. CLOCKS AND SUNDIALS. 



363 



6th. The wheel-work and hands are propelled by two gravity arms, one on 

 either side of the 'scape wheel, which are alternately raised out of action by 

 the pendulum in its vibration. 



The impulse pallets and stops are so adjusted that the wheel is impelled 

 forward half a tooth, and locked upon the opposite arm until released by the 

 return of the pendulum. The action of the propelment is shown in the large- 

 sized movement in the square case, and in Fig. D. 





Fig. D. 



In this system the standard or motor clock only requires winding, while the 

 sympathetic pendulums, being controlled as well as driven by the electric 

 currents transmitted by the motor clock, are caused to vibrate in unison, and 

 so produce perfect coincidence of time on any number of clocks in connexion 

 though miles distant from it. The electro-motive force being applied at the 

 lower end of the pendulum, a long leverage is obtained requiring only a weak 

 battery, which is less liable to derangement, maintains its constancy and 

 action for a longer time, and requires less attention than a strong one. Each 

 subsidiary clock, being dependent for the time shown upon its own pendulum, 

 is not affected by any trip or irregularity in the current, as the momentum 

 acquired by the pendulum will carry forward the wheel- work for some time 



