1.3 } 4.1 } 7.2 } 7.0 } The sum 19. 9.0 } The sum 24. 5.2 } 5.3 } 2.1 } 0.0 } The sum of which last numbers is equal with the former, and therefore both the sides of such a wheel in this situation will equiponderate. If it be objected, that the plummet A should be contrived to pull down the other at B, and then the descending side will be heavier than the other; for answer to this, it is considerable-- 1. That these bullets towards the top of the wheel, cannot descend till they come to a certain kind of inclination. 2. That any lower bullet hanging upon the other above it, to pull it down, must be conceived, as if the weight of it were in that point where its string touches the upper; at which point this bullet will be of less heaviness in respect of the wheel, than if it did rest in its own place; so that both the sides of it, in any kind of situation, may equiponderate. CHAP. XV.--_Of composing, a Perpetual Motion by Fluid Weights--Concerning Archimedes his Water Screw--The great probability of accomplishing this enquiry by the help of that, with the fallibleness of it upon experiment._ That which I shall mention as the last way, for the trial of this experiment, is by contriving it in some Water Instrument; which may seem altogether as probable and easy as any of the rest; because that element, by reason of its fluid and subtle nature (whereby, of its own accord, it searches out the lower and more narrow passages), may be most pliable to the mind of the artificer. Now, the usual means for the ascent of water is either by suckers or forces, or something equivalent thereunto; neither of which may be conveniently applied unto such a work as this, because there is required unto each of them so much or more strength, as may be answerable to the full weight of the water that is to be drawn up; and then, besides, they move for the most part by fits and snatches, so that it is not easily conceivable, how they should conduce unto such a motion, which, by reason of its perpetuity, must be regular and equal. But, amongst all other ways to this purpose, that invention of Archimedes is incomparably the best, which is usually called _Cochlea_, or the Water Screw; being framed by the helical revolution of a cavity about a cylinder. We have not any discourse from the author himself concerning it, nor is it certain whether he ever writ anything to this purpose; but if he did, yet, as the injury of time hath deprived us of many other of his excellents works, so likewise of this amongst the rest. [Near five pages are occupied in describing the use of this screw, and the form and manner of making it; then follows:]