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Before I proceed to the experiments themfelves, k 
will be proper to mention the principal methods ufed 
in making them. 
In order to fill a bottle with the air difcharged from 
metals or alcaline fubftances by folution in acids, or 
from animal or vegetable fubftances by fermentation, 
I make ufe of the contrivance reprefented in Tab. VII. 
Fig. i. where A reprefents the bottle, in which the 
materials for producing air are placed ; having a bent 
glals tube C ground into it, in the manner of a ftopper. 
E reprefents a vefiel of water. D the bottle to receive 
the air, which is firft filled with water, and then in- 
verted into the vefiel of water, over the end of the 
bent tube. F f reprefents the firing, by which the 
bottie is fufpended. When 1 would meafure the 
quantity of air, which is produced by any of thefe 
lubftances, I commonly do it by receiving the air in 
a bottle, which has divilions marked on its fides with 
a diamond, (hewing the weight of water, which it 
requires to fill the bottle up to thofe divifions : but 
fometimes I do it by making a mark on the fide of the 
bottle in which I have received the air, anfwering 
to the furface of the water therein; and then, fetting 
the upright, find how much water it requires to fill it 
up to that mark. 
In order to transfer the air out of one bottle into 
another, the fimpleft way, and that which I have ofteneft: 
made ufe of, is that reprefented Fig. 2 . where A is 
the bottle, into which the air is to be transferred : it is 
luppofed to be filled with water and inverted into the 
vefiel of water DEFG, and fufpended there by a 
firing: the line DG is the furface of the water: B 
reprefents a tin funnel held under the mouth of the 
-bottle ; C reprefents the inverted bottle, out of which. 
1 
