Hannibal saw that there was no time to be lost.  The next morning, at daybreak, the whole of his cavalry were posted to the south to cover the movements of the army and to check the Roman advance.  The infantry were then set in motion up the bank of the river and Hannibal, with a small party, remained behind to watch the passage of the elephants, which had not yet been brought across.

The elephants had not been trained to take to the water, and the operation was an extremely difficult one.  Very strong and massive rafts were joined together until they extended two hundred feet into the river, being kept in their place by cables fastened to trees on the bank above them.  At the end of this floating pier was placed another raft of immense size, capable of carrying four elephants at a time.  A thick covering of earth was laid over the whole, and on this turf was placed.  The elephants were then led forward.

So solid was the construction that they advanced upon it without hesitation.  When four had taken their place on the great raft at the end, the fastenings which secured it to the rest of the structure were cut, and a large number of boats and barges filled with rowers began to tow the raft across the river.  The elephants were seized with terror at finding themselves afoot, but seeing no way of escape remained trembling in the centre of the raft until they reached the other side.  When it was safely across, the raft and towing boats returned, and the operation was repeated until all the elephants were over.

Some of the animals, however, were so terrified that they flung themselves from the rafts into the river and made their way to shore, keeping their probosces above the surface of the water.  The Indians who directed them were, however, all swept away and drowned.  As soon as the elephants were all across Hannibal called in his cavalry, and with them and the elephants followed the army.

The Romans did not arrive at the spot until three days after the Carthaginians had left.  Scipio was greatly astonished when he found that Hannibal had marched north, as he believed that the Alps were impassable for an army, and had reckoned that Hannibal would certainly march down the river and follow the seashore.  Finding that the Carthaginians had left he marched his army down to his ships again, re-embarked them, and sailed for Genoa, intending to oppose Hannibal as he issued from the defiles of the Alps, in the event of his succeeding in making the passage.

Four days’ march up the Rhone brought Hannibal to the point where the Isere runs into that river.  He crossed it, and with his army entered the region called by Polybius “The Island,” although the designation is an incorrect one, for while the Rhone flows along one side of the triangle and the Isere on the other, the base is formed not by a third river, but by a portion of the Alpine chain.