623 
Again, it is often asserted that the state of the barometer 
has much to do with the liberation of gas, or confining it in 
these goaves or old workings. I am not prepared absolutely 
to admit or deny that there is any close connection between 
the atmosphere above ground and below ; but I think it is 
a delusion to suppose that the variations of the barometer are 
sufficient of themselves to liberate gas under ground in quanti- 
ties to cause an explosion, especially in deep mines, in the 
presence of moderate ventilation. But in the absence of a 
current of air in shallow mines, and where the gas has been 
drained off or its native force exhausted, then the state 
of the barometer might affect the otherwise passive mass. 
Liberated gas in the actual workings is very varied in its 
effects, sometimes it escapes gradually and is easily managed, 
at other times its power is demonstrated by the force with 
which it displaces the coal, floor, or roof of the mine. This is 
beyond doubt the most dangerous state in which a mine can 
be worked, especially when a large surface is being con- 
tinually opened night and day. It is to this state more 
particularly that the attention of all who are entrusted 
with the management of mines (and also valuable lives and 
property) should be directed, as it is universally found that 
all strata, and especially coal, is more or less open, or has 
cavities or cleavages out of which the gas is continually 
issuing. When an extensive mine is in progress of 
opening, many thousands of these natural drains are 
pouring their contents into the open space, under a 
pressure, as compared with the atmosphere of the mine, 
with which there is really no comparison. Under these 
circumstances one of two things is certain, either the gas 
emitted must be diluted and expelled from the mine, or there 
must be an explosion ; and I have no hesitation in avowing 
that it is to this cause alone that ninety-nine out of every 
hundred of the explosions in mines are to be attributed. 
