This thermopile contains 18 identical components consisting of a bar of bismuth and antimony welded together at the ends and surrounded by a solid insulator. These duplets are housed in the bottom of a brass cone and connected to two terminals. The thermopile is based on the thermoelectric effect discovered in 1821 by Thomas Seebeck (1770-1831): if the junction between two metals (e.g. antimony and bismuth) is heated, a current proportional to the temperature is produced in the “thermoelectric couple”. Thermopiles made up of a number of couples were used in around 1830 by Italian physicists Leopoldo Nobili (1784–1835) and Macedonio Melloni (1798-1854) to detect the intensity of thermal radiation, as part of pioneering studies on “radiant heat”.

Device on display.