Letter to J.E. Sutterlin from Thomas A. Edison. Letter reads: "Dear Sir, It is essential that the phonograph diaphragm should respond to all sounds and give none of its own. Like the drum of the ear. Yours truly, Thomas A. Edison." Stamped on front: "From the laboratory of T.A. Edison, Menlo Park, N.J., U.S.A." May 25, 1878.
Burton Historical Collection, Detroit Public Library
















