The bishopric was formed about 1200 by the separation of the districts, belonging to the bishopric of Dunkeld, which lay to the west of the great range of Drumalban. Eraldus was the first Bishop of Argyll, and had his seat at Muckairn, while his church bore the name of Killespeckerill, or the church of Bishop Erailt.[187] It is possible that some of the Keledei from Dunkeld may have accompanied the new bishop and been established there. In 1236 the see was transferred from Muckairn, on the south side of Loch Etive, to Lismore, where, long before, a Columban monastery had been founded by St. Lughadh or Moluoc. The see was afterwards known as the bishopric of Lismore, and contained the following deaneries: Kintyre, with twelve parishes; Glassary or Glasrod, with thirteen; Lorn, with fourteen; and Morvern, with eight.[188] The cathedral was perhaps the humblest in Britain, and was probably erected soon after the transference of the see in the thirteenth century. It is said to have been a structure 137 feet long by 29-1/3 wide, but of this there only now survives an aisleless choir, with traces of a chapter-house and sacristy; and, as re-roofed in 1749, this choir now serves as a parish church. It has four buttresses of simple form against the south wall, and two at each of the north and south angles of the east wall. In the south wall, and in the usual position near the east end, there are remains of a triple sedilia; there is a piscina in a pointed recess, having a trefoil-headed niche in the wall behind.[189] One of the deans of Lismore, Sir James MacGregor, between 1512 and 1540, compiled a commonplace book, filled chiefly with Gaelic heroic ballads, several of which are ascribed to the authorship of Ossian. 12. DIOCESE OF THE ISLES The history of Iona is associated with St. Columba, and, although its church did not attain full cathedral status until 1506, the island was one of the earliest centres of Christianity in Scotland.