The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

THE ENGLISH TELEGRAPH INVENTED. 181
THE ENGLISH ELECTRIC TELEGRAPH INVENTED.
After Mr. Cooke had witnessed the experiment upon the
above described arrangement, he devoted himself to the perfection of a contrivance to effect practically the ends of telegraphing, and within three weeks thereafter, he had, partly at
Heidelberg and partly at Frankfort, completed a device for
telegraphing, based upon the electrometer form, which, in
principle, was the same as the English needle telegraph that
has been for many years practically operated in Great Britain.
Six wires were used, forming three metallic circuits, and influencing three needles, by which an alphabet of 26 signals was
devised. The mechanical and scientific combinations produced
a perfect reciprocal telegraphic system, by which a mutual communication could be practically and conveniently carried on
between two distant places; the requisite connections and disconnections being formed by pressing the. fingers upon the keys,
and the signals were exhibited to the person sending them, as
well as the person receiving the communication. This important end was effected, by placing a system of keys permanently
at each extreme end of the metallic circuit, and by providing
each circuit with a cross-piece of metal for completing the
continuity of the wires when signals were being received from
the opposite terminus. The two signal apparatuses being thus
thrown into the course of the electric circuit, every signal was
given at both ends concurrently; and the cross-piece was made
to rest3re the circuit for a reply, on the first communication
being completed. The system of keys and signal-levers were
joined together in the one instrument, so that the pressure
upon the key at either station, produced the signal intended at
the receiving and sending stations.
Fig. 2.
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