Macedonio Melloni (11.04.1798-11.03.1854) was an Italian physicist. He was born in Parma. He studied at the University of Parma and also in Paris. In 1824—31 he was professor at the University of Parma. In 1831-39 he lived in Paris, and from 1839 he was director of the School of Arts and Crafts (Naples).
His work concerned the study of thermal radiation. He invented a device for measuring thermal radiation, consisting of a galvanometer and a thermocouple (the Melloni optical bench). In 1831, together with L. Nobili, he studied the thermal spectrum of the Sun and the “transparency” of various bodies to heat rays, and in 1833 he established that the latter are not homogeneous and are transmitted differently by different bodies. He studied thermal radiation from artificial sources (1834). He attempted to compare (1835) the emissive powers of bodies. He observed the reflection and refraction of heat rays, and showed that, depending on the character of the reflecting surface, their reflection may be specular or diffuse (1841). Independently of J. Forbes he discovered (1836) the polarisation of heat rays. He suggested that heat, light and ultraviolet rays are of the same nature and differ only in wavelength (1835). He constructed (1833) a thermopile.
A Fellow of the Royal Society (1839) and a corresponding member of the St Petersburg Academy of Sciences (1836).