98 Mechanick Powers. Book IV.ſecond manner, the weight will be more eaſily moved butit the power be leſs, as if it be to the weight as one to eight;eight Pulleys diſpoſed in this ſecond manner, or eight Pulleysdiſpoſed in two Snatch- blocks, Will eaſily overcome the wholereſiſtance of the weight; to wit, if there be a greater pro-portion of the motion of the power to the motion of the weight,than of the weight to the power. ö

——————

Mechanich-Pomers.OF THE

4XScrem is 4 linder wroug hot zn one or pꝛore ſolidSpere c, or Helices ſiwelling out, ar appears in thegure. 5 ö

Fig. 79. ND the uſe of it is common, for tis put intoanother concave cylinder, cut in like manner in-to concave Spires, ſo that the Sonvex Spires or

Helices of the former Cylinder, fit to the concaves which are

Put upon them. The concave Cylinder ſomet imes is fixt and im.

moveable, and in this caſe, he Screw beſides its circular motion,

hath alſo a right motion, whereby the whole Cylinder goesforth. Sometimes the Screw is immovable, and the concave Cy-linder is only moved, and commonly a ſimple Cylinder is addedto the Screw , into which a handle is grafted or fixt, as in ABthe handle B C is adjoyn d, that it md be moved round moreealily; hitherto Authors have recalled the Screw to theWedge, and the Wedge to the Leaver, or to the motion ofà weight on an inclined plane, as if you underſtand D E to

be