EXPERIiMENTS ON C li RONOMETE AS* 51 



the balance mufl be began quicker and quicker, as the 



points of the teeth of the Tcape wheel wear more and more. 



But on the contrary, let us now fuppofe that the points of the If the pafTing 



teeth do not wear, and the paffing fpring wears ; in this cafe, JfJ,';^\f^';'''a^5* 



as the balance in its vibration will have a greater fpace or por- confequently the 



tion of a circle to move, before it can arrive at the fpring, and 'mpulfe will be , 



unlock, the wheel, in order to receive the impulfe, every fuch 



impulfe will be made later and later, and the watch rauft ne- 



cetTarily go flower and flower as the point of that fpring wears 



away more and more. There is another part in this 'fcapement. If the face of 



namely, the ftriking faceoP the tooth, in which, if wear takes ^^^ ^'^l'^ f'""^^ 



J ' o . ^ . . wear, the drop 



place, the tendency I prefume will be to lofe, in confequence will be more and 

 of the wheel acquiring a greater drop, or having farther to go '^he impulfe /aw. 

 before it can overtake and ftrike the pallet. This part of the 

 tooth I herefuppofed to wear, and which firft comes into con- 

 tad with the pallet, is not the point, but a little nearer the 

 centre of the wheel; and as the wheel follows the pallet, it 

 muft be fome portion of time longer before it can arrive to be^ 

 gin the impulfe. In the above example I have fuppofed the 

 detent and both pallets to be jewelled: if they were not, the 

 errors would be greater. 



Now we find that, according to the above reafoning, al- Thus there ars 



though there are two parts of the 'fcapement in which, if wear '^^^° u'?^ . . 

 o t r » vvear which tend 



takes place, the tendency will be to lofe; leaving out of the to produce K.fs, 

 queftion the oil becoming glutinous, the fprings lofing their ^."'^ °"^. '^° P'^''' 

 elaftic force, &c. and only one part, in which if wearing lakes 

 'place the tendency will be to gain, yet, we find in mofl: ma- 

 <;hines the tendency to gain is generally predominant. I will — ^"^ the gain 

 fliew why I think the teeth of the wheel wear more than cither f^'^"'"'""^^ » 

 of the other two parts: there is not only fri6tion, but percuffion 

 alfo takes place in the three differ-iit parts of the 'fcapement 

 before-mentioned; the little rolie- or pallet that lifts the detent 

 out of the wheel ftrikes againll: the point of the paffing fpring 

 on coming into contad in order to unlock the wheel; in the 

 next place the wheel ftrikes againfl the pallet when it begins 

 the impulfe, and laftly, the wheel again firikes againfl: the 

 jewel of the detent when it locks upon it : I will not attempt 

 to determine which of the two former pereufiions is thegreat- 

 efl, or which will occafion the greatefl retardation of rate, but — aud this b«- 

 will fay, that the laft is greater than either of the other two by ""^^ the firoke 

 much, and in general we find that the wheel is locked upon Lkingls^micii 

 E 2 that greater, that 



