Tristan da Cunha, the largest of three small islands in the South Atlantic in lat 37° 6' S., long. 12° 16' W. The surface is mostly rugged and mountainous, with a volcanic cone of 7,640 feet in the centre. It takes its name from the Portuguese navigator who discovered it in 1506. The island has belonged to Great Britain since 1816. The settlers supply stores to whalers.