52 



2d method i 



3d. metiiod. 



MODES OF EQUALIZING ARCS OF VIBRATION. 



jured by the drop of the wheel upon the spring, as upon a 

 solid surface, nor the vibrations of the balance so much dis- 

 turbed by the impnlse. 



The second method is by a straight spring b c, fig. 1 and 4, 

 screwed to the under part of the cock, placed edgewise and 

 diametrically over the cylindrical spring, and having apiece 

 cut out to clear the arbor of the balance. This straight 

 Spring is at one extremity fastened to the end of the pendu- 

 lum-spring, and, at the other extremity, its elasticity is re- 

 duced so as to yield a little before the pendulum-spring 

 operates. On the opposite of the cock, where the spring is 

 screwed, is fixed a stud d projecting downward,and having a 

 slit to admit the small piece at the end of the spring b. On 

 each side of this slit is an adjusting screw e e, the points of 

 which face each other, and are placed so as that the spring 

 may move equally between them from its point of rest. The 

 action of the spring between the adjusting screws requires 

 to be somewhat less than the angle of escapement. Let the 

 balance be made to vibrate, so that the straight spring may 

 move up to the adjusting screws upon each side, and no far- 

 ther; being weaker than the pendulum-spring, its exertion 

 will be less ; hence the time of the vibrations will be pro- 

 longed, but as they increase, the exertion of the pendulum- 

 spring will commence and progressively accelerate them, and 

 this acceleration will always be in proportion as the exertion 

 of the pendulum-spring is to the action of the straight 

 spring between the two adjusting screws. Thus it will al- 

 ways counteract the accelerating efi^ect of the escape-wheel 

 in the small arcs of vibration, so that the whole of them 

 shall be performed in the same time. 



The third method is by connecting a piece of short spring- 

 wire to the pendulum-spring by a small piece f, fig. 5 and 

 6, with two holes; pinning the two springs together about 

 half a turn from the stud of the pendulum-spring; and 

 clamping the other end of the short spring at its natural 

 point of rest to a sliding piece, g, which projects out from 

 the pendulum-spring stud. By this manner of fastening, 

 both springs will act together, and each will retain its na- 

 tural point of rest; but by moving the sliding piece, which 

 clamps the end of the short spring, and placing the spring 



a little 



