Roman ships that voyaged to Britain probably gave to the wild men of the North—including those who later became the Vikings—the idea of the sail, and probably all the people of northern Europe learned the use of sails, directly or indirectly, from the Romans. Ultimately Rome fell beneath the onslaughts of the Barbarians, and the Mediterranean seat of power (although still called the Roman Empire) moved to Byzantium, now called Constantinople. Here Western civilization resisted for centuries the attacks of the Mohammedans, until the great city on the Bosphorus fell before the armies of Mohammed in 1453. [Illustration: A PHŒNICIAN BIREME _Despite the fact that the Phœnicians did more with ships than any other ancient peoples before the Greeks and Romans, little is known of Phœnician ships. They developed the bireme, an oar- and sail-driven ship with two “banks” of oars, and circumnavigated Africa._ ] During all of the centuries that Constantinople had been holding out against the growing power of the Mohammedans, the west and north of Europe were being remade. For a time Western civilization seemed doomed, for the Moorish Empire in North Africa had pushed across the Strait of Gibraltar, had subjugated Spain, and had crossed the Pyrenees into France, where, fortunately, their great army was put to rout at the battle of Tours in 732. But although they were driven from France they maintained their hold upon Spain, and not until the Granada Moors were defeated by Ferdinand and Isabella in 1492 was Spain again free of them. They controlled North Africa from Suez to Gibraltar and introduced many Eastern ideas. It is probable that the lateen sail, which originated in Egypt and is still in common use in the Mediterranean, owes at least some credit to the Moors for its introduction to western Europe. In addition to the influx of Mohammedans, civilized Europe had to contend with the hordes of barbarians that descended from the wild country to the north of the Alps, for the most of Europe except its Mediterranean fringe was a dark and barbarous land. But the centuries that we call the Middle Ages saw a growth of culture, a growth of learning, a growth of nationalism that were to make the modern world. In all of this ships played a vital part. The Vikings, with their open boats, propelled by oars and sometimes aided by great square sails, terrorized Britain and northern Europe for a time, even driving their boats up the Seine to the walls of the city of Paris, which was then built on a tiny island in the river. But at last the Saxons, under Alfred the Great, with the first ships of the long series of ships that were built to protect England, drove the wild sailor warriors away, and a new epoch had begun. During this time Venice and Genoa had developed, and the ships that sailed from those two cities were for a time the proudest of the world.