Brian Law's woodenclocks - Clock 16 - Verge and Foliot

Clock16 design is based on the traditional Verge and Foliot escapement with a spring drive mounted in the bottom gear. The original design was the first mechanical clock design to be developed in the middle of the 14th Century.
The escapement consists of two flaps mounted on the vertical Verge shaft that alternatively engage and disengage with the series of pegs around the periphery of the escape wheel, the speed at which this happens is controlled by two weights mounted on the horizontal Folio beam.
The larger the weight and the further out it is positioned the slower the Clock will run.
This type of clock design was never very accurate, but it persisted right up to the 18th century. the design was eventually superseded by the much more accurate Pendulum designs.

http://www.woodenclocks.co.uk/