This apparatus was made by Tecnomasio Italiano after the specimens built by Leopoldo Nobili for his electromagnetic kit (inv. 1553), but resembles one of the items (no IX) in the kit. A small rectangular coil is mounted on a wooden base. An adjacent support carried a thin conductor (missing), connected to a circuit comprising a battery by means of depressions filled with mercury. The conductor's position depended on the magnetic field produced by the coil.