Anchor escapement clocks. During the 19th century the deadbeat form gradually took over in most quality clocks, but the anchor form is still used in a few pendulum clocks today. The anchor escapement is reliable and tolerant of large geometrical errors in its construction, but its operation is similar to the old verge escapement, and retains two of the major disadvantages of the verge: The above two disadvantages were removed with the invention of an improved version of the anchor escapement: the deadbeat or Graham escapement. This is often erroneously credited to English clockmaker George Graham who introduced it around 1715 in
Anchor escapement is still a frictional rest escapement because the sliding of the escape tooth on the dead face adds friction to the pendulum's swing, but it has less friction than the recoil escapement because there is no recoil force. In contrast to the backward slant of the anchor escape wheel teeth, the deadbeat escape wheel teeth are radial or slant forward to ensure that the tooth makes contact with the 'dead' face of the pallet, preventing recoil. In 1826 British astronomer George Airy proved that a pendulum that is driven by a drive impulse that is symmetrical about its bottom equilibrium