This electromagnetic coil developed by Leopoldo Nobili consists of a wooden pedestal weighted with a lead ring set in the base supporting two flat coils. The inner coil rotates inside the outer one, its two ends dipping in mercury poured into two small wooden compartments. The electric circuit is completed by connecting one end of the fixed coil to terminals and the other end to one of the two compartments containing mercury. Both coils are activated when the apparatus is connected to a battery and their mutual action will cause the inner coil to rotate on its axis. Provenance: Lorraine collections.