I^K wouJ 

 I^H unali 



071 Sal Nitrum and Nitro- Aerial Spirit 85 



•quite unfit to sustain life and flame. But then you will 

 say that the air enclosed in the glasses is still possessed 

 of sufficient elastic force to resist the pressure of the 

 atmosphere, so that it would seem not to have been 

 deprived of its nitro-aerial and elastic particles. And 

 how then can it be that an animal or a lamp cannot 

 be sustained by it ? Nay, I have ascertained that the 

 air in which an animal or a lamp has expired is 

 possessed of no less elastic force than any other air, 

 for when the pressure of the atmosphere is removed 

 it expands with no less vigour than common air, 

 as will be shown in Chapter X. But this seems 

 flatly to contradict what has been said on this matter. 

 The answer to be given to this difficulty is, I think, 

 that the elastic force of the air referred to does not 

 result from the elasticity of its aerial particles being as 

 intense as that of unaltered air, but rather from this, 

 that as aerial particles when deprived of nitro-aerial 

 particles become less rigid, so they are also more bent 

 by the pressure of the atmosphere ; but a weaker rigid 

 body, provided it has been greatly bent and stretched, 

 will have no less elastic force than a stronger rigid 

 body less bent by the very same force. It should be 

 also noted that the elastic force of the said air results 

 in part also from this, that as that air deprived of 

 elastic particles is reduced to narrower space, aerial 

 particles in air of this sort are aggregated in greater 

 abundance and more densely than in common air. 



Here we remark in passing that if the elastic force 

 of the air resulted from certain agile particles inter- 

 spersed in it, and if these were exhausted by the 

 breathing of the animal or the burning of the lamp, 

 then air in which an animal or a lamp has been enclosed 

 would by no means expand with as much force as 

 unaltered air. So that even by this it is clearly proved 



