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forcing out the air. A mixture of 4540 grains of air 
from zinc and 960 of common air being then forced 
into the fame gut, it increafed 4 2. grains on forcing 
out the air. So that this factitious air fhould leem 
to be rather heavier than air from zinc; but the 
quantity tried was too fmall to afford any great degree 
of certainty. 
N.B. The weight of 4540 grain meafures of in- 
flammable air, is JJL grains, and the weight of the 
fame quantity of common air is 5-%. grains. 
On the whole it feemsthat this fort of inflammable 
air is nearly of the fame kind as that produced 
from metals. It fhould feem, however, either to be 
not exaClly the fame, or elfe to be mixed with fome 
air heavier than it, and which has in fome degree 
the property of extinguifhing flame, like fixed 
air. 
The weight of the inflammable air difcharged from 
the gravy appears to be about one grain, which is 
but a fmall part of the lofs of weight which it- 
fuffered in putrefaction. Part of the remainder, 
according to Mr. M‘Bride’s experiments, mu ft have 
been fixed air. But the colour and fmell, commu- 
nicated to the fope leys, fhew, that it muft have dit- 
charged fome other fubftance befides fixed and in- 
flammable air. 
Raw meat alfo yields inflammable air by putrefac- 
tion, but notin near fo great a quantity, an proportion 
to the lofs of weight which it fuffers, as gravy does. 
Four ounces of raw meat mixed with water, and 
treated in the fame manner as the gravy, loft about 
100 grains in putrefaction ; but it yielded hardly, 
more inflammable air than the gravy.. This air 
feemecL 
