Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/125

 velocity, to perform that, which might be done by the moderate motion of one alone about its own Centre?

I do not well understand, how this grand motion signifieth nothing as to the Sun, as to the Moon, as to the other Planets, and as to the innumerable multitude of fixed stars: or why you should say that it is to no purpose for the Sun to pass from one Meridian to another; to rise above this Horizon, to set beneath that other; to make it one while day, another while night: the like variations are made by the Moon, the other Planets, and the fixed stars themselves.

All these alterations instanced by you, are nothing, save onely in relation to the Earth: and that this is true, do but imagine the Earth to move, and there will be no such thing in the World as the rising or setting of the Sun or Moon, nor Horizons, nor Meridians, nor days, nor nights; nor, in a word, will such a motion cause any mutation between the Moon and Sun, or any other star whatsoever, whether fixed or erratick; but all these changes have relation to the Earth: which all do yet in sum import no other than as if the Sun should shew it self now to China, anon to Persia, then to Egypt, Greece, France, Spain, America, &c. and the like holdeth in the Moon, and the rest of the Cœlestial Bodies: which self same effect falls out exactly in the same manner, if, without troubling so great a part of the Universe, the Terrestrial Globe be made to revolve in it self. But we will augment the difficulty by the addition of this other, which is a very great one, namely, that if you will ascribe this Great Motion to Heaven, you must of necessity make it contrary to the particular motion of all the Orbs of the Planets, each of which without controversie hath its peculiar motion from the West towards the East, and this but very easie and moderate: and then you make them to be hurried to the contrary part, i. e. from East to West, by this most furious diurnal motion: whereas, on the contrary, making the Earth to move in it self, the contrariety of motions is taken away, and the onely motion from West to East is accommodated to all appearances, and exactly satisfieth every Phœnomenon.

As to the contrariety of Motions it would import little, for Aristotle demonstrateth, that circular motions, are not contrary to one another; and that theirs cannot be truly called contrariety.

Doth Aristotle demonstrate this, or doth he not rather barely affirm it, as serving to some certain design of his? If contraries be those things, that destroy one another, as he himself affirmeth, I do not see how two moveables that encounter each other in a circular line, should lesse prejudice one another, than if they interfered in a right line.