7 2 
Sir Benjamin Thompson's 
of its water ; if, therefore, the heat penetrated the mass of air 
from the centre to the surface, or passed through it from particle 
to particle, in the same manner as it is probable that it passes 
through water, and all other unelastic fluids, by far the greatest 
part of the air contained in the bottle would part with its heat, 
when not actually in contact with the glass, and a proportional 
part of its water being let fall at the same time, and in the same 
place, would necessarily descend in the form of rain ; and, 
though this rain might be too line to be visible in its descent, 
yet I was sure I should find it at the bottom of the bottle, if 
not in visible drops of water, yet in that kind of cloudy cover- 
ing which cold glass acquires from a contact with hot steam 
or watery vapour. 
But if the particles of air, instead of communicating their 
heat from one to another, from the centre to the surface of the 
bottle, each in its turn, and for itself, came to the surface of 
the bottle, and there deposited its heat, and its water, I con- 
cluded that the cloudiness occasioned by this deposit of water 
would appear all over the bottle, or, at least, not more of it 
at the bottom than at the sides, but rather less ; and this I 
found to be the case in fact. 
The cloudiness first made its appearance upon the sides of 
the bottle, near the top of it ; and from thence it gradually 
spread itself downwards, till, growing fainter as it descended 
lower, it was hardly visible at the distance of half an inch from 
the bottom of the bottle ; and upon the bottom itself, which 
was nearly flat, there was scarcely the smallest appearance of 
cloudiness. 
These appearances, I think, are easy to be accounted for. The 
air immediately in contact with the glass being cooled, and 
