The Greeks, like the Hebrews, were ignorant of the real figure of the earth. It is in Homer that we find the first written trace of the widely prevalent idea that the earth is a flat surface begirt on every side by the ocean. This was a natural belief in a region almost insular, like Greece, where the visible horizon and an enveloping sea suggested the idea of a flat circle. Homer took the lead among the poetic geographers of Greece, and his authority gave to the subject a fanciful cast, the traces of which are not yet obliterated. Beneath the earth he placed the fabled regions of Elysium and Tartarus: above the whole rose the grand arch of the heavens, which were supposed to rest on the summits of the highest mountains. The sun, moon, and stars were believed to rise from the waves of the sea, and to sink again beneath them on their return from the skies. Homer's distribution of the land was even more fantastic. Beyond the limits of Greece and the western coasts of Asia Minor his knowledge was uncertain and obscure. He had heard vaguely of Thebes, the mighty capital of Egypt, and in his verse sang of its hundred gates and of the countless hosts it sent forth to battle. The Ethiopians, who lived beyond, were deemed to be the most remote dwellers upon the habitable earth. Towards the centre of Africa were the stupendous ridges of the Atlas Mountains: Homer deified the highest peak, and made it a giant supporting upon his shoulders the outspreading canopy of the heavens. The narrow passage leading from the Mediterranean to the Atlantic, and now known as the Straits of Gibraltar, was believed to have been discovered by Hercules, and the mountains on either side--Gibraltar and Ceuta--were, from him, called the Pillars of Hercules.