Achille Brocot

Louis Achille Brocot was a French clockmaker and amateur mathematician, born on 11 July 1817 and died on 19 January 1878. He is remembered in mathematics for the Stern-Brocot tree, a structure for listing and approximating real numbers by rational numbers, which he found independently of, and at about the same time as, the German number theorist Moritz Stern. The idea mattered to him as a clockmaker, because choosing gear ratios for clocks is a problem of finding good fractions. In horology he is credited with the Brocot suspension, which lets a clock be regulated by changing the length of the pendulum suspension spring with a key turned at the dial, and with refining his father Louis-Gabriel Brocot's escapement and developing clocks with perpetual calendar mechanisms. In 1851 he founded the Paris firm Brocot and Delettrez with Jean-Baptiste Delettrez, a partnership that lasted until his death.