These two letters are from February 1914 and July 1925. The first is from Edison to U.S. Comptroller of the Currency John Skelton Williams, thanking him for persuading the postmaster general to allow cellulose acetate film in the mail. The second letter was sent to Edison by James Waldo Fawcett, who was collecting family data for a study of heredity. Edison's reply, including a comment on the nature of genius, appears in the margin. Courtesy of the University of Virginia Library.