HENRY, Joseph, physicist, born in Albany, New York, 17 December, 1797 or 1799; died in Washington, D. C., 13 May, 1878. The date of his birth is given in duplicate on account of its illegibility in the family Bible. He was descended from Scottish ancestry, and his grandparents emigrated to this country about the beginning of the Revolutionary war. His father died when the boy was very young, but his mother was a woman of great refinement, intelligence, and strength of character. She was a staunch Presbyterian, and exacted from her children the strictest performance of religious duties. Joseph's education began in Galway, near Albany, where for several years he attended the district school, while residing with his grandmother. At about the age of ten he was placed in a store, and for the five ensuing years his time was divided between his duties as a clerk and his studies. He then returned to Albany, and was apprenticed to a watch-maker and silversmith, and also joined a private dramatic company called "The Rostrum," of which he soon became the leading spirit. There seemed every prospect of his studying for the stage, when, during a brief illness, he read Dr. Gregory's "Lectures on Experimental Philosophy, Astronomy, and Chemistry." Thenceforth he determined to devote his life to the study of science, and secured private lessons during the evening from the teachers of the Albany academy. Later he taught, and so acquired sufficient money to enable him to follow a regular course of instruction at the academy. On the completion of his studies he obtained, through the influence of Dr. Theodoric R. Beck, the appointment of private tutor to the family of General Stephen Van Rensselaer, the patroon, and devoted three hours daily to teaching. Meanwhile he assisted Dr. Beck in his chemical experiments, and pursued studies in anatomy and physiology with a view to becoming a physician. In 1825 he received the appointment of engineer on the survey of a road to run through the state of New York, from the Hudson river to Lake Erie, and a year later he was made professor of mathematics in the Albany academy, and almost at once began the series of brilliant experiments in electricity which have linked his name with that of Franklin as one of the two most original investigators in that branch of science that this country has ever produced. His first work was the improving of existing forms of apparatus, and in 1827 he read a paper before the Albany institute, in which he described how electro-dynamic actions can be shown by simpler means than those employed at that time. Soon afterward he made his first important discovery--that of producing the electro-magnet, properly so called, by showing that in a piece of soft iron the magnetism produced may be greatly increased by multiplying the number of coils around the polar limbs. He continued his investigations, and in 1829 he exhibited electromagnets possessing greater power than any before known, and later he built several larger magnets, among which was the one now in the physical cabinet of Princeton, capable of sustaining 3,600 pounds with a battery, occupying a single cubic foot of space. His experiments further showed that in the transmission of electricity over great distances the electro-motive force of the battery must be proportional to the length of the conductor. This led in 1830 to the development of the "intensity" magnet, which made the electric telegraph a possibility, and in 1831, in a paper published in Silliman's "American Journal of Science," he suggested its use for that purpose. Indeed, during the same year he constructed the first electro-magnetic telegraph, transmitting signals through a wire more than a mile in length, causing a bell to ring at the farther end of the wire. "This," said President Garfield, "was the last step in the series of great discoveries which preceded the invention of the telegraph." And another authority says: "The thing was perfect as it came from its author, and has never been improved from that day to this as a sounding telegraph." Professor Henry's own words, brought forth by Morse's attempt to expose "the utter non-reliability of Henry's testimony," were: "The principles I had developed were applied by Dr. Gale to render Morse's instrument effective at a distance." This statement, sustained by Dr. Leonard D. Gale himself, has never been confuted. In 1831 he devised the first electro-magnetic engine for maintaining continuous motion by means of an automatic pole-changer. During the same year he discovered the secondary currents produced in a long conductor by the self-induction of the primary current, and also obtained an electric spark by a purely magnetic induction. In November, 1832, he removed to Princeton, where he had been called to fill the chair of natural philosophy. For some years afterward his ex-elusive attention was occupied with the duties pertaining to his professorship, especially as he delivered the lectures on chemistry, mineralogy, and geology during the absence of Dr. John Torrey in Europe in 1833, and afterward also lectured on astronomy and architecture. In resuming his electrical researches, he first devoted special attention to the subject of electrical self-induction. In 1835 he renewed his investigation of combined circuits, and extended a series of wires across the college-yard, through which signals were sent, and the local circuit with strong" receiving magnet "used at that time has since become a most important adjunct in the manipulation of the electric telegraph. Papers giving the results of his researches in electricity appear in the" Proceedings of the American Philosophical Society," under the title of "Contributions to Electricity and Magnetism," during the years 1835-'42. The study of meteorology was one to which he devoted considerable thought, having previously, from 1827 till 1832, been associated with Dr. Beck in the development of his system of meteorological observations established in the state of New York, and in 1839 he was active in endeavoring to persuade the United States government to designate stations for magnetic and meteorological observations. The results of special phenomena that were examined by him at this time were published, but a large collection of original notes of determinations of magnetic variations in auroras, with attempts at ascertaining their extreme height, on violent whirlwinds, on hail-storms, on thunderstorms, and the deportment of lightning-rods, were destroyed by fire. Many other investigations that were conducted by him during his residence in Princeton, in various branches of physics, have been of permanent value to science. In 1846 he was elected first secretary and director of the Smithsonian institution, and in December of that year removed with his family to Washington. The organization, equipment, and development of this great scientific establishment, thenceforth until his death, occupied his principal attention. He was nominated to the chair of natural philosophy in the University of Pennsylvania, with a salary twice as large as that which he was receiving in Washington, and efforts were made to induce him to return to Princeton as its president in 1853, and also in 1867, but these offers were steadily refused. Like Agassiz, he may have answered when tempted by larger salaries, "I can not afford to waste my time in making money." Professor Simon Newcomb says of him: "He never engaged in an investigation or an enterprise which was to put a dollar into his own pocket, but aimed only at the general good of the world." On the organization of the lighthouse board in 1852 he was made one of its members, and from 1871 till his death was its chairman. The establishment of the National lighthouse system is very largely due to him, although his services, during his later years especially, were principally advisory, though he continued his investigations in its behalf until his death, being occupied in its work when the final illness came. During the civil war he was constantly called on to consider plans and devices for facilitating military and naval operations. Throughout his career in Washington he acted as confidential adviser on scientific matters to the government, and the composition of commissions for technical purposes was generally referred to him. He received the degree of LL. D. from Union in 1829, and from Harvard in 1851. In 1849 he was elected president of the American association for the advancement of science, and he was one of the original members of the National academy of science, succeeding Alexander D. Bache in 1868 as president. Professor Henry was also a member of other societies, both in the United States and Europe. His published papers include over 150 titles, and were contributed principally to American scientific journals. He also wrote valuable articles for the "American" and other cyclopedias, and was the author of a series of papers on "Meteorology in its Connection with Agriculture," contributed to the "Agricultural Reports " (1855-'9). His single book was "Syllabus of Lectures on Physics" (Princeton, 1844), although he edited the annual volumes of the "Smithsonian Reports" from 1846 till 1877. In 1886 two volumes of the "Scientific Writings of Joseph Henry" were published by the Smithsonian institution. See "A Memorial of Joseph Henry," published by order of congress (Washington, 1880).