126 EXPERIMENTS on EVAPORATION. 
In order to obferve this procefs with more accuracy, I 
fixed an empty tin jar in a tub, and filled the tub with a 
mixture of falt and {now, fo that the veffel was completely 
furrounded with the mixture, and the air in it was foon 
reduced to the temperature of falt and fnow, or to o° of 
Fahrenheit’s fcale. 
In this fituation, I fufpended in it, a rag which had 
been dipped in water of the temperature of 40°—as foon 
as it defcended within the veffel, it began to emit {moke 
or fenfible vapour, and continued doing fo, a confiderable 
time.—While fmoking it was drawn out, and the fmoke 
ceafed.—After this, it was replaced in the veflel, and a- 
gain began to {moke. 
This was repeated frequently, and always with a fimi- 
Jar refult, fo that I had no doubt of the fa&t.—In the firft 
cafe in which I obferved this fmoke to arife, the moift body 
muft have enjoyed a heat of 9&° or near it, as it was my 
hand; by this experiment it appeared that a moift body - 
of 40° would fmoke alfo in the fame circumftances, and 
Inow wifhed to know whether this would be the cafe with 
a body ftill colder.—For this purpofe a fmall piece of Ice 
was fufpended in the veflel, as the rag had been before— 
it, {moked when firft fufpended there, this {moking ceafed 
when it was drawn out, and returned when it was placed 
in the veflel again; precifely as it had happened when the 
rag was ufed.—Another lump of ice was dropped into the 
veflel and allowed to remain there, it {moked for twelve 
or fifteen minutes and then ceafed.—Snow {moked in the 
fame manner, but not fo long. 
To be certain that this vapour really arofe from the j Ice, 
a {mall mirror was fufpended horizontally in the cold vef- 
fel—tIt continued fo along time without contrating any 
moifture or dullnefs on its furface—The ice was then in- 
troduced under it, and, although there was a confiderable 
diftance between them, the mirror foon became encrufted 
with 
