C *+? 3 
XIX, Obfervations on different 
Air . By Jofeph 
F. R. S. 
Kinds of 
LL. A 
Read March s, f | *HE following obfervations on the 
* 2 ’ 19 ’ 26, 1772* properties of feveral different kinds 
of air, I am fenfible, are very imperfect, and fome of 
the courfes of experiments are incomplete ; but a 
confiderable number of fads, which appear to me 
to be new and important, are fufficiently afeertained j 
and I am willing to hope, that when philofophers 
in general are apprized of them, fome perfons may 
be able to purfue them to more advantage than my- 
felf. I therefore think it my duty to give this So- 
ciety an account of the progrefs I have been able to 
make ; and I fhall not fail to communicate any far- 
ther lights that may occur to me, whenever I refume 
thefe inquiries. 
In writing upon this fubjed, I find myfelf at a 
lofs for proper terms, by which to diftinguifh the 
different kinds of air. Thofe which have hitherto 
obtained are by no means fufficiently charaderiftic, 
or diftind. The terms in common ufe are, fixed air, 
mephitic, and inflammable. The lad, indeed, fuffi- 
ciently charaderizes and diflinguifhes that kind of 
air which takes fire, and explodes on the approach 
of flame; but it might have been termed fixed with 
U 2 as 
