Jules Louis Gabriel Violle (November 16, 1841, Langres

Langres

Langres is a commune in north-eastern France. It is a subprefecture of the Haute-Marne département in the Champagne-Ardenne region.-History:As the capital of the Romanized Gallic tribe the Lingones, it was called Andematunnum, then Lingones, and now Langres.The town is built on a limestone...

, Haute-Marne

Haute-Marne

Haute-Marne is a department in the northeast of France named after the Marne River.-History:Haute-Marne is one of the original 83 departments created during the French Revolution on March 4, 1790...

 - September 12, 1923, Fixin

Fixin

Fixin is a commune in the Côte-d'Or department in the Bourgogne region on the Grand Crus route in eastern France.-Administration:- Population :-Sights:...

) was a French

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 physicist

Physicist

A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

 and inventor.

He is notable for having determined the solar constant

Solar constant

The solar constant, a measure of flux density, is the amount of incoming solar electromagnetic radiation per unit area that would be incident on a plane perpendicular to the rays, at a distance of one astronomical unit...

 at Mont Blanc

Mont Blanc

Mont Blanc or Monte Bianco , meaning "White Mountain", is the highest mountain in the Alps, Western Europe and the European Union. It rises above sea level and is ranked 11th in the world in topographic prominence...

 in 1875, and, in 1881, for proposing a standard for luminous intensity

Luminous intensity

In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye...

, called the Violle, equal to the light emitted by 1 cm² of platinum

Platinum

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...

 at its melting point

Melting point

The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

. (It was notable as the first unit of light intensity that did not depend on the properties of a particular lamp, but it was made obsolete by the candela

Candela

The candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function . A common candle emits light with a luminous intensity of roughly one candela...

, the standard SI

Si

Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...

 unit.)

Throughout his life, Violle taught at several colleges including the University of Lyon

University of Lyon

The University of Lyon , located in Lyon and Saint Etienne, France, is a center for higher education and research comprising 16 institutions of higher education...

 and the Conservatoire des Arts et Métiers in Paris

Paris

Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

. He was one of the founders of the Institut d'optique théorique et appliquée and the École supérieure d'optique

École supérieure d'optique

The École supérieure d'optique , nicknamed "SupOptique", is the leading French grande école in the field of optics and its industrial and scientific applications, and a member of the prestigious UniverSud Paris and ParisTech...

. He improved and invented a number of devices for measuring radiation, and determined the freezing

Freezing Point

Freezing Point is a news journal in the People's Republic of China which has been the subject of controversy over its criticism of Communist Party officials and the sympathetic ear it lent to a Chinese historian who had criticized official history textbooks...

 and melting point

Melting point

The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

s of palladium

Palladium

Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired...

.

Violle is believed by some to be the secret identity of Fulcanelli

Fulcanelli

Fulcanelli is almost certainly a pseudonym assumed, during the early 20th century, by a French alchemist and esoteric author, whose identity is still debated. The name Fulcanelli seems to be a play on words: Vulcan the ancient Roman god of fire plus El, a Canaanite name for God and so the Sacred Fire...

, a contemporary French alchemist whose true identity is still debated.