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quent upon such operations, may be reduced to its lowest 
possible amount. The duty becomes still more urgent and 
imperative, when we contemplate the rapidly increasing ratio 
in which the mining operations of the country are being 
extended ; and nowhere, perhaps, is this increase more percep- 
tible than in the coal-fields of West Yorkshire, and of this 
immediate locality in particular. Not only have we to reflect 
upon a production, which has nearly doubled itself within the 
last 20 years, and now amounting to about 100,000,000 tons 
per annum from the collieries of Britain, but we must bear 
in mind, the increased and increasing difficulty and risk, which 
necessarily attend upon the extraction of this enormous 
quantity of coal from greater depths, and from expanded 
areas more vigorously worked, both of which conditions 
imply a far more active generation of gas, and the exposure 
of a much greater number of lives to all the dangers and 
consequences of explosion and death. 
Proceeding from a commencement in which expediency 
and economy exert the dominant sway, the systems of ventila- 
tion now in common use, are but the expansions of an evil 
theory, and are unentitled to be regarded as the offspring or 
result of any scientific principle, adequately applied to the 
exigencies of so vast and precarious an enterprise. Our 
objections are against all attempts to render ventilation 
dependent upon downward currents ; or, in other words, 
against a system of ventilation, which relies for its action, 
upon the ability to compel the exudation of gas, and vitiated 
air, along passages and currents, to which, by their natural 
gravity, such gases are utterly opposed. 
In our previous papers we asserted, and mining experience 
has confirmed, the truthfulness of the observation, that a 
part only of the conditions are considered, which ought to 
govern the selection of the points from which the products of 
our coal fields should be won. The mechanical operations of 
