A late 19th century mirror galvanometer, unsigned, possibly French, the mirror suspension viewed through a double apperture, the two coils arranged to slide on the horizontal limb, one coil bound in red, the other in green, coded copper wire, on tripod stand, the cabriole legs terminating in adjustable screw feet - 23in. (58.5cm.) high; and a difference reflecting galvanometer, the mirror with fine micrometer adjustment, the suspension wire encased within a lacquered brass tube, the viewing chamber with two windows, the two coils mounted on glass panels over the circular horizontal base, arranged to rotate over the tripod stand, signed Edelmann, München, No. 36, overall height - 34¼in. (87cm.) (2)