In 1858 Thomson patented his telegraph receiver, called a mirror galvanometer, for use on the Atlantic cable.

Mirror Galvanometer after Thomson - Szymanski; with astatic magnet system and directing magnet with wire connecting blocks for putting the coils in parallel in 2 groups and in series.
The 4 coils have a resistance of 4 ohms each. By removing the front wall the galvanometer can be opened and therefore easily and quicly adjusted. The case is mahogany.

Functioning:
The instrument is highly sensitive and is very suitable for experiments with thermo-electric currents and for demonstrating the currents on cutting the lines of force.