OF SELBORNE. 
elevated pools fome unnoticed recruits, which in the night time 
counterbalance the wafte of the day ; without which the cattle alone 
muil foon exhauft them ? And here it will be neceffary to enter 
more minutely into the caufe. Dr. Hales, in his Vegetable Statics, ad- 
vances, from experiment, that " the moifter the earth is the more 
" dew falls on it in a night : and more than a double quantity of 
dew falls on a furface of water than there does on an equal 
furface of moift earth." Hence we fee that water, by it's coolnefs, 
is enabled to affimilate to itfelf a large quantity of moifture' nightly 
by condenfation ; and that the air, when loaded with fogs and 
vapours, and even with copious dews, can alone advance a con- 
fiderable and never-failing refource. Perfons that are much 
abroad, and travel early and late ; fuch as Ihepherds, fifhermen, 
&c, can tell what prodigious fogs prevail in the night on elevated 
downs, even in the hotteft parts of fummer; and how much the 
furfaces of things are drenched by thofefw.imming vapours, though, 
to the fenfes, all the while, little moifture feems to.fall. 
I am, 
LETTER 
