That the Norwegians did not so thoroughly colonise the Western Isles and absorb its Gaelic population, as was the case with the Orkney and Shetland Islands, may have arisen from their finding in the former a more dense population, and also that they appear to have used the Sudreys more as a kind of stepping-stone to other settlements, or as temporary strongholds, rather than as places for lasting settlements, and thus their Norwegian population was generally of a more transient and fluctuating character;[22] but this was mainly true of the earlier period of their occupation only, and a more important ground of difference arose from the Gaelic population of the Western Isles more nearly assimilating themselves to the character of the Norwegian sea-robbers. They seem to have submitted easily to their rule, and to have adopted their habits, so that when one of the great Norwegian Vikings, Ketill Flatnose, succeeded in establishing a petty kingdom in the Isles in opposition to the rapidly increasing power of Harald Harfager, the first monarch who acquired the dominion of all Norway, we find the Isles said by the Sagas to be in the possession of Scotch and Irish Vikings, and Ketill appears in the Irish Annals under the name of Caittil Finn as the leader of a people called the Gallgaidheal, a name applied to those Gaidheal who became subject to the Norwegians, and conformed to their mode of life. Harald, however, eventually conquered both the Orkney Islands and the Sudreys or Western Isles. The former came under the rule of a line of Norwegian Jarls, who, by the marriage of one of them with the daughter of ‘Dungadr, Jarl of Katenes,’ that is, of Duncan, the Celtic Mormaer of Caithness, added that province to their dominions; and the Norwegian population seem to have as completely colonised the eastern and level part of Caithness as they did the Orkney Islands.