by Harvey & Peak, in mahogany with copper disc, glass plate and steel needle, with label 'Harvey & Peak' successors to W Ladd & Co. Beak St, London, tested and working, base 47cm; Note: A copper disk is rotated rapidly with a hand crank and a step-up pulley system. Balanced on a pivot above the center of the disk is a compass needle. The motion of the needle relative to the highly conducting copper disk induces eddy currents and in turn, these produce a torque on the magnetic needle, which starts to rotate.