**François Folie** was a Belgian mathematician and astronomer.

- Belgium had declared itself independent of the Netherlands in 1830, before François was born, but after a military conflict in 1831 there was a long period during which the status of Belgium was decided by the international community.
- Anselme Folie moved to Liège, in Belgium, where he was appointed commander of the School of Pyrotechnics.
- It was in Liège that François Folie was educated and, indeed, he spent most of his life in this city.
- At the College in Liège, Folie made an important friendship which lasted for over 50 years.
- This was with Joseph Delboeuf who went on to have an academic career similar to that of Folie.
- After leaving the College, Folie studied at the University of Liège and was awarded a doctorate in mathematics and physics, with distinction, on 13 August 1855.
- Seven years later, he began an investigation of variable stars and, at around the time that Folie began to study with him, he was beginning to publish the Bonner Durchmusterung Ⓣ(Observations from Bonn), a major star catalogue of over 300,000 northern hemisphere stars which he had spent twenty-five years compiling.
- Folie made longer visits to Bonn in 1859 and 1862 and during these visits he got to know Rudolf Clausius and, as a consequence, became very familiar with the mechanical theory of heat.
- Folie requested that he be allowed to deliver a free course at the University of Liège on the mechanical theory of heat and he was given permission to begin teaching such a course in 1867.
- It was after making these visits to Bonn that Folie began publishing papers.
- Jean-Baptiste Brasseur had been a senior member of the faculty at Liège during the years that Folie had been a student there, and later the two had become colleagues.
- Brasseur died in 1868 and, later that year, Folie published lecture notes of his teacher, to which he had added notes, Exposition nouvelle des principes du calcul différentiel et du calcul intégral de J-B Brasseur, publiée et augmentée de notes et d'un avant-propos par F Folie Ⓣ(New exposition of principles of calculus and calculus of J-B Brewer, published and augmented with notes and a foreword by F Folie) (1868).
- In the same year Folie published the first of two volumes of Théorie mécanique de la chaleur, de R Clausius which he had translated from the German into French.
- The second volume, also translated by Folie, appeared in 1869.
- Although he continued to be interested in applied mathematical topics, Folie had learnt about the latest developments in geometry from Jean-Baptiste Brasseur and soon he began to publish in this area.
- Le Paige took over teaching the Geometry Course that Folie had been giving in 1879.
- Folie and Le Paige collaborated on a number of important works, particularly Sur les courbes du troisième ordre Ⓣ(On the curves of the third order)(1882, 1884).
- Folie was appointed director in 1885 and, during the next years, he supervised the construction of a new national Observatory at Uccle.
- Although we have considered only scientific contributions by Folie above, he did in fact make other contributions.
- Folie was honoured for his contributions by being elected a corresponding member of the Royal Belgium Academy of Science (Académie Royale des Sciences, des Lettres et des Beaux Arts) on 15 December 1869.

Born 11 December 1833, Venlo, Belgium (now Netherlands). Died 29 January 1905, Liège, Belgium.

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Astronomy, Origin Netherlands

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive