50 ON THE FIRE-DAMP OF COAL-MINES, 



the depth is 57 or 60 fathoms ; in the Grange Colliery, in West 

 Lothian, where an explosion happened some time ago, the 

 depth is about 50 fathoms ; and in the Ayrshire mines, the first 

 bed of coal is at a depth of 30 fathoms ; the second at a depth 

 of 26 below this, not deeper, therefore, than that of the Mid 

 Lothian collieries, where the gas does not occur ; and farther, 

 from the upper bed of the Ayrshire coal, fire-damp is given 

 out as abundantly as from the lower. But the collieries of 

 Mid Lothian are perfectly dry ; the coal being what are called 

 edge seams, that is, in strata vertical, or highly inclined, a dis- 

 position which allows the water to pass off more readily. In 

 Ayrshire again, at Borrowstounness, an<l at Valleyneld, where 

 there is the generation of fire-damp, I am informed there is 

 much water, which seems even to percolate the coal. This is 

 particularly the case in Ayrshire, the water dropping from the 

 wall of coal,, and a current or blower as it is called, of fire-damp 

 sometimes escaping with water. The still greater production 

 of fire-damp in the English mines, is probably owing to the 

 much larger scale on which they are wrought, and to the deep 

 and extensive workings being favourable to. the collection of 

 water. It accordingly appears, from the accidents which 

 have repeatedly happened from water bursting into mines, that 

 it is accumulated in old pits and excavations in immense quan- 

 tities, and that it transudes through the mass of coal. The 

 last accident which occurred, that at the Heaton Colliery, in 

 which seventy-five individuals were destroyed from the burst- 

 ing of water into the mine, is a melancholy proof of this. 

 These causes, too, particularly the depth of the workings, fa- 

 vour the accumulation of the gas. This in some measure ac- 

 counts for the accidents from explosion having become more 

 frequent in these mines, notwithstanding the improvements in 

 their ventilation, and gives some ground for the fear that its 



accumulation 



