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particles lie very near each other, will be better able to 
dilTolve and keep fufpended a greater quantity of water, 
than the fame air when diffufed thro’ a greater I'pace. 
But that this is really fo we have an experimental 
proof. For when a receiver is partly exhaufted, we 
lee the rarefied air begin to let go the water it con- 
tained, which gathering into fmall particles appears 
like fteam or fmoak falling to the bottom. In order 
to prove the fame thing by another experiment, I 
.took from the air pump a large exhaufled receiver 
twenty inches long, having at the bottom a brafs 
plate, with a ftop-cock in the middle of it ; when 
the flop-cock was opened, the external air, rulhing 
in violently, and being much rarefied, let go the wa- 
ter it contained, and threw it againfl the other end 
of the receiver, where it ftuck on the glafs, and co- 
vered it with a thin dew, which I found to increafe 
.until the receiver was almoft full of air. 
Thefe experiments prove that air, when rarefied, 
cannot keep as much water diffolved as it does in a 
more condenfed ftate. Hence we muft conclude, 
that when the atmofphere is much faturated with 
water, and changes from a denfer to a rarer date, 
the higher and colder parts of it efpecially, will 
begin to let go fome part of the water dilTolved ; 
which will form new clouds, or add to the fize and 
number of the particles before formed, and thereby 
render them more apt to fall down in rain. On the 
contrary, when the atmofphere changes from a rarer 
to a denfer date, it will then be able to flop the pre- 
cipitation of the water, and again diffolve in the 
whole, or in part, fome of thofe clouds that were 
formed before, and confequently will render their 
particles 
