In a Paper read before this Society on February 9, the Eötvös Torsion Balance was described in detail, and the theory of its operation considered, the preparation of suitable torsion wires was mentioned, but no practical tests with the instrument were discussed.
In view of the sensitivity of the balance, which, as previously stated, measures derivatives of gravity of the order of 10-9 C.G.S. units, it was anticipated that a gravitational survey of the laboratory would disclose the varying effects of the neighbouring masses of the walls, pillars, &c. The balance was therefore set up at different stations in the laboratory, and the derivatives at each station measured. The measurements at several stations were checked by repetition, and the results compared with the theoretical values.
The mutual consistency of the results obtained at each station, and their general agreement with the calculated effects exceeded expectations, as the local gravitational field varied so rapidly that the theoretical assumption of a uniformly varying field in the neighbourhood of a station was obviously vitiated.