It was about the year 470 when the sons of Erc, Fergus and his brothers went from Ireland to Scotland. Fergus was king of Dál Riada in the north-eastern corner of Ireland. We are not to understand that the main Irish migration to Scotland took place at that time. There are no data to show when the earliest Irish settlements were made in Argyleshire and the adjoining islands, but we have seen that, at the close of the third century, when Constantius Chlorus commanded the Roman power in Britain, the Britons were already "accustomed" to Irish enemies. If the Irish were then strong enough to raid the Roman frontier, they were probably in possession of the Cantire peninsula. The crossing over of the Sons of Erc means that these princes established their rule over the Irish settlements in that region. It is a common mistake of histories to suppose that Fergus, when he became king on the other side, established there a new dynasty. Editors of the Irish annals, taking this for granted, actually undertake to tell us that certain men whom the annals style kings of Dál Riada were kings of the Scottish Dál Riada, and certain others who are also entitled kings of Dál Riada, were kings of the Irish Dál Riada. Here again the genealogies supplement the annals and show clearly that all these kings belonged to one undivided dynasty. Dál Riada in Ireland and the Irish settlers in Scotland were ruled by the same kings from the time of Fergus macEirc until the Norsemen occupied Cantire and the neighbouring islands, and thus cut off the Irish territory of these kings from the Scottish territory in which the kings of Dál Riada had become resident. When this separation took place, the title "king of Dál Riada" was abandoned. The last king who bears that title in the Irish annals is Donn Coirci, who died in 792; and in 794 the same annals record "the devastation of all the islands of Britain by the heathens." The account of the Irish migration given by the Venerable Bede has often been repeated. It is true in so far as it indicates that the migration did not begin under the Sons of Erc. In other respects it is a fictitious legend. "In process of time," writes Bede, "besides the Britons and Picts, Britain received a third nation, the Scots, who, migrating from Ireland under their leader Reuda, either by fair means or by force of arms, secured to themselves those settlements among the Picts which they still possess. From the name of their commander they are to this day called Dalreudini; for in their language _dal_ signifies a part.