of Meteorological Operations. 245 
before, or the third, fourth or fifth days after the 
change and full of the moon, than at the precife 
time of thefe.. 
11th. That the difappearing or thorough folu- 
tion of clouds in the night time, and particularly 
in winter, is always accompanied with an immediate 
increafe of cold. 
12th. ‘That the formation of clouds or feparation 
of watery vapour from the air, and the con- 
fequent falls of rain, fnow, and hail, abftra& the 
cold from the atmofphere, and precipitate it to 
the furface of the earth,* which caufes the air to 
become warmer in the time of, and immediately 
after -falls, than it was before; but when thefe 
are accompanied with lightning and other pheno- 
mena by which the inherent or latent heat is dif- 
chaiged from the atmofphere, the whole is rendered 
colder than at firft. 
13th. ‘That when the wind blows over a fpace 
of country drenched with water or covered . with 
f{now; from the great evaporation thereby occafioned, 
a much greater degree of cold is foon produced : 
and when it continues to blow in fuch circum-' 
ftances 
* Mr. Copland feems here to {peak of cold as a pofitive 
quality, but it accords better with our prefent ideas, to 
fay, that on the vapours being condenfed into clouds, rain, 
and fnow, the heat which was chemically combined with 
them in a latent ftate, and preferved them in their vaporous 
form, is fet at liberty, and thus caufes an increafe of warmth 
in the atmofphere. 
