districts were laid waste in Alban, until the men of Alban submitted to Rechtgidh Righdearg, so that he was king of Erin and Alban; and it was from them sprang the two _Tuaths_ or tribes, _Tuath Forc_ and _Tuath Iboth_ in Alban.’[247] Rechtgidh Righdearg was one of the mythic pagan kings of Ireland, and Irial Glumnar a traditionary hero of the _Cruithnigh_, or Picts of Ulster; but it is a fair inference from it that two _Tuaths_ or tribes bearing the names of Forc and Iboth were known in Scotland, and the name Forc, which is the old form of that of the river Forth, indicates their situation on the northern shore of that river or estuary, that is, among the southern Picts. That a social organisation similar to the Irish tribal system prevailed among the southern Picts, to whom St. Columba’s mission was mainly directed, is confirmed by the Gaelic entries in the Book of Deer, which open with the statement that ‘Columba and Drostan, son of Cosgrach, his pupil, came from Hi, as God had shown them, unto _Abbordoboir_ or Aberdour, and Bede the _Cruthnech_ or Pict, who was _Mormaer_ of Buchan, gave them that town in freedom for ever from _Mormaer_ and _Toisech_;’ thus exactly corresponding to the grant of land to the church of Kells, quoted in a former chapter as free from rent, tribute, hosting, coigny, or any other claim of king or _Toisech_. Where there are _Toisechs_ there are _Tuaths_, and the district of Buchan probably formed a _Mortuath_ like the other districts ruled over by a _Mormaer_, the equivalent in Scotland of the _Ri Mortuath_ of the Irish system. [Sidenote: The tribe in Dalriada.]