by John Muir
by Hiram Martin Chittenden
by John Burroughs
by Merrill D. Beal
by Emerson Hough
by Geological Survey (U.S.)
by Merrill J. Mattes
by Alma White
by Edward F. Colborn
by Carter H. (Carter Henry) Harrison
by James (Geologist) Richardson
by John Burroughs
by Hugo de Vries
by Charles J. Gillis