the FfHssian (Jo((l- Mines. 185 



nished with a copper funnel and lengthened tube in 1816-17. 

 It occurs in a principal fissure in slate-clay, at the bottom of the 

 level. At some distance from the blower a bore of 119 feet 

 has been made under the floor of the level, and a coal-bed 

 of 70 to 80 inches in' breadth has been penetrated at a depth 

 of 42 to 49 feet. The occurrence of this gas, that is, its evo- 

 lution from the water covering the floor of the shaft, allo^vs 

 us to conclude, that it must flow out with a pressure greater 

 than that of the atmospheric air. There is no doubt, indeed, 

 that all gas-canals, however complicated theu* ramifications 

 }nay be, must be restrained by means of Avater throughout the 

 whole rocky mass up to the floor of the level. It was, there- 

 fore, likewise possible that this gas should be collected by the 

 usual pneumatic method. It overcame the pressure of a co- 

 lumn of v.ater 3 inches in height. 



The difference in the flowing out of this gas and that of 

 Gerhard'' s level, is easily explained. The evolution of the lat- 

 ter takes place about seven feet above the floor of the level, 

 and the gas is therefore not hemmed in by the pit water. The 

 fissure, doubtless, extends far towards the surface, and is pro- 

 bably branched there. When, therefore, the flowing out in the 

 level encounters the slightest opposition, it turns aside else- 

 where, where no hindrance stands in the way. The tempe- 

 rature of the gas in IFellestveil level was 10°.05 R. (54\61 F.), 

 and that of a bore in the surrounding rock, eight inches deep, 

 was 8^.7 R. (51°.57 F.) According to the data stated above, 

 this gas must have come from a depth of about 155 feet. The 

 same remarks which were made in regard to the gas of Ger- 

 hard's level, apply likewise to this case. 



The quantity of gas evolved in JFellesiceU level amounts in 

 twenty-four hours to at least eighteen cubic feet. I was unable 

 to measure the quantity evolved in Gerhard's level, as it could 

 not be collected in a pneumatic trough ; by a comparison, how- 

 ever, of the size of its flame with that of the other, it nnist 

 amount to at least twenty times as much, that is, to about 360 

 cubic feet in twenty-four hours. If now we take into consi- 

 deration the innumerable unnoticeable evolutions besides that 

 out of this blower, we can form an idea of the extent of the 

 process of formation of the gas. 



