Book VII. Mechanic Powers. 119
toßether eaſie, and others of the like nature may be inven-red.
For let the leaver be AB C, vchoſe prop is in B, and thepower in A; by weighing down, or depreſling this leaver, its
other end C lays hold on the teeth of che wheel D E, andmoves it, the iron Pin G hindering it to go back; and at the ſame
time the rope E F being turn d about the Axis of the wheel
takes up the weight FP; but the prop B ought to be furniſut
with a ring above, in Which the leaver muſt be put, leſt it becaſily movcd to and fro, being only a little bert, that it may.be transferred from one tooth to another below it.
Some things to be obſerved in che compoſition and uſe ofMachines, or Engins. In the compoſition and uſe of the Enginsaforeſaid. and of others of the like nature, ſome things occurwhich deſerve a peculiar obſervation.
Firſt, Tis to be noted, that ſince in every Engin, that partwhich is next to the weight, feels a greater impreſſion, or re-ſiſtance of the faid weight, and alſo ought to be more ſolid,farm, and ſtrong: Example, In Axis in Peritrochio, or à toothedwheel ard à fcrew-, it will be convenient ſo to fit them toge-ter that the weight may be fuſtain d immediately from thecrew, and tlie Wheels applied t0 he moving power; and theſcrew ought to be of more ſolid matter, and made more firm,ſince in topthed welicel they cannot be made ſo ſtrong, a8 toſuſtain great weight.
This thing is of great moment, and therefore to be obſer-ved diligently in uſe, a ſcrevs, and alſo pulleys are ont to beapplied immediately to 4 weight, for although a pulley ſeems10 be leſs frm and ſtrong to ſuſtain a purden, becauſe that theAxes of the wheels cannot be made ſothick; notwithſtanding.each of chem bears not the whole weight, cven as neither anyOne rope chat is drawn, but it is in à manner diſtributed toevery one, ſo that from all, one as it were makes the reſiſtancea to Overcome the weigh.
Secondly, is to be Obſerved, that ſome ugs may modea weight, or alſo take it up to ſome height, d vt notwith-ganding of it ſelf cannot move it to ah further height; fuchare the wedge and the Icaver; the firſt of chem ſerving only forcleaving, but the ſecond, if it be immediately applied to aweight, tis manifeſt that it can raiſe it but à little height:Whereföre às need requires, it benoves As to ube divers linde.
O