[ i64 ] 
and afterwards thofe that are thinner and higher up, 
fo that the mill: will be low at firll, but will increale 
in height afterwards 5 but belides, thefe grounds, and 
the water they contain, will acquire fuch a heat from 
the fun, that they may retain it for fome time, and 
communicate it to the contiguous air, fo that the va- 
pours may continue to rife for fome time after fun- 
let, and will become vifible when they get up a little 
way in the cooler air. Thofe cold thick morning 
fogs, I mentioned juft now, are often attended with 
a very light fmall rain; for we then fee the drops at 
their firft formation, and they are fuch as are gene- 
rally met with in palling over high mountains; fo that 
it feems the drops of rain are very fmall when firft 
formed in the clouds ; but being driven about by the 
motion of the air, in their defcent, fome of them 
will probably touch each other, and run into a drop 
of a larger fize, and the farther they have to fall, 
the more will their fize be increafed before they 
come to the ground. And, for this realbn, the drops, 
which fall from the higher clouds in fummer, arc 
found to be generally larger than they are in winter, 
when the clouds are low. It has been likewife ob- 
fcrved, that the drops of rain are remarkably large 
that fall in thunder Ihowers ; of which the realon 
may be, that the lightning burfting from a cloud, 
and expanding itfelf greatly, will fuddenly remove 
the air from its place, which air, therefore, muft re- 
turn to its place with great violence, and thereby the 
watery particles in the clouds will be ftrongly agi- 
tated and dallied againft each other, by which means 
they will form themfelves into larger drops than at 
Ollier times ; or, perhaps it may be faid, that when 
a cloud 
