* * * * *
THE ADER RELAY.
This new instrument has excited considerable interest among telegraph
and telephone men by its exceeding sensitiveness. It is so sensitive
to the passage of an electric current that a battery formed with an
ordinary pin for one electrode and a piece of zinc wire for the other,
immersed in a single drop of water, will give sufficient current
to operate the relay. In practice it has successfully worked as a
telephonic call on the Eastern Railroad Company's line between Nancy
and Paris, a distance of 212 miles, requiring but two cups of ordinary
Leclanche battery.
The instrument consists of two permanent horseshoe magnets, fixed
parallel with each other and an inch apart. A very thin spool or bobbin
of insulated wire is suspended, like the pendulum of a clock, between
these permanent magnets, in such a manner that the bobbin hangs just
in front of the four poles. A counterpoise is fixed at the top of the
pendulum bar, which permits the adjusting of the antagonistic forces
represented by the action of the swinging bobbin, and two springs, which
are insulated from the mass, and which form one electrode of the local
or annunciator circuit, while the pendulum bar forms the other.
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