119 
and respiration, and the several processes of fermen- 
tation and putrefaction, would all fall under the same 
denomination ; but who, that duly considers the na- 
ture, th purpose, and end of these several opera- 
tions, would desire thus to confound them, under 
the general title of combustion? It is evident that 
the black residuum which M. Berthollet seems to 
consider as evidence of actual combustion, was not 
the result of the natural combination of these bodies, 
but of the artificial heat to which he submitted them 
in the process of evaporation. 
364. Dr Bancroft, in his valuable treatise on the 
" Philosophy of Permanent Colours," remarks, that 
it cannot be M. Berthollet's intention to apply the 
term combustion^ to alterations which result from 
a simple addition of oxygen to colourable matters, 
without a destruction or separation of any of their 
component parts. Various acids, says he, which 
contain oxygen, weaken or extinguish colours, not, 
however, by any effect which can properly be term- 
ed combustion ; for none of the colourable parts are 
destroyed or carried away, and the addition of an al- 
kali restores the original colour. Many dyed sub- 
stances, he adds, have their colours dissipated by ex- 
posure to the sun and air, without any other change 
of tint than the simple diminution of their original 
body, or quantity of colouring matter ; so that the 
cloth is left as white as before it was dyed, without 
any thing like combustion having ever taken place in 
it, or in the matter with which it was dyed *. Instead, 
* Philos, of Perm. Colours, vol. 5. p. 49, 50, 
