MOVEMENT OF HANDS. 



produce the motion of the hands, does not differ in any important 

 respect from the arrangement explained above. Nevertheless, it 

 may be satisfactory to show the details of the mechanism. The 

 train of wheels connecting the weight with the anchor of the pen- 

 dulum is shown in fig. 18 (p. 17). 



A side view of the mechanism, showing the wheels which more 

 immediately govern the motion of the hands, and also the pen- 

 dulum, with its appendages, is given in fig. 19 (p. 33). 



The weight w acts by a cord on a barrel, as already explained. 

 This barrel and the ratchet-wheel, with its catch, are mounted 

 upon the axis of the great wheel c, and are behind it, as repre- 

 sented in fig. 18, their form and position being shown by the 

 white lines. The catch is attached to the wheel c by the screw n, 

 and its point o acts on the teeth of the ratchet-wheel, which is 

 attached to the barrel on which the rope is coiled. The spring 

 which presses the catch against the teeth of the ratchet is also 

 shown. When the clock is wound up by the key applied to the 

 square end T (fig. 19) of the axis of the barrel, the barrel is turned 

 in the direction opposite to that indicated by the arrows, and the 

 catch falls from tooth to tooth of the ratchet-wheel, making the 

 clicking noise which attends the process of winding up. When 

 the clock has been wound up, the weight acting on the barrel 

 presses the tooth of the ratchet-wheel against the catch, and 

 thereby carries round with it the wheel c. This wheel transmits 

 the motion to the escapement wheel G, fig. 17, through the series 

 of wheels and pinions, d, D, e, E, /, F, and g, in the same 

 manner exactly as has been already described (35) ; and the 

 pendulum, by means of the anchor NN, regulates the motion in 

 the manner described in 19. 



The wheels which more immediately govern and regulate the 

 motion of the hands are those which appear in fig. 19 in front of 

 the plate XY. 



The pendulum consists of a heavy disc of metal, seen edgeways 

 at v in fig. 19, attached to the end of a metal rod, RK, represented 

 broken, to bring it within the limits of the figure. This rod is 

 suspended by various means, but often, as in the figure, by two 

 elastic ribbons of steel, ss, which permit its swing right and left. 

 It passes between the prongs of a fork tr, by which a rod rr is 

 terminated, so that this rod swings right and left with the pen- 

 dulum. Upon the axis of this rod, and over the escapement 

 wheel G, is fixed the anchor N of the escapement. 



37. Whether the movement be regulated by a pendulum or a 

 balance wheel, it is necessary to provide some means of adjustment 

 by which the rate of vibration may be increased or diminished 

 at pleasure within certain limits, for although in its original 



31 



