Person: De Billy, Jacques
Jacques de Billy was a French Jesuit who corresponded with Fermat and produced a number of results in number theory which have been named after him.
Mathematical Profile (Excerpt):
 The Jesuit Order had been created about sixty years before de Billy was born and, from the very beginning, education and scholarship became the principal work of the Order.
 By the time Billy entered the Order it contained around 15,000 men.
 Billy taught mathematics and theology at Jesuit colleges all his life, in particular those colleges which were in the administrative region of Champagne, a region which covered the presentday northeastern French districts of Marne and parts of Ardennes, Meuse, HauteMarne, Aube, Yonne, SeineetMarne, and Aisne.
 From 1631 to 1633 Billy taught mathematics at the Jesuit college at Rheims.
 After this Billy taught in Grenoble and then was rector of a number of Jesuit Colleges in Chalons, Langres and in Sens.
 Billy corresponded with Fermat and produced a number of results in number theory which have been named after him.
 He also published astronomical tables such as Tabulae Lodoicaeae seu universa eclipseon doctrina tabulis, praeceptis ac demonstrationibus explicata.
 Adiectus est calculus, aliquot eclipseon solis & lunae, quae proxime per totam Europam videbuntur Ⓣ(Tables of eclipses, the principles and explanations.
 This was a table of eclipses for the years 1656 to 1693 and included solar and lunar tables.
 Billy is also important in being one of the first to reject the role of astrology in science, along with superstitious notions about the malevolent influence of comets.
 Among Billy's most important works are: Abrégé des préceptes d'algèbre Ⓣ(Abstract algebraic precepts) (1637); Nova geometricae clavis algebra Ⓣ(New key geometrical algebra) (1643); Tractatus de proportione harmonicae Ⓣ(Treatise on the harmonic ratio) (1658); and Diophantus geometria sive opus contextum ex arithmetica et geometria simul Ⓣ(The work of Diophantus on geometry and arithmetic and geometry) (1660).
Born 18 March 1602, Compiègne, France. Died 14 January 1679, Dijon, France.
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Tags relevant for this person:
Astronomy
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 nonGithub:
 @JJO'Connor
 @EFRobertson
References
Adapted from other CC BYSA 4.0 Sources:
 O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive