COLLIERY EXPLOSIONS. 
221 
We are now, however, in a position to ask the question, 
whether explosions in collieries are alone due to the contamination 
of the air passing through the mine with explosive gas. If 
this he so, the atmospheric variations will exercise an important 
influence. Say the barometer stands at 30 inches, which is 
equal to 14*7 lbs. to the square inch. Suppose the mercury to 
fall 1 inch, then the pressure would he reduced hy ’40 of a lb. 
The question then is, as to whether the less pressure against the 
coal would allow of a greater quantity of gas to issue from the 
coal. For my own part I do not think it would make much 
difference. Again, a fall of the barometer is not unfrequently 
attended with an increase of temperature, which means, that the 
column of air in the “ down-cast ” has become warmer. It is 
easier to ventilate a mine in winter than in summer, especially 
where furnace ventilation is the method adopted. The reason is 
plain. The atmosphere at the surface is colder in winter than 
in summer, therefore the temperature of the air descending the 
“ down-cast ” shaft is lower. Now, if colliery explosions were 
entirely due to fire-damp, we ought to be freer from explosions in 
cold weather. This, however, is not so ; some of the most fatal 
explosions have occurred in the winter months.^ For instance, 
an explosion occurred at the Kisca Colliery on December 1st, 
1862, in which 142 men were killed; and, again, the fearful 
explosion at the Oaks Colliery took place in December, 1866, 
when 334 miners lost their lives. In the last instance a shot 
was fired a few seconds before the explosion, in what appeared to 
be air free from gas. How are we, then, to explain this fact ? 
If we enter a coal mine, we cannot fail to notice the coal 
dust which is lying about and in the atmosphere. In the year 
I Mr. W. Gallaway gave an elaborate table in a paper contributed 
to the Boyal Society, in which he gives the dates of a number of 
explosions. — Proc. Boyal Society ^ 1874, p. 441. 
