84 On the Atomic Theory, 



There is very little doubt, if any, but the whole of tlie caloric 

 of the gases which fonstitute nitrous acid is retained in this cu- 

 rious substance ; for when nitrous air condenses half its bulk of 

 oxygen gas, with more rapidity than most inflammable substances, 

 neither light nor heat is evolved, except indeed some increased 

 temperature occasioned by the action of the newly-formed acid 

 on the moisture suspended in the gases ; and when the acid is 

 again united to potash, very little caloric is given out. It is eu- 

 TUJUs, as I first observed in my Comparative Flew, that nitrous 

 gas should be lighter than the gaseous oxide of azote, more 

 especially when the atoms of tlie former contain twice the quan- 

 tity of oxygen : — this I attribiited at the time to the different size 

 of their respective atmospheres of caloric and light conjointly. 

 But the most extraordinary difference in property between those 

 gases is, that the gaseous oxide of azote v;hich contains but half 

 the quantity of oxygen contained in the nitrous air, will not unite 

 to oxygen when both are mixed : perhaps (as I hinted at in my 

 Comparative Vieiu) this depends upon a superior density or su- 

 perior force of attraction of the atoms of the gaseous oxide for 

 their calorific atmospheres, so as to prevent the particle of oxy- 

 gen from passing through them. 



When muriate of annuonia and sulphate of soda, in fine pow- 

 der, are mixed, they decompose each other, and new compounds 

 which demand less water are formed, and nearly a liquid mix- 

 ture is produced. This is perfectly illustrative of the liberation 

 of caloric in the foregoing experiments, for the two salts are dry 

 before they are mixed. 



The next way of setting free the caloric and light of bodies is 

 by means of the electric fluid ; for when a metallic wire or char- 

 coal is placed in the way of that fluid, circulated by a powerful 

 Voltaic battery, the caloric of their respective particles is disen- 

 gaged, and a prodigious degree of heat and light is produced. 



Substances that retain their calorific atmospheres with the 

 greatest force nuist be the worst conductors ; because the electric 

 fluid has to force its way by removing the whole or a certain 

 portion of it, which obstructs its passage; and the quantity of ca- 

 loric thus dislodged depends upon the density or energy of the 

 electric matter ; for when a space is fully occupied by one fluid, it 

 can only receive another by the expulsion of the former ; both 

 cannot exist in the same space. The quantity of caloric, I say, 

 thus liberated depends upon that of the electric fluid ; and the 

 effects it produces as free caloric, depend upon the size of the 

 masses through which it circulates. Instance; — the electricity of 

 a large cloud will melt a mass of metal, whereas that produced by 

 a Voltaic battery will only fuse small wires. 



Metals, charcoal, and living animals and living vegetables are 



the 



