Museo Galileo
Virtual Museum
Chain fusee
Chain fusee

The fusee is a cone-shaped device mounted on a gear wheel meshing with the clock's first drive wheel. It carries a helical groove running from top to bottom, in which the gut is wound when the spring is loaded. The spring's force causes the fusee to rotate, unwinding the gut. Beginning in the mid-seventeenth century, the gut was gradually replaced by the chain with jointed links.