A Novel Magnetometer
  A magnetometer has been developed by a simple modification of the TEL-Atomic Cavendish balance designed by the author. The usual tungsten wire fiber has been replaced with a silk thread, and a rare earth magnet has been attached to the boom near where the fiber connects. Because of the mechanical common mode rejection feature of the instrument, pendulous noise is largely removed from this compass-like magnetometer that is quite sensitive to direction changes in the Earth's field. 
Randall D. Peters