. Bulletin. 95-419; andby L. L. Belinfaut. Trans. Fed. Inst. Min. vol. 4. 1S93. pp. 645-646. THE GASES IN COAL. 85 Hilt thought that the experiments proved absolutely that varia-tions in atmospheric pressure affected the emission of gas in bothmines. The barometric variations were small at the time of the tests,but their effect was plainly discernible in corresponding variations inmethane content, especially in the returns of the Ath-Gouley rise in barometer was followed by diminution of the volume ofmethane and carbon dioxide, and a fall in barometer by an increasein the volume o
. Bulletin. 95-419; andby L. L. Belinfaut. Trans. Fed. Inst. Min. vol. 4. 1S93. pp. 645-646. THE GASES IN COAL. 85 Hilt thought that the experiments proved absolutely that varia-tions in atmospheric pressure affected the emission of gas in bothmines. The barometric variations were small at the time of the tests,but their effect was plainly discernible in corresponding variations inmethane content, especially in the returns of the Ath-Gouley rise in barometer was followed by diminution of the volume ofmethane and carbon dioxide, and a fall in barometer by an increasein the volume of methane, and always within 24 hours. The morerapid the rise or fall the greater was the variation in the percentageof gas. Moreover, the outflow of methane showed a tendency towardequilibrium, for when, by reason of a considerable fall in barometricpressure, the flow had risen much above the mean, it appeared to have Tnra, days12 8 4 5 6 7 8 9 10 All 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30. Figure 10.—Curves showing variations in volume of methane and carbon dioxide in relation to varia-tions in atmospheric pressure, Gemeinschaft and Ath-Gouley mines, Prussia, September, Hilt. a tendency to decrease. The absolute pressure was found to be ofless importance than the relative changes, especially when the changeswere rapid. In tests made at the Ath-Gouley pits, October 11 to 17,in a region of old workings having open spaces aggregating 9,110,000cubic feet, comparatively slight variation of atmospheric pressurecaused variations of 70 per cent in the mean volume of gas in thereturns, and these variations appeared to be independent of theamount of coal being mined. The opinion was stated that at thismine a great decrease of atmospheric pressure might double the vol-ume of methane. In the long-wall and dip workings of the Gemein-schaft mine, where most of the gas was from solid coal, the effect ofchanges of atmospheric pressure was much less marked and i
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