Bock VII. Mechanic Power. 139

But the little Veſſels of both Crowns may be made equal,and nevertheleſs the Water may be raiſed to any height, toWit, if che wheels G which bite each other, be made une-qual; for if the upper wheel hath its Diameter doubly greatercan the under Wlieel, this will move that with a weight ofWater doubly leſs, and therefore a crown of little Veſſels dou-bly leſſer will be equal to the little Veſſels of the upper Crown;J ſay, the ſame of any other proportion, triple, quadruple,c. Wherefore amends may be made divers ways for the height,and plenty of water aſcending, either by means of a greaterupper wheel, or by means of greater little Veſſels of the lowerwheel , or Tympane, or partly by means of the greater wheel,and partly of the greater ſmall Veſſels.

But if from all the Water in the Ciſtern A continnally flow-ing, the greater part of it is to be raiſed in the upper CiſternB, as if you were to raiſe three parts of four of the water, andbut one part only to deſcend, than the lower Crown muſt be3 times as long as the upper Crown, and the little Veſſels ofche ſame muſt be at leaſt three times leſſer, if both the Axes ofthe wheels Gand I be equal. But if the wheels GI be une-qual, the proportion may be made fit another way; for if thelower wheel be three times greater than the upper heel, thelittle veſſels of the Crowns may be made equal, but the lowerCrown ought to be three times greater; for in this caſe, whilethe lower Wheel is turn'd about only once, ſuppoſing ſive of itslittle veſſels to be fill d, the upper Wheel is turn' d about thrice,and therefore fifteen of its veſſels draw water, and in like man-ner 15 veſſels of water they pour into the Ciſtern B.

Alſo both crowns, or chains, to which the little veſſels arefaſtned, may be accommodated to one and the ſame upperwheel, but it will be neceſſary to fit to the Wheel two hcelswith Axes, as is declared before: But if the altitude to whichthe water is to be raiſed, be ſo high that it requires very greatwheels, other wheels may be diſpoſed in the middle betweeneach Wheel , which may be moved ſucceſſively by the lowerwheel, equally or unequally, according to the proportion ofthe quantity of water, or the magnitude of the little veſſels;for this will be very commodious, as if the water be to aſcendhigher, we add to the Engin one, or more wheels, if not ſohigh, we take away the ſame, making no mutation or altera-tion of the Crowns, or Veſlels; morcover the veſlels of boch.

T 2 crovens