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had already been established on what may be termed the 
old-fashioned principle. By the definition " old-fashioned/' 
is implied a system of working out the entire area of the 
colliery by means of the two shafts — down-cast and up-cast 
— which had been sunk in close proximity to each other, at 
the commencement of the undertaking. These, for very 
obvious reasons, as pertaining to the mechanical process of 
extracting the coal, were generally placed in such position 
(having some regard to the convenience of delivery on the 
surface) as would command the coal to be worked at its 
lowest level or dip. And so far as the down-cast shaft is 
concerned, — usually applied to the two-fold object of admit- 
ting the fresh air for ventilation, and the drawing up of 
minerals out of the mine, — it is not presumed that this 
principle of selection is in any respect defective or objection- 
able. But whilst recognising the policy with regard to one 
of the shafts, the gravest objection may be taken to the 
other, as a permanent portion of the arrangements for 
working the mine. It may be that the balance of mechanical 
force in extracting the coal is greatly accommodated, by 
placing the drawing pit on the lowest dip of the stratum. 
But the very reverse is true in relation to the vitiated air 
which it is a grand object of ventilation to expel from the 
mine. And in these two conflicting elements, the principle 
arises which this paper aims at supporting. The coal, by 
its weight, when placed in the miner's corf, will gravitate 
towards an outlet on the dip. The air to be expelled will, in 
obedience to an equally natural and energetic law, seek its 
escape in the opposite direction, and upon the rise. It is 
unnecessary here to enter minutely into the constituents of 
that which for brevity's sake we have denominated u vitiated 
air," and which by ventilation is, or ought to be, expelled. 
The fact, however, must be noted, that the ingredient by far 
the most important, and that which constitutes in itself the 
