Skeleton clock, French, 1850.
© Science Museum / Science & Society Picture Library
This timepiece is provided with a centre seconds hand and its escapement is of the 'pinwheel' type invented in France about 1740 by Amant, which became very popular on the European Continent, both in its original form and in the modified version devised by Lepaute, also in France, in 1753. The effect of temperature on the pendulum is compensated by the 'gridiron' invented by the British chronometer pioneer, John Harrison (1693-1776) in 1726. The main driving power is provided by a spring in a barrel, and transmitted through a device called a 'remontoire'.