Obfervations on inflammable Air. 353 
fome experiments I have made with common air ren- 
dered more light by fire. This air I have found may be 
breathed much eafier, although not for fo long a time, as 
when it is more condenfed. It mult be faid, indeed, that 
this is occalioned by another particular caufe, which has 
nothing to do with the cafe of the inflammable air, and 
which cannot be properly examined in this place. 
After all, it ltill remains to be known, why inflamma- 
ble air, which kills animals fo foon, may be breathed 
without any oppreflion, when in a fmall quantity, viz. 
when it is mixed with common air; and the following 
experiments, which are very analogous to thofe related 
above, will fhew that the queftion is not uninterefting. 
I introduced 350 cubic inches of common air into a 
bladder, and after having made as ftrong an expiration as 
I could, I applied the neck of the bladder to my mouthy 
and breathed the air it contained forty times fuccefiively. 
Afterwards, having taken the air out of the bladder, I 
found that it extinguifhed a light feveral times fuccef- 
flvely. It formed various cryftals with the oil of tartar* 
but after a very confiderable time ; fome of thefe cryftals 
had the fhape of needles, others were like flowers r 
being tried with the nitrous air, it gave II- 1 8, III -t- 1 8. 
This air, therefore* was very much phlogifticated, nor 
could I poffibly have breathed it longer than I did, with- 
out 
