VENTILATION OP MINES OR HOSPITALS. 33\ 



Itieir employers are put to considerable additional expense 

 by the unavoidable hinderaucc and the waste of candles and 

 other materials. 



I mean to confine the following remarks to such mines as 

 are worked upon metalliferous veins, according to the prac- 

 tice of this district, and that of the great seat of mining in 

 the neighbouring county of Cornwall, from which indeed 

 ours is borrowed. We find then, that a single shaft, not 

 communicating by levels to another, can hardly be sunk to 

 any considerable depth, nor can a level (or, as the foreign 

 miners call it, a gallery) be driven horizontally to any great 

 distance without some contrivance being had recourse to 

 for procuring currents of air to make up the deficiency of 

 oxigen, which is so rapidly consumed by respiration and 

 combustion in situations like these, where otherwise the 

 Tvhole remains in nearly a stagnant condition. 



We are here unacquainted with the rapid production of 

 those gasses, which occasionally in the collieries are the cause 

 of such dreadful effects; such as hidrogen gas, or t\ie fire- 

 damp, carbonic acid, or the choke-damp; the inconvenience 

 we experience takes place gradually as we recede from 

 the openings to the atmosphere, and seems to arise solely 

 from the causes I have before assigned, though it is found 

 to come on more rapidly in certain situations than in others. 



The most obvious remedy, and that which is most fre- Usual resource, 

 quently resorted to, is the opening a communication either 

 to some other part of the mine, or to the surface itself, and 

 as soon as this is done the ventilation is found to be com- 

 plete, by the currents which immediately take place, often 

 with considerable force, from the different degrees of tem- 

 J)erature in the subterranean and upper atmospheres; and 

 these currents may be observed to change their directions as 

 the temperatures alternate. 



The great objection to this mode of curing the evil is the Objectionable 



enormous expense, with which it is most commonly attended. ^"^'""^ ^^^ ^^' 

 * ' -^ pense. 



In driving a long level, or tunnel, for instance, it may happen 

 to be at a great depth under the surface, and the intervening 

 jrock of great hardness; in sucli a case every shaft which 

 must be sunk upon it for air alone, \vhere not required (as 

 pftea they might not) to draw up the waste, would cost 



scye|-al 



