Page:The Periplus of the Erythræan Sea.djvu/63



Periplus 053 Ancient Egyptian Ship.png (From a sketch by R. T. Pritchett)

trader, which perpetuates in many ways the shipbuilding ideas of ancient Egypt, probably gives a better idea of our author's ship than any of the Greek or Roman coins or reliefs, which were all of Mediterranean shipping, built for different conditions and purposes.

In the Indian Ocean navigation depended on the trade-winds, and voyages were times so that the ship could run before the wind in either direction, without calling the rudder into much use. This was at the quarter, the steersman plying the tiller from his station high in stern, overlooking the whole vessel.

Hippalus' discovery of the periodicity of the trade-winds, described in §57, carried with it a knowledge of steering the boat somewhat off the wind, to reach a destination farther south than the straight course would make possible. This was done partly by the rudder, but largely by shifting the yard.