4 wy i bres 
I i , 
382 Mr. Wuvewoon’s Method of conneding 
Inthe remarkable inftance of the coating of ice on the out- 
fide of the throat of the funnel, there are fome other circum- . 
flances which it may be proper to take notice of., Neither the 
cover of the outer veflel, nor the aperture in its bottom which ! 
the ftem of the funnel pafied through, were air-tight, and the _ 
melting of the furrounding ice had left a vacancy of about an 
inch round that part of the funnel on which the cruft had 
formed. As there was, therefore, a paflage for air through the 
veffel, a circulation of it would probably take place: the cold 
and denfe air in the veffel would defcend into the rarer air of 
the room ‘then about 50°, and be replaced by /air from above. 
The effect of this circulation and fudden refrigeration of the. 
air will be a condenfation of part of the mozfture it contains 
upon the bodies it is in contaét with: the throat of the funnel, 
being one of thofe bodies, muft receive its fhare; and the de- 
eree of cold in which the ice thaws being fuppofed fufficient 
for the freezing of this moift vapour, the contact, condenfa- . 
tion, and freezing, may happen at the fame inftant. 
fs 
‘The fame principles apply to every inftance of congelation 
that took place in thefe experiments; and a recollection of par- 
ticulars which pafled under my own eye convinces me, that 
the congelation was ftrongeft in thofe circumftances where va- 
pour was moit abundant, and on thofe bodies which, from 
their natural or mechanic ftructure, were capacious of the 
greateft quantity of it; ftronger, for inflance, on fponge 
than on woollen, {tronger on this than on the clofer texture of. 
linen, and far ftronger-en.all thefe than.on the compact furface 
of porcelain. 
If, neverthelefs, the principle I have aflumed (that water 
highly attenuated will congeal with a lefs degree of cold than. 
swater in the mafs) fhould not be admitted; another has above 
ee 
been 
