196 Mr, Cavenvisu’s Anfwer to 
namely, firft, the calcination of metals, either by themfelves 
or when amalgamated with quickfilver; fecondly, the burn- 
ing of fulphur or phofphorus; thirdly, the mixture of nitrous 
air; fourthly, the explofion of inflammable air; and, fifthly, 
the electric fpark ; and Mr. Kirwan has not pointed out any 
other which he confiders as unexceptionable. Now the laft of 
thefe I by no means confider as unexceptionable, as it feems 
much moft likely, that the phlogiftication of the air in that 
experiment 1s owing to the burning or calcination of fome fub- 
{tance contained in the apparatus*. It is true, that I have no 
proof of it; but there is fo much probability in the opinion, 
that till it is proved to be erroneous, no conclufion can be 
drawn from fuch experiments in favour of the generation of 
fixed air., As tothe firft method, or the calcination of metals, 
there is not the leaft proof that any fixed air is generated, 
though we certainly have no dire&t proof of the contrary; nor 
did I in my paper infinuate that we had. ‘The fame thing may 
be faid of the burning of fulphur and phofphorus. As to the 
mixture of nitrous air, and the combuftion of inflammable air, 
it is proved, that if any fixed air 1s generated, it is fo {mall as 
to elude the niceft teft we have. It is certain too, that if it 
had been fo much as .3,th of the bulk of the common air em- 
ployed, it would have been perceived in the firft of thefe me- 
thods, and would have been fenfible in the fecond though 
ftill lefs. So that out of the five methods enumerated, it has 
been fhewn, that in two no fenfible quantity 1s generated, and 
not the leaft proof has been affigned that any is in two of the 
* In the experiment with the litmus I attribute the fixed air to the burning of © 
the litmus, not decompofition, as Mr. Kirwan reprefents it, which is a fufficient 
seafon why no fixed air fhould be found when the experiment is tried with air in 
which bodies will net burn, 
7 others 3 
