Proportion Compafs. 973 
Hill continues flat, one muft therefore fhorten the fmall 
tooth in prqportion to the fize of the larger. 
§ 31. When the teeth were ufed to be finifhed by hand, 
there was great care taken to keep all the teeth of the 
fame length, even when it was impaffible in irely to cor- 
re£f or take off their inequality : in confequence of this 
care, the wheel at leafl ufed to be always perfectly 
round; whereas when the tool is ufed, the wheels are 
unavoidably as ill-rounded as they are unequal in their 
divifions, fo that the teeth ought never to be finifhed 
with the tool, unlefs they are thoroughly equally cut. 
§ 32. It is therefore eafy to conceive, that the pinion 
becomes fometimes too large, and fometimes too fmall, 
upon the fame unequal . wheel, and that the angle of the 
tooth 
raccourcir la petite dent dans la meme proportion qu’il y a plus de matiere a la 
groffe. 
§ 31. Lors qu’on finiftoit les dentures a la main on s’attachoit foigneufe- 
ment a tenir toutes les dents de la meme longueur, meme lots qu’on ne pouvoit 
corriger ou remedier efficacement a leur inegalite; la roue par cette precaution 
fe trouvoit du moins toujours parfaitement ronde, au lieu qu a .l’outii les roues 
de viennent inevitablement auffi mal rondes qu’elles font inegales dans leurs divi- 
fions; en forte que l’on ne devroit jamais finir les dentures a l’outii a moins 
qu’elles ne fuffent fendue - parfaitement egales. 
§ 32. II eft done aife de comprendre que le pignon devient tantot trop gros et 
tantot trop petit fur la meme roue inegale et .tres fouvent a l’exces et que l’angle 
dc 
