Meteorology   

provided that the freezing takes place in a shorter time than its

fall. The nearer to the earth, and the more suddenly, this process

takes place, the more violent is the rain that results and the

larger the raindrops and the hailstones because of the shortness of

their fall. For the same reason large raindrops do not fall thickly.

Hail is rarer in summer than in spring and autumn, though commoner

than in winter, because the air is drier in summer, whereas in

spring it is still moist, and in autumn it is beginning to grow moist.

It is for the same reason that hailstorms sometimes occur in the

late summer as we have said.

The fact that the water has previously been warmed contributes to

its freezing quickly: for so it cools sooner. Hence many people,

when they want to cool hot water quickly, begin by putting it in the

sun. So the inhabitants of Pontus when they encamp on the ice to

fish (they cut a hole in the ice and then fish) pour warm water

round their reeds that it may freeze the quicker, for they use the ice

like lead to fix the reeds. Now it is in hot countries and seasons

that the water which forms soon grows warm.

It is for the same reason that rain falls in summer and not in

winter in Arabia and Ethiopia too, and that in torrents and repeatedly

on the same day. For the concentration or recoil due to the extreme

heat of the country cools the clouds quickly.

So much for an account of the nature and causes of rain, dew,

snow, hoar-frost, and hail.



13



Let us explain the nature of winds, and all windy vapours, also of

rivers and of the sea. But here, too, we must first discuss the

difficulties involved: for, as in other matters, so in this no

theory has been handed down to us that the most ordinary man could not

have thought of.