242 
Book III. 
NATURE OF 
sion between the particles of any body, and of the af 
finity betwéen the particles of that body and of any 
other, we could easily reduce the temperature necessary 
to calculation. 
That caloric or temperature acts in this manner, can 
not be doubted, if we consider that other methods of 
diminishing the attraction of cohesion may be substi 
tuted for it with success. A large lump of charcoal, 
for instance, will not unite with oxygen at so low a tem 
perature as the same charcoal will do when reduced to 
a very fine powder; and charcoal will combine with 
oxygen at a still lower temperature, if it be reduced to 
its integrant particles, by precipitating it from alcohol, 
as Dr Priestley did by passing the alcohol through 
red hot copper. And to shew that there is nothing in 
the nature of oxygen and carbon which renders a high 
temperature necessary for their union, if they be pre 
sented to each other in different circumstances, they 
combine at the common temperature of the atmosphere; 
for if nitric acid, at the temperature of 60°, be poured 
upon charcoal powder, well dried in a close crucible, 
the charcoal takes fire, owing to its combining with 
the oxygen of the acid * : And in some other situations, 
carbon is so completely divided that it is capable of 
combining with the oxygen of the atmosphere, or, 
which is the same thing, of catching fire at the com 
mon temperature : this seems to be the case with it in 
those pyrophori that are formed by distilling to dry 
ness several of the neutral salts which contain acetous 
acid†. These observations are sufficient to shew, that 
* Proust and Morveau, Encyc. Method. Cbim. 1. 474. 
t Morveau, ibid.