the pendulum and the balance spring in the mid-17th century made clocks and watches much more isochronous, by making the timekeeping element a harmonic oscillator, with a natural "beat" resistant to change. The pendulum clock with an anchor escapement, invented in 1670, was sufficiently independent of drive force so that only a few had fusees. In pocketwatches, the verge escapement, which required a fusee, was gradually replaced by escapements which were less sensitive to changes in mainspring force: the cylinder and later the lever escapement. In 1760, Jean-Antoine Lépine dispensed with the fusee, inventing a going barrel to power the watch gear train directly. This contained a very long mainspring, of which only a few turns were used to power the watch. Accordingly, only a part of the mainspring's 'torque curve' was used, where the torque was approximately constant. In the 1780s, pursuing thinner watches, French watchmakers adopted the going barrel with the cylinder escapement. By 1850, the Swiss and American watchmaking industries employed the going barrel exclusively, aided by new methods of adjusting the balance spring so that it was isochronous. England continued to make the bulkier full plate fusee watches until about 1900. They were inexpensive models sold to the lower classes and were derisively called "turnips". After this, the only remaining use for the fusee was in marine chronometers, where the highest precision was needed, and bulk was less of a disadvantage, until they became obsolete in the 1970s. References , p. 121 , p. 127-128 , p. 63-69 Notes External links Kover, London - 18th Century Watchmaker Blog to discover Kover pocket watches that still exist and documents that refer to the watchmaker Timekeeping components