Proportion Compafs . 981 
one of ten, to a tenth, &c. The moft ordinary work- 
man is able to judge at fir ft fight, whether the pinion is 
deep and open to the center as it ought to be, and if the 
wheels are of a proper flatnefs, See. 
§ 4 5. And though there fhould be fome little varia- 
tion as of fix to fix and a half, and from fix to five and 
a half per tooth of a pinion of fix; this difference,,, 
though very ftriking to the fight, would not either in- 
creafe or diminifh the apparent diameter by even a forty- 
eighth, whence ftrictly fpeaking there would only be a 
twenty-fourth part of a tooth, more or lefs, which would 
raife about two-thirds of a degree per tooth, fo that one 
may in fail look upon all objections of this nature as 
being as vague as they are groundlefs. 
§ 46., 
pour 10 a la io®, Vu que Ie plus fimple ouvrier en ce genre eft affes habile , 
pour juger du premier coup d’ceil, ft un pignon eft enfonce et vuide a fon pointy . 
et fi le ailesfotit bien formee en planches, &c. 
§ 45. C^uand il y auroit meme quelque petit ecart coime de 6 a 6J et de 6 a 
5| par aile$ . d’un pignon de lix, cette difference, quoi que tres franpante a la . 
vue, n’augmenteroit ni nediminuerok.fon diametre apparent, pas feulement d’un 
48' d’ou il refulteroit a toute rigueur feulement la 24 s partie d’une dent de plus 
on de moins qui opereroit environ | de degre de levee par aile; de forte que i’on- 
pourroit judicieufement envifager les objections. de cette nature comme aufli 
¥agues qu’inconiequentes*. 
6 §-46* 
