C M9 ] 
the fame caufe ; and that what we call evapora- 
tion is no more than a gradual folution of water in 
air. But that I may not propofe this meerly as an 
hypothefis, I Ihall endeavour to prove the truth 
of it, by confdcring the nature of folution in ge- 
neral, and comparing its properties and effedts 
with thofe of evaporation. By folution we un- 
derftand, The uniting fo intimately the particles of a 
body with thofe of a fluids that the whole f^ll appear 
an homogeneous mafs, as tranfparent as the fluid was be^ 
fore Juch union, and Jhall fo continue till feme external 
caufe produces a change. The nature of folution has 
been explained by the writers on chymiftry in this 
manner. When the particles of any body furrounded 
by a fluid are lefs flrongly attracted by each other 
than by the fluid, they feparate from each other, and 
join themfelves to thofe of the fluid, and remain 
fufpended therein. 
Thus various falts are diflblved in water, elTential 
oyls are diflblved in Ipirits of wine, gold in aqua 
regia, mercury, filver, and other metals, in other 
acid fpirits. 
And indeed it feems to be with great appearance 
of reafon, that the attradlion between the minute par- 
ticles of bodies (of which we have fo many other 
inftances) is afiigned as the caufe of that union be- 
tween them, which we experience in folutions. 
The chief properties of which I fhall now mention, 
fo far as may be neceffary for the purpofe to which 
I mean to apply them. 
In moft cafes a diflblving fluid, or menflruum, as 
the chymills call it, will diflblve or take up only a 
certain proportion of the body immerfed.i and if 
then any more of the fame body be added, it will 
precipitate 
