Invention of the "chronomètre à doubles secondes"
A.-L. Breguet was behind the modern chronograph, notably with his “observation chronometer with split seconds”, the ancestor of all split-seconds chronographs.
Observation chronometer
Invention of the “montre à double secondes” or observation chronometer, forerunner of the modern chronograph.
Chronographs indicate the length of a period of time elapsed. With his split-seconds, or observation, chronograph of 1820 which allowed the measurement of intermediate periods, or of the time elapsed during two separate but simultaneous events, Breguet laid the foundations for modern chronographs.
Breguet watch no. 4009, a ‘double-seconds “observation” chronograph’, or split-second stop watch, sold on 6 January 1825 to Mr Whaley. The two chronometer hands are started by means of the two push-pieces set to either side of the pendant.