The Roman dominion in Britain came to an end in 410, when the troops were withdrawn from the province and the provincial cities left to protect themselves. Roman Britain thus ceased, to all intents and purposes, to form part of the empire; her intercourse with the Continent was almost entirely cut off by the incursions of the barbarian tribes into Roman Gaul; and, with the exception of a few contemporary notices of the Church during some years after the termination of the Roman dominion, all is silence for a century and a half, till it is broken in the succeeding century by the querulous voice of Gildas. The few facts which we learn from contemporary sources are these: that in the year 429 the churches of Britain had been corrupted by the ‘Pelagian Agricola, son of the Pelagian bishop Severianus,’ who had introduced the Pelagian heresy among them to some extent;[4] that the orthodox clergy communicated the fact to the Gallican bishops, by whom a synod was held, when it was resolved to send Germanus bishop of Auxerre, and Lupus bishop of Troyes, to Britain; and that, at the instance of Palladius the deacon, Germanus received a mission from Celestine, bishop of Rome, to bring back to the Catholic faith the Britons tainted with this heresy.[5] Two years after, in 431, according to the same chronicler, Pope Celestine ordained Palladius a bishop, and sent him to the Christian Scots of Ireland as their first bishop; and thus, ‘having ordained a bishop to the Scots, while he endeavoured to preserve Roman Britain as Catholic, he made the barbarian island Christian,’[6] in this sense at least that he had formed into a regular church those of its inhabitants who had already become Christian. Whether the Christian religion had been introduced into Ireland by the preaching of Ninian, or whether it had existed there from even an earlier period, there are now no materials to indicate;[7] but the mission of Palladius seems to imply that Ninian was at this time dead.