Meteorology   

region. Why this is so will be clear when we have explained the nature

of hail.



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But we must go on to collect the facts bearing on the origin of

it, both those which raise no difficulties and those which seem

paradoxical.

Hail is ice, and water freezes in winter; yet hailstorms occur

chiefly in spring and autumn and less often in the late summer, but

rarely in winter and then only when the cold is less intense. And in

general hailstorms occur in warmer, and snow in colder places.

Again, there is a difficulty about water freezing in the upper region.

It cannot have frozen before becoming water: and water cannot remain

suspended in the air for any space of time. Nor can we say that the

case is like that of particles of moisture which are carried up

owing to their small size and rest on the iar (the water swimming on

the air just as small particles of earth and gold often swim on

water). In that case large drops are formed by the union of many

small, and so fall down. This cannot take place in the case of hail,

since solid bodies cannot coalesce like liquid ones. Clearly then

drops of that size were suspended in the air or else they could not

have been so large when frozen.

Some think that the cause and origin of hail is this. The cloud is

thrust up into the upper atmosphere, which is colder because the

reflection of the sun's rays from the earth ceases there, and upon its

arrival there the water freezes. They think that this explains why

hailstorms are commoner in summer and in warm countries; the heat is

greater and it thrusts the clouds further up from the earth. But the

fact is that hail does not occur at all at a great height: yet it

ought to do so, on their theory, just as we see that snow falls most

on high mountains. Again clouds have often been observed moving with a