and inlets, and follow the course of rivers far above their mouth. The greater ships might reach the length of seventy-five feet and carry as many as one hundred and twenty men, but these were the largest, and even these offered but a slow means of migration. We must think of the whole movement at first as one of small and scattered bands, terrible more for their fierce, sudden, and skilful methods of attack, than for force of superior numbers or organization. The truth is that sea-power, whose strategic significance in modern warfare Admiral Mahan did so much to make us appreciate, was in the ninth and tenth centuries, so far as western Europe was concerned, a Scandinavian monopoly. Masters of the seas, the Northmen harried the coasts and river-valleys as they would, and there was none to drive them back. Outside of the Baltic, where the Danes ravaged the southern coast and the Swedes moved eastward to lay the foundations of the Russian state and to penetrate as far as Constantinople, two main routes lay open to the masters of the northern seas. One led west to the Orkneys, the Shetlands, and the coast of Scotland, and then either south to the shores of Ireland, or further west to Iceland, Greenland, and America. The other led through the North Sea to England, the Low Countries, and the coast of Gaul. Both were used, and used freely, by the Vikings, and in both directions they accomplished enduring results:--Iceland and the kingdoms of the isles in the north, the beginnings of town life and commerce in Ireland, the Danelaw in England, and the duchy of Normandy. When the great northern invasions began at the close of the eighth century, Charles the Great ruled all the Christian lands of the western Continent. By fire and sword he converted the heathen Saxons of the north to Christianity and civilization and advanced his frontier to the Danish border, so that the pious monk of St. Gall laments that he did not conquer the Danes also--“be it that Divine Providence was not then on our side, or that our sins rose up against us.” And this same gossiping chronicler--not the best of authorities it is true--has left us a striking picture of Charlemagne’s first experience with the Scandinavian invaders:--