Description

This instrument is a black metal box mounted to a board. The instrument has a glass rectangular window that reveals the central chamber, which has a small circular mirror attached to a metal piece. There are two electrical connectors on the base. The front of instrument is stamped with "Leeds and Northrup Co Philadelphia.”

Mirror galvanometers measure the strength of an electric current. When a current passes through the instrument (via the two connectors on the base), the current passes through the cord that suspends the mirror, twisting it slightly. When a light is shined on the mirror, the twisting causes the reflected light to move. The position of that reflected light on a graduated scale indicates the current running through the instrument. At the time they were invented, these galvanometers were more sensitive than other similar instruments, and were used to sense very weak currents. Instruments like these were also used in physics classrooms to demonstrate electrical principles.

MIT No. 652617, Serial No. 652617, "Sens: .002 uc/mm, CDRX: 12000, Period: 21.8 seconds, Resist: 2103, CAT No. 2239-D"