78 PLIFY's ITATUEAL HISTOET. [Book II. winds blow in their turn, so that when one ceases its oppo- site springs up. AVTien winds which are contiguous succeed each other, they go from left to right, in the direction of the sun. The fourth day of the moon generally determines their direction for the whole of the monthly period^ We are able to sail in opposite directions by means of the same wind, if we have the sails properly set ; hence it frequently happens that, in the night, vessels going in different directions rim against each other. Auster produces higher winds than Aquilo, because the former blows, as it were, from the bot- tom of the sea, while the latter blows on the surface ; it is therefore after south winds that the most mischievous earth- quakes have occurred. Auster is more violent during the night, Aquilo during the day ; winds from the east continue longer than from the west. The north winds generally cease blowing on the odd days, and we observe the prevalence of the odd numbers in many other parts of nature ; the male winds are therefore regulated by the odd numbers^. The sun sometimes increases and sometimes restrains winds ; when rising and setting it increases them ; while, when on the meridian, it restrains them during the summer. They are, therefore, generally lulled during the middle of the day and of the night, because they are abated either by excessive cold or heat ; winds are also lulled by showers. "We gene- rally expect them to come from that quarter where the clouds open and allow the clear sky to be seen. Eudoxus^ sup- poses that the same succession of changes occurs in them after a period of four years, if we observe their minute re- volutions ; and this applies not only to winds, but to what- ever concerns the state of the weather. He begins his lus- trum at the rising of the dog-star, in the intercalary year. So far concerning winds in general. 1 The influence of the fourth day of the moon is referred to by Yirgil, Geor. i. 432 et seq. " Sin ortu quarto," &c. 2 This refers to the genders of the names of the winds, analogous to the remark in note ^j p. 71. ^ Eudoxus was a native of Cnidus, distinguished for his knowledge in astrology and science generally ; he was a pupil of Plato, and is referred to by many of the ancients ; see Hardouin's Index Auctorum, in Lemaire, i. 187, and Enfield's Hist, of Phil. i. 412, with the very copious list of references.
