Dr. dobson’s Obfervations , 8cc. 245 
It is well known, that air is an active folvent of water, 
and that its powers of folution are in proportion to its 
drynefs. It is likewife well known, that in chemical fo- 
lutions, the action of the menjiruum is greatly promoted 
by heat and agitation. If the temperature of the air 
then, and the ftate of the winds, be afcertained, which 
in the prefent cafe denote the heat and agitation of the 
menjiruum , the evaporation will be the true index of the 
drynefs of any particular feafon, lituation, or climate. 
To determine the annual evaporation in the neigh- 
bourhood of Liverpool, I procured two weli-varnifhed 
tin veffels; one of which was to ferve the purpofe of a 
rain-gage; the other was to be employed as my evapo- 
rating veffel. The evaporating veffel was cylindrical, 
twelve inches in diameter and fix inches deep. The 
rain-gage confiHed of a funnel twelve inches likewife in- 
diameter, the lower end of which was received into the 
mouth of a large ftone-bottle ; and, to prevent any eva- 
poration from the bottle, the pipe of the funnel w r as 
Hopped with a grooved cork. Thefe veffels were placed 
in the middle of a grafs-plot, on a riling ground adjoin- 
ing and immediately overlooking the town, about fe- 
venty-five feet above the level of the fea, and with a free 
expofure to the Sun, winds, and rain. The cylindrical 
veffel was filled with water within two inches of the 
