The facility with which the Liburnians handled the two-banked ships in their Adriatic campaign induced the Romans to adopt these vessels as models for their own two-banked ships, and in course of time they adopted the name of _liburna_ for all war-vessels of from one to five banks. If some of the historians may be believed, anything that could be piled upon the ancient ship and did not capsize it was permissible. One is said to have had a tower at the stern and another at the prow. Another bore “a large tower of masonry with a great gate. Here appear some vases, probably filled with combustibles.” Another _libernus_ has a mast or yard, suspended perpendicularly by the side of the forward tower, and having at each end a crossbeam. Yet another _libernus_, besides carrying a protector for the helm at the stern, is said to have had six round towers; the largest, of embattled masonry, was at the prow, two others, also of masonry, surmounted by domes, and connected by a bridge, were near the stern, and the other three were nearer the fore part of the ship, were roofed, and two of them had windows. Shipping in the Mediterranean extended with extraordinary rapidity in the recovery after the stagnation caused by the fall of the Roman Empire and the relapse into semi-barbarism which followed the successful invasion of Italy by the wild tribesmen of the North. The advent and rise of the Moslem power caused a series of struggles in which every state was in a more or less constant condition of warfare against its neighbour, and the Crusades served but to add fuel to the fire of internecine and religious conflict. Some immense ships are stated to have been employed up to and at the fall of Constantinople. The early centuries of the Christian era saw the evolution of a flat, shallow vessel, fitted with one or two masts carrying sails, from which the lateen rig developed, equipped with a long ram above the water line, with two or at most three banks of oars. It appears from illustrations that some of these boats carried a superstructure extending beyond the beam on either side. War vessels of this type became common throughout the length and breadth of the Mediterranean, and remained in use long after the introduction of firearms.