The Teutonic invaders stopped at the Irish Sea. At the fall of the Empire, therefore, Ireland did not share in the ruin of its civilisation. And while all continental roads were interrupted, traffic from Irish ports still passed safely to Gaul over the ocean routes. Ireland therefore not only preserved her culture unharmed, but the way lay open for her missionaries to carry back to Europe the knowledge which she had received from it. In that mission we may see the strength and the spirit of the tribal civilisation. Two great leaders of the Irish mission were Columcille in Great Britain and Columbanus in Europe. In all Irish history there is no greater figure than St. Columcille--statesman and patriot, poet, scholar, and saint. After founding thirty-seven monasteries in Ireland, from Derry on the northern coast to Durrow near the Munster border, he crossed the sea in 563 to set up on the bare island of Hii or Iona a group of reed-thatched huts peopled with Irish monks. In that wild debatable land, swept by heathen raids, amid the ruins of Christian settlements, began a work equally astonishing from the religious and the political point of view. The heathen Picts had marched westward to the sea, destroying the Celtic churches. The pagan English had set up in 547 a monarchy in Northumbria and the Lowlands, threatening alike the Picts, the Irish or "Scot" settlements along the coast, and the Celts of Strathclyde. Against this world of war Columcille opposed the idea of a peaceful federation of peoples in the bond of Christian piety. He converted the king of the Picts at Inverness in 565, and spread Irish monasteries from Strathspey to the Dee, and from the Dee to the Tay. On the western shores about Cantyre he restored the Scot settlement from Ireland which was later to give its name to Scotland, and consecrated as king the Irish Aidan, ancestor of the kings of Scotland and England. He established friendship with the Britons of Strathclyde. From his cell at Iona he dominated the new federation of Picts and Britons and Irish on both sides of the sea--the greatest missionary that Ireland ever sent out to proclaim the gathering of peoples in free association through the power of human brotherhood, learning, and religion.