After instructing Hephaestion to fortify the citadel in Patala, he sent men into the adjacent country, which was waterless, to dig wells and to render the land fit for habitation. Certain of the native barbarians attacked these men, and falling upon them unawares slew some of them; but having lost many of their own men, they fled into the desert. The work was therefore accomplished by those who had been sent out, another army having joined them, which Alexander had despatched to take part in the work, when he heard of the attack of the barbarians. Near Patala the water of the Indus is divided into two large rivers, both of which retain the name of Indus as far as the sea. Here Alexander constructed a harbour and dockyard; and when his works had advanced towards completion he resolved to sail down as far as the mouth of the right branch of the river.[774] He gave Leonnatus the command of 1,000 cavalry and 8,000 heavy and light-armed infantry, and sent him to march through the island of Patala opposite the naval expedition; while he himself took the fastest sailing vessels, having one and a half bank of oars, all the thirty-oared galleys, and some of the boats, and began to sail down the right branch of the river. The Indians of that region had fled, and consequently he could get no pilot for the voyage, and the navigation of the river was very difficult. On the day after the start a storm arose, and the wind blowing right against the stream made the river hollow[775] and shattered the hulls of the vessels violently, so that most of his ships were injured, and some of the thirty-oared galleys were entirely broken up. But they succeeded in running them aground before they quite fell to pieces in the water; and others were therefore constructed. He then sent the quickest of the light-armed troops into the land beyond the river’s bank and captured some Indians, who from this time piloted him down the channel. But when they arrived at the place where the river expands, so that where it was widest it extended 200 stades, a strong wind blew from the outer sea, and the oars could hardly be raised in the swell; they therefore took refuge again in a canal into which his pilots conducted them. CHAPTER XIX. VOYAGE DOWN THE INDUS INTO THE SEA.