The apparatus consists of a bar magnet (length 22 cm) with pointed ends, arranged vertically between two metal capsules so that it can rotate around its axis.
Two conducting wires soldered perpendicularly, one at the bottom and the other in the centre and bent downwards by ninety degrees, so that they are inside two wooden cups full of mercury at the bottom surrounding the magnet. The higher up of the two cups is supported by three finely-worked wooden columns.
Two small ivory funnels communicating with the two cups are for the purpose of establishing the contacts with the poles of a pile and sending the current to the lower half of the magnet.
Boato - Bruzzaniti (1993), p. 48
Daguin (1878), T. III, p. 703
De La Rive (1854), T. I, p. 243
Jamin (1869), T. III, p. 241