IT has often been observed in the motion of the waves caused by the north winds or by any current of air from that quarter of the heaven [that it is different from that caused by] the south and southwest winds. For the waves raised by the blowing of the north wind are very high and follow hard upon one another, but as soon as the wind has ceased, they flatten out and subside, and soon there are no waves at all. But it is not the same when the wind blows from the south or southwest; for although these have wholly ceased to blow, still the waves that they have caused continue to swell, and though they have long been undisturbed by wind, yet the sea keeps continually surging. The reason of this is inferred to be, that the winds from the north, falling upon the sea from a higher part of the sky, are borne straight down, as it were headlong, into the depths of ocean, making waves that are not driven forward, but are set in motion from within; and these, being turned up from beneath, roll only so long as the force of that wind which blows in [p. 231] from above continues. The south and southwest winds, on the contrary, forced down to the southern zone and the lowest part of the heavens, are lower and flatter, and as they blow over the surface of the sea, they push forward 1 the waves rather than raise them up. Therefore the waters are not struck from above but are forced forward, and even after the wind has fallen they retain for some time the motion given by the original impulse. Moreover, this very suggestion of mine may be supported by the following lines of Homer, if one reads them carefully. For he wrote thus of the blasts of the south wind: 2
Then Notus drives huge waves against the western cliff,but on the other hand he speaks in a different way of boreas, which we call aquilo: 3
And Boreas aetherborn, uprolling a great wave.For he means that the waves stirred up by the north winds, which are high and blow from above, are so to speak rolled downward, but that by the south winds, which are lower than these, they are driven forward in an upward direction by a somewhat greater force and pushed up. For that is the meaning of the verb ὠθεῖ, as also in another passage: 4
The stone toward the hilltop pushed he up.This also has been observed by the most learned investigators of nature, that when the south winds blow, the sea becomes blue and bright, but, under the north winds, darker and more gloomy. I noted the cause of this when I was making excerpts from the Problems of Aristotle. 5
