COPPERMINE, a river of Mackenzie district, Canada, about 475 m. long, rising in a small lake in approximately 110° 20′ W. and 65° 50′ N., and flowing south to Lake Gras and then north-westward to Coronation Gulf in the Arctic Ocean. Like Back’s river, the only other large river of this part of Canada, it is unnavigable, being a succession of lakes and violent rapids. The country through which it flows is a mass of low hills and morasses. The river was discovered by Samuel Hearne in 1771, and was explored from Point Lake to the sea by Captain (afterwards Sir John) Franklin in 1821.