When different tribes were desirous of exchanging with each other the commodities their countries respectively produced, their first consideration would naturally be the means of transport; and though we may not be able to fix the period when it commenced, the interchange of goods by barter must have been nearly coexistent with the existence of man himself. In the most ancient times the chief commercial routes were undoubtedly overland; but it may safely be assumed that at a scarcely less early period trading vessels had begun to creep along the shores of the Red Sea, Persian Gulf, and Mediterranean, and to pass from island to island amid the land-locked waters of the Levant. [Sidenote: Coasting.] There can, indeed, be no doubt that, till a period comparatively recent, the characteristic of all early navigation was that of a coasting trade, the mariners seldom quitting the land except when constrained to do so by some unavoidable necessity, such as the violence of a gale or the force of currents, or when a great saving of distance could be effected by crossing the mouths of deep bays where the headlands were at a moderate distance from each other. But a coasting navigation is really subject to greater difficulties and dangers than any other, and hence has in all times had the property of forming the most expert seamen. Thus it was that the seamen of Tyre found their way to Carthage, and ultimately through the pillars of Hercules to Gades and the tin-bearing islands of the West: and thus, too, the States of Tyre and of her great colony, Carthage, for centuries maintained their power and lofty position in the midst of nations in other respects greatly their superiors. By the prosecution, too, of coasting voyages the Portuguese, in later ages, passed the Cape of Good Hope, and reached the East Indies. Indeed nothing was more likely to advance discovery than voyages of such a character, for which the position of the three continents of the ancient world afforded considerable natural facilities, especially when taken in connection with the two long narrow seas known as the Red Sea and the Persian Gulf. Again, the Mediterranean, with its subordinate portions, comprising the Adriatic and the Levant, with the Black Sea and the Sea of Azov, was peculiarly adapted for the commencement of an over-sea trade with a shipping still rude and with sailors little skilled; while its position in the centre, as it were, of these three continents, surrounded by the most fruitful and civilized regions of the then known world, prepared it, naturally, to be the principal scene of such an intercourse.