Where he does not know he imagines, and some of his imaginings have had a most important influence upon the progress of geographical knowledge.

Thus he conceives of the world as being a sort of flat shield, with an extremely wide river surrounding it, known as Ocean.

The centre of this shield was at Delphi, which was regarded as the "navel" of the inhabited world.

According to Hesiod, who is but little later than Homer, up in the far north were placed a people known as the _Hyperboreani_, or those who dwelt at the back of the north wind; whilst a corresponding place in the south was taken by the Abyssinians.

All these four conceptions had an important influence upon the views that men had of the world up to times comparatively recent.