§92 On Evaporation. : 
20° below that temperature. At first view theres 
fore it should seem that ether evaporates quicker 
than the general law assigns.—But it must be 
allowed that the temperature of the air has some 
effect upon evaporation, though it has certainly 
very little. Now ether in the above experi- 
ments is acted upon by a current of air of an 
equal or higher temperature than itself; but 
water of 160° is usually acted upon by air 100” 
lower than itself, which is every moment pre- 
cipitating the vapour formed, and thus ob- 
structing its circulation. This appears to be 
a sufficient cause for the small difference ob- 
served. 
With respect to mercury, sulphuric acid, 
muriate of lime, &c. there can be no doubt 
but they experience a real evaporation like those 
above; but it must be very small in proportion 
as their boiling points are high. And it would 
be difficult to make experiments upon ‘such of 
these as have an affinity for aqueous vapour ; 
because their acquisition from the aqueous at- 
mosphere would far exceed their loss by eva~ 
poration. 
\ 
Since writing the above essay, opportunities 
have occurred to ascertain whether the evapor- 
ation from ice is conformable to the same law 
as that from water. Every one, who has tried 
the experiment, admits the fact that ice is eva- 
