MACEDONIO

MELLONI (1798-1854)  , Italian physicist, was born at Parma on the lath of April 1798 . From 1824 to 1831 he was professor at Parma, but in the latter year he was compelled to escape to France, having taken part in the revolution . In 1839 he went to Naples and was soon appointed director of the Vesuvius observatory, a post which he held until 5848 . Melloni received the Rumford medal of the Royal Society in 1834 . In 1835 he was elected correspondent of the Paris Academy, and in 1839 a .foreign member of the Royal Society . He died at Portici near Naples of cholera on the lath of August 1854• Melloni's reputation as a physicist rests especially on his discoveries in radiant heat, made with the aid of the thermomultiplier or combination of thermopile and galvanometer, which, soon after the discovery of thermoelectricity by T . J . Seebeck, was employed by him jointly with L . Nobili in 1831 . His experiments were especially concerned with the power of transmitting dark heat possessed by various substances and with the changes produced in the heat rays by 'passage through different materials . Substances which were comparatively transparent to heat he designated by the adjective " diathermane," the property being " diathermaneite," while for the heat-tint or heat-coloration produced by passage through different materials he coined the word " diathermansie." In English, however, the terms were not well understood, and " diathermancy," was generally used as the equivalent of " diathermaneite." In consequence Melloni about 1841 began to use " diathermique " in place of " diathermdne," " diathermasie " in place of "diathermaneite," and " thermocrose " for " diathermansie." His most important book, La thermocrose au la coloration calorifique (vol. i., Naples, 1850), was unfinished at his death . He studied the reflection and polarization of radiant heat, the magnetism of rocks, electrostatic induction, daguerrotypy, &c .