Amongst the earliest fields in which the energy and enterprise of the Irish monastic missionaries found an outlet were naturally the adjoining lands of Kintyre and the islands on the West Coast of Scotland. From the beginning of the sixth century an emigration had been going on from Dalriada, in Ulster, to these regions, and settlements had been formed and a large part of the country taken possession of, extending as far north as Mull, and including part of the mainland of Argyll. In 560, however, Brude, King of the Northern Picts, led an expedition against the invaders, and drove them back from most of their possessions. A desire to retrieve this reverse, combined with zeal to spread the benefits of religion amongst the heathen Picts, is supposed to have led to St. Columba’s mission, and to the foundation of the Monastic Church in Scotland. In 563 St. Columba, with twelve disciples, sailed from Ireland for Dalriada, in Scotland. After visiting some of the islands and founding a cave-chapel at Loch Coalisport, which is still traceable, he finally, with consent of the Picts, settled at Iona. There he found a remnant of an early Church of Secular Bishops, but they yielded to the stronger monastic element now prevailing.[24] The monastery founded by Columba at Iona was of the ordinary style of the Irish establishments above described. Adamnan, in his _Life of Columba_, mentions that the buildings were constructed with wattles and turf, and the roofs covered with thatch. Besides the church and the huts for the brethren, there was a special cell for the abbot, a larger hut for a refectory, and another for strangers. The whole was enclosed, as usual, with a high wall or rampart. About a century after Columba’s time some improvement seems to have been made on the rude system of building with wattles. Adamnan, who lived about that date, describes how, in renewing the structures of the monastery, oak boards were used, and the roof was covered with thatch. The Church established in Iona followed the example of its Irish founders, and sent out missionaries in all directions. In 565 St. Columba visited King Brude in his stronghold on the river Ness, and succeeded in converting the king and the Northern Picts. This mission seems to have been partly political, as it was also successful in establishing the Irish colony of Dalriada in possession of its territory under its own king.[25] During the sixth century numerous churches were founded throughout Scotland and in the Western Islands by St. Columba and his companions, St. Brendan, St. Comgall, and St. Cainnech,[26] whose names still survive in the dedications of many of these structures.