Sir George Biddell Airy (1801 - 1892) was Astronomer Royal of the UK from 1835 to 1881.
The small escape-wheel is driven by the helical spring (seen in side view, fig. 8), and gives impulse on the pallets of the large anchor: the train is locked by the large escape-wheel on one or other pallet of the small anchor. The pendulum moving the anchor unlocks the train, the larger escape-wheel runs on and locks, winding up the helical spring. The small escape-wheel impelled by the spring lifts the pallet of its anchor, and thus gives impulse. http://www.westwood-tech.com/lemur/dmh-frodsham-remontoire.html
