The name given to a congeries of morasses in Kildare, King's County, Queen's County and Westmeath, Ireland. Clane Bog, the eastern extremity, is within 17 m. of Dublin, and the morasses extend westward almost to the Shannon. Their total area is about 238,500 acres. They do not form one continuous bog, the tract of the country to which the name is given being intersected by strips of dry cultivated land. The rivers Brosna, Barrow and Boyne take their rise in these morasses, and the Grand and Royal canals cross them. The Bog of Allen has a general elevation of 250 ft. above sea level, and the average thickness of the peat of which it consists is 25 ft. It rests on a subsoil of clay and marl.