While their vessels were moored here, the phenomenon of the ebb and flow of the tide in the great sea occurred, so that their ships were left upon dry ground. This caused Alexander and his companions no small alarm, inasmuch as they were previously quite unacquainted with it. But they were much more alarmed when, the time coming round again, the water approached and the hulls of the vessels were raised aloft.[776] The ships which it caught settled in the mud were raised aloft without any damage, and floated again without receiving any injury; but those that had been left on the drier land and had not a firm settlement, when an immense compact wave advanced, either fell foul of each other or were dashed against the land and thus shattered to pieces. When Alexander had repaired these vessels as well as his circumstances permitted, he sent some men on in advance down the river in two boats to explore the island at which the natives said he must moor his vessels in his voyage to the sea. They told him that the name of the island was Cilluta.[777] As he was informed that there were harbours in this island, that it was a large one and had plenty of water in it, he made the rest of his fleet put in there; but he himself with the best sailing ships advanced beyond, to see if the mouth of the river afforded an easy voyage out into the open sea. After advancing about 200 stades from the first island, they descried another which was quite out in the sea. Then indeed they returned to the island in the river; and having moored his vessels near the extremity of it, Alexander offered sacrifice to those gods to whom he said he had been directed by Ammon to sacrifice. On the following day he sailed down to the other island which was in the deep sea; and having come to shore here also, he offered other sacrifices to other gods and in another manner. These sacrifices he also offered according to the oracular instructions of Ammon. Then having gone beyond the mouths of the river Indus, he sailed out into the open sea, as he said, to discover if any land lay anywhere near in the sea; but in my opinion, chiefly that he might be able to say that he had navigated the great outer sea of India. There he sacrificed some bulls to Poseidon and cast them into the sea; and having poured out a libation after the sacrifice, he threw the goblet and bowls, which were golden, into the deep as thank-offerings, praying the god to escort safely for him the fleet, which he intended to despatch to the Persian Gulf and the mouths of the Euphrates and Tigres.[778] CHAPTER XX. EXPLORATION OF THE MOUTHS OF THE INDUS.