Macedonio Melloni (11 April 1798 – 11 August 1854) was an Italian

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

, notable for demonstrating that

radiant heat Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electro ...

has similar physical properties to those of light.

Life

Born at

Parma Parma (; ) is a city in the northern Italian region of Emilia-Romagna known for its architecture, Giuseppe Verdi, music, art, prosciutto (ham), Parmesan, cheese and surrounding countryside. With a population of 198,986 inhabitants as of 2025, ...

, in 1824 he was appointed professor at the local

University A university () is an educational institution, institution of tertiary education and research which awards academic degrees in several Discipline (academia), academic disciplines. ''University'' is derived from the Latin phrase , which roughly ...

but was compelled to escape to France after taking part in the revolution of 1831. In 1839 he went to

Naples Naples ( ; ; ) is the Regions of Italy, regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 908,082 within the city's administrative limits as of 2025, while its Metropolitan City of N ...

and was soon appointed director of the

Vesuvius Observatory The Vesuvius Observatory () is the surveillance centre for monitoring the three volcanic areas of Campania, Italy: Mount Vesuvius, the Phlegrean Fields and Ischia. Founded in 1841 on the slopes of Mount Vesuvius by Ferdinand II of Bourbon, Ki ...

, a post that he held until 1848. In 1845, he was elected a foreign member of the

Royal Swedish Academy of Sciences The Royal Swedish Academy of Sciences () is one of the Swedish Royal Academies, royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for promoting nat ...

. He died at Portici, near Naples, of

cholera Cholera () is an infection of the small intestine by some Strain (biology), strains of the Bacteria, bacterium ''Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea last ...

, aged 56.

Work

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 A thermopile is an electronic device that converts thermal energy into electrical energy. It is composed of several thermocouples connected usually in series or, less commonly, in parallel. Such a device works on the principle of the thermoel ...

and

galvanometer A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely. Galvanomet ...

. In 1831, soon after the discovery of

thermoelectricity The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...

by Thomas Johann Seebeck, he and Leopoldo Nobili employed the instrument in experiments especially concerned with characteristics of (in modern language)

black-body radiation Black-body radiation is the thermal radiation, thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific ...

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 Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The ...

refracted In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenome ...

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 Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, ...

rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wale ...

electrostatic induction Electrostatic induction, also known as "electrostatic influence" or simply "influence" in Europe and Latin America, is a redistribution of electric charge in an object that is caused by the influence of nearby charges. In the presence of a charg ...

and

photography Photography is the visual arts, art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is empl ...

Honours

Rumford Medal The Rumford Medal is an award bestowed by the Royal Society for "outstanding contributions in the field of physics". The award is named in honour of British scientist Sir Benjamin Thompson, Count Rumford, who is noted for his works on thermody ...

of the

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

(1834); *Correspondent of the

Académie des Sciences The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...

(1835); *Foreign member of the Royal Society, (1839).

References

{{DEFAULTSORT:Melloni, Macedonio 1798 births 1854 deaths People from Parma Deaths from cholera in Italy 19th-century Italian physicists Foreign members of the Royal Society Members of the French Academy of Sciences Members of the Royal Swedish Academy of Sciences Recipients of the Pour le Mérite (civil class) Infectious disease deaths in Campania

Life

Work

Honours

See also

References