Achille Brocot

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Achille Brocot (pronounced "broco"[1]) (11 July 1817 – 19 January 1878) was a French clockmaker[2] and amateur mathematician.[3]

He is known for his discovery (contemporaneously with, but independently of, German number theorist Moritz Stern) of the Stern–Brocot tree, a mathematical structure useful in approximating real numbers by rational numbers; this sort of approximation is an important part of the design of gear ratios for clocks.[4]

He also made many practical horological innovations including refinement of his father Louis-Gabriel's Brocot escapement and the development of clocks with perpetual calendar mechanisms.[5][6] In order to commercially exploit his original designs, together with Jean-Baptiste Delettrez he established the clockmaking company "Brocot & Delettrez" in Paris on 20 October 1851, a partnership that would continue until his death.


  1. ^ Phonetic blunder
  2. ^ Player, J. W. (ed.), Britten's Watch & Clock Makers' Handbook Dictionary & Guide (15th ed.), Taylor & Francis, p. 380.
  3. ^ Mansuy, Roger, Achille Brocot, mathématicien à ses heures (French), CultureMath.
  4. ^ Hayes, Brian (2008), "On the Teeth of Wheels", Group Theory in the Bedroom, and Other Mathematical Diversions, Hill and Wang.
  5. ^ Kirk, John G., The Brocots: A Dynasty of Horologers (PDF). Powerpoint presentation based on Chavigny (1991).
  6. ^ Chavigny, Richard (1991), Les Brocot: une dynastie d'horlogers (French), Antoine Simonin, ISBN 978-2-88175-003-8.