In 1898, Bell experimented with tetrahedral box kites and wings constructed of multiple compound tetrahedral kites covered in maroon silk.[N 23] The tetrahedral wings were named Cygnet I, II and III, and were flown both unmanned and manned (Cygnet I crashed during a flight carrying Selfridge) in the period from 1907–1912. Some of Bell's kites are on display at the Alexander Graham Bell National Historic Site.