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 SECONDARY CIRCUIT INVENTED. 195
Fig. 17.
Fig. 18.
If
as A - - -| p i e l s-,
secondary circuit, represented by figs. 17 and 18; to be applied to Mr. Cooke's original alarum, which was subsequently
superseded in practice by Mr. Cooke's alarum, described in the
second English specification. The principle of this new improvement was the motion imparted to an electrometer needle
by a distant battery, being made to complete the circuit of a
second battery, which second battery, excited temporary magnetism in an electro-magnet, and by its attraction removed the
detent of clock-work mechanism.
The part 2G is of the distant electrometer instrument forming the discharger; 3G is the secondary battery operating
with the second circuit; 3b is the battery or circuit wire, terminating in the stop 10g, and the wire 4c, in the cross-piece
11G; so that, when the magnetic needle was moved by an