630 
ciple, that the up-cast shaft could become a natural drain, 
and draw off the gas merely because it was placed 
on the extreme rise of a coal field. It is true that the 
workings on the outcrop of coal are outlets, but the drain 
from a shaft simply is very limited ; as, indeed, however great 
the pressure of the gas emitted from the coal in the mine, 
there must be sufficient barriers to support the main roads 
leading to the up-cast shaft, as well as to all the workings 
in operation, or the shaft itself would be of no use. The 
coal could not be worked out, and throw all the workings 
open to the up-cast shaft ; this would close the shafts and 
roads. Then what becomes of the ascending principle ? for 
when the goaves are formed, they are invariably the highest 
part of the mine, and the gas being lighter than atmospheric 
air, rises to the highest part, but does not as a whole escape 
to the up-cast shaft, only such portion as is forced out by the 
pressure of the gas emitted, such pressure being greater than 
the resisting force of the atmosphere by which it is surrounded. 
The goave forms an extensive reservoir of inflammable gas 
that has no way of escape except by ventilation, which is simply 
impossible and unnecessary in perpetuity, whatever the prin- 
ciple of the said ventilation may be. But, on the ascending 
principle, the greatest danger is to be apprehended from 
the fact that if the coal is worked from the rise to the dip, 
and no pack walls or pillars are left, the fall of the roof and 
ground-sweighs, so called in the thick coal, would be 
constantly forcing the gas from the goaves on to the men 
at work ; and, mixing in the air in the separate setts, would 
pass from place to place, and the slightest derangement in 
the safety lamp would be fraught with the direst consequences, 
and on this ground alone would defeat the end proposed. 
Besides, working coal from rise to dip in a commercial point 
of view, would be attended with considerable danger, 
inconvenience, and loss, both in coal and timber ; the 
