The attempt to send signals by electricity had been made many
times before Henry became interested in the problem. On the
invention of Sturgeon's magnet there had been hopes in England of
a successful solution, but in the experiments that followed the
current became so weak after a few hundred feet that the idea was
pronounced impracticable. Henry strung a mile of fine wire in the
Academy, placed an "intensity" battery at one end, and made the
armature strike a bell at the other. Thus he discovered the
essential principle of the electric telegraph. This discovery was
made in 1831, the year before the idea of a working electric
telegraph flashed on the mind of Morse. There was no occasion for
the controversy which took place later as to who invented the
telegraph. That was Morse's achievement, but the discovery of the
great fact, which startled Morse into activity, was Henry's
achievement. In Henry's own words: "This was the first discovery
of the fact that a galvanic current could be transmitted to a
great distance with so little a diminution of force as to produce
mechanical effects, and of the means by which the transmission
could be accomplished. I saw that the electric telegraph was now
practicable." He says further, however: "I had not in mind any
particular form of telegraph, but referred only to the general
fact that it was now demonstrated that a galvanic current could
be transmitted to great distances, with sufficient power to
produce mechanical effects adequate to the desired object.
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