182 



FRAGMENTS OF SCIENCE. 



During exhalation this valve closes ; the breath escapes 

 by a second valve, v', into the open air. The wool is 



FIG. 4. 



thus kept dry and cool ; the air in passing through it 

 being filtered of everything it holds in suspension. 

 The respirator has since taken other forms. 



Fireman's Respirator. 



We have thus been led by our first unpractical 

 experiments into a thicket of practical considerations. 

 But another step is possible. Admiring, as I do, the 

 bravery of our firemen, and hearing that smoke was a 

 more serious enemy than flame itself, I thought of 

 devising a fireman's respirator. 



Our fire-escapes are each in charge of a single man, 

 and it would be of obvious importance to place it in 

 the power of each of those men to penetrate through 

 the densest smoke, into the recesses of a house, and 

 there to rescue those who would otherwise be suffocated 

 or burnt. Cotton-wool, which so effectually arrested 

 dust, was first tried; but, though found soothing in 



