CHAP. 44.—THE ORIGIN OF WINDS.
In like manner I would not deny that winds, or rather sudden gusts, are produced by the arid and dry vapours of the earth; that air may also be exhaled from water, which can neither be condensed into a mist, nor compressed into a cloud; that it may be also driven forward by the impulse of the sun, since by the term ‘wind’ we mean nothing more than a current of air, by whatever means it may be produced341. For we observe winds to proceed from rivers and bays, and from the sea, even when it is tranquil; while others, which are named Altani, rise up from the earth; when they come back from the sea they are named Tropæi, but if they go straight on, Apogæi342.
(44.) The windings and the numerous peaks of mountains, their ridges, bent into angles or broken into defiles, with the hollow valleys, by their irregular forms, cleaving the air which rebounds from them (which is also the cause why voices are, in many cases, repeated several times in succession), give rise to winds.
(45.) There are certain caves, such as that on the coast of Dalmatia, with a vast perpendicular chasm, into which, if a light weight only be let down, and although the day be calm, a squall issues from it like a whirlwind. The name of the place is Senta. And also, in the province of Cyrenaica, there is a certain rock, said to be sacred to the south wind, which it is profane for a human hand to touch, as the south wind immediately rolls forwards clouds of sand343. There are also, in many houses, artificial cavities, formed in the walls344, which produce currents of air; none of these are without their appropriate cause.