HENRY
HENRY
Charles Carroll of Carroll ton were chosen U.S.
senators, and the full term fell to Senator Henry.
At the expiration of his term, March 3, 1795, he
was re-elected for the term to expire March 3,
1799. He was, however, elected governor of
Maryland in 1797, resigned his seat in the senate
Dec. 10, 1797, and was inaugurated Jan. 8, 1798.
He died inEaston, Md., Dec. 16, 1798.
HENRY, John Flournoy, physician, was horn at Henry's Mills, Ky., Jan. 17, 1793; son of Gen. William Henry (1761-1824) , soldier. He was edu- cated at Georgetown academy, Ky., at Jefferson Medical college, Philadelphia, and at the College of Physicians and Surgeons where he was gradu- ated M.D. in 1817. He served as surgeon's mate in the war of 1813 under liis father, who was major- general of Kentucky troops at the battle of the Thames. He practised medicine in Hopkinsville, Ky., and then in 1825 organized the first temper- ance society in the state. On the death of his brother, Robert Pryor Henry, Aug. 23, 1826, he was elected a representative from the Logan district in the 19th congress to complete the un- expired term, 1826-27. He was a professor in the Ohio Medical college, Cincinnati, 1831-34, and during the cholera epidemic of 1832 was in con- stant attendance on the suffering victims. He practised in Bloomington, 111., in 1834, and in Burlington, Iowa, 1835-73. He published Causes and Treatment of Cholera (1833). He died in Burlington, Iowa, Nov. 12, 1873.
HENRY, Joseph, scientist, was born in Albany, N.Y.. Dec. 17. 1799: son of "William and Annie (Alexander) Henry. He was of Scottish ancestry, his grandparents on both sides having come in the same vessel to America, June 17, 1775, and pur- chased large tracts of land in the north- ern part of the state of New York, in Rhode Island and in Virginia, settling finally near Galway, Saratoga county, N. Y. Here Joseph lived in apparently unrestrained liberty from the age of seven to about fifteen, under the care of an indulgent grandmother, attending irregularly a school in the village, but passing his time chiefly in de- vouring every book of romance, drama, poetry and fiction he could find, feeding thus a vivid imagination, invaluable to him as an investi- gator in after years. During this period his father died in Albany when the boy was
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eight or nine years old. Joseph was awakened
suddenly from his world of dreams by a book of
lectures on natural science, placed opportunely
in his way during a brief illness, and immedi-
ately began with ardor the pursuit of knowledge
which ended only with his death. He was at
this time in Albany and his mother was in
straitened circumstances. He studied in the
evenings with the instructors of the Albany
academy, and later, by teaching, lie acquired
the means to pursue a regular course at the
academy. He then obtained an appointment as
tutor in the family of Stephen Van Rensselaer,
the patroon, an old friend of the family, who
had watched his course with interest, and gave
to his pupils three hours of his time ej'ch day.
In the meantime lie was assistant to Dr. T.
Romeyn Beck in his chemical experiments, and
under his direction pursued a course in anatomy
and physiology. In 1825 he was appointed chief
surveyor of a proposed state road from Albany
to Buffalo. He was professor of mathematics at
the Albany academy, 1826-32; professor of
natural philosophy at the College of New
Jersey, Princeton, 1832-48, and professor emer-
itus, 1848-78; and first secretary and director
of the Smithsonian Institution, 1867-78. In
the field of electrical science Henry's re-
searches were profound and extensive and the
results attained by him were of the greatest im-
portance and value. He repeated many of the
experiments of Arago, Ampex'e, Schweigger,
Stui-geon and otliers, elucidated man}' principles
not discovered by earlier investigators and added
much to the knowledge of electro-magnetism.
His experiments in electro-magnetic induction
were especially far-reaching and brilliant and
led to the discovery of principles which became
the foundations of many brandies of the elec-
trical industries. His accomplishments in this
direction have been recognized by the scientific
world by giving the name "henry" to the unit
of self-induction. He also made important in-
vestigations in the subject of atmospheric elec-
tricity and formulated plans for the protection of
buildings from damage bj' lightning. Between
1828 and 1840, he made elaborate experiments to
determine the best method of constructing elec-
tro-magnets and of adopting batterj* currents of
varying strengths to them. These experiments
were carried on simultaneously with and reached
the same result as those made by Ohm, The
principle, now universally known as " Ohm's
law," that the current in any circuit is equal to its
intensity divided by the resistance of the con-
ductor, was independently discovered and applied
by Hem-y. When he began his researches in 1827
the electro-magnet was an inefficient instrument,
consisting of a bar of iron wound loosely with a
