Tourbillon

In horology, a tourbillon is an addition to the mechanics of a watch escapement to increase accuracy. Conceived by the British watchmaker and inventor John Arnold, it was developed by his friend, the Swiss-French watchmaker Abraham-Louis Breguet, and patented by Breguet on 26 June 1801. In a tourbillon the escapement and balance wheel are mounted in a rotating cage, with the goal of eliminating errors of poise in the balance giving a uniform weight.