Ptolemy I. (son of Lagus) afterwards made himself master of Jerusalem, by entering the town on the Sabbath, under pretence of offering sacrifice (Josephus, Antiq. Jud. xii. 1). Tyre was situated on an islet nearly half a mile from the mainland;[315] the channel between the two being shallow towards the land, but reaching a depth of eighteen feet in the part adjoining the city. The islet was completely surrounded by prodigious walls, the loftiest portion of which, on the side fronting the mainland, reached a height not less than 150 feet, with corresponding solidity and base.[316] Besides these external fortifications, there was a brave and numerous population within, aided by a good stock of arms, machines, ships, provisions, and other things essential to defence. [315] Curtius, iv. 2, 7, 8. The site of Tyre at the present day presents nothing in the least conformable to the description of Alexander’s time. [316] Arrian, ii. 18, 3; ii. 21, 4; ii. 22, 8. It was not without reason, therefore, that the Tyrians, when driven to their last resource, entertained hopes of holding out even against the formidable arm of Alexander; and against Alexander as he then stood, they might have held out successfully; for he had as yet no fleet, and they could defy any attack made simply from land. The question turned upon the Phenician and Cyprian ships, which were for the most part (the Tyrian among them) in the Ægean under the Persian admiral. Alexander—master as he was of Aradus, Byblus, Sidon, and all the Phenician cities except Tyre—calculated that the seamen belonging to these cities would follow their countrymen at home and bring away their ships to join him. He hoped also, as the victorious potentate, to draw to himself the willing adhesion of the Cyprian cities. This could hardly have failed to happen if he had treated the Tyrians with decent consideration; but it was no longer certain, now that he had made them his enemies.