There was a strong fortress situated at the head of the pier or mole leading to the island of Pharos, which was without Cæsar'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 Cæsar, 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. In the harbor, too, which, as will be seen from the engraving, was on the south side of the mole, and, consequently, on the side opposite to that from which Achillas was advancing toward the city, there were lying a large number of Egyptian vessels, some dismantled, and others manned and armed more or less effectively. These vessels had not yet come into Achillas's hands, but it would be certain that he would take possession of them as soon as he should gain admittance to those parts of the city which Cæsar had abandoned. This it was extremely important to prevent; for, if Achillas held this fleet, especially if he continued to command the island of Pharos, he would be perfect master of all the approaches to the city on the side of the sea. He could then not only receive re-enforcements and supplies himself from that quarter, but he could also effectually cut off the Roman army from all possibility of receiving any. It became, therefore, as Cæsar thought, imperiously necessary that he should protect himself from this danger. This he did by sending out an expedition to burn all the shipping in the harbor, and, at the same time, to take possession of a certain fort upon the island of Pharos which commanded the entrance to the port. This undertaking was abundantly successful. The troops burned the shipping, took the fort, expelled the Egyptian soldiers from it, and put a Roman garrison into it instead, and then returned in safety within Cæsar's lines. Cleopatra witnessed these exploits from her palace windows with feelings of the highest admiration for the energy and valor which her Roman protectors displayed.