This beloved country was thought to lie on the center of the earth, which was marked by the oracle of Apollo, at Delphi. In those days, the earth was supposed to hang like a disk in the great hollow globe of the world, its land divided into two parts by the Mediterranean Sea and its edges washed by the turbulent river of the ocean. The upper part of this globe was illuminated by the sun, moon and stars and was called Heaven, but the lower part extended below the earth-disk and formed a terrifying pit of utter darkness. The Milky Way was a road which led to the home of the gods, but this pit was a place of dire punishment. One of the many duties of the gods was to see that the earth was properly lighted by the sun and the moon, and that the stars were "penned in" at dawn and "unpenned" nightly. The sun, moon and stars rose and sank in the stream of the ocean, but the sun, instead of being submerged, was carried around the stream from west to east in a winged cup or golden boat made by the god Vulcan. [Figure 05] It was at first thought that Vulcan, with a mighty heave, threw the hot sun-ball over the Caucasus mountains in the east to the Atlantic ocean in the west, and then hastily paddled around the world stream to catch it as it fell, but later it was believed that Apollo, the Sun-god, drove it across the sky in a chariot, the return journey to the country of the sunrise being accomplished by placing both chariot and sun in Vulcan's remarkable boat. Centuries later (about 336 B. C.) Eudoxus evolved the theory of the concentric crystalline spheres which brought the tracks of the heavenly bodies under and above the motionless disk of the earth with the stars rolling round in long-drawn notes of celestial sweetness audible only to the gods.