The first measure to be adopted was, as Caesar plainly perceived, to concentrate and strengthen his position in the city, so that he might be able to defend himself there against Achillas until he should receive re-enforcements from abroad. For this purpose he selected a certain group of palaces and citadels which lay together near the head of the long pier or cause way which led to the Pharos, and, withdrawing his troops from all other parts of the city, established them there. The quarter which he thus occupied contained the great city arsenals and public granaries. Caesar brought together all the arms and munitions of war which he could find in other parts of the city, and also all the corn and other provisions which were contained either in the public depôts or in private warehouses, and stored the whole within his lines. He then inclosed the whole quarter with strong defenses. The avenues leading to it were barricaded with walls of stone. Houses in the vicinity, which might have afforded shelter to an enemy, were demolished and the materials used in constructing walls wherever they were needed, or in strengthening the barricades. Prodigious military engines, made to throw heavy stones, and beams of wood, and other ponderous missiles, were set up within his lines, and openings were made in the walls and other defenses of the citadel, wherever necessary, to facilitate the action of these machines. There was a strong fortress situated at the head of the pier or mole leading to the island of Pharos, which was without Caesar's lines, and still in the hands of the Egyptian authorities. The Egyptians thus commanded the entrance to the mole. The island itself, also, with the fortress at the other end of the pier, was still in the possession of the Egyptian authorities, who seemed disposed to hold it for Achillas. The mole was very long, as the island was nearly a mile from the shore. There was quite a little town upon the island itself, besides the fortress or castle built there to defend the place. The garrison of this castle was strong, and the inhabitants of the town, too, constituted a somewhat formidable population, as they consisted of fishermen, sailors, wreckers, and such other desperate characters, as usually congregate about such a spot. Cleopatra and Caesar, from the windows of their palace within the city, looked out upon this island, with the tall light house rising in the center of it and the castle at its base, and upon the long and narrow isthmus connecting it with the main land, and concluded that it was very essential that they should get possession of the post, commanding, as it did, the entrance to the harbor.