The sight of an apple dropping from its branch, the story goes, was what sparked Newton's mind to formulate the laws of gravity. His contribution to the advancement of science was soon helping watchmakers to a better understanding as to why their watches so annoyingly refused to keep good time for very long. The reason, they found, was the influence exerted by the earth's attraction on the moving parts of their watches according to their position in space: it gradually eroded the accuracy of their timekeeping. In 1795, an answer was provided with A.-L. Breguet's historic invention, which he called the tourbillon regulator (patented on June 26th 1801). It consists of a round carriage or cage, containing the sprung balance determining the movement's beat, and the escapement that 'releases' the mechanical energy stored in the mainspring. As the tourbillon carriage rotates on itself with utter regularity, the balance and escapement successively assume every vertical position - those most subject to gravitational pull - so that the resulting rate errors cancel each other out instead of accumulating.