The one item in this collection is an 1877 letter by Edison to astronomer and physicist Samuel Pierpont Langley (1834-1906), director of the Allegheny Observatory, professor of physics and astronomy at Western University of Pennsylvania in Pittsburgh, and, later, Third Secretary of the Smithsonian Institution. The letter discusses Edison's idea for a heat-measuring apparatus that would subsequently evolve into the tasimeter. A related letter by Edison, written two days earlier, can be found in Edison, T.A. -- General (D-77-02), Document File Series. Langley's response to Edison's second letter can also be found in that folder.
The letter can be found in Record Unit 30: Office of the Secretary (Spencer F. Baird, Samuel P. Langley), 1882-1890, Incoming Correspondence. We are grateful to Marc Rothenberg of the Joseph Henry Papers for bringing this letter to our attention. Courtesy of the NMAH Archives Center.