Escapement of clocks, points to the late 13th century as the most likely date for the development of the modern clock escapement. Astronomer Robertus Anglicus wrote in 1271 that clockmakers were trying to invent an escapement, but hadn't been successful yet. On the other hand, most sources agree that mechanical escapement clocks existed by 1300. Actually, the earliest description of an escapement, in Richard of Wallingford's 1327 manuscript "Tractatus Horologii Astronomici" on the clock he built at the Abbey of St. Albans, was not a verge, but a variation called a "strob" escapement. It consisted of a pair of escape wheels
Grasshopper escapement in the stable block at Brocklesby Park in Lincolnshire. This proved to be unreliable, needing repeated attention by which Harrison was inconvenienced, so around 1722 he modified the escapement by putting a hinge in the middle of each arm of the anchor. The hinged pallets both pointed the same way, opposing the rotation of the escape wheel. As the escape wheel pushes the pallet, the hinge moves away from the escape wheel. The pallet pivots about its contact point with the wheel as it pushes the anchor. At the same time, the other pallet is approaching the wheel. When it