VIBRATION OF THE BALANCE SPRING. 387 



III. 



A Method of rendering all the Vibrations of the Balance of a 

 Timepiece equal. In a Lttterjrom Mr. William Hardy. 



To Mr. NICHOLSON. 

 SIR, 



JL BEG leave to communicate to your readers a new and New method of 

 easy method of correctuig the l<m£ avid short arches of vi - vX^tiiSn'I'of a^ 

 bration in the balance cf a nmckeeper ; that is to say, thai talance. The 

 they shall all he performed iii equal times, so short as the t\^'i^^^"'ai;on'-r^ 

 angle of e&capement will admit. play endwise 



The spring, a b, Fir. 4, 5, 6, Plate XI., screwed to the under 

 part of the coc'\, h, lies o\er tie upper part of the pendulum 

 spring, proceeding in a right liu > to the axis, e, of the balance, , 

 g, having a bend to clear the verge, and so passes on to the 

 other side, where the end of the pendulum sprnig is fastened 

 to it. This straigl^.t spring i-% reduced to such a consistency, as 

 to allow it to be brought n-ito action a lutie before the piHidu- 

 lum spring. The other piece, c, wliich projects down from the 

 imder side ot the cock, lies iii a line with this spring, and is 

 screwed to the cock on the < pposite s^ide of tne centre to 

 that where the spnng is fastened. It is ot an oblong form, and 

 has a slit cut down, with an adjusting screw, d d, on each side, 

 Avhose points face each other in the same right line to receive 

 the small projecting piece, b, which is at the end of the straight 

 spring, so as to move freely between them. The points of the 

 screws should be at equal distances from the spring. When the 

 balance is at rest, the space between the two screws must be 

 cgnsiderably less than the angle of 'scapement, but the pro- 

 per quantity must be determined by trial. As this straight 

 spring is weaker than the pendulum spring, it will be first 

 brought into action; therefore, if the balance be made to 

 move only so far as to cause the spring to act between the 

 two adjusting screws, the motion of the balance will be pro- 

 longed ; but on being stopped by the adjusting screws, the 

 action of the straight spring will cease, and that of the pen- 

 dulum spring will commence, and " consequently progressively 

 accelerate the vibrations of the balance. It will, therefore, 

 B d d 2 always 



