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.