During the first century B.C. two new types of warships appeared in the bireme and the liburnian. The latter was really a lightly built trireme, and originally was a swift lembos with a ram attached. The Romans built liburnians also as biremes, which they employed for scouting and fighting. The name was derived from the Liburnians of Dalmatia, from whom the shape of the hull was borrowed; but later on the expression came to denote simply a ship of war. Just before the dawn of the Christian era the Romans began to build those bigger and stouter ships, mounting heavy catapults, which were probably not very different from the tall ships which the Crusaders had to contend with some hundreds of years later. [Illustration: SKETCHES OF ANCIENT SHIPS. By RICHARD COOK, R.A., from Montfarreon’s “Antiquities,” showing Roman Warship under sail; the lower sketches well illustrate species of stems and sterns.] Before the close of the second century A.D. there were afloat not only the Italian fleets, but also those of the Roman provinces. There was the Egyptian fleet based on Alexandria, the Syrian fleet, the Libyan fleet, the Euxine fleet, besides two fleets on the Danube and the Rhine. Furthermore, there must not be omitted the Romano-British fleet--the Classis Britannica--which was based on Boulogne (Gesoriacum), with stations at Dover, Lympne, and Gloucester. This dated from the invasion by Claudius and assisted Agricola in his Scottish expedition in A.D. 83. It circumnavigated Britain, discovered for the Romans the Orkneys, and saw the long line of the outer Hebrides. The classiarii also on shore helped to build Hadrian’s wall. But as to the exact nature of such ships we shall speak in greater detail presently. Each of the fleets just mentioned was commanded by a præfectus and had also a sub-præfectus. The Egyptian fleet-præfect was sometimes also præfect of the Nile revenue boats. Each ship was commanded by a trierarch, the classiarii being organised as a century under a centurio-classicus, or fleet-centurion. Thus whenever the men had to be put on shore for duty their organisation went with them. The term of service for the classiarii was twenty-five or twenty-six years. The Roman fleets illustrated at an early date in the world’s history what every nation has since been compelled to realise: that a standing navy cannot be dispensed with among the essential attributes of peace and self-defence. Rome’s fleets kept off Carthage and Philip and enabled Rome to be mistress of the sea route between Hannibal and Spain; and, as is usually the case, the decadence of the Government was promptly followed by the decadence of the fleet. [Illustration: TWO COINS DEPICTING “NAUMACHIÆ.” (From Scheffer’s “De Militia Navali.”)]