Previous to that the object was always either military conquest or the extension of trade. [Illustration: SHIP OF PTOLEMY PHILOPATOR. (About 240 B. C. Banks of oars and lug-sails.)] Attention was now turned to the eastern seas, overland routes to India and even to China having become well known both to conquering armies and to mercantile caravans. The coasts of Abyssinia, of Arabia, of the Persian Gulf, and of western India were settled by a semi-civilized people for a thousand, perhaps two thousand, years before the Christian era; but they were broken into many independent tribes; and their ships, if they had any, only crept from one harbor to another near by, and neither knew nor cared what lay beyond the farther headlands. As time went on, however, and strong kingdoms arose in Egypt, Arabia, Syria, and Persia, consolidating these scattered tribes into nations, it became necessary to learn the sea-routes between more distant ports. Thus it came about that while the Pharaohs still flourished, Arabic commerce extended regularly along the coast of Abyssinia, and doubtless as far southward as Zanzibar, while the Malays had probably already reached and colonized Madagascar. There seems no reason to doubt that those remarkable ruins in stone which the late Mr. Thomas Bent has studied at and near Zimbabwe, in Mashonaland, East Africa, are the work of Arabian gold-miners, made perhaps a thousand or more years ago; and it is pretty certain that Arabic seamen even at that date regularly traded as far as the island of Madagascar. The Persian Gulf has been another nursery of a seafaring people since long before the record of history begins; yet so slow were they to learn of anything outside their capes, that it was accounted a wonderful thing when, in the winter of 325-4 B. C., Nearchus, the admiral of the fleet of Alexander the Great, voyaged from the mouth of the Indus to the head of the Persian Gulf. Soon afterward, however, under the house of the Ptolemies, rulers of Egypt, fleets sailed regularly between Red Sea ports and India and Ceylon. But now for many long centuries the boundaries of the known world were not to be much enlarged (although methods of navigation were improved and commerce continued within the limits of Roman and Arabic dominion), for we know of the discovery of no new coasts until we begin to hear of the doings of an independent and far northern people, scarcely known to the civilized world, and certainly not regarded as a part of it.