Some of the epithets which Homer applies to the heaven, seem to imply that he considered it as a solid vault of metal. But it is not necessary to construe these epithets so literally, nor to draw any such inference from his description of Atlas, who “holds the lofty pillars which keep earth and heaven asunder.” Yet it would seem, from the manner in which the height of heaven is compared with the depth of Tartarus, that the region of light was thought to have certain bounds. The summit of the Thessalian Olympus was regarded as the highest point on the earth, and it is not always carefully distinguished from the aerian regions above. The idea of a seat of the gods,--perhaps derived from a more ancient tradition, in which it was not attached to any geographical site,--seems to be indistinctly blended in the poet’s mind with that of a real mountain. Hence Hephæstus, when hurled from the threshold of Jupiter’s palace, falls “from morn to noon, from noon to dewy eve,” before he drops on Lemnos; and Jupiter speaks of suspending the earth by a chain from the top of Olympus. NAVIGATION AND ASTRONOMY A wider compass of geographical knowledge, and more enlarged views of nature, would scarcely have been consistent with the state of navigation and commerce which the Homeric poems represent. The poet expresses the common feelings of an age when the voyages of the Greeks were mostly confined to the Ægean. The vessels of the heroes, and probably of the poet’s contemporaries, were slender half-decked boats: according to the calculation of Thucydides, who seems to suspect exaggeration, the largest contained one hundred and twenty men, the greatest number of rowers mentioned in the catalogue: but we find twenty rowers spoken of as a usual complement of a good ship. The mast was movable, and was only hoisted to take advantage of a fair wind, and at the end of a day’s voyage was again deposited in its appropriate receptacle. In the day-time, the Greek mariner commonly followed the windings of the coasts, or shot across from headland to headland, or from isle to isle: at night his vessel was usually put into port, or hauled up on the beach; for though on clear nights he might prosecute his voyage as well as by day, yet should the sky be overcast his course was inevitably lost. Engagements at sea are never mentioned by Homer, though he so frequently alludes to piratical excursions. They were probably of rare occurrence: but as they must sometimes have been inevitable, the galleys were provided with long poles for such occasions. The approach of winter put a stop to all ordinary navigation. Hesiod fixes the time for laying up the merchant ship, covering it with stones, taking out the rigging, and hanging the rudder up by the fire. According to him, the fair season lasts only fifty days: some indeed venture earlier to sea, but a prudent man will not then trust his substance to the waves.