Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/46

 of natural bodies some are moveable by nature, and others immoveable; especially having before defined Nature, to be the principle of Motion and Rest.

Aristotle, though of a very perspicacious wit, would not strain it further than needed: holding in all his argumentations, that sensible experiments were to be preferred before any reasons founded upon strength of wit, and said those which should deny the testimony of sense deserved to be punished with the loss of that sense; now who is so blind, that sees not the parts of the Earth and Water to move, as being grave, naturally downwards, namely; towards the centre of the Universe, assigned by nature her self for the end and term of right motion deorsùm; and doth not likewise see the Fire and Air to move right upwards towards the Concave of the Lunar Orb, as to the natural end of motion sursùm? And this being so manifestly seen, and we being certain, that eadem est ratio totius & partium, why may we not assert it for a true and manifest proposition, that the natural motion of the Earth is the right motion ad medium, and that of the Fire, the right à medio?

The most that you can pretend from this your Discourse, were it granted to be true, is that, like as the parts of the Earth removed from the whole, namely, from the place where they naturally rest, that is in short reduced to a depraved and disordered disposure, return to their place spontaneously, and therefore naturally in a right motion, (it being granted, that eadem sit ratio totius & partium) so it may be inferred, that the Terrestrial Globe removed violently from the place assigned it by nature, it would return by a right line. This, as I have said, is the most that can be granted you, and that onely for want of examination; but he that shall with exactness revise these things, will first deny, that the parts of the Earth, in returning to its whole, move in a right line, and not by a circular or mixt; and really you would have enough to do to demonstrate the contrary, as you shall plainly see in the answers to the particular reasons and experiments alledged by Ptolomey and Aristotle. Secondly, If another should say that the parts of the Earth, go not in their motion towards the Centre of the World, but to unite with its Whole, and that for that reason they naturally incline towards the centre of the Terrestrial Globe, by which inclination they conspire to form and preserve it, what other All, or what other Centre would you find for the World, to which the whole Terrene Globe, being thence removed, would seek to return, that so the reason of the Whole might be like to that of its parts? It may be added, That neither Aristotle, nor you can ever prove, that the Earth de facto is in the centre of the Universe; but if any Centre