Glossary/Barrel
Barrel
The barrel is a hollow drum which serves to hold the mainspring of a clock or watch. Into its perimeter are cut a series of regularly formed teeth, which allow the barrel to serve as the "first" wheel in a watch or clock.
A spring barrel in conjunction with a fusee has no teeth and drives by winding a chain or gut line round itself. The drum around which the gut, rope, or chain of a weight-driven clock is wound is also a barrel.
Other Meanings
The term barrel can also be used to refer to the drum carrying pins or cams to operate the striking hammers in musical clocks and watches.