group of islets and reefs lying 1.5 to 6 miles (2.5 to 10 km) off the North Sea coast of Great Britain in the administrative and historic county of Northumberland, England. The islands are composed of resistant dolerite (lava) rocks. The largest of these islands, House, spans 16 acres (6.5 hectares) and has precipitous cliffs reaching up to 80 feet (24 metres) in height. The lighthouse on Longstone island was the home of Grace Darling (Darling, Grace), Victorian heroine of sea-rescue fame; the modern lighthouse, however, is on House. The Farne Islands are preserved as a bird sanctuary by the National Trust.