The thermoelectric pile designed by Leopoldo Nobili (1784-1835), professor of physics at the Institute and Royal Museum of Florence, consists of a series of bismuth and antimony bars connected in a zigzag pattern so as to form a right parallelepiped with a square base.
In this exemplar, which is quite similar to Nobili's original model, the antimony-bismuth couples are thirty-six in all and are arranged in six files of six couples each.
Both the bases of the parallelepiped have a side of 3.8 cm and the odd-numbered connections are all on one of them and the even-numbered ones are all on the other.
The two elements at the end of the series are connected to two clamps dislocated horizontally on the surface of the side of a cylindrical brass case (diameter 9 cm, height 12 cm) containing the entire parallelepiped and is connected to a trumpet-shaped receiver.
The apparatus is held by a hinged brass staff which, being capable of sliding inside a column (with a circular base in lathed wood), allows variation both of its orientation and its height (maximum 72 cm, minimum 45 cm). If one of the bases is heated, a difference in potential forms, depending on the difference in temperature and equal to thirty-six times what there would be if only a single couple were used between the two clamps.
The device, when connected to Nobili's astatic galvanometer, represents a differential thermoscope of very high sensitivity (which Nobili called a Termo-Scopio Elettrico or Termo-Moltiplicatore) and the two blackened bases make it a good detector of integral radiation.
The sensitivity of this thermoelectric pile is greatly increased by the use of the trumpet receiver; in fact, on turning the trumpet towards the source, the radiation that strikes the internal surface of the two walls, which have a very high degree of reflectivity, is concentrated on the pile.
The other face of the pile is protected by the cylindrical brass case and a lid, it too brass, which closes the free base.
This pile, which was modified on the suggestion of Macedonio Melloni (1798-1854) professor of physics in Parma, was used by Nobili and Melloni for research on radiant heat, the results of which were presented to the French Academy of Science in Paris on 5 September 1831.
M. Melloni, La thermocrôse ou la coloration calorifique, Napoli 1850, p. XII
L. Nobili, Memorie ed osservazioni edite ed inedite, Firenze 1834, Tav. VII fig. 3, Vol. 1, p. 157, p. 195
Privat Deschanel (1869), p. 404
Ragozzino-Schettino (1993), p. 162