The device, built by the machine-operator of the Physics Laboratory and Assistant Preparer Giuseppe Dessì (on one of the sides of the base we find the words: "Cagliari G. Dessì 1865"), is composed of a thin brass staff (length 38 cm) with a very fine point fixed, by means of an insulating glass rod, to a square wooden base (10 x 10 cm). It was used in electrostatic experiments on pointed conductors.