10. Land has been submerged by earthquakes; the Grecian cities of Helice and Buris, for example, are to be seen under the sea, with their walls inclined. 11. Plains have been upheaved into hills by the confined air seeking vent; as at Troezene in the Peloponnesus. 12. The temperature of some springs varies at different periods. The waters of others are inflammable.[16] 13. There are streams which have a petrifying power, and convert the substances which they touch into marble. 14. Extraordinary medicinal and deleterious effects are produced by the water of different lakes and springs.[17] 15. Some rocks and islands, after floating and having been subject to violent movements, have at length become stationary and immovable; as Delos and the Cyanean Isles.[18] 16. Volcanic vents shift their position; there was a time when Etna was not a burning mountain, and the time will come when it will cease to burn. Whether it be that some caverns become closed up by the movements of the earth, and others opened, or whether the fuel is finally exhausted, &c., &c. The various causes of change in the inanimate world having been thus enumerated, the doctrine of equivocal generation is next propounded, as illustrating a corresponding perpetual flux in the animate creation.[19] In the Egyptian and Eastern cosmogonies, and in the Greek version of them, no very definite meaning can, in general, be attached to the term "destruction of the world;" for sometimes it would seem almost to imply the annihilation of our planetary system, and at others a mere revolution of the surface of the earth. _Opinions of Aristotle._--From the works now extant of Aristotle, and from the system of Pythagoras, as above exposed, we might certainly infer that these philosophers considered the agents of change now operating in nature, as capable of bringing about in the lapse of ages a complete revolution; and the Stagyrite even considers occasional catastrophes, happening at distant intervals of time, as part of the regular and ordinary course of nature. The deluge of Deucalion, he says, affected Greece only, and principally the part called Hellas, and it arose from great inundations of rivers, during a rainy winter. But such extraordinary winters, he says, though after a certain period they return, do not always revisit the same places.[20]