Abstract
INTRODUCTORY NOTE. THE Horizontal Pendulum.—The observations described in the subjoined article were made with the horizontal pendulum designed by Prof. Zöllner, and modified by Dr. von Rebeur-Paschwitz. This instrument consists of three thin brass tubes jointed together in the form of an isosceles triangle, the vertical angle of which is about 45°. The two equal sides are prolonged slightly beyond the base, and to the ends are attached two small spherical agate cups, the concavity of the lower one being directed from the centre of gravity of the pendulum, and that of the upper one towards it. When the pendulum is placed in position, these cups rest on two steel-points attached to the stand of the instrument and directed normally to the surfaces of the agate cups. One steel-point is almost exactly above the other, so that the axis of rotation is nearly, but not quite, vertical, its inclination to the vertical being still great compared with the movements of the ground we wish to investigate. The pendulum rests in the vertical plane passing through the axis of rotation, and on the side towards which it inclines. If this is towards the east, and if the axis is slightly tilted in the east and west plane, there will be no deflection of the pendulum; the only change will be in its sensitiveness. But if the axis is tilted in any other plane, it will no longer incline towards the east, and the pendulum will be deflected from its original position, in order to remain in the same vertical plane with the axis of rotation. It is evident that the smaller the original inclination of the axis to the vertical, the greater will be the deflection for a given tilt of the axis in the north and south plane; that is, the greater will be the sensitiveness of the pendulum.
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References
NATURE, (July 12, 1894), vol. 50, pp. 246–249; Brit. Assoc. Rep., 1893, pp. 291–303.
Brit. Assoc. Rep., 1892, pp. 107–109.
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DAVISON, C., VON REBEUR-PASCHWITZ, E. On a Remarkable Earthquake Disturbance Observed at Strassburg, Nicolaiew, and Birmingham, on June 3, 1893. Nature 51, 208–211 (1894). https://doi.org/10.1038/051208a0
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DOI: https://doi.org/10.1038/051208a0