574 OBSERVATIONS ON THE BAROMETER, 
Rain is a great regulator of Temperature both 
in summer and winter. Rain is the cause of cold 
in summer, and of heat in winter: the reason is 
pretty obvious. Clouds in summer prevent the 
earth being heated by the sun’s rays; and rain 
causes a copious evaporation, requiring a propor- 
tionate expenditure of heat. In winter the vapour 
is chiefly imported from the south and south-west, 
and being deposited here, the heat arising from 
the condensation of the vapour is diffused through 
the atmosphere, and the evaporation in that sea- 
son being insignificant, it requires no material 
supply of heat. Hence we have a well founded 
maxim for this climate ; that a wet summer ts a 
cold one, and a wet winter a warm one. 
Or Rar. 
Ir is well known that in some regions of the 
earth the vicissitudes of the seasons, especially as 
regards rain, may be predicted with tolerable cer- 
tainty. Some months of the year are invariably 
rainy and others are mostly fair. But these 
characteristics do not apply to climates like ours 
situate in the middle of the Temperate Zone. 
Any one month in the year may be the wettest 
or driest in that year, for any thing that is previ- 
ously known to the contrary. I have sometimes 
