A short biography of Silvestre-François Lacroix

Part of the Science Networks. Historical Studies book series (SNHS, volume 35)


A detailed biography of Lacroix is still lacking, despite the articles by René Taton [1953a; 1953b; 1959]. In this chapter the main focus is on his education (in a broad sense) and his career until the publication of the large Traité.


Descriptive Geometry Early Career Integral Calculus Universal Physic Detailed Biography 
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  1. 1.
    In his Procés-verbal d’individualité for the Légion d’Honneur (probably the most official document one may hope for), dating of 1837, Lacroix’s surname appears as “Lacroix (de)”, and the christian names as “Silvestre François”. In a transcript of his baptism certificate the christian names are written “Silvestre françois”, and the family name is “De la Croix” [Lacroix LH] According to his own statement, Lacroix stopped using the particle “de” when addressing a petition to a court in Besançon in 1793 (a time when any hint at aristocracy would not be favourable); having published several works afterwards without the particle, he never retook it [Lacroix IF, ms 2399]. Variations in capitalization and word splitting in names like Lacroix/La Croix/la Croix (or Lagrange/La Grange/la Grange) were common in the 18th and early 19th centuries. As for whether his first name was “Silvestre” or “Sylvestre” (most modern authors refer to him as “Sylvestre”): late 18th/early 19th century Frenchmen had the annoying habit of almost never using their christian names in public, at least not in full — nearly all of Lacroix’s books appeared under the name “S.F. Lacroix”; in manuscript sources there are some (not many) occurrences of his christian names in full, and both “Sylvestre” and “Silvestre” occur (even within his Légion d’Honneur file [Lacroix LH]), but the more official documents tend to have “Silvestre”; this is also how the name appears in its two contemporary printed occurrences that I know of — [Anonymous 1818] and the title page of the first edition of [Lacroix 1795] (see fig. 1.1). I have decided to stick with “Silvestre”. Of course, this is not a very important issue — but one must acknowledge it in an era of computerized searches.Google Scholar
  2. 2.
    On Champigny, see [Grison 1996, 24].Google Scholar
  3. 3.
    All or nearly all the Letters kept in [Lacroix IF, ms 2397] are in fact drafts of letters. It will be assumed that there were not significant changes in the versions posted.Google Scholar
  4. 5.
    The courses of the Collège Royal were open to anyone, and had traditionally been free. It appears that fees were introduced precisely around this time [Torlais 1964, 267]; but presumably these newly introduced fees were not very high.Google Scholar
  5. 7.
    Taton [1951, 24] indicates the years 1781–1782, but Lacroix [Traité, II, 487] spoke clearly of 1780. Since Monge spent the winters in Paris and summers in Mézières, the autumn-winter of 1780–1781 is the most likely. But they certainly contacted again in 1781–1782.Google Scholar
  6. 10.
    According to Libri [1843, 6] it was Monge who recommended him for the post. Grison [1996, 27] has attributed that recommendation to Champigny, citing a letter from the minister of navy to Champigny, dated 8 October 1782 [Lacroix IF, ms 2398]. This letter shows that Lacroix’s protector was interceding in his favour, although with a different place in view, and unsuccessfully: Champigny tried to secure Lacroix a place as “aspirant élève ingénieur constructeur” — something like cadet student of (ship-)building engineering. The minister was sympathetic, but there were no vacancies at the moment.Google Scholar
  7. 12.
    From this period, four letters from Monge to Lacroix survive, dated: 27 January 1783 [Lacroix IF, ms 2396], c. 12 January 1784 [Éc. Pol. Arch, IX GM 1.19], end of August 1785 [É. Pol. Arch, IX GM 1.20–21] (partly transcribed in [Taton 1959, 130], wrongly cited as being kept in the Institut), and end of 1785 [Lacroix IF, ms 2396; Taton 1959, 138–142]; while five drafts of letters from Lacroix to Monge are kept in [Lacroix IF, ms 2397], dated: 10 March 1783, 28 April 1783, 5 August 1783, 11 July 1785, and 9 October 1785 (extract). Their content makes it clear that there were more.Google Scholar
  8. 15.
    Following a complicated path: Lacroix — Champigny — Hassenfratz — Monge — Le Monnier [Grison 1996, 52].Google Scholar
  9. 16.
    Not 15 July, as Wilson [1994, 280] has it.Google Scholar
  10. 19.
    The marriage contract was signed on 5 June 1787 [Lacroix LH].Google Scholar
  11. 23.
    Two lists of his public posts (omitting private jobs, namely at the Lycée), are kept at [Lacroix LH; UF].Google Scholar
  12. 25.
    In 1804 Lacroix published an introduction to mathematical and physical geography, as a first volume of a larger geographical work directed by J. Pinkerton and C. Walkenaer [Lamandé 2004, 105].Google Scholar
  13. 28.
    Grattan-Guinness [1990, I, 143] suggests that Lacroix’s participation in the third volume of Montucla’s Histoire was more extensive. However, I have not seen any other traces of it.Google Scholar
  14. 29.
    Taton [1953a, 593] mentioned an Essai sur l’Histoire des Mathématiques written by Lacroix, unpublished and whose manuscript had apparently vanished. Itard [1973, 550] repeated this. I do not know Taton’s source, but I find it likely that this Essai was simply the Compte rendu... (see page 397).Google Scholar
  15. 31.
    Itard [1973, 550] wrongly gives Borda and Condorcet as examples of Lacroix’s contributions to [Michaud Biographie]. Borda’s entry is in fact by Biot and De Rossel.Google Scholar
  16. 32.
    The diploma is kept at [Lacroix IF, ms 2398]Google Scholar

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