Present status of the investigation on dynamic and tilting deviations in the Department of Terrestrial Magnetism, Carnegie Institution of Washington

This investigation began in 1928 with the study of tilting deviations produced by the inclinations of the planes of the compass-card when subjected to simple harmonic motion over or under a horizontal axis, as in the ideal rolling of a ship in a non-resisting medium or the bed of a swing under its horizontal axis, Such a swing was used in the first experiments, but the results showed the necessity of automatic action and of continuous records throughout the phases of the swing-motion, which are not possible in visual observations. A swing was then designed and constructed in the instrument-shop of the Department. It is made entirely of brass and actuated by an electric motor installed so far away that the motor has no magnetic effect on the compasses to be used in the experiments. The record is obtained by a motion-picture camera located on the swing-frame.