Joseph Henry (1797-1878) was an American scientist who served as the first Secretary of the Smithsonian Institution, and founding member of the National Institute for the Promotion of Science (precursor of the Smithsonian Institution). While building electromagnets, Henry discovered the electromagnetic phenomenon of self-inductance. He also discovered mutual inductance independently of Michael Faraday, though Faraday was the first to publish his results. The SI unit of inductance, the henry, is named in his honor. Henry's work on the electromagnetic relay was the basis of the electrical telegraph. Henry identified the room acoustics phenomena we now call direct sound, early reflections, and reverberation. He demonstrated the early sound integration period and laid the groundwork for further fundamental research on early reflections. In 1915 Henry was inducted into the Hall of Fame for Great Americans in the Bronx, New York.
