124 PHILOSOPHY OF 



even in vacuo, as when burnt in atmospheric 

 oxygen ; which proves that a large amount of 

 caloric is concentrated around the particles of the 

 nitric acid of the saltpetre, and set at liberty 

 during its decomposition. 



Philosophy of Explosion or Detonation. 



Immediately connected with the foregoing 

 theory, is the rationale of explosion, a pheno- 

 menon which has never been explained, and 

 has been often adduced as an argument against 

 the materiality of caloric. It has been supposed 

 that the quantity of heat given out during explo- 

 sion, and that which is requisite to convert gun- 

 powder into the gaseous state, could not have 

 existed in a state of combination with its particles. 



This has arisen from not attending to the law 

 by which caloric is concentrated around the atoms 

 of ponderable matter, with a force that increases 

 in proportion to the augmentation of their size, 

 other things being equal ; and by which its self- 

 repulsive force is counteracted. I have shown 

 that the elastic force of nitrogen is equal to a 

 pressure of 1200 atmospheres; but that when 5 

 volumes of oxygen are combined with 2 of nitro- 

 gen, they contract into 2 volumes of nitric acid, 

 without any material loss of caloric, and yet that 

 the elastic force of nitric acid is very small ; that 

 when 5 atoms of oxygen 40, unite with an atom 



