Mr, Bvddle's Account of the Explosion in Jarro^ Colliery. 185 



barometer should rise, the evolvement of inflammable air, would be 

 much diminished. Hence it is, that we frequently find some of our 

 Coal-mines in an explosive state, when the barometer is low, while 

 the presence of inflammable air, is scarcely perceptible when the atmo- 

 sphere is in a very dense state. 



The cause of this fluctuation in the discharge is evident. When the 

 density of the atmosphere is just equal to the elastic force of the gas, 

 contained in the pores, or fissures, of the Coal or adjoining rock, the two 

 fluids balance each other. But whenever the density of the atmo- 

 sphere is diminished, the equilibrium is destroyed, and the elastic force 

 of the gas preponderates. 



We observe, however, that the discharge of the gas generally pre- 

 cedes the fall of the barometer, by a brief interval, probably owing to 

 the more delicate nature of the balance. 



I shall now proceed to explain the proximate causes of explosion. 



First — by a change in the density of the atmosphere, as indicated by 

 the fall of the barometer. 



In this case, the circulating current of atmospherical air, becomes 

 mixed to the point of explosion by the increased discharge of inflam- 

 mable air, as already explained, and ignites at the first flame that may 

 happen to be within its range. Explosions have happened from this 

 cause, by the inflammable current igniting at the furnace placed at the 

 bottom or top of the upcast shaft, for carrying on the ventilation — I 

 have known them happen in both ways. 



This case does not, however, very frequently occur, as the over-load- 

 ing of the current of atmospherical air, seldom takes place so suddenly 

 as to elude the vigilance of the persons in charge of the mine. Yet I 

 have seen the whole circulating current of a pit's workings rendered 

 explosive in the course of fifteen or twenty minutes. 



This was the cause of the accident in the A pit, Bensham seam. Walls- 

 end colliery, on the 2Sd October, 1821, when fifty-two lives were lost. 

 The workings of this pit were subject to be charged to the firing 

 point, in the manner already described, but accidents had always been 

 avoided b}'^ the vigilance of two young men — the overmen of the pit. 



