Joseph Henry

Joseph Henry
Joseph Henry
	Photograph of Henry, c. 1865–1878
1st Secretary of the Smithsonian Institution
	In office; 1846–1878
Succeeded by	Spencer Fullerton Baird
2nd President of the National Academy of Sciences
	In office; 1868–1878
Preceded by	Alexander Dallas Bache
Succeeded by	William Barton Rogers
Personal details
Born	December 17, 1797; Albany, New York, U.S.
Died	May 13, 1878 (aged 80); Washington, D.C., U.S.
Resting place	Oak Hill Cemetery; Washington, D.C., U.S.
Spouse	Harriet Henry (née Alexander)
Children	William Alexander (1832–1862); Mary Anna (1834–1903); Helen Louisa (1836–1912); Caroline (1839–1920)
Signature
Alma mater	The Albany Academy
Known for	Electromagnetic induction, Inventor of a precursor to the electric doorbell and electric relay
	Scientific career
Fields	Physics
Institutions	The Albany Academy; The College of New Jersey; Smithsonian Institution; Columbian College

Joseph Henry (December 17, 1797^[1]^[2]– 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.^[3] He also served as president of the National Academy of Sciences from 1868 to 1878.

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.^[4]^[5]^[6] 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)^[7] and electric relay (1835).^[8] His work on the electromagnetic relay was the basis of the practical electrical telegraph, invented separately by Samuel F. B. Morse and Sir Charles Wheatstone. In his honor, the SI unit of inductance is named the henry^[9] (plural: henries; symbol: H^[10]).

^ According Keith Laidler there is some doubt about the year of his birth, with strong evidence from a member of his family that he was born in 1799.
^ Laidler, Keith J. (1993). To Light such a Candle. Oxford University Press. p. 136.
^ "Planning a National Museum". Smithsonian Institution Archives. Archived from the original on 3 August 2009. Retrieved 2 January 2010.
^ "A Brief History of Electromagnetism" (PDF).
^ Ulaby, Fawwaz (2001-01-31). Fundamentals of Applied Electromagnetics (2nd ed.). Prentice Hall. p. 232. ISBN 978-0-13-032931-8.
^ "Joseph Henry". Distinguished Members Gallery, National Academy of Sciences. Archived from the original on 2006-12-09. Retrieved 2006-11-30.
^ Scientific writings of Joseph Henry, Volume 30, Issue 2. Smithsonian Institution. 1886. p. 434. ISBN 9780598400116.
^ "The electromechanical relay of Joseph Henry". Georgi Dalakov. 4 January 2021.
^ "Henry | Definition & Facts".
^ Ambler Thompson & Barry N. Taylor (2008). "NIST Special Publication 811: Guide for the Use of the International System of Units (SI)" (PDF). National Institute of Standards and Technology. Retrieved 2013-03-21. {{cite journal}}: Cite journal requires |journal= (help)

[1] According Keith Laidler there is some doubt about the year of his birth, with strong evidence from a member of his family that he was born in 1799.

[2] Laidler, Keith J. (1993). To Light such a Candle. Oxford University Press. p. 136.

[3] "Planning a National Museum". Smithsonian Institution Archives. Archived from the original on 3 August 2009. Retrieved 2 January 2010.

[4] "A Brief History of Electromagnetism" (PDF).

[5] Ulaby, Fawwaz (2001-01-31). Fundamentals of Applied Electromagnetics (2nd ed.). Prentice Hall. p. 232. ISBN 978-0-13-032931-8.

[6] "Joseph Henry". Distinguished Members Gallery, National Academy of Sciences. Archived from the original on 2006-12-09. Retrieved 2006-11-30.

[7] Scientific writings of Joseph Henry, Volume 30, Issue 2. Smithsonian Institution. 1886. p. 434. ISBN 9780598400116.

[8] "The electromechanical relay of Joseph Henry". Georgi Dalakov. 4 January 2021.

[9] "Henry | Definition & Facts".

[Taylor-10] Ambler Thompson & Barry N. Taylor (2008). "NIST Special Publication 811: Guide for the Use of the International System of Units (SI)" (PDF). National Institute of Standards and Technology. Retrieved 2013-03-21. {{cite journal}}: Cite journal requires |journal= (help)

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Joseph Henry
Photograph of Henry, c. 1865–1878

1st Secretary of the Smithsonian Institution
In office 1846–1878
Succeeded by	Spencer Fullerton Baird
2nd President of the National Academy of Sciences
In office 1868–1878
Preceded by	Alexander Dallas Bache
Succeeded by	William Barton Rogers

Personal details
Born	(1797-12-17)December 17, 1797 Albany, New York, U.S.
Died	May 13, 1878(1878-05-13) (aged 80) Washington, D.C., U.S.
Resting place	Oak Hill Cemetery Washington, D.C., U.S.
Spouse	Harriet Henry (née Alexander)
Children	William Alexander (1832–1862) Mary Anna (1834–1903) Helen Louisa (1836–1912) Caroline (1839–1920)
Signature

Alma mater	The Albany Academy
Known for	Electromagnetic induction, Inventor of a precursor to the electric doorbell and electric relay
Scientific career
Fields	Physics
Institutions	The Albany Academy The College of New Jersey Smithsonian Institution Columbian College