Page:Appletons' Cyclopædia of American Biography (1892, volume 3).djvu/200

172 resigned, having been elected governor of his state. He held this office until the time of his death.

HENRY, Joseph, physicist, b. in Albany, N. Y., 17 Dec, 1797 or 1799 ; d. in Washington, D. C, 13 May, 1878. The date of his birth is given in du- plicate on account of its illegibility in the fam- ily Bible. He was de- scended from Scot- tish ancestry, and his grandparents emi- grated to this coun- try about the begin- ning of the Revolu- tionary war. His fa- ther died when the boy was very young, but his mother was a woman of great refinement, intelli- gence, and strength of character. She was a staunch Presby- terian, and exacted from her children the strictest performance of religious duties. Joseph's educa- tion began in Galway, near Albany, where for sev- eral 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, dur- ing a brief illness, he read Dr. Gregory's "Lec- tures on Experimental Philosophy, Astronomy, and Chemistry." Thenceforth he determined to de- vote his life to the study of science, and secured private lessons during the evening from the teach- ers 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 Gen. Stephen Van Rensselaer, the pa- troon, 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 inves- tigators in that branch of science that this country has ever produced. His first work was the im- proving 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 em- ployed 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 num- ber of coils around the polar limbs. He continued his investigations, and in 1829 he exhibited electro- magnets possessing greater power than any before known, and later he built several larger magnets, among which was the one now in the physical cabi- net 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 conduc- tor. This led in 1830 to the development of the " intensity " magnet, which made the electric tele- graph a possibility, and in 1831, in a paper pub- lished in Silliman's "American Journal of Sci- ence," he suggested its use for that purpose. In- deed, 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 author- ity 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." Prof. Hen- ry's own words, brought forth by Morse's attempt to expose " the utter non-reliability of Henry's tes- timony," were : " The principles I had developed were applied by Dr. Gale to render Morse's instru- ment 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 natu- ral philosophy. For some years afterward his ex- clusive attention was occupied with the duties per- taining to his professorship, especially as he deliv- ered 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 elec- trical 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 Philo- sophical Society," under the title of "Contribu- tions to Electricity and Magnetism," during the years 1835-42. The study of meteorology was one to which he devoted considerable thought, having greviously, from 1827 till 1832, been associated with »r. Beck in the development of his system of meteorological observations established in the state of New York, and in 1839 he was active in en- deavoring to persuade the U. S. government to designate stations for magnetic and meteorological observations. The results of special phenomena that were examined by him at this time were pub- lished, but a large collection of original notes of determinations of magnetic variations in aim >ras. 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