48ft Proceedings of the 



in which ab is a portion of the escape wheel having a tendency to 

 jnove in the direction shown by the arrow ; cd is that sort of escape- 

 ment called the anchor escapement, the parts e/and gh are its pal- 

 lets, I is its centre of motion, and Im is part of the pendulum rod 

 which is connected and moves with the escapement ; the pendulum 

 being" in the diagram, nearly at the extremity of its motion to the 

 right, the end c of the escapement nearly at its greatest depression, 

 and the end c?, of consequence, at its greatest elevation ; the tooth 

 b of the escape wheel is supposed just to have escaped from 

 the angle to the right hand pallet, and the tooth a to have just 

 fallen on the left hand pallet between e and /; as the pendulum 

 returns to the left, the tooth a will rub along the surface ef till 

 it escapes at f, when the tooth k will be immediately caught some- 

 where between g and h ; thus at every vibration of the pendulum a 

 tooth of the wheel would escape, and the wheel be instantly detained 

 on alternate sides of the escapement. The impulse is given to 

 the pendulum by the pressure which the teeth of the escape wheel 

 exert on the surfaces e/and gk alternately tending to elevate the 

 opposite ends of the escapement, and thus to move the pendulum. 



But it must be recollected, that at the instant the tooth b escaped 

 from the pallet at A, and that the tooth a fell on the other pallet at 

 7if the pendulum had not finished its vibration to the right, or there 

 would be a danger of the wheel not escaping at all ; there must 

 be a considerable quantity of motion left in the pendulum, which 

 will carry it, say to o, and during this time the pallet will be rubbing 

 from w to e against the tooth c, and forcing the escape wheel back, 

 in opposition to the direction of the arrow. This effect, which is 

 visible in the second's hands of all common clocks, is called the 

 recoil, and was a property of all the early escapements. It is got 

 rid of by making the pallets of the form shown by the dotted 

 lines, by which it will be seen that each pallet consists of two 

 faces pq, qf, and rs, sh, of which pq and rs are concentric with 

 Z, the centre of the escapement's motion, consequently, when the 

 teeth of the wheel are rubbing against them, no motion can be 

 transmitted either way, and the impulse to the pendulum is given 

 only while the teeth are pressing against the surfaces qfor sh. 

 This sort of escapement is called the dead beat, from the absence 

 of that recoil which gives name to the other. 



The objection to the recoil is, that it is caused by the pendulum, 

 and thus interferes with that freedom of motion on which the iso- 

 chronism of the pendulum depends. It is prejudicial on account 

 of the inequality of resistance which is made to the recoil by the 



