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Jean Sylvain Bailly

Jean Sylvain Bailly
Jean Sylvain Bailly by Jean-Laurent Mosnier (1789) (Carnavalet Museum, Paris)
1st Mayor of Paris
In office
15 July 1789 – 18 November 1791
Preceded by Office established
Succeeded by Jérôme Pétion de Villeneuve
1st National Constituent Assembly
In office
17 June 1789 – 3 July 1789
Preceded by Office established
Succeeded by Jean Georges Lefranc de Pompignan
Deputy of the Estates-General
In office
5 May 1789 – 9 July 1789
Constituency Paris
Personal details
Born (1736-09-15)15 September 1736
Paris, France
Died 12 November 1793(1793-11-12) (aged 57)
Paris, France
Nationality French
Political party Independent
(Supported by Jacobins)
Residence Paris (1736–1791)
Nancy (1791–1793)
Alma mater Academy of Sciences
French Academy
Profession Astronomer, mathematician, politician
Religion Roman Catholicism

Jean Sylvain Bailly (French: ; 15 September 1736 – 12 November 1793) was a French astronomer, mathematician, freemason,[1][2] and political leader of the early part of the French Revolution. He presided over the Tennis Court Oath, served as the mayor of Paris from 1789 to 1791, and was ultimately guillotined during the Reign of Terror.


  • Scientific career 1
    • Scientific papers 1.1
  • During the French Revolution 2
    • Mayor of Paris 2.1
    • Execution 2.2
  • References 3
    • Works 3.1
    • Sources 3.2
    • Further reading 3.3
  • External links 4

Scientific career

Born in Paris, Bailly was the son of Jacques Bailly, an artist and supervisor of the Louvre, and was the grandson of Nicholas Bailly, also an artist and a court painter. As a child he originally intended to follow in his family tradition and pursue a career in the arts, but he became deeply attracted to science, particularly astronomy, by the influence of Nicolas de Lacaille. An excellent student with a "particularly retentive memory and inexhaustible patience",[3] he calculated an orbit for the next appearance of Halley's Comet (in 1759), and correctly reduced Lacaille's observations of 515 stars. He participated in the construction of an observatory at the Louvre. For such achievements he was elected to the 31st seat of the French Academy of Sciences in 1763.[3]

Scientific papers

Bailly published his Essay on the theory of the satellites of Jupiter in 1766, an expansion of a presentation he had made to the Academy in 1763. It was followed up in 1771 by a noteworthy dissertation, On the inequalities of light of the satellites of Jupiter. and in 1778, he was elected a foreign member of the Royal Swedish Academy of Sciences.

Bailly also gained a high literary reputation by his Éloges of King Charles V of France, Lacaille, Molière, Pierre Corneille and Gottfried Leibniz, which were issued in collected form in 1770 and 1790. He was admitted to the Académie française on 26 February 1784, and to the Académie des Inscriptions in 1785, when Bernard le Bovier de Fontenelle's simultaneous membership of all three Academies was renewed in him. From then on, Bailly devoted himself to the history of science, publishing A history of ancient astronomy in 1775, followed by A history of modern astronomy (3 vols., 1782). Other works include Discourse on the origin of the sciences (1777); Discourse on Plato's 'Atlantide' (1779); and A treatise on Indian and Oriental astronomy (1787). Though his works were "universally admired" by contemporaries,[3] later commentators have remarked that "their erudition was… marred by speculative extravagances."[4]

The lunar crater Bailly was named in his honour.

During the French Revolution

The Revolution interrupted his studies. Elected deputy from Paris to the Estates-General (12 May 1789), he was elected inaugural president of the National Assembly (17 June 1789), and led the famous proceedings in the Tennis Court (20 June), being the first to take the Tennis Court Oath. Shortly after the storming of the Bastille (14 July 1789) he became the first mayor of Paris under the newly adopted system of the Commune (15 July 1789 to 16 November 1791).

Sketch by Jacques-Louis David of the Tennis Court Oath. Bailly is pictured in the centre, facing the viewer, his right hand raised.
J.S.Bailly, by Garneray and Alix, after the David's scene above

Mayor of Paris

When Louis XVI made his momentous visit to the Hôtel de Ville to endorse the Revolution (17 July), Bailly presented him with the new symbol of the revolution, the tricolour cockade. Along with the Marquis de Lafayette, he is considered the indisputable hero of the early days of the revolution.

In his function as mayor, he was attacked by Camille Desmoulins and Jean-Paul Marat as too conservative. He continuously sought to promote the authority of the mayor while limiting the power of the General Assembly of the Commune.

One of his actions in this position was to secure, with others, and in the face of threats and ridicule, the passage of a decree of 27 September 1791 (confirmed by Legislative Assembly on 30 November of the same year), which declared Jews to be French citizens, with all rights and privileges. This decree repealed the special taxes that had been imposed on the Jews, as well as all the ordinances existing against them.

The dispersal by the National Guard, under his orders, of the riotous assembly in the Champ de Mars (17 July 1791) made him extremely unpopular, and he retired to Nantes, where he composed his Mémoires d'un témoin (published in 3 vols. by MM. Berville and Barrière, 1821–1822), an incomplete narrative of the extraordinary events of his public life. He was replaced as mayor by Jerôme Pétion (16 November 1791).


In July 1793, Bailly left Nantes to join his friend Pierre Simon Laplace at Melun, but was there recognised and arrested. He was pressed to testify against Marie Antoinette (14 October), but he refused. He was brought (10 November) before the Revolutionary Tribunal in Paris, speedily tried, and sentenced to death the next day. On 12 November he was guillotined at the Champs de Mars, a site selected symbolically as the location of his great betrayal of the democratic movement. He was forced to endure the freezing rain and the insults of a howling mob. When a scoffer shouted, "Tu trembles, Bailly?" ("Do you tremble, Bailly?"), he stoically responded, "Oui, mais c'est seulement de froid." ("Yes, but it is only the cold.") In the words of the 1911 Encyclopædia Britannica, "He met his death with patient dignity; having, indeed, disastrously shared the enthusiasms of his age, but taken no share in its crimes."


  1. ^
  2. ^
  3. ^ a b c Stephens, p. 51.
  4. ^ Encyclopædia Britannica, 1911.


  • ^ a: Essai sur la théorie des satellites de Jupiter, 1766
  • ^ b: Sur les inégalités de la lumière des satellites de Jupiter, 1771
  • ^ c: Histoire de l'astronomie ancienne, 1775
  • ^ d: Histoire de l'astronomie moderne, 1782
  • ^ e: Lettres sur l'origine des sciences, 1777
  • ^ f: Lettres sur l'Atlantide de Platon et sur l'ancienne histoire de l'Asie, 1779
  • ^ g: Traite de l'astronomie indienne et orientale, 1787


  •  This article incorporates text from a publication now in the public domain

Further reading

  • Eloges by Merard de Saint Just, Delisle de Salles, Jérôme Lalande and Lacretelle
  • A memoir by François Arago, read on 26 February 1844 before the Academie des Sciences, and published in Notices biographiques, t. ii. (1852)
  • Delambre, Histoire de l'astronomie au 18me siecle, p. 735
  • Jérôme Lalande, Bibliographie astronomique, p. 730.

External links

  • Portrait of Jean Sylvain Bailly from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections

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