TENTILATION OF MINES OR HOSPITALS, - 337 



Messrs. Allea and Pepys); and allowing farther, that their 

 candles vitiate as much as the men, there will be six times 

 twenty-seven cubic inches and a half of air to be drawn out 

 in a minute, equal to one hundred and sixty-five. 



Now a cylinder five inches in diameter, working with a 

 stroke of nine inches, will effect this by one stroke in a mi- 

 nute, though it would certainly be advisable to make it 

 larger. 



'■ Not being practically acquainted with collieries, or mines Its application 

 that suffer from peculiar gasses that are produced in them, ' 



I cannot state, from actual experiment, what effect this ma- 

 chine might have in relieving them; but it must appear, 

 I conceive, evident to every person at all acquainted with 

 the first principles of pneumatics, that it must do all that 

 can be wished; as it is obvious, that such a machine must in 

 a given time pump out the whole volume of air contained ia 

 a given space, and thus change an impure atmosphere for a 

 better one. And in constructing the machine it is only 

 necessary to estimate the volume of gas produced in a certain 

 time, or the capacity of the whole space to be ventilated. 

 It is easy to judge how much more this must do for such and to fire- 

 cases as these, than such schemes as have lately been pro-^^"^^' 

 ■ posed of exciting jets of water, or slacking lime, both of 

 which projects, likewise, must fail when applied; as one of 

 them has, I believe, been proposed to be io the case of hi- 

 drogen gas. But with such a machine as this, if the dreadful 

 effects of explosions of this air are to be counteracted, it 

 may be done by one of sufiicient size to draw off this air 

 as fast as it is generated; and by carrying the pipes into the 

 elevated parts of the mine, where from its lightness it would 

 collect. If, on the other hand, it is desired to free any sub- orchoke-damp; 

 teirraneous work from the carbonic acid gas, it may as 

 certainly be done by suffering the pipe to terminate in the 

 lower parts, whither this air would be directed by its gravity. 



In workhouses, hospitals, manufactories, &c., it is always to workhou<:efj, 

 easy to calculate the quantity of air contained in any j^uf^^^^^^'-gg^^i^ 

 room, or number of rooms, and easy to estimate how often 

 it is desirable to change this in a certain number of hours, 

 and to adjust the size and velocity of the engine accordingly. 

 Where this change of foul air for pure is to take place in 



Vol. XXIX.— Supplement. Z th^ 



