Besides opening out this world-wide trade, the Scandinavians made a revolution also in the manner of trading. Up to this time buying and selling had been carried on by travelling dealers, Syrian and Italian. Now however Norsemen and Danes, who had no towns in their own lands, planted themselves in their new countries in fortified cities; and, for example, showed their enterprise by forming in the Five Danish Burghs in England the earliest federation of towns known outside Italy. In the new towns a settled class of merchants was established, who learned to group themselves according to the English system of guilds. The Scandinavians learned also to strike coins after the manner of the Frisians. In all these ways, by their new ships, their new trade routes, their money, their guilds, and their settled merchants in towns, the Scandinavians won a pre-eminence on the sea, which they were to hold in their own hands for some two hundred years. What was the effect in Ireland of this new peril, an attack on Europe from the sea? In the first place the highways of the sea, never before closed, were barred by the Scandinavian free-booters. A few Irish travellers (even from Leinster) did even in 800 and 850 take the old accustomed journey to the Loire and so across France to Germany; but the passage was now dangerous. The terrors of the sea journey drove travellers to the land route, and the way across England to the Continent became so important that clerics of the tenth century could not imagine that any other way had ever been possible. The new sea-kings, moreover, were not the people to forget the ancient and profitable trade routes of the wine commerce, or the Irish harbours into which trading ships from north and south had sailed for the last two thousand years, or the gold that had been dug from Irish mines in old days. They seized every harbour, sent their boats up every creek and river, plundered the monasteries and wealthy houses, broke into every burial mound for treasure, and put a poll-tax on the men. Scholars and Christian monks fled from the heathen barbarians, carrying to Europe their treasures and manuscripts. The time of mere destruction, however, was not long. The Scandinavians were practical men of affairs, and Norsemen and Danes had settled in Ireland for business. The “Great Island,” as they called it, was a natural centre of their new world-wide commerce; lying within the trade circle formed by the ships that swept from the Orkneys and Hebrides round the Atlantic coast to the Loire and the Garonne, or that traversed the Irish Sea from Cantyre to Devonshire and Brittany. It was the shelter of voyaging ships, the recruiting ground of raiders, the winter-quarters of fleets; its commerce fell in naturally with the traffic of the western world. Danes and Irish were presently to the full as busy in trading as in fighting. Ireland became a commercial centre, a meeting place of the peoples. There came Grett with the