Page:The geography of Strabo (1854) Volume 1.djvu/100

86 STRABO. BOOK i. the ebb of the ocean, and commences as soon as the moon has reached either zenith or nadir, and ceases the moment she reaches the point of her rising or setting. [So far Eratosthenes.] 12. The nature of the ebb and flow has been sufficiently treat- ed of by Posidonius and Athenodorus. Concerning the flux and reflux of the currents, which also may be explained by phy- sics, it will suffice our present purpose to observe, that in the various straits these do not resemble each other, but each strait has its own peculiar current. Were they to resemble each other, the current at the Strait of Sicily l would not change merely twice during the day, (as Eratosthenes himself tells us it does,) and at Chalcis seven times ; 2 nor again that of Constantinople, which does not change at all, but runs always in one direction from the Euxine to the Propontis, and, as Hipparchus tells us, sometimes ceases altogether. However, if they did all de- pend on one cause, it would not be that which Eratosthenes has assigned, namely, that the various seas have different levels. The kind of inequality he supposes would not even be found in rivers only for the cataracts ; and where these cataracts occur, they occasion no ebbing, but have one continued down- ward flow, which is caused by the inclination both of the flow and the surface ; and therefore though they have no flux or reflux they do not remain still, on account of a principle of flowing which is inherent in them ; at the same time they cannot be on the same level, but one must be higher and one lower than another. But who ever imagined the surface of the ocean to be on a slope, especially those who follow a sys- tem which supposes the four bodies we call elementary, to be spherical. 3 For water is not like the earth, which being of a solid nature is capable of permanent depressions and risings, but by its force of gravity spreads equally over the earth, 1 Strait of Messina. 2 Gosselin observes that Le Pfere Babin, who had carefully examined the currents of the Euripus of Chalcis, says that they are regular during eighteen or nineteen days of every month, the flux and reflux occurring twice in the twenty-four hours, and following the same laws as in the ocean ; but from the ninth to the thirteenth, and from the twenty- first to the twenty-sixth, of each lunar month they become irregular, the flux occurring from twelve to fourteen times in the twenty-four hours, and the reflux as often. 3 See Plutarch, de Plac. Philos. lib. i. c. 14, and Stobams, Eel. Phys. lib. i. c. 18.