He spent his career from 1911 to 1937 as a professor of biology and botany at Goucher College in Towson, Maryland.
[1] Longley's most notable scientific work focused on the coloration and patterning of tropical reef fish.
He conducted this research with the support of the Carnegie Institution's Dry Tortugas Laboratory in Washington, D.C., where he served as director from 1922 to 1937.
He conducted extensive botanical studies in various locations, including Hawaii, Samoa, the Tortugas islands, and the Pacific region.
His research also involved examining plant specimens housed in European and American museums.