VIBRATIONS OF A BALANCE. 5& 



©fcillations precifely in equal times, whatever was their (J / 



extent, whether they confided of thirty degrees, or of three 

 thoufand. It therefore returned to the place at which it was 

 at reft with velocity exa&Iy proportioned to the fortes employ- 

 ed to remove it. From this experiment I concluded, that the 

 balance fpring of a watch is not in a fituation to exert this 

 natural quality, but that the diftortion into which it is 

 thrown, is fuch as deftroy this valuable property oi' ifochro- 

 nifm. 



The principal circumftanee by which the fpiral balance The fpiral fpring 

 fpring appears to me to be cramped, and prevented from " j cra ™P ed b y 

 operating by its natural action throughout, is, that the outer 

 extremity is fixed by the ftud, fo that it cannot expand and 

 contract in its coils every where alike, as it ought to do. To but wIlen j ts 

 remedy this, I attached the ftud to a ftraight fpring, lying in made free by a 

 the direction of the tangent of the fpiral, continued from that ftraight fpring 

 extremity. This fpring by its eafy aftion allows the fpiral to jjj j^ff ^ ** 

 approach the centre, and retire from it with great regularity ; 

 and, what is moft material, it can with certainty be reduced 

 to fuch a ftrength, that the long and fhorl vibrations of the 

 balance will prove perfectly equal when this adjuftment is 

 made. For upon the ftrength of this fhort fpring depends 

 the freedom with which the axis of the balance is enveloped ' 



by that fpring which regulates its motion. The fpring ftud 

 affords a good banking ; for the banking pin on the balance 

 may be eatily placed fo as to ftrike upon the end of the ftud in 

 the cafe of extreme vibration. 



I am, Sir, 



Your's moft refpeft fully, 



CHARLES YOUNG, 

 Wood Street, Aug. 23, 1 805. 



SCIENTIFIC 



