. Bulletin. pes pass overa low anticline and some distance down its north side. The depth beneath the surface varies from about 1,000 feet on thecrest of the anticline to 1,050 and 1,150 feet in the synclines north andsouth. The average thickness of the bed is about 14 feet. The47004°—Bull. 72—15 9 130 EXPLOSIVE CASES IN COAL MINES. length of faces, pillars, gangways, and other coal surfaces in theworkings was about 72,S00 feet and as the average height is 14 feetthere were 1,019,200 square feet of coal exposed. At the time of sam-pling there, were 50 working faces, some of which were also min
. Bulletin. pes pass overa low anticline and some distance down its north side. The depth beneath the surface varies from about 1,000 feet on thecrest of the anticline to 1,050 and 1,150 feet in the synclines north andsouth. The average thickness of the bed is about 14 feet. The47004°—Bull. 72—15 9 130 EXPLOSIVE CASES IN COAL MINES. length of faces, pillars, gangways, and other coal surfaces in theworkings was about 72,S00 feet and as the average height is 14 feetthere were 1,019,200 square feet of coal exposed. At the time of sam-pling there, were 50 working faces, some of which were also mined onthe night shift, so that there was a large area of fresh coal surface ex-posed. The gas is believed to be given off uniformly, the greatestamount coming from the working faces. If the total emanation ofmethane, 1,024 cubic feet a minute, bo compared with the areaexposed, it is equal, to slightly more than 1 cubic foot a minute foreach 1,000 square feet of coal surface, but doubtless the outflow was. i. Dips «•— River b»nk — — Propettj lii Figure* and contour lines 6ldepths belo* sea levelSCALE0 100 200 300 -100 500 FEET Fiqxtre 28.—Map of Red Ash workings in Dorrance mine, Wilkes-Barre, Pa. many times as much from working faces as from pillars. The pro-duction at time of sampling was 620 tons a day, including waste, sothat the methane emanation was somewhat less than 2 cubic feetper minute for every ton mined. COMPOSITION OF RED ASH COAE. A sample of Red Ash coal was taken from a typical working faceon January 2, 1911, 600 feet northwest of the main Dorrance sample, which represents the entire face, was analyzed in thelaboratory of the Bureau of Mines at Pittsburgh, with the followingresults. GAS IN NORTHERN PENNSYLVANIA ANTHRACITE FIELD. Analysis of Red Ash coal from Dorrance mine, Wilkes-Barre, Pa.[A. C. Fieldner, analyst.) 131 Condition. Air dried. As re-ceived. Moisturefree. Referred to coal moisture and ash free. Proximate analysis: Moisture
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