Harrison's eight-day clock movement, 1715.
© Science Museum / Science & Society Picture Library
This clock was made by the chronometer pioneer John Harrison (1693-1776) at the age of 22, before he began his celebrated project to build a chronometer accurate enough to find a ship's longitude at sea. The clock movement is made almost entirely of wood; partly, it is thought, to reduce the need for lubrication, but also because Harrison was a carpenter by trade. The clock movement was weight-driven and would have been mounted in a long case with a pendulum. Side view.