1 6 8 Analyfis of the Air. 
Then before I took them out of the water, 
I fet the bolthead and lower part of the cy- 
lindrical glafs *2/ into the earthen veffel x x, 
full of water, and having lifted all out of 
the great veffel of water, I marked the fur- 
face z of the Water in the glafs a y. 
If the ingredients in the bolthead, upon 
fermenting generated Air, then the water 
would fall from z to/, and the empty fpace 
zy was equal to the bulk of the quantity 
of Air generated : Eut if the ingredients, 
upon fermentation, did abforb or fix the 
aftive particles of Air, then the furface of 
the water would afeend from z to n, and 
the fpace z n, which was filled with water, 
was equal to the bulk of Air, which was 
abforbed by the ingredients, or by the fume 
arifing from them: When the quantities of 
Air, either generated or abforbed, were very 
great, then I made ufe of large chymical re- 
ceivers inftead of the glafs ay: But if thefe 
quantities were very fmall, then inftead of 
the bolthead and deep cylindrical glafs ay, 
I made ufe of a fmall cylindrical glafs, or 
a common beer glafs inverted, and placed 
under it a Viol or Jelly glafs, taking care 
that the water did not come at the ingredi- 
ents in them, which was eafily prevented 
by 
