File:Bulletin (1910) (14779645144).jpg

Identifier: bulletin190unit (find matches)
Title: Bulletin
Year: 1910 (1910s)
Authors: United States. Bureau of Mines
Subjects: Mines and mineral resources Mines and mineral resources Mining engineering
Publisher: Washington U.S. Govt. Print. Off. (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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-ing engine is sometimes used to drop the loaded cars from the minemouth to the tipple and to haul back the empties. MINING METHODS. The Roslyn bed averages a trifle less than 4^ feet in thickness. Itis overlain by a bed of shale, or cap rock, varying from about 3inches to nearly 2 feet in thickness. On account of thinness of thebed and presence of the cap rock, which easily falls, it was thoughtin the earlier days of operation that the longwall system could beapplied successfully, but experience showed that better results areobtained with room and pillar methods. As mining is now carried on the cap rock is taken down andgobbed when it is less than 1 foot thick and is friable, but where itis more than 1 foot thick an attempt is made to hold it. Other im-purities of the bed, which sometimes occur in rather large quantities,are removed by the miners and gobbed. There is nowhere pitch 62 COAL-MINING PROBLEMS IN THE STATE OF WASHINGTON. Hoisting engineA Boiler house A I ) I—tS—Trestle
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Sca/e200 30O 4O0 500 ft. Figure 27.—One method of working Roslyn bed in Roslyn field; also arrangement of surface Buildings. EASTERN WASHINGTON. 63 enough to make impossible the separation of impurities underground.The coal breaks in rather large lumps and has a bright, -lean surface;therefore it finds a ready market in competition with other coalsof less pleasing appearance. The smaller sizes are washed and arereadily sold in the steam and gascoal markets. The general plan of operationin this field is shown in Figure 27.The slope is usually sunk on thefull dip of the bed. Parallel tothe slope and separated from it bya pillar about 100 feet wide isthe return airway. Crosscuts aredriven every 50 or 60 feet. Figure 28 shows the dimensions ofslopes as ordinarily driven and also indicates that single tracksare used.

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