Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/163

 Earth, doth not onely follow the course of that person, but doth much out go him. Which Problem is connexed with this, that the moveable being thrown by the projicient above the plane of the Horizon, may acquire new velocity, greater by far than that confer'd upon it by the projicient. The which effect I have with admiration observed, in looking upon those who use the sport of tops, which, so soon as they are set out of the hand, are seen to move in the air with a certain velocity, the which they afterwards much encrease at their coming to the ground; and if whipping them, they rub at any uneven place that makes them skip on high, they are seen to move very slowly through the air, and falling again to the Earth, they still come to move with a greater velocity: But that which is yet more strange, I have farther observed, that they not onely turn always more swiftly on the ground, than in the air, but of two spaces both upon the Earth, sometimes a motion in the second space is more swift than in the first. Now what would Simplicius say to this?

He would say in the first place, that he had never made such an observation. Secondly, he would say, that he did not believe the same. He would say again, in the third place, that if you could assure him thereof, and demonstratively convince him of the same, he would account you a great Dæmon.

I hope then that it is one of the Socratick, not infernal ones. But that I may make you understand this particular, you must know, that if a person apprehend not a truth of himself, it is impossible that others should make him understand it: I may indeed instruct you in those things which are neither true nor false; but the true, that is, the necessary, namely, such as it is impossible should be otherwise, every common capacity either comprehendeth them of himself, or else it is impossible he should ever know them. And of this opinion I am confident is Salviatus also: and therefore I tell you, that the reasons of the present Problems are known by you, but it may be, not apprehended.

Let us, for the present, pass by that controversie, and permit me to plead ignorance of these things you speak of, and try whether you can make me capable of understanding these Problems.

This first dependeth upon another, which is, Whence cometh it, that setting a top with the lash, it runneth farther, and consequently with greater force, than when its set with the fingers?

Aristotle also makes certain Problems about these kinds of projects.

He doth so; and very ingenious they are: particularly, That, Whence it cometh to pass that round tops run better than the square?