. Bulletin. ple (Lai). No. 1272) of return air from the slopes and anirregular flat basin to the east was taken at the point designated A GAS IN NORTHERN PENNSYLVANIA ANTHRACITE FIELD. 115 (fig. 24) in No. 23 tunnel, where the volume of air was 41,500 feet aminute. This air contained per cent, equivalent to 431 cubicfeet a minute, of methane. About 428,500 square feet of coal wasexposed in the area ventilated by this air, so that slightly morethan 1 cubic foot of gas was given off for every 1,000 square feet ofcoal exposed. The daily coal production in these workings aver-aged 193 tons, a
. Bulletin. ple (Lai). No. 1272) of return air from the slopes and anirregular flat basin to the east was taken at the point designated A GAS IN NORTHERN PENNSYLVANIA ANTHRACITE FIELD. 115 (fig. 24) in No. 23 tunnel, where the volume of air was 41,500 feet aminute. This air contained per cent, equivalent to 431 cubicfeet a minute, of methane. About 428,500 square feet of coal wasexposed in the area ventilated by this air, so that slightly morethan 1 cubic foot of gas was given off for every 1,000 square feet ofcoal exposed. The daily coal production in these workings aver-aged 193 tons, and the methane calculated to this factor gives arate of 3,230 cubic feet to the ton. Another sample (Lab. No. 1277) was taken at the point designatedB (fig. 24) from the west return in the No. 11 tunnel, an air coursethat ventilates all the workings to the extreme south. The regionpresents an anticline and a syncline in which the beds are consid-erably disturbed. The volume of the return air was 18,957 cubic. Figure 25.—Sketch map of worked area in Five-foot bed, Lance mine. feet a minute. It carried per cent of methane, equivalent to 508cubic feet a minute, a remarkably large volume of gas when thesmall extent of the workings is considered. A precise measurementof the area of these workings was not made, but the gas emanationwas equivalent to at least 5 cubic feet a minute for every 1,000square feet of coal exposed. The average daily production fromthe area was 228 tons, and the volume of methane considered in thisrelation was at the rate of about 3,200 cubic feet to the ton of coalmined. FIVE-FOOT RETURNS. The Five-foot bed has been extensively developed in the Lancemine, the workings extending far under the river and beyond itssouth bank in places. The principal features are shown in figure 25. 116 EXPLOSIVE GASES IN COAL MIXES. The length of the workings up and down the river was 6,400 feet,and their width south of the shafts was 3,200 feet, comprising anarea of abou
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
