Correspondence Letter File - H-O, 1892-1909

Patents, articles and clippings concerning electrical engineering; thesis for graduate degree in electrical engineering, University of Illinois, 1912; manuscript of book THE POWER-FACTOR (not published). Also, bibliography, clippings and correspondence relating to DuBois' work as an ornithologist, especially his photography. Includes correspondence with Arthur A. Allen. Also, a catalog of glass negatives and photo albums organized by bird species as well as other black and white photographs and ornithological notes.