AND PREVENTING ITS EXPLOSION. 51 
accumulation may still increase. The more numerous and ex- 
tensive the excavations become, it is justly remarked, in a pam- 
phlet published bythe Literary and Philosophical Society of New- 
castle, the greater will be the difficulty of guarding against sur- 
rounding wastes filled with water, or carburetted hydrogen, or 
carbonic acid gas; and when, at a future period, it shall be 
found necessary to work the lower seams in this coal-field, the 
operations of the miner must be carried on under immense ac- 
cumulations of water. If these views be just, the propriety of 
impressing on the coal proprietors the necessity of conducting 
the workings en a better system than has hitherto been follow- 
ed, will be obvious; and from the apparent indifference of 
many of them on this subject, the propriety of legislative inter- 
ference to regulate the economy of the mines, which has been 
repeatedly suggested, will scarcely be questioned. 
Tt is a curious circumstance, that in those mines in which 
the fire-damp does not occur, the production of choak-damp, 
or carbonic acid gas, is not unfrequent. Thus it often occurs 
in the Mid Lothian collieries, and sometimes at no great 
depth. 
Note C. page 37.—It is been said, that the infammable air 
sometimes issues from the floor of the mine, and this has been 
stated as a sufficient objection to the method I have proposed. 
The fact is, that it seldom comes from the floor, but usually 
from the sides of the wall of coal ; and in general even the dis- 
charge is rather from nigh the roof than from beneath, as must 
indeed be the case in the escape of an elastic fluid from an im- 
perfectly solid mass. But even if it did issue from the floor 
much more frequently than it does, it does not remain there, 
but rises to the roof, where the accumulation of it, and the 
mixture of it with the atmospheric air which renders it explo- 
G2 sive, 
