[ 167 ] 
has of keeping fire alive, is very much diminifhed by a 
fmall mixture of fixed air. 
This experiment was tried, by fetting the candle in a 
large cittern of water, in fuch manner that the flame 
was raifed but a little way above the furface ; the re- 
ceiver being inverted full of water into the fame 
cittern. The proper quantity of fixed air was then let 
up, and the remaining fpace filled with common air, 
by railing the receiver gradually out of water 5 after 
which, it was immediately whelmed gently over the 
burning candle. 
'Experiments on the Quantity of Fixed Air , contained 
in Alcaline Subjlances. 
Experiment X. 
The quantity of fixed air contained in marble was 
found by diflolving fome marble in fpirit of fait, and 
finding the lofs of weight, which it {uttered in effer- 
vefcence, in the fame manner as I found the weight 
of the inflammable air difeharged from metals by 
foiution in acids, except that the cylinder was filled 
with fhreds of filtering paper inttead of dry pearl 
afhes ; for pearl allies would have abforbed the fixed 
air that patted through them. The weight of the 
marble diffolved was 3114- grains. The lofs of 
weight in effervefcence was 125-igrains. The whole 
empty fpace in the bottle and cylinder was about 
2700 grain meafures : the excefs of weight of that 
quantity of fixed, above an equal quantity of common, 
air is 1 2. grains. Therefore the weight of the fixed 
air difeharged is 1274. grains. The cylinder with the 
filtering paper was found to have increafed iA grains 
in weight during the effervefcence. The empty fpace 
in 
