wMch are evolved in Coal-Mines. 315 



As the blower in the mine of Wellesweiler affords a bottle 

 of gas in three minutes, the current thus amounts to about 

 18 Parisian cubic feet in twenty-four hours. I found that one 

 volume of this gas still formed an explosive mixture with 15 

 to 16 volumes of atmospheric air. In twenty-four hours, there- 

 fore, such a mixture of 306 cubic feet can be formed, which 

 would occupy a length of 14 feet. Should, therefore, such an 

 issue of gas continue for months, without the inflammable gas 

 being removed by means of a current of air, we may well ima- 

 gine what powerful effects the explosion of so considerable an 

 amount of fire-damp can produce. Notwithstanding the con- 

 siderable evolution of gas, which, in Gerhard's mine, judging 

 from the size of the flame, amounts to at least twenty times 

 as much as in the Wellesweiler mine, yet both mines can be 

 visited with the usual miner's lamp without the least danger. 

 One cannot even perceive the presence of the inflammable gas 

 in the miner's lamp.. Hence, we see that, by means of a 

 strong current of air, which exists in both mines, the most 

 considerable evolutions of inflammable gas can be made com- 

 pletely harmless. 



On account of its inconsiderable specific gravity, the in- 

 flammable gas is always collected at the top of the gallery, 

 and there forms the fire-damp. Hence, in general, the miner 

 can visit without dread, places which are filled with weak fire- 

 damp, with the ordinary miner's lamp, if he keep the same, 

 near the floor ; and it is only when he approaches it to the 

 upper part that an explosion ensues. This is only the case, 

 however, in places where either there is no movement of the 

 air, or only a feeble one ; for, in an atmosphere which is in a 

 state of movement, the pit gas is either entirely removed, or 

 so mixed with the atmospheric air, that the whole space is 

 filled with fire-damp. 



The ascent of the inflammable gas to the higher portions of 

 a mine, is turned to account in the working of beds, in order 

 to protect the miners from the frightful effects of fire-damp. 

 Thus, should an inclined stratum, proceeding from a principal 

 gallery, be worked from below upwards, and should there be an 

 evolution of inflammable gas, an accumulation takes place gra- 

 dually at the working place, and the mining must be suspended. 



