Signedon brass cover: THE LEEDS & NORTHRUP CO. / PHILADELPHIA
Inscribedon plaque, on top: PATENTED / June 20th 1905
FunctionElectrical apparatus used in measuring very low voltage potentials for calibrating equipment. When a current is applied to the galvanometer, a small variation will create a torque motion on the mirror. A light is then beamed on the mirror, which will be redirected away from the galvanometer towards a graduated scale. The position of the reflected light on that scale will indicate the variation of the current detected by the galvanometer.
ProvenancePsychology Department, William James Hall, Harvard University.