170 Analyfis of the Air. 
they drew the Air briskly out of the glafs 
zzaa thro* the fyphon $ the other leg of 
which fyphon I immediately drew from un- 
der the glafs veffel, marking the height of 
the water z z. 
When the materials on the pedeftal ge- 
nerated Air, then the water would fubfide 
from z z to a a, which fpace z z a a was 
equal to the quantity of Air generated : 
But when the materials deftroyed any part 
of the Air’s elafticity, then the water would 
rife from a a (the height that I in that cafe 
at firft fucked it to) to z z , and the fpace 
aazz was equal to the quantity of Air, 
whofe elafticity was deftroyed. 
I fometimes fired the materials on the 
pedeftal by means of a burning glafs, viz, 
fuchas phofphorus and brown paper dipped 
in water, ftrongly impregnated with nitre 
and then dried. 
Sometimes I lighted the candle or large 
matches of brimftone before I whelmed the 
glafs z z a a over them ; in which cafe I 
inftantly drew up the water to a a , which 
by the expanfion of the heated Air would 
at firft fubfide a little, but then immediately 
turned to a rifing ftate, notwithftanding the 
flame continued to heat and rarify the Air 
i 
for 
