~, 
50 ON THE FIRE-DAMP OF COAL-MINES, 
the depth is 57 or GO 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, and at Valleyfield, 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- 
your 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: 
