[^62] 
other folutlons ; of which I gave an inflance in the 
vapours that are fufpended in the heat of the day, 
and by the cold of the night are precipitated, and 
fuffered to coalefce into drops of dew. From the 
fnow that lies fo long on the tops of mountains, and 
from the experience of thofe who have palTed over 
them, we find that the higher parts of the atmofphere 
are much colder than the lower. Now, though 
vapours are firfi: raifed, and abound moftin the lower 
parts of the atmofphere, yet they cannot there form 
themfelves into clouds, becaufe the heat that helped 
to difiblve them helps allb to keep them difiblved. 
But when they are carried by the winds into the 
higher parts, where the fame heat is wanting, the 
cold air will not be able to keep difiblved all that 
are carried up, but mufi: fufibr fome of them to 
coalefce into fmall particles, which (lightly atcradting 
each other, and- being intermixed with- air, will form 
clouds^ having the very fame appearance with fleam, 
or fmoak, which alfo confifts of fmall particles of 
water, mixed with air, and not yet difiblved in it. 
Thefe clouds, when firfi: formed, will remain fuf- 
pended, though they confifi of water as well as air, 
bccaufe the weight of their particles will not be able 
to overcome the refifiance they mufi meet with in de- 
fcending through the air. For when bodies are di- 
minifiied, their quantities- of matter, to which their 
weights^ are proportional, decreafe fafier, or ifi' a 
greater ratio, than their furfaces, to which the re- 
fifiance they meet with is proportional j and, there- 
fore, in very fmall particles, this refifiance may be- 
come greater than their weight. The different heights 
at which clouds arc formed, depend on the quan- 
tity 
2 
