The device has a large rectangular wooden base (67.5 x 34 cm) and is composed of a copper disk (diameter 20.5 cm), mounted on a pin passing through its centre and of a large wooden pulley with a knob for making it rotate by hand.
The rotation of the pulley is transmitted to the copper disk by a belt connecting it to a smaller pulley, it too made of wood, attached to the disk's rotation axis.
Missing is the instrument's glass case which must have contained the magnetic needle (or bar magnet) suspended from a small vertical pin above the centre of the copper disk. In any case, the experiment can be performed by placing a plate of glass lying on the wooden supports which originally held the entire case as the supporting plane for the magnetic needle.