34 



the arc of vibration, and accordingly this escapement is never 

 adopted in an astronomical clock. 



" To avoid the bad effects of a recoil, the justly celebrated 

 Graham invented that species of escapement which is called 'dead 

 beat,' in which the faces of the pallets are circular as well as 

 concentric, and allow the teeth of the escapement wheel to rest on 

 them, while the pendulum is completing its vibration, after receiving 

 its impulse ; this wheel, therefore, never recedes, and the hand 

 carried by it remains motionless, or dead, for a certain portion of 

 each vibration. The rubbing of the teeth against the circular 

 portion of the pallet, however, produces some friction, that requires 

 a little fine oil to lubricate the parts of action, and an addition 

 given to the maintaining power by increasing this friction retards 

 the rate of going. Hence the wheel work is usually made with the 

 greatest care, and pinions of not fewer than eight or ten leaves 

 each, are nicely fitted, hardened, and polished, to diminish the 

 irregularities of transmitted force ; the pivot holes also of the 

 two wheels' last arbors, as well as the pallets themselves, are 

 frequently jewelled in the best clocks, to avoid friction as much as 

 possible, and to supersede the necessity of applying much oil. 

 Escapements of this description have long been held in high 

 estimation when they have had the advantage of being united with 

 a well-compensated pendulum. Indeed, till within these few years, 

 no other escapement was put in competition with it, and the 

 observations made in the different public observatories for half a 

 century back bear testimony to its competency. The circumstance 

 of its giving the impulse to the pendulum at or near the lowest 

 point of its arc when its momentum is a maximum, affords a most 

 important advantage." 



This was written more than fifty years ago, and Graham's 

 "dead beat" still holds its own, though it has been improved upon 

 by the escapements of the Astronomer-Royal, Hardy, and others. 

 In a private letter to me, Sir Edmund Beckett, the well known 

 parliamentary counsel, and a great authority in horology, says, 

 " Graham's dead escapement has been used for more than a 

 century in nearly every astronomical clock in the world, and 



