IT is said that a fleet made its way round Africa about 600 B.C. in the time of the Pharaoh Necho. During the Dark Ages, however, the ancients' knowledge of the world had been forgotten. China and India became lands of fable. Travel was very expensive, and few people travelled except for trade, to visit holy places in hope of salvation, or to escape from enemies. In the Middle Ages there was a certain amount of travel by pilgrims and by students seeking knowledge. " Foreigners," even from a few miles away, were generally received as enemies.

Norsemen reached America nine hundred years ago, though nothing came of their voyages. Almost every household was self-contained, but ships carried wine, wool, fine steel, and grindstones across the narrow European seas. A sailing ship was evolved capable of riding out storms and keeping the sea for months-a bluff-bowed, broad-beamed, half-decked, single-masted vessel of fifty or a hundred tons.

Navigation was assisted in the fourteenth century by the introduction from the East of the Chinese compass and later of the astrolabe, which gave the latitude. Small half-decked ships were dangerous craft in which to grope along unknown coasts. Fresh food could not be kept for more than a few days. Salt meat for months on end led to scurvy; it was an even chance that any man condemned to a voyage would die. A host of imaginary and superstitious terrors, fears of devils, whirlpools, sea monsters, pools of flame, and skies of pitchy night, caused exploration when it began to be carried out by crews of sentenced criminals.