The Greeks possessed ships of war and merchant-vessels. That a war-galley was of large size may be inferred from the fact that she carried two hundred seamen, besides on some occasions thirty Epibatoe-- literally, marines, trained to fight at sea. These war-vessels moved with wonderful rapidity, darting here and there with the speed of a modern steam-vessel. The ordinary war-ships were triremes, or had three banks of oars. The merchant-vessels or transports were much more bulky, had round bottoms, and although rowers were employed on board, yet they were propelled chiefly by their sails. After the time of Alexander, vessels with four, five, and even more ranks of rowers became general, and ships are described with twelve and even thirty ranks of rowers and upwards--but they were found of no practical use, as the crew on the upper benches were unable to throw sufficient power into the immensely long oars which it was necessary to employ. Fully B.C. 500, the Carthaginians invented the quadremes, and about B.C. 400, Dionysius, first tyrant of Syracuse, whose ambition was to create a powerful navy, built numerous vessels of the same description, unused till that time by the Greeks. The rowers in these ships, with numerous banks of oars, could not have sat directly one above another, as some suppose; but the feet of those on the upper tier must have rested on the bench or thwart on which those immediately below them sat. Thus the tiers of oars were probably not more than two feet, if so much, one above another; and supposing the lowest tier was two feet above the water, the highest in the quadremes could not have been more than ten feet, and even then the length of the oar of the upper tier must have been very great, and it must have required considerable exertion on the part of the rower to move it. The most interesting part, however, of an ancient ship to us at the present day was the beak or rostra. At first these beaks were placed only above water, and were formed in the shape of a short thick-bladed sword, with sharp points, generally three, one above another, and inclining slightly upwards, so that they might rip open the planks of the vessels against which they ran. They were sometimes formed in the shape of a ram's head fixed to the end of a beam; and hence in modern days we have adopted the name of rams, which we give to ships of war built on the same principle.