|1st secretary of the smithsonian institution|
|succeeded by||spencer fullerton baird|
|2nd president of the national academy of sciences|
|preceded by||alexander dallas bache|
|succeeded by||william barton rogers|
|born||december 17, 1797|
albany, new york, u.s.
|died||may 13, 1878 (aged 80)|
washington, d.c., u.s.
|spouse(s)||harriet henry (née alexander)|
|children||william alexander (1832–1862)|
mary anna (1834–1903)
helen louisa (1836–1912)
|alma mater||the albany academy|
|known for||electromagnetic induction, inventor of a precursor to the electric doorbell and electric relay|
|institutions||the albany academy|
the college of new jersey
joseph henry (december 17, 1797 – may 13, 1878) was an american scientist who served as the first secretary of the smithsonian institution. he was the secretary for the national institute for the promotion of science, a precursor of the smithsonian institution. he was highly regarded during his lifetime. 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 make the discovery and publish his results. henry developed the electromagnet into a practical device. he invented a precursor to the electric doorbell (specifically a bell that could be rung at a distance via an electric wire, 1831) and electric relay (1835). the si unit of inductance, the henry, is named in his honor. henry's work on the electromagnetic relay was the basis of the practical electrical telegraph, invented by samuel f. b. morse and sir charles wheatstone, separately.