Mechanical watch

A mechanical watch is a watch that uses a clockwork mechanism to measure the passage of time, as opposed to quartz watches which function using the vibration modes of a piezoelectric quartz tuning fork. A mechanical watch is driven by a mainspring which must be wound either periodically by hand or via a self-winding mechanism. Its force is transmitted through a series of gears to power the balance wheel, a weighted wheel which oscillates back and forth at a constant rate.

A device called an escapement releases the watch's wheels to move forward a small amount with each swing of the balance wheel, moving the watch's hands forward at a constant rate.
The escapement is what makes the 'ticking' sound which is heard in an operating mechanical watch.
Mechanical watches evolved in Europe in the 17th century from spring powered clocks, which appeared in the 15th century.

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Source: Wikipedia · Image: Wikimedia Commons · CC BY-SA 3.0