Wheel composed of a toothed disc and a cylindrical box closed by a cover. The barrel turns freely on an arbor and contains the mainspring, which is hooked to the barrel at its outer end and to the arbor at its inner end. The barrel meshes with the first pinion of the (watch)train of a watch; it rotates slowly, its arc of rotation varying between one ninth and one sixth of a revolution per hour.

• Hanging Barrel: i.e. fixed to the movement only by its upper portion, under a bar

Plain Barrel: i.e. without teeth, used in fusee watches; the chain, or catgut, was coiled round the plain barrel, connecting it to the fusee.

Source: G.A. Berner 4-language Glossary, 1988 re-edition, courtesy FH, Federation of the Swiss Watch Industry, Bienne, Switzerland

External Berner Glossary Source:

• FH Glossary (http://fhs.ch/en/glossary.php?PHPSESSID=6f6571e99b125238ac18a59f24bff8f5/)