The earliest writer of British race to throw any light on the Islands is Adamnan, who mentions that in the sixth century Cormac, a cleric of Iona, with certain companions, visited the Orkneys, and adds that the contemporary Pictish ruler of the Islands was a hostage in the hands of Brude Mac Meilcon, King of the Northern Picts. Whatever degree of power this Pictish king may have exercised over the Islands, we learn from the _Annals of Ulster_ that in the year 580 they were invaded by Aidan, King of the Dalriadic Scots, and as the next mention of the Orkneys in the native chronicles is the record of their devastation by the Pictish King Brude Mac Bile in the year 682, it is perhaps a fair inference that Dalriadic influence had predominated there during the intervening century. That the Islands were christianised about this period by clerics of the Columban or Irish Church, is a point too firmly established by archaeological, topographical, and other data to require any insistence on here. Many pre-Norse church dedications to St Columba, St Ninian, and other Celtic saints, tell their own story. Little is known of the state of the Islands during two centuries preceding the date of the Norse settlement _c._ 872 A.D., but from that era until the year 1222 Orkney possesses in the _Orkneyinga Saga_ a record of the highest value. The _Saga_ states that the Islands were settled by the Norsemen in the days of Harald the Fair-haired (Harfagri), but had previously been a base for Vikings. Harald Harfagri had about the year 870 made himself sole King of Norway, and in so doing had incurred the odium of a large section of the Odallers, or landowners, many of whom in consequence emigrated to Iceland, Shetland, Orkney, the Hebrides, and the coasts of Ireland. The settlers in Orkney, Shetland, and the Western Islands took to piracy, and so inflicted the coasts of old Norway, that in 872 Harald followed up the fugitives, conquered all the islands of the Scottish seas, and placed his partisan Rognvald, Earl of Moeri, as hereditary Jarl over Orkney and Shetland. This nobleman, however, preferring to live in Norway, gifted his western jarldom to his brother Sigurd, who is commonly considered the first, as he proved one of the greatest, of the long line of Orcadian Jarls. Sigurd speedily spread his power over northern Scotland as far south as Moray, and from his time until the close of the thirteenth century the Orkney Jarls had the controlling hand in Caithness, Sutherland, and Easter Ross. Jarl Sigurd died in 875, and was ultimately succeeded by the scarcely less strenuous Torf-Einar, a son of Jarl Rognvald, and a half-brother of Hrolf (Rollo), the conqueror of Normandy. Einar got his _sobriquet_ of “Torf” from the fact of his having learned in Scotland, and taught the islanders, the practice of cutting turf for fuel. He was succeeded by three sons, of whom the two elder, Arnkell and Erlend, fell in the battle of Stanesmoor in England, in 950.