This apparatus was designed by Leopoldo Nobili to repeat the experiment invented by Michael Faraday on the rotation of conductors. There are two parts: the lower is a Voltaic battery with two funnels at opposite sides for pouring in the electrolyte (acidified water); the upper carries an upright cylindrical magnet. This rests on the battery's zinc electrode, while the mercury poured into the top's surface depression is connected by means of two wires to the copper container forming the second electrode. The thin rotating brass wire is missing.