farther,”—a persuasion not uncommon in ancient times, and even down to Columbus, that there was a point, beyond which the ocean,—either from mud, sands, shallows, fogs, or accumulations of sea-weed,—was no longer navigable.[546] [546] Skylax, after following the line of coast from the Mediterranean outside of the strait of Gibraltar, and then south-westward along Africa as far as the island of Kernê, goes on to say, that “beyond Kernê the sea is no longer navigable from shallows, and mud, and sea-weed:” Τῆς δὲ Κέρνης νήσου τὰ ἐπέκεινα οὐκέτι ἐστὶ πλωτὰ διὰ βραχύτητα θαλάττης καὶ πηλὸν καὶ φῦκος. Ἐστὶ δὲ τὸ φῦκος τῆς δοχμῆς τὸ πλάτος καὶ ἄνωθεν ὀξὺ, ὥστε κεντεῖν (Skylax, c. 109). Nearchus, on undertaking his voyage down the Indus, and from thence into the Persian gulf, is not certain whether the external sea will be found navigable—εἰ δὴ πλωτός γέ ἐστιν ὁ ταύτῃ πόντος (Nearchi Periplus, p. 2: compare p. 40, ap. Geogr. Minor. vol. i, ed. Hudson). Pytheas described the neighborhood of Thulê as a sort of chaos—a medley of earth, sea, and air, in which you could neither walk nor sail: οὔτε γῆ καθ᾽ αὑτὴν ὕπηρχεν ἔτι οὔτε θάλασσα οὔτε ἀὴρ, ἀλλὰ σύγκριμά τι ἐκ τούτων πλεύμονι θαλασσίῳ ἐοικὸς, ἐν ᾧ φησὶ τὴν γῆν καὶ τὴν θάλασσαν αἰωρεῖσθαι καὶ τὰ σύμπαντα, καὶ τοῦτον ὡς ἂν δεσμὸν εἶναι τῶν ὅλων, μήτε πορευτὸν μήτε πλωτὸν ὑπάρχοντα· τὸ μὲν οὖν τῷ πλεύμονι ἐοικὸς αὐτὸς (Pytheas) ἑωρακέναι, τἄλλα δὲ λέγειν ἐξ ἀκοῆς. (Strabo, ii, p. 104). Again, the priests of Memphis told Herodotus that their conquering hero Sesostris had equipped a fleet in the Arabian gulf, and made a voyage into the Erythræan sea, subjugating people everywhere, “until he came to a sea no longer navigable from shallows,”—οὐκέτι πλωτὴν ὑπὸ βραχέων (Herod. ii, 109). Plato represents the sea without the Pillars of Hêraklês as impenetrable and unfit for navigation, in consequence of the large admixture of earth, mud, or vegetable covering, which had arisen in it from the disruption of the great island or continent Atlantis (Timæus, p. 25; and Kritias, p. 108); which passages are well illustrated by the Scholiast, who seems to have read geographical descriptions of the character of this outer sea: τοῦτο καὶ οἱ τοὺς ἐκείνῃ τόπους ἱστοροῦντες λέγουσιν, ὡς πάντα τεναγώδη τὸν ἐκεῖ εἶναι χῶρον· τέναγος δὲ ἐστὶν ἰλύς τις, ἐπιπολάζοντος ὕδατος οὐ πολλοῦ, καὶ βοτάνης ἐπιφαινομένης τούτῳ. See also Plutarch’s fancy of the dense, earthy, and viscous Kronian sea (some days to the westward of Britain), in which a ship could with difficulty advance, and only by means of severe pulling with the oars (Plutarch, De Facie in Orbe Lunæ, c. 26, p. 941). So again in the two geographical productions in verse by Rufus Festus Avienus (Hudson, Geogr. Minor. vol. iv, Descriptio Orbis Terræ, v, 57, and Ora Maritima, v, 406-415): in the first of these two, the density of the water of the western ocean is