Henry, Joseph, 1797–1878, American physicist, b. Albany, N.Y., educated at Albany Academy. He taught (1826–32) mathematics and natural philosophy at Albany Academy and was professor of natural philosophy (1832–46) at Princeton (then the College of New Jersey). From 1846 he served as the first secretary and director of the newly founded Smithsonian Institution; he introduced and developed many of its activities and established its general policies. Before assuming his responsibilities at the Smithsonian, he had made notable contributions to the physical sciences, especially in electromagnetism. Henry improved the electromagnet, increasing its strength and fitting it for practical use. He invented and operated the first electromagnetic telegraph, which formed the basis for the commercial telegraphic system. He discovered self-inductance, and the unit of inductance inductance, quantity that measures the electromagnetic induction of an electric circuit component; it is a property of the component itself rather than of the circuit as a whole.
..... Click the link for more information. is often called the henry in his honor. Independently of Michael Faraday Faraday, Michael (fâr`ədē, –dā'), 1791–1867, English scientist.
..... Click the link for more information. , he discovered the principle of the induced current, basic to the dynamo, transformer, and many other devices. Henry invented a small electromagnetic motor, and extended the work on induced currents to show that an induced current can be used to induce another current in a nearby circuit and that resulting currents in turn can induce others. His numerous other contributions include the institution of the weather report system.

Bibliography

See his Papers, ed. by N. Reingold et al. (15 vol., 1972–); biographies by S. R. Riedman (1961) and A. E. Moyer (1997).

Henry, Joseph

(born Dec. 17, 1797, Albany, N.Y., U.S.—died May 13, 1878, Washington, D.C.) U.S. physicist. He aided Samuel F.B. Morse in developing the telegraph. He discovered several important principles of electricity, including self-induction. He observed electromagnetic induction a year before Michael Faraday announced its discovery. He made improvements to electromagnets, discovered the laws on which the transformer is based, investigated electric discharge, and demonstrated that sunspots radiate less heat than the general solar surface. In 1846 he became the first secretary and director of the Smithsonian Institution, where he organized a corps of volunteer weather observers that led to creation of the U.S. Weather Bureau. He was a chief technical adviser to Abraham Lincoln during the Civil War and a primary organizer of the National Academy of Science. In 1893 the standard unit of electrical inductance, the henry, was named in his honour.

Henry, Joseph (1797–1898) physicist; born in Albany, N.Y. He worked as a tutor, then as a surveyor (1825–26) before becoming a professor at his alma mater, Albany Academy (1826–32). He began research on electromagnetism (1827), constructed the first electromagnetic motor (1829), and discovered electrical induction independent of English physicist Michael Faraday. The "henry" unit of inductance is named after him. He continued his research after transferring to Princeton (1832–46), demonstrating the oscillatory nature of electrical discharges (1842), and diversifying into the fields of astronomy, galvanometry, and telegraphy. In 1846 he was named first secretary and director of the Smithsonian Institution; through his leadership (1846–77), the Smithsonian supported internationally cooperative scientific research. While administrative duties left him little time for the "pure" scientific endeavors he favored, Henry introduced a system of weather forecasting, investigated the propagation of light and sound waves by lighthouses, and encouraged the museum's patronage of anthropology and ethnology.