92 Mechanic Power g. Book IV.

it about the Wheel of the movable Snatch-block I, and letthe power be in the point C, drawing the rope upwards. Iay, the force of the power is tripled.

Toe Demumſtration. Suppoſe the power C ſo to be moved,that the Pulley I. touch the Pulley B; In this caſe there is leftonly ſo much of the rope as is fequired to compaſs both theWheels, to wit, as much as the portion EB E, and G Hl,and the motion of the drawing power from C is equal to thereſt of the rope, or to the parts A E, F G, N C; but thoſeparts taken together, are triple the motion of the weight, towit, the line I E, therefore the motion of the power is triplethe motion of the weight, therefore the forces of the powerare tripled: Which was to be ſfiewn.

RO P OC. XI.A Theorem.

In Tripaſto, or three Pulleys. f to Pulleys aremmovable, and one only movable, tb power 19

tripled.

Fig. 76. Et there be three Pulleys, wherein two of themN A and B are immovable, or immovable in theSnatch- blocks, and let the rope be faſtned in the point Cthen turn the rope about each wheel, as you ſee in the figure,and let the weight be D, and the power in E: I ſay, thepower is tripled.2be Demonſtrarion. The point E is not more moved than the.point P, and therefore the pulley B is only uſed for convenien-cy ſake. But the point F(by the roth of this) is moved triply,or threefold ſwifter than the weight D, therefore in this dilpo-ſition the power is triplicated 5 which was to be ſhewn.But the end of the rope C could not be faſtned to che up-

per Snatch- block, other wiſe one of the upper Pulleys wouldhave been uſeleſs.

FROP OS.