Inchmarnock, an island of North Bute parish, Buteshire, off the W side of the Isle of Bute, adjacent to the meeting-point of the Kyles of Bute, the Sound of Bute, and Loch Fyne, 6 ½ furlongs W of St Ninian's Point. Extending N and S, it has an utmost length and breadth of 2 miles and 5 1/3 furlongs, in the S attains a summit altitude of 165 feet above sea-level, and grows splendid crops of barley. It belonged anciently to the monastery of Saddel in Kintyre; and contains the site of a small chapel, which was dedicated to St Marnock. Pop. (1871) 30, (1881) 18.—Ord. Sur., shs. 21, 29, 1870-73.

(F.H. Groome, Ordnance Gazetteer of Scotland (1882-4); © 2004 Gazetteer for Scotland)