The enterprise of the sea-rovers and the merchant settlers created on Irish shores two Scandinavian "kingdoms"--kingdoms rather of the sea than of the land. The Norsemen set up their moot on the Mound over the river Liffey (near where the Irish Parliament House rose in later days), and there created a naval power which reached along the coast from Waterford to Dundalk. The Dublin kingdom was closely connected with the Danish kingdom of Northumbria, which had its capital at York, and formed the common meeting-ground, the link which united the Northmen of Scandinavia and the Northmen of Ireland. A mighty confederation grew up. Members of the same house were kings in Dublin, in Man, and in York. The Irish Channel swarmed with their fleets. The sea was the common highway which linked the powers together, and the sea was held by fleets of swift long-ships with from ninety to a hundred and fifty rowers or fighting men on board. Dublin, the rallying-point of roving marauders, became the centre of a wide-flung war. Its harbour, looking east, was the mart of the merchant princes of the Baltic trade: there men of Iceland and of Norway landed with their merchandise or their plunder. "Limerick of the swift ships," "Limerick of the riveted stones," the kingdom lying on the Atlantic was a rival even to Dublin; kings of the same house ruled in Limerick and the Hebrides, and their fleets took the way of the wide ocean; while Norse settlements scattered over Limerick, Kerry and Tipperary, organised as Irish clans and giving an Irish form to their names, maintained the inland trade. Other Munster harbours were held, some by the Danes, some by the Irish. The Irish were on good terms with the traders. They learned to build the new ships invented by the Scandinavians where both oars and sails were used, and traded in their own ports for treasures from oversea, silken raiment and abundance of wine. We read in 900 of Irishmen along the Cork shores "high in beauty, whose resolve is quiet prosperity," and in 950 of "Munster of the great riches," "Munster of the swift ships."