To take one example, Harold Fairhair, in bringing the whole of Norway under his sway effected quite a revolution, changing the old ödal tenure by which the land was held into a feudal one. Rather than submit to the new order many nobles and people simultaneously sought freedom elsewhere. They settled in Shetland, Orkney, and the Hebrides, occasionally raiding back to harass the king. But by the year 872 the latter had so far established his rule at home that he was free to tackle these islands with their Norwegian rebels and annex the territory to Norway. Whereupon the more daring and independent spirits who had settled there and in Ireland, and had contracted alliances in marriage with leading native families, once more hived off, this time sailing away for Iceland to join friends and relations who had migrated thither from the mother country. And these were the nucleus of the colony whose descendants produced the wonderful Icelandic literature which is now reckoned among the most valuable assets of medieval Europe. Among the settlers were men who bore Gaelic names and left their impress upon this Norse heritage. From the parchments lately discovered upon which the history of the Vikings is written, and which are begrimed by the smoke of the Icelandic cabin and worn by the centuries that have passed over them, we learn many things that tend to show the Northmen in a new light. These men, who held undisputed sway of the seas for more than nine centuries, were not by any means barbarians. They had a civilisation rivalling that of the Gael, though of a different warp and woof, and they were not even without a script or mode of writing. The characters they used are known as runes, and may have been in use as early as the second or third century. In the sagas we are often told that drawings on shields and embroidery on cloth were made by them to preserve the memory of heroic deeds and important events. And though the set who invaded our shores, in the stress of war and sailing were not likely to trouble much with learning or letters, their nation had doubtless retired _literati_ just like our own. To trace the effect of these Norse invasions on Celtic literature will now be our main endeavour.