126 On Ventilating Mines or Hospitals. 



-nule ; though it would certainly be advisable to make it 

 larger. 



Not being practically acquainted with collieries, ermines 

 .that suffer from peculiar gases that are produced in them, 

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

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

 I conceive, evident to every person at all acquainted with 

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

 tan be wis^hed, as it is obvious that such a machine must in 

 a given time pump out the whole volume of air contained 

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

 a belter one. And in constructing the machine it is Only 

 necessary to estimate the volume of gas produced in a cer- 

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

 Jt is easy to judge how much more this must do for such 

 cases as these, thati such schemes as have lately been pro- 

 posed of exciting jets of water, or slaking lime, both of 

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

 of iheni has, I believe, when apnlicd to the case of hy- 

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

 fid eflccts of explosions of this air are to be counteracted, 

 it may be done by one of sufficient 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- 

 terraneous work trom the carbonic acid gas, it may as cer- 

 tainly be done by suffering the pipe to terminate in the 

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

 In workhouses, hospitals, manufactories, &c. it is always 

 easy to calculate the qunntity of air contauied in any room, 

 or nun-.ber of rooms, and easy to estimate how often it is 

 desirable to change this in' a cerlain number of hours, and 

 to adjust the >^ize and velocity of the engine accordingly. 

 Where this ch.tnge of foul air for pure is to take place in 

 the night, means for working the iniichme may be provided 

 by pumping up a quantity ci water into a reservoir of suffi- 

 cient height to admit of its flowing out during the night in 

 a small stream, with sufficient fall, so as to give motion to 

 theencine; or by wiudmg up a weight <>t sufficient size, 

 or by many other means which are easily devised. 



If, for instance, a room in which fiity persons slept was 

 eiuhty feel long, twenty wide, and ten high, it would con- 

 tan> 16,000 ciiuic feet of air, and if this was to be removed 

 twice in eight hcnu's, it would require a c\ tinder of thirty 

 inches diauieler, worknig with a iour-feel stroke four times* 



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