Bock VII. Mechanic Powers. 13 1

middle part of the lower Pole, they ſharpen it ſo, chat thewhole weight is born on a ſmall part of the Cavity , that, as Ihave ſaid, therefore, the wheel may move the others with more

aſe. ä N

Laſtly, The ſame Wheel , of which we are ſpeaking, maybe uſed doubly in a vertical ſite: Firſt, ſo that it ſtand whollyhang' d up in the air, and: equilibriated, as in the preceęding

Engin. Secondly, S0 that it inſiſt or ſtand on the ſubjectedpavement, and turn d about upon ir; in Which caſe it hathallo more force, than if it were ſuſpended wholly in ſomeaxis: But che Pavement ought to be made level and plain, andſolid, as of poliſſit marble, or ſuch like matter, and the cir-cumference of the wheel, which immediately touches thepavement, ought to be exactly turned, that no impedimentretard the motion. So the wheel AB being appliedto the extream part of the leaver C D, to which Fig. 104.leaver in like manner, apply a power moving theCylinder, or Axis D E, and by this means, the Wheel E, andOftentimes other wheels, for while the Cylinder is turned aboutby the Leaver, the Wheel A B, roles about its Leaver, lean-ing on the pavement, and from a double motion, to wit, oneabout its centre, or about the Leaver C D, which is inſteadof an Axis, and the other about the Cylinder D E, vhile itruns out from B to P,&. And in this manner, it may be ap-plied almoſt to all Engins, but eſpecially, to thoſe with whichwe uſe to move great weights. And the greater this Wheelis, che better it performs the effect, ſo that the weight be inpropo tion to the power applied. 2

5

82 Engin.