[ *54 ] 
or watery vapours that could have afcended along with 
it. The ufe of the glafs tube B was to colled; the 
minute jets of liquor, that were thrown up by the 
effervefcence, and to prevent their touching thepearl- 
afhes ; for which reafon, a (mail fpace was left between 
the glafs-tube and the pearl- allies in the cylinder. 
When the zinc was diffolved, the whole apparatus was 
weighed again, and was found to have loft i ii- grains in 
weight*; which lofs is principally owing to the 
weight of the inflammable air difcharged. But it 
muff be obferved, that, before the effervefcence, that 
part of the bottle and cylinder, which was not oc- 
cupied by other more l'olid matter, was filled with 
common air; whereas, after the effervefcence, it was 
filled with inflammable air ; fo that, upon that account 
alone, fuppoflng no more inflammable air to be dif- 
charged than what was fufficient to fill that fpace, the 
weight of the apparatus would have been diminifhed 
by the difference of the weight of that quantity of 
common air and inflammable air. The whole 
empty fpace in the bottle and cylinder was about 980 
grain meafures, there is no need of exadnefs ; and 
the difference of the weight of that quantity of com- 
mon and inflammable air is about one grain : therefore 
the true weight of the inflammable air difcharged, is 
10 A. grains. The quantity of zinc ufed was 254 
grains, and confequently the weight of the air dil- 
eharged is * or -- of the weight of the zinc. 
i 3 2 . 4 O 
* As the quantity of lute ufed was but final!, and as this kind 
of lute dues not lofe a great deal of its weight by being kept in a 
moderately dry room, no fonfible error could arife fYom the diy- 
ing of the lute during the experiment. 
It 
