[ J 49 ] 
With 7 parts of inflammable to 3 of common air, 
there was a very gentle bounce or rather puff: it 
contined burning for fome feconds in the beliy of the 
bottle. 
A mixture of 8 parts of inflammable to 2 of com- 
mon air caught fire on applying the flame, but without 
any noife : it continued burning for fome time in the 
neck of the bottle, and then went out, without the 
flame ever extending into the belly of the bottle. 
It appears from thefe experiments, that this air, like 
other inflammable fubftances, cannot burn without the 
affiflance of common air. It feems too, that, unlefs 
the mixture contains more common than inflammable 
air, the common air therein is not fufficient to con- 
fume the whole of the inflammable air; whereby 
part of the inflammable air remains, and burns by 
means of the common air, which rufhes into the bottle 
after the explofion. 
In order to find whether there was any difference in 
point of inflammability between the air produced from 
different metals by different acids, five different forts of 
air, namely, 1. Some produced from zinc by diluted 
oil of vitriol, and which had been kept about a fort- 
night ; 2. Some of the fame kind of air frefh made; 
3. Air produced from zinc by fpirit of fait ; 4. Air 
from iron by the vitriolic acid ; 5. Air from tin 
by fpirit of fait ; were each mixed feparately with 
common air in the proportion of 2 parts of in- 
flammable air to 7 _ 7 _ of common air, and their 
inflammability tried in the fame bottle, that was 
ufed for the former experiment, and with the fame 
precautions. They each went off with a pretty loud 
noife, and without any difference in the found that I 
could 
