The Continent was therefore well known to Ireland when about 800 A.D. a new revolution passed over Europe.
Continental trade, as we have seen, had perished with the Roman Empire. Commerce had fallen to its lowest point. There was scarcely any money, nor in any country, neither England, nor France, nor Germany, a native class of merchants; wandering Jews and Greeks and Syrians, and later Italians, carried on what little buying and selling still survived. On the shores of the North Sea, however, the Frisians had made their town of Duurstede, near the mouth of the Rhine, a centre for traffic carried down the river; and in their stout, flat-bottomed, high-boarded sailing ships traded across the North Sea and the Baltic. Duurstede became for a time the chief port of western Europe. There Charles the Great coined money, and the lines along which the Frisian traders carried their wares may still be traced by the finding of the Duurstede coins. But even in the time of the Emperor Charles came the change which was to sweep away the Frisian traders. This was the rise of the new lords of the sea--the Scandinavians--who were to wrest commerce from Frisians and Gauls, and open a new trade for northern Europe.
The Scandinavians got their training in a hard school. They had a thousand miles of stormy shores to practice seamanship, fishing along their mountain coasts, and sailing against Arctic tempests round the North Cape. They had to build better ships than anyone else, and to sail them better. They invented a new kind of vessel where both oars and sails were used. And in a short time the Frisians were outdone both in seamanship and in trade.
East and west the Scandinavians sailed. As early as the eight century colonies of Swedes were passing by the Baltic and the gulf of Finland to settle on the opposite coast about Novgorod and along the Dnieper--the East way, as they called it. They left Scandinavian names along the rapids of the river as their travellers pushed forward, till in 839 they came in contact with the Greeks, and Swedes who had journeyed by the Dnieper were introduced by the Emperor of the East to the Western Emperor Louis the Pious. Their ships were soon the terror of the Black Sea shores--laden with warriors tall like palm trees, ruddy, fairhaired, who were in turn traders and plunderers, conquerors and slave-dealers. In 865 two hundred of their vessels appeared before Constantinople; in 880 they had reached the Sea of Azof, the Don and the Volga; in 913 they had five hundred ships, each carrying a hundred men, in the Caspian. Novgorod was the mart of their vast eastern commerce. There have been found in Sweden nearly twenty thousand Arabian coins, dating from 698 to 1002 A.D., carried across the Baltic by home-going merchants. Gothland became the general centre of exchange for the Eastway trade, where Danes sailed from their settlements on the Mecklenburg coast and the mouth of the Oder, to buy Russian furs, Greek and Arabian silks, and Indian spices, and here have been discovered thirteen thousand coins of the tenth and eleventh centuries--Byzantine, Arabian, and from central Asia.