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 MECHANICAT TELEGRAPH INVENTED. 185
Fig. 8.
M c ad s ssl ws M. C
of larch, 1836. So energetic and successful was Mr. Cooke
in the perfection of his telegraph, that within three weeks after
he saw the experiment of Moncke, he had the model of his reciprocating telegraphic system in operation.
INVENTION OF THE ALARUM APPARATUS.
Before the end of March, 1836, Mr. Cooke invented the apparatus known as the alarum, which is still extant, in his first
mechanical telegraph. The arrangement was of ordinary combination, worked by clock-work mechanism, on the removal of
a detent. The invention consisted in placing an electro-magnet in such proximity to an armature of soft iron forming the
tail end of a lever detent, that when an electric current passed
round the electro-magnet, the magnetism which was, for the
moment, excited in it, attracted the tail end of the lever, and
by so doing, drew its detent end out of the clock-work; but,
on the temporary magnetism ceasing with the cessation of the
current, the attraction of the tail-end of the lever ceased also,
and the detent-end of it was then replaced in the clock-work
by a re-acting spring or balance weight. The principle of
removing a detent, by' magnetic attraction, and replacing it
by mechanical re-action, was not, however, confined to the
alarum, but, on the contrary, it was the basis of Mr. Cooke's
mechanical telegraphic system, hereinafter described.
THE MECHANICAL TELEGRAPHI INVENTED.
in the invention of the mechanical telegraph, Mr. Cooke applied the idea to a musical snuff:box, and in less than six
weeks from the time he saw the experiment of Professor