by wear in the 

 ■'zcapement^ 



50 EXPERIMENTS ON CHRONOMETERS. 



4. General ob- And ftill more it is the obfervation of every watch-maker^ 



whin the Tc!""-^'^^'-'" ^P^'^l^'^g ^^ ^'^^ ^'"^S^ ^"^ horizontal Tcapements, 

 ment wears that when once tlie verge or cylinder begins to wear, there is 

 there IS no more gj^ g,-,^} ^f ^I! good performance, and that the going of the 



watch becomes from that period totally incorrect. 

 Inference: that Thefe feveral teftimonies tend to induce a belief, that the 

 the errors in the errors which ftill remain in the befl; tirae-keepers, are pro- 

 are thus caufed. duced chiefly by this caufe ; and this caufe mufi exift from the 

 moment the machine is firft put in motion, although the errors 

 will not manifeft themfelves to any confiderable extent, (par- 

 ticularly if the materials are of the beft kind,), until the ma- 

 chine has been going for fome time. 

 Diiliuaftate- I therefore fabmit it as a fundamental principle, that the 



ment: that the p,|f^cipal caufe of the errors found in the beft adjufted time- 



alterations of ' * _ _ _ •' 



rate are C3i;f?d keepers, confift in the wearing of the different parts of the 



'fcapement ; that fo long as by the adl of wearing the relative 



proportions of its parts are preferved, that errors of contrary 



kinds compeniate each other in the general adion, the machine 



will go correflly ; but fo foon as thofe ratios of the parts are 



altered by wearing, the watch will go either too faft or too 



flow. 



Short defcription The fcape wheel of what is termed the detached efcape- 



ta'chtd rMFl*^'" ^^"^> ^'^y ^^ ^^^ '^^^ ^■' Arnold, or any other of them in ufe, 



ment. 1. Scape (for their principles are the fame, and differ only in modifica- 



whee!, 2. (face tion,) is looked Upon a jewel in the detent. The detent has a 

 of) detent, 3. r j 



paffing fpring, fmali fpring faftened to it, which reaches confiderably beyond 

 4- unlocking the locking jewel. Some watch-makers have given the name 

 puife pallet.'"' ^^ patling fpring to it, becaufe, the little pallet in one vibra- 

 tion of the balance paffes it without difiurbing the detent, and 

 in the nt-t vibration, the fame pallet by laying hold of its 

 point, lifts the detent out of the wheel, which immediately 

 impels the balance by means of the great or impulfe pallet*. 

 Confequences of To fimplify our dedu6tions, let it be fuppofed that the 

 wear, i. If the point of tlie paffing fpring does not wear at all, and I think it 

 wheel (point) ... '^ ° ' ° • , . , , .^ - 



ihould wear, it ^ill appear to every perlon actjuamted with the 'fcapement, 



will /oa«fr efcape that if the points of the teeth of the wheel fhould wear, the 



paileJ' ^ ' ^ watch muft go fafter. For the wheel muft then efcape the 



locking jewel of the detent fooner, and will necefl!ari!y impel 



the balance fooner alfo ; confequently each impulfe given tq 



* Philof. Journal. Quarto II. 54. 



5 the 



