Jrom Water and other Liquids, &c. 574 
SECTION Il. 
On Vapour in Air. 
The experiments under this head were made 
with manometers, or straight tubes of different 
lengths, hermetically sealed at one end, of +5 
inch internal diameter, and their capacities di- 
vided into equal portions. A drop or two of 
the liquid, the subject of experiment, was con- 
veyed to the bottom or sealed end of the tube; 
the internal surface was then dried by a wire and 
thread, and atmospheric, (or any other air) was 
admitted into the tube, upon which a column 
of mercury was suspended of <4 of an inch, or 
of go inches, less or more, according to the 
nature of the experiment. By immersing the 
end of the manometer, containing the air thus 
circumstanced, into a tall glass vessel containing 
water of any temperature, the effect of the 
vapour in expanding the air could be perceived. 
It was first indeed necessary to determine the in- 
crease air unaffected by any liquid (except mer. 
cury) would obtain by increase of temperature: 
that was done, as will be particularly shewn in 
the next essay. The expansion of all elastic . 
fluids, it seems probable, is alike or nearly so, 
