According to the common Greek idea it was the countries of the Mediterranean and of the East that formed the disc of the earth, or "œcumene" (the habitable world). Around this disc, according to the Homeric songs (the Iliad was put into writing about 900 B.C.), flowed the all-embracing river "Oceanus," the end of the earth and the limit of heaven. This deep, tireless, quietly flowing river, whose stream turned back upon itself, was the origin and the end of all things; it was not only the father of the Oceanides and of the rivers, but also the source whence came gods and men. Nothing definite is said of this river's farther boundary; perhaps unknown lands belonging to another world whereon the sky rested were there; in any case we meet later, as in Hesiod, with ideas of lands beyond the Ocean, the Hesperides, Erythea, and the Isles of the Blest, which were probably derived from Phœnician tales. Originally conceived as a deep-flowing river, Oceanus became later the all-embracing empty ocean, which was different from the known sea (the Mediterranean) with its known coasts, even though connected with it. Herodotus (484-424 B.C.) is perhaps the first who used the name in this sense; he definitely rejects the idea of Oceanus as a river and denies that the "œcumene" should be drawn round, as though with a pair of compasses, as the Ionian geographers (Hecatæus, for example) thought. He considered it proved that the earth's disc on the western side, and probably also on the south, was surrounded by the ocean, but said that no one could know whether this was also the case on the north and north-east. In opposition to Hecatæus[1] and the Ionian geographers (the school of Miletus) he asserted that the Caspian Sea was not a bay of the northern Oceanus, but an independent inland sea. Thus the "œcumene" became extended into the unknown on the north-east. He mentions several peoples as dwelling farthest north; but to the north of them were desert regions and inaccessible mountains; how far they reached he does not say.
[Illustration: The world according to the ideas of Herodotus (J. MURRAY)]
He thus left the question undetermined, because, with the sound cool-headedness of the inquirer, which made him in a sense the founder of physical geography, he trusted to certain observations rather than to uncertain speculations; and therefore he maintained that the geographers of the Ionian school had not provided adequate proofs that the world was really surrounded by sea on all sides. But nevertheless, it was, perhaps, his final opinion that the earth's disc swam like an island in Oceanus.