158 Analyfts of the Air. 
head into a- large veffel of water, to a the 
top of the bolthead 5 as the water rufhed in 
at the bottom of the bolthead, the Air was 
driven out thro’ the fyphon : When the 
bolthead was full of water to then I clofed 
the outward orifice of the fyphon with the 
end of my finger, and at the fame time drew 
the other leg of it out of the bolthead, by 
which means the water continued up to 
and could not fubfide. Then I placed under 
the bolthead, while it was in the water, the 
veffel X Xf which done, I lifted the veffel x x 
with the bolthead in it out of the water, 
and tyed a waxed thread at z to mark the 
height of the water : And then approached 
the retort gradually to the fire, taking care 
to fereen the whole bolthead from the heat 
of the fire. 
The defeent of the water in the bolthead 
fhewed the fums of the expanfion of the 
Air, and of the matter which was diftil- 
ling : The expanfion of the Air alone, when 
the lower part of the retort was beginning 
to be red hot, was at a medium, nearly 
equal to the capacity of the retorts, fo that 
it then took up a double fpace 5 and in a 
white and almoft melting heat, the Air took 
