"*
* Deposition of Joseph Henry, September 7, 1849, printed in
Morse, "The Electra-Magnetic Telegraph", p. 91.
Henry next turned to the possibility of a magnetic engine for the
production of power and succeeded in making a reciprocating-bar
motor, on which he installed the first automatic pole changer, or
commutator, ever used with an electric battery. He did not
succeed in producing direct rotary motion. His bar oscillated
like the walking beam of a steamboat.
Henry was appointed in 1839. Professor of Natural Philosophy in
the College of New Jersey, better known today as Princeton
University. There he repeated his old experiments on a larger
scale, confirmed Steinheil's experiment of using the earth as
return conductor, showed how a feeble current would be
strengthened, and how a small magnet could be used as a circuit
maker and breaker. Here were the principles of the telegraph
relay and the dynamo.
Why, then, if the work of Henry was so important, is his name
almost forgotten, except by men of science, and not given to any
one of the practical applications of electricity? The answer is
plain. Henry was an investigator, not an inventor. He states his
position very clearly: "I never myself attempted to reduce the
principles to practice, or to apply any of my discoveries to
processes in the arts.
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