no l)r, Priestley’s Observations, &c. 
of union, fo that, though they may be completely feparated by 
fome chemical proceffes, they are not entirely fo in this ; but that 
the dephlogifticated air, paffing the membrane of the lungs, 
carries along with it fome part of the phlogifticated with which 
it was previoufly combined. But, at the obliging fuggeftion of 
Dr. Blagden, I now think it more probable, that the defici- 
ency of phlogifticated air was owing to the greater proportion 
of it in the lungs after the procefs than before. 
T here will always be fome uncertainty in the refults of the 
long-continued refpiration of any kind of air, as at the laft the 
operation becomes laborious, and the quantity inspired and ex- 
pired is therefore much greater than at the firft. But I was aware 
of this circumftance, and endeavoured to obviate the effects of 
it, by leaving off with my lungs as nearly as I could judge in 
the fame ftate of diftentiou as when I began, which was always 
after a moderate expiration ; fo that two or three ounce mea- 
fures would have made a very fenfible difference, as any perlbn 
will find by adlual trial. 
