. Bulletin. rentpressures were all supposed to be caused by the open workings thevolume of pure methane in the voids in the mine, if the voids were as-sumed to be filled, would range from 107,660 to 10,266,100 cubic feet,the larger volume corresponding to a longer period of time. Thisresult could be explained only by the hypothesis that the gas and airmight be in strata of varying composition, those mixtures richest ingas occupying the highest levels. Under such a condition a slightdiminution in atmospheric pressure might affect only the mixturespoor in gas occupying the lower levels, whereas
. Bulletin. rentpressures were all supposed to be caused by the open workings thevolume of pure methane in the voids in the mine, if the voids were as-sumed to be filled, would range from 107,660 to 10,266,100 cubic feet,the larger volume corresponding to a longer period of time. Thisresult could be explained only by the hypothesis that the gas and airmight be in strata of varying composition, those mixtures richest ingas occupying the highest levels. Under such a condition a slightdiminution in atmospheric pressure might affect only the mixturespoor in gas occupying the lower levels, whereas further diminutionwould bring out mixtures containing more gas. However, carefulsampling of the air in the old workings did not reveal such a condi-tion, which moreover is not consistent with the laws of Morin concluded that in these experiments the old workings THE GASES IN COAL. 93 were not the only cause, nor even the most important one in the varia-tion of the amount of methane 3 s a a a e. a. a ss NNHSiS as a §3 s ^ 65 In order to test this question further Morin made some precisedeterminations of the amount of methane m old workings at Lievm. 94 EXPLOSIVE GASES IN COAL MINES. In a chamber in the most gaseous part of the mine, a tube 16 feetlong was fastened along the roof and the chamber was then filled withgob. The end of the tube that projected into the gangway wasplugged. After three months, samples drawn from the pipe con-tained as much as per cent methane. A similar experimentin another chamber gave per cent. Meanwhile the amount ofmethane in the ventilating currents in returns near by varied to per cent. In old workings in another part of the minewhere the ventilation was mostly cut off, some of the air from the gobwas found to contain 2 to per cent of methane. These tests in-dicate that although some gas is given off by old workings, even ifclosely filled, it does not increase to any important extent the volume
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