f ‘xii 2] 
“PR kek AC 
‘HE common air, that element 
in which we live, that invi- 
fible fluid which furrounds the 
whole earth, has never been fo 
much the object of contemplation 
as it has in our days: it never en- 
Sagcd {o much the attention of the 
-jJearned as it has of late years. This 
fluid, diffafed every where, the 
breath of life, deferves fo much the 
more the attention and inveftigation 
of philofophers, as it is the only 
fubftance without which we can 
-fcarce fubfitt alive a {ingle moment, 
-and whofe good or bad qualities 
have the greateft influence upon 
BF gliog our 
