Magh Ailbhe — This, which is latinised Campus Albus, was the ancient name of an extensive plain in Leinster, extending from Slewmargy, in the Queen's County, in an eastern direction, and comprising portions of the barony of Idrone, in the county of Carlow, and of the baronies of Kilkea and Moone, in the county of Kildare. Bealach Mughna, now Ballaghmoone, to the north of Carlow, is described in all Irish authorrities as in Magh Ailbhe. Ussher, in his Primordia, pp. 936, 937, thus describes this plain, on the authority of an ancient Life of St. Munnu: — ‘Campus ad ripam fluvii quem Ptolemeus Birgum, nos Barrow vocamus, non procul a monte Margeo positus.’ In a curious ancient poem, describing the monuments of Leinster, it is called the finest plain in Ireland.