Early measurements of extremely small currents used sensitive galvanometers which depended on the deflection of a mirror on a coil to determine the current. To increase the length of the path from the mirror to the observer and hence increase the deflection seen and therefore the sensitivity, a lamp and mirror system was used between the observer and the galvanometer. This system was developed by Leeds and Northrup for use with the galvanometers catalogued as artifacts 2022-048 and 2022-050. This device was used by Nuclear Physics Branch at Chalk River.
