Each spring and tongue is connected with
terminals affixed to the base of the apparatus. One of the poles of one
element, P, of the pile is connected with the tongue and corresponding
screw, while the other pole is connected with the screw in front of it
through the intermedium of a galvanometer, g squared, which gives the
intensity of the intermittent current, and of a resistance coil,
b squared, which performs the role of an artificial telegraph line. The
apparatus being set in operation, it will be seen that the current from
the pile is emitted once at every vibration.
Thus there may be exhausted as many pile elements as there are springs,
and that, too, simultaneously; and the contacts of the screws and
springs can be regulated in such a way that the duration of the
emissions shall be the same for all.
At the laboratory of the School of Telegraphy one of these instruments
has operated without interruption, day and night, during eighteen
months.
[Illustration: FIG. 4.--VERY RAPID ELECTRIC TUNING FORK]
The apparatus shown in Fig. 4 is also an interrupting electro-tuning
fork, but it makes a much greater number of vibrations than the
preceding, and may serve for other electric tests.
The operation of the tuning fork is kept up electrically by the aid of
the screw, v, and the corresponding plate; of the style, s, and of
the fine wire spiral spring, f, both insulated from the fork, from the
electro-magnet, N, and from the two wires, F F', which communicate with
a pile.
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