(473 3 
in the Earth, wherein they lofe theiHaltnefe. This befides 
many others labouring under this principal Abiurdicy, 
that the greateft Rivers have their mod copious Foun- 
tains fartheft from die Sea, and whither fo great Quanti- 
ties of frefh Water cannot reafonably be derived any other 
way than in Vapour. This, if we may allow final Caufes, 
feems to be the defign of the Hills, that their Ridges being 
placed through the midft of the Continents, might ferve as 
it were for Alembicks to diftil frelh Water for the ufe 
of Man and Bead, and their heights to give a defcent 
to thofe Streams to run gently, like fo many Veins of the 
Macrocofm, to be the more beneficial to the Creation. It 
the difference between Rain and Dew, and the caufe why 
fometimes 'tis Cloudy, at other times Serene, be enquired, 
I can offer nothing like a proper folution thereof, only 
with fubmiffion to propofe Conjectures which are the 
beft I can find, viz. That the Air being heap'd up by 
the meeting of two contrary Winds, when the Mercury is 
high, the Vapours are the better fuftained and kept from 
Coagulating or condenfing into Drops, whereby Clouds 
are not fo eafily generated : and in the Night the Vapouts 
fall down fingle as they arofe in imperceptible Atoms of 
Waters Whereas w ? hen the Mercury is low and the Air 
carified by theexhauftion thereof, by two contrary Winds 
blowing from the place} the-Atoms of Air keep the Va- 
pours not fo well feparated, and they coalefce into vifible 
drops in the Clouds ; and from thence are eafily drawn 
into greater drops of Rain. To which 'tis poffible and not 
improbable, that fome fort of Saline or Angular particles 
of Terreftrial Vapour being immixt with the Aqueous, 
which I take to be Bubbles, may cut or break their Skins 
or Coats, and fo contribute to their more fpeedy Conden- 
fation into Rain* 
I- 
