The first telegraph of Wheatstone and Cooke consisted of five magnetic
needles pivoted on a vertical dial. The letters of the alphabet were
marked on the dial, and the needles were deflected by currents made to
pass through wires by the depression of keys, so that two needles would
point towards the required letter. Fig. 26 is a sketch of the dial of
this apparatus. This telegraph was tried successfully on the London
and North-Western Railway, over a wire a mile and a half in length.
Wheatstone and Cooke afterwards invented a single-needle telegraph in
which the letters were indicated by movements of the needle to the
right or to the left, according to the direction of a current sent
through a coil of wire. Wheatstone subsequently produced an apparatus
which printed the letters on paper.
In the United States, Morse had thought out a scheme of telegraphy
in 1832, but it was not until 1837 that he got his apparatus into
working order. He was an artist by profession, and for a long time he
was unable to develop his ideas for lack of money. After many efforts
he succeeded in obtaining a State grant of £6000 for the construction
of a telegraph line between Baltimore and Washington, and the first
message over this line was sent in 1844, the line being thrown open
to the public in the following year. Amongst the features of this
telegraph were a receiving instrument which automatically recorded the
messages on a moving paper ribbon, by means of a pencil actuated by
an electro-magnet; and an apparatus called a relay, which enabled the
recording instrument to be worked when the current was enfeebled by the
resistance of a very long wire. Morse also devised a telegraphic code
which is practically the same as that in use to-day.
The great discovery of the German Steinheil was that a second wire for
the return of the current was not necessary, and that the earth could
be used for this part of the circuit.
In reading the early history of great inventions one is continually
struck with the indifference or even hostility shown by the general
public. In England the electric telegraph was practically ignored
until the capture of a murderer by means of it literally forced the
public to see its value. The murder was committed near Slough, and the
murderer succeeded in taking train for London. Fortunately the Great
Western Railway had a telegraph line between Slough and London, and a
description telegraphed to Paddington enabled the police to arrest the
murderer on his arrival. In the United States too there was just the
same indifference. The rate for messages on the line between Baltimore
and Washington was one cent for four words, and the total amount taken
during the first four days was one cent!
Public-domain text, read in full here on John Shaqi.
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