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courses. But as a general rule it seems obvious that ascend- 
ing modes of exit have advantages of the first consequence, 
not only in favouring the natural tendency of the element to 
be dealt with, but by ejecting it from shafts in advance of 
the workings, and upon the " rise" of the coal, all possibility 
of lodgment is removed, and the chances of explosion 
materially lessened, by the gases being carried off without 
returning through the active parts of the mine, and under 
circumstances which may be suddenly affected by changes of 
weather, variations of the barometer, and other conditions, 
which it is less difficult to conceive than enumerate. 
The doctrine of advance shafts for ventilation is not pre- 
sumed to be at all a novelty, and it is not set forward here 
except for the purpose of asserting its soundness in theory ; 
and moreover, of expressing a strong belief, that much greater 
advantage might, and ought to be taken of this principle, in 
every system of colliery ventilation; although there may 
be cases where the time and expense to be incurred in the 
uniting, by underground drifts, of two shafts at opposite 
ends of the territory, would swamp the pecuniary prospects 
of success which a particular enterprise might indicate. 
Having regard to the future, and when the workings are to 
be pressed along the dip of the coal, as also in the opening up 
of deeper and underlying seams, it is clear that very important 
advantages might be taken of existing shafts and workings, 
in forming air passages on the rise or ascending principle 
for use of our own, as well as of generations yet to come. 
This proposition assumes for its practical application and 
value, an immediate survey by competent parties, of entire 
districts of coal, in order that provision should be at once 
made by giving greater permanency to some of the shafts now 
and hereafter to be sunk, as well as in securing the driftways 
intended to be left open, by an adequate amount of pillar coal 
to be left for their support and continuance. 
