Melloni's reputation as a physicist rests principally on his discoveries in radiant heat, made with the aid of the
thermomultiplier, a combination of
thermopile and
galvanometer. In 1831, soon after the discovery of
thermoelectricity by
Thomas Johann Seebeck, he and
Leopoldo Nobili employed the instrument in experiments especially concerned with characteristics of (in modern language)
black-body radiation transmitted by various materials. He used an
optical bench fitted with thermopiles, shields and light and heat sources, such as
Locatelli's lamp and
Leslie's cube, in order to show that radiant heat could be
reflected,
refracted and
polarised in the same way as light. His most important book,
La thermocrose au la coloration calorifique (Vol. I., Naples, 1850), was unfinished at his death. He also studied the
magnetism of
rocks,
electrostatic induction and
photography. ==Honours==