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

308 BAKEWELL S ELECTRIC COPYING TELEGRAPH.
the wheel D, the break is thus put in operation just sufficiently to
make the movements of the two instruments correspond. By
this arrangement, it will be observed that one instrument regulates the other; and it has it under such complete control that
if the speed of B be diminished, the movement of A will be retarded by the longer continued action of the bre ak, and be made
to rotate equally slowly, and even to stop by stopping the
motion of B.
When the instruments are worked at a distance from each
other, the electro-magnet Ai is put into action by a local battery,
and the contact is made and broken by an intermediate small
electro-magnet, as in Mr. Morse's telegraph. In that manner
the copying telegraph has transmitted messages with perfect
accuracy from Brighton to London.
When a single conmmunicating wire only is used, the instruments are regulated independently of each other by means of
pendulums. Clock-movements, with pendulums that beat four
times in a second, are employed at each instrument. These
pendulums at every vibration strike against springs, at each
contact with which the electro-magnets which regulate the
instruments are brought into action.
The arrangement of the mode of making and breaking contact by the pendulum will be easily understood by the diagram.
Fig. 3.
the coil of the electro-magnet It will be evident, therefore,
that when the rod of the pendulum vibrates against s s, the
voltaic circuit is completed through the magnet, which is
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