ELECTRICITY APPLIED TO THE STUDY OF SEISMIC MOVEMENTS.


Italy, with her volcanic nature, has very naturally made a specialty of
movements of the ground, or seismic perturbations. So the larger part of
the apparatus designed for such study are due to Italians. Several of
these instruments have already been, described in this journal, and on the
present occasion we shall make known a few others that will serve to give
an idea of the methods employed.

For the observation of the vertical and horizontal motions of the ground,
different apparatus are required. The following is a description of those
constructed for each of such purposes by the Brassart Brothers.

[Illustration: FIG. 1.--APPARATUS FOR THE STUDY OF HORIZONTAL SEISMIC
MOVEMENTS.]

_Apparatus for Studying Horizontal Movements._--A lever, (Fig. 1), movable
about a horizontal axis, carries a corrugated funnel, _i_, at one of its
extremities. At the other extremity it is provided with a counterpoise
which permits of its being exactly balanced, while not interfering with
its sensitiveness.

[Illustration: FIGS. 2 AND 3.--DETAILS OF THE APPARATUS.]

The opening of the funnel passes freely around a column, _v_ (Fig. 2),
upon which is placed in equilibrium a rod that terminates in a weight, P.
The corrugations of the funnel carry letters indicating the four cardinal
points, and the funnel itself is capable of revolving in such a way that
the marked indications shall always correspond to the real position of the