everywhere as it rushes along, produces
gales and constantly increasing currents by its mighty blasts. Wherever
the winds carry the vapour which rolls in masses from springs, rivers,
marshes, and the sea, it is brought together by the heat of the sun,
drawn off, and carried upward in the form of clouds; then these clouds
are supported by the current of air until they come to mountains, where
they are broken up from the shock of the collision and the gales, turn
into water on account of their own fulness and weight, and in that form
are dispersed upon the earth.

3. That vapour, mists, and humidity come forth from the earth, seems due
to the reason that it contains burning heat, mighty currents of air,
intense cold, and a great quantity of water. So, as soon as the earth,
which has cooled off during the night, is struck by the rays of the
rising sun, and the winds begin to blow while it is yet dark, mists
begin to rise upward from damp places. That the air when thoroughly
heated by the sun can make vapours rise rolling up from the earth, may
be seen by means of an example drawn from baths.

4. Of course there can be no springs above the vaultings of hot
bathrooms, but the atmosphere in such rooms, becoming well warmed by the
hot air from the furnaces, seizes upon the water on the floors, and
takes it up to the curved vaultings and holds it up there, for the
reason that hot vapour always pushes upwards. At first it does not let
the moisture go, for the quantity is small; but as soon as it has
collected a considerable amount, it cannot hold it up, on account of the
weight, but sprinkles it upon the heads of the bathers. In the same way,
when the atmospheric air feels the heat of the sun, it draws the
moisture from all about, causes it to rise, and gathers it into clouds.
For the earth gives out moisture under the influence of heat just as a
man's heated body emits sweat.

5. The winds are witnesses to this fact. Those that are produced and
come from the coolest directions, the north and northeast winds, blow in
blasts that are rarefied by the great dryness in the atmosphere, but the
south wind and the others that assail us from the direction of the sun's
course are very damp, and always bring rain, because they reach us from
warm regions after being well heated there, and licking up and carrying
off the moisture from the whole country, they pour it out on the regions
in the north.

6. That this is the state of the case