Working at the top-end of haute horlogerie, Van Cleef & Arpels watches must, of course, be flawless examples of the many trades involved. For the watchmaker, the most novel and complex of these is the Ronde des Papillons. The hours are indicated by the wing of a swallow and the minutes by circling butterflies which move at varying speeds. This variation becomes more obvious when the one-hour relay is run in ten seconds – a performance that can be repeated at will at the press of a lateral pusher.
Gears – or “wheels” as horologists tend to call them – are usually round, and a sequence of such wheels will turn at constant speeds depending on their relative numbers of teeth. There has long been a fascination, however, in producing gears that are not round. Producing novelty systems using triangular, square, or even clover-leaf shapes was a popular pastime for Victorian gentlemen in their home workshops. Enthusiasts now conceive of even more elaborate systems using CAD programs on home computers. The varying speed of the butterflies in the Ronde des Papillons is due to the use of oval gears.