The two other parts of the apparatus are designed for
registering horizontal motions. The first is a pendulum which causes a
contact with four distinct springs, and whose movements are watched with a
spy-glass. The second is a steel spring which carries at its upper part a
heavy ball that vibrates at the least shock. This ball is provided with a
point which is movable within a second ball, so that its motion produces
a contact. All these different contacts are signaled or registered
electrically.
[Illustration: FIG. 7.--SCATENI'S SEISMOGRAPH.]
_Scateni's Registering Seismograph._--This apparatus, which is shown in
Figs. 7 and 8, consists of two parts--of a transmitter and of a
registering device.
[Illustration: FIG. 8.--REGISTERING APPARATUS.]
The transmitter consists of a glass vessel supported upon a steel point
and provided beneath with a platinum circle connected with a pile. All
around this circle are four strips of platinum, against one of which abuts
the circle at every movement of the glass. Each strip of platinum
communicates, through a special wire, with one of the electro-magnets of
the registering device (Fig. 8). This latter consists of an ordinary clock
that carries three concentric dials--one for minutes, one for hours, and
one for seconds.
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