CHRONOMETERS. 85 



ZZ; the whole together being called the frame. 

 On the end of the barrel C, of which a iront view 

 is again represented in %. 2. at R, is a ratchet 

 wheel K K, the inclined teeth of which strike 

 against a click C kept to its place by a slender 

 spring. This click and spring are screwed to a 

 wheel D, which is not fastened on the arbor of the 

 barrel: consequently when the weight pulls down- 

 wards, the ratchet wheel pushes the click, and 

 with it the wheel P. But when the weight has 

 run down, and it is necessary to wind it up again, 

 the click suffers the ratchet wheel to pass, while 

 the wheel D stands still. 



This wheel D in fig. 2. is the same as D in fig. 1., 

 where the profiles of it and of the ratchet wheel 

 are represented. A small wheel d fixed upon an 

 axis c c is carried round by the wheel D. A larger 

 wheel E E is fixed upon the same axis c c. The 

 wheel E E drives a small pinion e, on the axis of 

 which is fixed the wheel F F, which moves the 

 pinion f, on the axis of which the scape wheel 

 G H is fixed. The pivots of the pinion f play in 

 holes of the plates L, M, which are fixed horizon- 

 tally to the plates T, S. Thus the motion begun by 

 the weight is transported to the scape wheel G H. 



This scape wheel has teeth acting upon it, and 

 suspended over it are two flat pieces called pallets, 

 fixed upon a horizontal axis, called the verge. 

 These pallets fall into the teeth of the scape wheel, 

 so that as it moves round they are alternately 

 moved backward and forward, and at the same time 

 they suffer the wheel to pass. Connected with the 

 axis of the pallets by means of the fork X U, is the 

 pendulum A B, which is suspended upon thehook A. 



If the pendulum be once put in motion by a push 

 of the hand, it will continue to go alternately back- 



c 8 



