Navigation of the Tigres. Alexander now ordered Hephaestion to lead the main body of the infantry as far as the Persian Sea, while he himself, his fleet having sailed up into the land of Susiana, embarked with the shield-bearing guards and the body-guard of infantry; and having also put on board a few of the cavalry Companions, he sailed down the river Eulaeus to the sea.855 When he was near the 380place where the river discharges itself into the deep, he left there most of his ships, including those which were in need of repair, and with those especially adapted for fast sailing he coasted along out of the river Eulaeus through the sea to the mouth of the Tigres. The rest of the ships were conveyed down the Eulaeus as far as the canal which has been cut from the Tigres into the Eulaeus, and by this means they were brought into the Tigres. Of the rivers Euphrates and Tigres which enclose Syria between them, whence also its name is called by the natives Mesopotamia,856 the Tigres flows in a much lower channel than the Euphrates, from which it receives many canals; and after taking up many tributaries and its waters being swelled by them, it falls into the Persian Sea.857 It is a large river and can be crossed on foot nowhere as far as its mouth,858 inasmuch as none of its water is used up by irrigation of the country. For the land through which it flows is more elevated than its water, and it is not drawn off into canals or into another river, but rather receives them into itself. It is nowhere possible to irrigate the land from it. But the Euphrates flow............