220 
COLLIEEY EXPLOSIONS. 
to work, owing to tlie extended underground workings, and I 
will now endeavour to explain the reason of this. 
If we take a section of stratified rocks, we generally find 
them inclined at a certain angle. If we trace these beds, we 
find that they eventually reach the surface, unless faulted. The 
point at which the surface is reached is termed the “ out-crop,” 
and in mining language the upward inclination of the strata is 
termed the rise ” and the downward the “ deep.” (See Fig. 1.) 
jRtSC 
-To 
In the early days of mining, the workings w^ere carried on 
near the out-crop as represented at shaft A. These workings, 
too, w^ere mostly to the ‘‘ rise,” rendered necessary by the 
inadequate means which the old miners had for bringing coal 
from the “ deep ” workings to the bottom of the shaft. These 
shallow and “ rise ” workings were some protection against 
explosions, owing to seams of coal becoming less gaseous as they 
near the out-crop. Now, however, by the increased haulage 
power which has been brought into use, it is as easy to work from 
the deep as the rise (shaft B). But what does this involve ? It 
means that the air current has further to travel, thus encountering 
greater friction. More “ splits ” are required to supply the 
numerous galleries, and a greater quantity of gas has to be 
encountered. 
