classed as Permanent Total and the victim receives a certain compensation from the State Industrial Accident Commission; sometimes the amount is awarded in a lump sum, but usually it is paid weekly. When the amount allotted to the victim of such an accident has been expended, either in a lump sum or weekly payments, the victim of the accident is dependent on public charity. Some efforts have been made to physically rehabilitate the victims and make them at least partly self-supporting before the expiration of their compensation payments. The State Industrial Accident Com-mission has done some of this rehabilitation. The Maryland Bureau of Mines, in cooperation with R. C. Thompson, Supervisor of Vocational Rehabilitation, State Department of Education, and his assistants, has, through an informal cooperative arrangement, placed several of the victims in hospitals in Baltimore for treatment. Six years ago, through the efforts of the Maryland Bureau of Mines, a dozen or more broken-back victims were examined by an orthopedic surgeon and report was made to the Bureau regarding such cases and the possibility of their rehabilitation. This paper details the result of such examinations.

Jan 1, 1936

By W. G. Woolnough

There has been no noteworthy increase in production during 1935; but, on the other hand, there have been ample manifestations of a considerable increase in interest and activity in connection with petroleum prospecting. The Lakes Entrance field, in the State of Victoria, on the coast some 120 miles east of Melbourne, remains the only actual producer; and this production, consisting of lubricating stock devoid of light fractions, is very small in amount. Arrangements have been completed under which a series of "scout bores" for structure testing in the region of Lakes Entrance will be sunk by the Government of the State of Victoria, assisted by a subsidy from the Federal Government. Prospecting In the State of New South Wales, brilliant geological research in very difficult country, carried out by geologists of Oil Search Ltd., has revealed several previously unsuspected domal structures in the Sydney-Newcastle coal basin. These have been mapped in detail, and a test well is being sunk at Kulnura, 10 miles west of Wyong and 40 miles north of Sydney. At the date of writing this well has reached a depth of 1250 ft., 10-in. casing having been set at 1248 feet. Superficial formations consist of the Hawkesbury sandstone and Narrabeen beds of the Hawkes-bury system (fresh-water Triassic). It is anticipated that the upper coal measures of the Kamilaroi (Permo-Carboniferous) will be entered almost immediately. The objectives of the drilling are the upper and lower marine beds of the Kamilaroi system, which are regarded as promising as potential source—and reservoir—beds for oil. At Mulgoa, 30 miles west of Sydney, a bore is being sunk by the same company, Oil Search Ltd., to test for natural gas on a well defined structure located by the company's geologists. Noteworthy flows of gas have been encountered, but nothing approaching a commercial supply has been struck. It is considered probable that the gas has been derived

Jan 1, 1936

By Gerald, Sherman

INCREASED production and con¬sumption of all metals, indicate the progress of industry toward that condition formerly thought to be normal. With no market limitations on silver and gold the two new precious-metal mines, the Silver Queen (now the Golden Queen), in southern California, and the Sunshine, at Kellogg in northern Idaho have made progress toward a high routine production. The Golden Queen 300-ton mill is finished and ready. The Sunshine mill has been enlarged and production is now at the rate of 500 tons per day of high-grade silver ore. The Hecla Mining Co. is developing the Polaris vein, which should be the extension of the Sunshine to the east. Some rich ore is reported. The developments of the' East African Gold Fields, Ltd., in the Lupa gold field of Tanganyika Territory, have made good progress, but operation in an isolated locality is not rapid and a large plant will be required. There have been no other discoveries reported that can be compared with the three mentioned, but production has increased, with greater capacity in dredging equipment and underground mines more adequately prepared for production.

Jan 1, 1936

In setting out to describe the methods and machinery employed at Iron Knob the writer does not attempt to give any information as to the situation, topography or geological features of the locality. This, together with estimates of the quantities of ore still available, has been carried out in a most thorough manner by R. L. Jackr and F. R. Hockey. This essay is intended to deal with working methods as they exist to-day, beginning with drilling, blasting, quarry traction, etc., and touching on such details as the supplyof electricity, water and compressed air.At the present time almost the entire output of ore is won from the hill known as Iron Monarch. The form of the hill, a smooth, rounded dome, rising some 640 ft. above the plain and having a base diameter of n miles, lends itself ideally to the "bench" system of open-cut quarrying.Fig. 1 shows the relationship of the benches "A," "B" and "E" in their order of development. Bench "E" is at present the principal working, but, as the greater part of the ore above this level has now been removed, bench "A," some...

Jan 1, 1936

By L. C. McCabe

THIS paper is a progress report on a study, of the distribution of the banded ingredients (Figs. 1 and 2) in- Illinois screenings and the method of determining their distribution. Proximate analyses and screen tests1 have been reported and a further report on the washability characteristics of the screenings is in preparation. The microscopic study of the screen-ings is not yet far enough advanced to permit a conclusive report on the effect of mining, screening and washing on the distribution of the banded ingredients in the coals of Illinois. However, considerable fundamental data-have been collected as a background for the screenings investigation and for a proposed study of fuels composed of known quantities of vitrain, clarain and fusain, the three common banded ingredients of Illinois coals. These fundamental data and the preliminary information now available from the microscopic study of screenings are broadly indicative of the reaction of the coals to the physical processes affecting them in mining and preparation. Proximate analyses of samples of vitrain, clarain, and fusain from several Illinois mines have been published 2, but those given in Table 1 serve to show the differences that are apparent in proximate analyses. The vitrain samples are consistently low in ash, and the unit-coal value is uniformly lower than in clarain. The average .fuel ratio (F.C./V.M.) of the vitrain samples in the table is 1.57-whereas the clarain average is 1.42. The fusain analyses vary considerably in ash and moisture. In the two samples from this mine the moisture values range from 8.99 to 22.80 and the ash from 4.86 to 16.91 per cent. Fusain has higher fixed carbon than either vitrain or clarain but the percentage is erratic from sample to sample.

Jan 1, 1936

By E. J. Lintner

This paper is one of a series being prepared by the United States Bureau of Mines describing clay mining, crushing and grinding methods, and costs, at various operations throughout the United States. These papers are designed to disseminate technical information regarding methods used. The, cost tabulations represent local operating expenditures only and not total production costs. It is recognized that publication of total production costs may in many instances cause embarrassment to the individual operator as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulation shall ensue. The following report deals specifically with the methods employed by the Evans Pipe Co., Uhrichsville, Tuscarawas County, Ohio. The author wishes to acknowledge the assistance of the following company officials: T. J. Evans, II, president; T. J. Evans III, vice president and general manager; and L. P. Young, general superintendent.

Jan 1, 1936

By E. L. Jr. Spain

THE deposits described in this paper occur over much of Wayne County and in the southeast portion of Hardin County, Tennessee, and in the northeast and northwest portions of Mississippi and Alabama respec-tively. The presence of tripoli in this region has been known for some time and descriptions of various occurrences in Tennessee have been made by Jewell1 and Miser2, while Hilgard3, Lowe4 and Logan5 have treated the deposits that occur in the adjacent portions of Alabama and Mississippi, but there has not been a general survey of the entire field summarizing completely the geology of the deposits with respect to their origin and stratigraphic relationships. During 1934, while engaged in surveys of mineral resources through this region for the Tennessee Valley Authority, the writer collected data with this in mind, and has assembled them in this report. He is indebted to H. S. Rankin and N. A. Rose, of the Tennessee Valley Authority Geology Division, for field assistance.

Jan 1, 1936

By W. F. Vietti

Operations in the Texas Gulf Coast during the past year have resulted in the discovery of a number of new fields arid the extension of a few of the older fields, both by deeper drilling and by lateral development. Twenty-six new oil and gas-producing areas and discovery of oil or gas in three subsequently abandoned wells have been recorded for a total of 29 new fields of varying importance. Producing areas at Conroe, Manvel, Greta, Pierce Junction, Hastings, Dirks, Thompson, Batson, Mykawa, Tomball, Raccoon Bend, Samfordyce arid Saxct have been increased. Primary geologic studies followed by geophysical mapping or straight geophysical prospects have been responsible for the more important discoveries. These methods have further proved themselves an aid to limiting wildcatting to the more prospective areas and as the chief means to discover reserves in the future. Production for 1935 totaled 69,560,720 bbl. as compared with 60,850,-360 bbl. for 1934. Strict proration has been in force throughout the discovery of more oil than has been produced. The number of producing oil wells has steadily increased to 4851 at the end of 1935, as compared with 3858 at the end of 1934, owing in part to the prolonged life, because of proration. There were 1272 oil and gas wells completed during 1935, as against 835 in 1934. New Fields Pertinent data on the new fields discovered during 1935 are includrd in Tables 1 and 2. Hence, the discussion of these discoveries will be limited. Bee County.—Three new gas fields were added during the year: Beeville, discovered by G. M. Church in No. 1 Wood on Sept. 21; Foley, discovered by Dirks Bros. in No. 1 Foley on Feb. 8; and Plummer, discovered by Hynes and Fisher in No. 1 T. M. Plummer on Sept. 2. The three new oil fields added are: Hartzendorf, drilled on fee land by Hartzendorf and completed on May 17 as a small pumper; Ray, southwest of Tuleta, and discovered by Jameson and Burns in No. 1 Campbell

Jan 1, 1936

By William Meyer

DURING the seventeen years Fairchild has been making aerial surveys and aerial photographic equipment many changes and improvements have been made in the equipment and in the technique of using it. Aerial photographic operations have, been developed from the crude methods and apparatus of wartime to a science upon which exact engineer-ing calculations can be based. In the early days there was no airplane specially designed to meet aerial photographic requirements. One type of camera was used in all types of operations. Projects were made to conform to the products we could make and deliver. Obviously this entailed definite limitations. We now have airplanes designed specially for aerial photographic operations in accordance with the conditions encountered in actual service experience. We have cameras for every photographic purpose and our laboratory technique and equipment have been developed to the point where it is possible to make contour maps from vertical aerial photographs with contour intervals as close as five feet. Therefore, the selection of equipment now can be made in accordance with the time at our disposal, the justifiable cost, the scale desired, and the general requirements of the client. This does not mean, however, that arbitrary deliveries can be set for aerial photographic products. The factors in each project vary and each job must be considered in accordance with the factors involved. This accounts for the fact that products of aerial surveys may readily vary from $1.25 to $200 a square mile. Sherman M. Fairchild became interested in the design of a radically different aerial camera during the war. At its close he was about ready to demonstrate his design to the War Department. By 1920, he was able to bring out his first completed model. It had a number of radical features, one of which was the first dependable high-speed between-the-lens shutter, which makes for accuracy in aerial photographic work. Another feature was the use of metal throughout, eliminating the wooden parts that had been employed in wartime cameras. Another feature was the interchangeability of parts.

Jan 1, 1936

By Adrien Berton

FOR nearly a century, the Corocoro deposit has been renowned among geologists from the fact that it shares with the Lake Superior deposits of the United States the distinction of being the only important copper districts where native copper is worked commercially. The Corocoro district, named after the city of Corocoro, the capital of the Province of Pacajes (Department of La Paz, Bolivia) is situated towards the western edge of the Bolivian high plateau, at an altitude of a little over 13,000 ft. The most interesting part of the district is that immediately surrounding the city of Corocoro, at a distance, by railway, of 65 miles from La Paz and 210 miles to the Chilean port of Arica on the Pacific Coast. The climate of the region is that of the semi-desert, dry and relatively cold, with big differences of temperature between day and night. The rainy season begins in December and ends in March. The cupriferous lodes of Corocoro have not attracted as much interest as the silver mines of Potosi but they have been known for a long time. In the precolonial period the Indians were using the charquis, or natural native copper sheets, to make small brass objects, and the beautiful pale green brochantite of the outcrops as a source of green pigments. During the colonial period, the oxidized ores of the outcrops were worked for copper, which was used by the mint at Potosi for making currency. The native copper ores were neglected because the Spanish miners were at a loss how to concentrate and smelt them. About 1830, work by rudimentary processes, which were improved little by little, was begun on the native copper ores. The total production of native copper in the following hundred years amounted to 100,000 tons. This native copper, which was remarkably pure, was much appreciated on the European markets before the introduction of electrolytic copper. It was useful for making special ornamental brass or bronze and the granular concentrates of native copper, called barrilla, containing 80 to 85 per cent copper were suitable for making copper sulfate by direct oxidation and subsequent leaching with sulfuric acid.

Jan 1, 1936

By Walter H. Voskuil

Illinois supplies coal to seven states in the Upper Mississippi Valley —Illinois, Missouri, Iowa, Minnesota, Wisconsin, and portions of the Dakotas, Nebraska and Kansas. In this same area are marketed large quantities of coal from West Virginia, Kentucky, Pennsylvania, and elsewhere; fuel oil from the crude petroleum supplies of the Mid-Continent fields, and natural gas from Louisiana, Kansas and the Texas Panhandle. The boundaries of this "Illinois coal-market area" are determined by competition from other coal fields and from other forms of fuel. Within the area so described 90 per cent of Illinois coal is marketed. Thus in the Southwest, an abundance of fuel-oil supplies and natural gas dominates the market almost to the exclusion of coal. The westward movement of Illinois coal in Kansas, Nebraska and the Dakotas is met by an eastward flow of high-grade coals from Colorado, Wyoming and Montana. In the lake-shore counties of Minnesota and Wisconsin, the market is dominated by Appalachian coals, cheaply carried over the Great Lakes and reaching the ports of Lake Michigan and at the head of Lake Superior. Illinois coals find their largest market in the southern and western sections of these two lake states. Only small quantities of Illinois coals are shipped east of the state line. This market area is occupied entirely by the neighboring coal fields of Indiana and the Appalachian coal fields in Ohio, West Virginia, Kentucky and Pennsylvania. Illinois Coal-makket Area , With these factors in mind, the map of the Illinois coal-market area may be drawn. Within this boundary is the area that is logically and economically served by Illinois coal. However, this area is by no means exclusively dependent upon coal from Illinois mines. The preponderance. of Appalachian coal in Wisconsin and Minnesota has been mentioned. Appalachian coal, also, moves in large tonnages into Illinois itself, particularly the Chicago district. The Iowa and Missouri local coals share the market with imported coal from Illinois; throughout the market area, fuel oil and natural gas are important factors in the total energy supply.

Jan 1, 1936

By F. V. Hicks

THE similarity of mining practices in bituminous coal fields through-out America is due to the fact that certain fundamental conditions are encountered in all fields. The problems of labor, housing and mining are somewhat similar whether the mine is in Pennsylvania, Illinois, Wyoming or the State of Washington. Each field has had its particular problems, resulting in advantages or disadvantages over a competing field. This might take the form of a wage differential, a better natural condition more favorable to cheap production, or proximity to a market that allows freight rate advantages, etc. In any event, no matter how favorably situated, the mining companies that have been slow to recog-nize and accept the advantage of mechanization, clinging too long to the old hand methods, have found themselves unable to meet competition. Throughout the Wyoming coal fields, production methods have so changed in the last decade as to be almost unrecognizable to an old-time coal miner who has had no connection with the industry during; that period. The old contract system, with its peculiar labor relationship between employer and employee, based upon the long-established custom that the miner's working place was his castle, and that it was his privilege to carry on operations within that place largely in his own way and to his own liking, is a condition that has passed away. The present-day, 100 per cent mechanized mine bears but little resemblance to the old. A change -in system has naturally altered the old-time labor relationship. Contract labor has been almost entirely eliminated and a straight day-wage basis established, with certain classes of work calling for different rates, which places the entire personnel of the underground operating force more directly under the direction and supervision of the mine foreman and his assistants. The transition from the old order to the new has gradually done away with the system of penalties, personal- rights and privileges existing under the contract system, which were so controversial in the past that the average mine management was constantly involved in labor disputes in fields where organized labor was employed.

Jan 1, 1936

By G. Stafford Whitby

N ATURAL gas is found in several provinces of Canada, particularly Ontario, New Brunswick, and Alberta. The largest producer is Alberta, and there the most important field is the Turner Valley, where some low-gravity crude oil and naphtha are associated with the gas. Last year there was produced from the Turner Valley field an average of 3,462 barrels, or about 450 tons, of oil a day. The gas flow from the wells in this field bears such a high ratio to the oil which comes from them that, despite the enforcement of a measure of conservation, it amounted to the vast quantity of 6,000 tons a day, or more than 2,000,000 tons a year. Prior to the application of any conservation measures, the gas flow was at one time of the order of 12,000 tons a day. The heat content of one ton of the gas is almost equal to that of two tons of coal. A certain amount, say, 10 per cent," of the gas is used in Calgary and surrounding towns and in re-pressuring the Bow Island gas field, but the greater part of it goes to waste. What are the possibilities of making use of this waste gas, in whole or part? The possibilities of using it profitably as fuel for domestic and industrial purposes have undoubtedly been carefully considered by the Company which now distributes a part of the gas to cities and towns in Alberta. But the relative sparness of the population and the cost of pipe lines makes such possibilities strictly limited. There are, however, distinct possibilities of making use of at !east a part of the gas for the production of a variety of chemical products and of liquid motor fuel. The present paper is devoted to outlining some of these possibilities. About three-quarters (by weight) of the Turner Valley waste gas consists of methane, the lightest and, chemically speaking, the simplest of hydrocarbon gases. The remaining quarter consists of heavier hydrocarbon gases-ethane, propane, and butane. Formerly, naphtha was separated from the well gas by a simple process of self-refrigeration. The gas coming from the wells at a pressure of, say, 1,200 to 1,800 lb., was passed through simple cylindrical vessels fitted with baffles and known as 'separators'. The pressure was allowed to drop to, say, 300 lb. in the separators, and the cooling effect secured by this expansion brought about separation of the naphtha. The naphtha thus obtained was 'wild', that is, it had a high vapour pressure owing to the presence in it of dissolved and liquefied gas. In order to reduce the vapour pressure to a level at which the naphtha could be shipped, this gas was removed either by distilling it out through a 'stabilizing' column or, according to the practice at many wells, merely by allowing the naphtha to 'weather' in open tanks (heated by coils if necessary) until the gas had been driven off in to the air.

Jan 1, 1936

By H. F. Yancey, M. R. Greer

At the annual meeting of this Institute held two years ago a new method1 of estimating the grindability of coal was described, based on experimental work carried on by the Bureau of Mines at its Northwest Experiment Station. Since that time, several organizations concerned with the testing or utilization of coal as pulverized fuel have adopted and used the method in determining the grindability of several hundred samples of coal. In addition, a series of comparative tests of this method and three others has been carried out in five laboratories under the auspices of Committee D-5 of the American Society for Testing Materials. As a result the Committee has recommended that the Bureau of Mines method, designated as the "ball-mill method," and the Hardgrove method2, previously advanced, be accepted as tentative standards3. Since the ball-mill method was originally developed and published, an opportunity has been presented to apply it to a larger number of coals and to study intensively some of the principles upon which the method is based. This paper presents a résumé of these further studies and includes a comparison with the Hardgrove-machine method. Trial runs were also made with another procedure recently proposed—the C.I.T. roll-test method4. Principles of Methods In the ball-mill method, the relative amounts of energy necessary to grind coals to the same fineness are determined by the number of revolutions of the mill required to reduce 80 per cent of the feed (500 grams of 10 to 200-mesh coal) fine enough to pass a 200-mesh screen. This is a

Jan 1, 1936

[AARONSON, E.: Discussion on Recent Developments in Fractionation as Applied to Tube Still Distillation, G26, 418 Abbe. See Microscope. Abbe apertometer, 95, 16 ABBOTT, W. L.: A.S.M.E. president, M26,113 biography, M26,113 ABORN, R. H.: Discussions: on Effects of Columbium in Chromium-nickel Steels 113, 159 on Pure Iron and Allotropic Transformations 84, 342 on Prevention of Intergranular Corrosion, 100,329 ABORN, R. H. AND BAIN, E. C.: Discussion on Widmanstätten Structure in Ironcarbon Alloys 105, 252]

Jan 1, 1936