In 1830 the great American scientist Professor Joseph Henry transmitted the
first practical electrical signal. A short time before Henry had invented
the first efficient electromagnet. He also concluded similar thoughts about
induction before Faraday but he didn’t publish them first. Henry’s place in
electrical history however, has always been secure, in particular for
showing that electromagnetism could do more than create current or pick up
heavy weights — it could communicate.In a stunning demonstration in his Albany Academy classroom, Henry created
the forerunner of the telegraph. In the demonstration, Henry first built an
electromagnet by winding an iron bar with several feet of wire. A pivot
mounted steel bar sat next to the magnet. A bell, in turn, stood next to
the bar. From the electromagnet Henry strung a mile of wire around the
inside of the classroom. He completed the circuit by connecting the ends of
the wires at a battery. Guess what happened? The steel bar swung toward the
magnet, of course, striking the bell at the same time. Breaking the
connection released the bar and it was free to strike again. And while
Henry did not pursue electrical signaling, he did help someone who did. And
that man was Samuel Finley Breese Morse.
For more information on Joseph Henry, visit the Joseph Henry Papers Project
at:
http://www.si.edu/archives/ihd/jhp/papers00.htm (external link)
From the December, 1963 American Heritage magazine, „a sketch of Henry’s
primitive telegraph, a dozen years before Morse, reveals the essential
components: an electromagnet activated by a distant battery, and a pivoted
iron bar that moves to ring a bell.“ See the two books listed to the left
for more information.In 1837 Samuel Morse invented the first workable telegraph, applied for its
patent in 1838, an
d was finally granted it in 1848. Joseph Henry helped Morse build a
telegraph relay or repeater that allowed long distance operation. The
telegraph later helped unite the country and eventually the world. Not a
professional inventor, Morse was nevertheless captivated by electrical
experiments. In 1832 he heard of Faraday’s recently published work on
inductance, and was given an electromagnet at the same time to ponder over.
An idea came to him and Morse quickly worked out details for his telegraph.As depicted below, his system used a key (a switch) to make or break the
electrical circuit, a battery to produce power, a single line joining one
telegraph station to another and an electromagnetic receiver or sounder
that upon being turned on and off, produced a clicking noise. He completed
the package by devising the Morse code system of dots and dashes. A quick
key tap broke the circuit momentarily, transmitting a short pulse to a
distant sounder, interpreted by an operator as a dot. A more lengthy break
produced a dash.
Telegraphy became big business
as it replaced messengers, the Pony Express, clipper ships and every other
slow paced means of communicating. The fact that service was limited to
Western Union offices or large firms seemed hardly a problem. After all,
communicating over long distances instantly was otherwise impossible. Yet
as the telegraph was perfected, man’s thoughts turned to speech over a
wire.
[pic]
Bell continued harmonic telegraph work through the fall of 1874. He wasn’t
making much progress but his tinkering gathered attention. Gardiner Greene
Hubbard, a prominent Boston lawyer and the president of the Clarke School
for The Deaf, became interested in Bell’s experiments. He and George
Sanders, a prosperous Salem businessman, both sensed Bell might make the
harmonic telegraph work. They also knew Bell the man, since Bell tutored
Hubbard’s daughter and he was helping Sander’s deaf five year old son learn
to speak.In October, 1874, Green went to Washington D.C. to conduct a patent search.
Finding no invention similar to Bell’s proposed harmonic telegraph, Hubbard
and Sanders began funding Bell. All three later signed a formal agreement
in February, 1875, giving Bell financial backing in return for equal shares
from any patents Bell developed. The trio got along but they would have
their problems. Sanders would court bankruptcy by investing over $100,000
before any return came to him. Hubbard, on the other hand, discouraged
Bell’s romance with his daughter until the harmonic telegraph was invented.
Bell, in turn, would risk his funding by working so hard on the telephone
and by getting engaged to Mabel without Hubbard’s permission.In the spring of 1875, Bell’s experimenting picked up quickly with the help
of a talented young machinist named Thomas A. Watson. Bell feverishly
pursued the harmonic telegraph his backers wanted and the telephone which
was now his real interest. Seeking advice, Bell went to Washington D.C. On
March 1, 1875, Bell met with Joseph Henry, the great scientist and
inventor, then Secretary of the Smithsonian Institution. It was Henry,
remember, who pioneered electromagnetism and helped Morse with the
telegraph. Uninterested in Bell’s telegraph work, Henry did say Bell’s
ideas on transmitting speech electrically represented „the germ of a great
invention.“ He urged Bell to drop all other work and get on with developing
the telephone. Bell said he feared he lacked the necessary electrical
knowledge, to which the old man replied, „Get it!“ [Grosvenor and Wesson]
Bell quit pursuing the harmonic telegraph, at least in
spirit, and began
working full time on the telephone.After lengthy experimenting in the spring of 1875, Bell told Watson „If I
can get a mechanism which will make a current of electricity vary in its
intensity as the air varies in density when a sound is passing through it,
I can telegraph any sound, even the sound of speech.“ [Fagen] He
communicated the same idea in a letter to Hubbard, who remained unimpressed
and urged Bell to work harder on the telegraph. But having at last
articulated the principle of variable resistance, Bell was getting much
closer.On June 2, 1875, Bell and Watson were testing the harmonic telegraph when
Bell heard a sound come through the receiver. Instead of transmitting a
pulse, which it had refused to do in any case, the telegraph passed on the
sound of Watson plucking a tuned spring, one of many set at different