Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/234

 and concrete: therefore let Simplicius plead in excuse of this Author; and whether he thinks that the Physicks can differ so very much from the Mathematicks.

The substractions are in my opinion insufficient to salve this difference, which is so extreamly too great to be reconciled: and in this case I have no more to say but that, Quandoque bonus dormitet Homerus. But supposing the calculation of *Salviatus to be more exact, and that the time of the descent of the ball were no more than three hours; yet me thinks, that coming from the concave of the Moon, which is so great a distance off, it would be an admirable thing, that it should have an instinct of maintaining it self all the way over the self-same point of the Earth, over which it did hang in its departure thence, and not rather be left a very great way behind.

The effect may be admirable, and not admirable, but natural and ordinary, according as the things precedent may fall out. For if the ball (according to the Authors suppositions) whilst it staid in the concave of the Moon, had the circular motion of twenty four hours together with the Earth, and with the rest of the things contained within the said Concave; that very vertue which made it turn round before its descent, will continue it in the same motion in its descending. And so far it is from not keeping pace with the motion of the Earth, and from staying behind, that it is more likely to out-go it; being that in its approaches to the Earth, the motion of gyration is to be made with circles continually lesser and lesser; so that the ball retaining in it self that self-same velocity which it had in the concave, it ought to anticipate, as I have said, the vertigo or conversion of the Earth. But if the ball in the concave did want that circulation, it is not obliged in descending to maintain it self perpendicularly over that point of the Earth, which was just under it when the descent began. Nor will. Copernicus, or any of his followers affirm the same.

But the Author maketh an objection, as you see, demanding on what principle this circular motion of grave and light bodies, doth depend: that is, whether upon an internal or an external principle.

Keeping to the Probleme of which we speak, I say, that that very principle which made the ball turn round, whil'st it was in the Lunar concave, is the same that maintaineth also the circulation in the descent: yet I leave the Author at liberty to make it internal or external at his pleasure.

The Author proveth, that it can neither be inward nor outward.

And I will say then, that the ball in the concave did