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current of air to pass up each of the branch roadways to 
the coal face, from whence it is drawn into the goaf, in the 
same proportion as the air is withdrawn from that waste by 
the action of the ventilator, which may be either a steam 
jet, a furnace, or a fan, as circumstances may dictate. It 
will be seen that by this plan of ventilation the upcast 
windway is an extension of the upcast shaft, drawing a 
portion of foul air from every goaf, and, indeed, every 
separate part of the mine, independent of any other. The 
quantity of air removed being regulated by the size of the 
opening of the overhead airways, the sura of the areas of 
the whole of which must not exceed the area of the upcast 
shaft. 
The advantages of this plan are : — 
1st. Should a blower occur opposite a goaf, the workmen 
can be withdrawn until it has exhausted itself, without the 
gas causing any injury to any other portion of the mine. 
2nd. The gas would be immediately withdrawn from the 
lamps of the miners, for although the diffusion of gases goes 
on somewhat rapidly, still as there is the difference of specific 
gravity to be overcome, the probability of an explosion would 
be lessened. 
3rd. When a change in the pressure of the atmosphere 
occurs, and the barometer falls, say from 30 to 29 inches, 
the atmosphere of the goaves expands in the inverse propor- 
tion, every 29,000 feet becoming 30,000 feet; but by the 
plan proposed it would escape by the upcast airway, instead 
of being driven into the workings, as in the old plan. 
4th. Allowing of the possibility of an explosion, it would 
be entirely local in its effects, for the after-damp would not 
pass through the workings, but through the goaf to the 
upcast ; the ventilation would not be disarranged as it now 
is by the blowing down of traps and stoppings, which 
frequently prevent any succour being given to those who, by 
