Thomson's Mirror Galvanometer

A sensitive galvanometer designed by William Thomson (later Lord Kelvin) in 1858 to detect the current through the Atlantic cable. A small mirror is suspended by a thread between two coils, and on the back of the mirror are glued several short and light magnets. The curved bar over the galvanometer case is a permanent magnet which can be rotated and raised or lowered to minimize the effect of the earth's magnetic field and to center the supension system. The instrument was purchased from Queen & Co. for $30, but the date is not known.

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Electricity_and_Magnetism

Galvanometers

James W. Queen & Co.

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