A Longitude Timekeeper by Isaac Thuret with the Balance Spring Invented by Christiaan Huygens

The recent discovery of an extremely interesting clock signed Thuret A Paris reveals that this clockmaker was much more closely involved in the development of a clock to be used for finding longitudes at sea than has generally been assumed. Isaac Thuret was the clockmaker who made for Christiaan Huygens the first watch with a spiral spring regulating the movements of the balance wheel in 1675. The conflict about his contribution to the invention is usually seen as having ended their cooperation. However, a closer study of Huygens's correspondence strongly suggests that this was not the case. This longitude timekeeper, provided with the pirouette as published by Huygens but abandoned by the makers of pocket watches, supports this view. Its close correspondence in design with the later marine chronometers (no remontoire or fusee) confirms that Huygens and Thuret, apart from the pirouette, were on the right track. However, it would take a century before the reliability and accuracy of the mechanical timekeeper reached the level required for measuring longitudes.