On Rain, Evaporation, &ec. 363 
mer months, and something more in the au- 
tumnal.* 
From these experiments it seems we may 
conclude—ist, That the quantity of water eva- 
porated, zn the circumstances above related, amounts 
to 25 inches of rain annually ; to which if we add 
5 inches for the dew, it will give 30 inches of 
water raised annually. 
2d. That the quantity of evaporation in- 
creases with the rain, but not proportionally. 
Thus, 1797 gave the most rain and the greatest 
evaporation, &c. 
ad. That it does not appear there is much 
difference betwixt the evaporation from bare 
earth, when there is sufficient depth of soil, and 
that from ground covered with vegetating grass, 
The account in 1796 is much what might have 
been expected, if the earth had been covered with 
grass. — 
As this account of evaporation, amounting 
to 30 inches, exceeds the medium reserve of 
rain of 29 inches, it demands an enquiry whether 
the rain is adequate, or whether the earth de- 
rives a supply of water from some subterranean 
reservoir, according to the opinion of some phi- 
losophers, 
* N.B. The earth in the vessel always appeared as 
well supplied with moisture as the ground around it, in 
the driest weather, 
