Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/320

 buckler of the little Treatise of Conclusions, or Disquisitions Mathematical, the oppugnations of which it would be good to begin to produce.

I will, if you so please, reserve them to the last, as those that are of latest invention.

It will therefore be necessary, that in conformity to the method hitherto observed, you do orderly, one by one, propound the arguments, on the contrary, aswell of Aristotle, as of the other ancients, which shall be my task also, that so nothing may escape our strict consideration and examination; and likewise Sagredus, with the vivacity of his wit, shall interpose his thoughts, as he shall finde himself inclined.

I will do it with my wonted freedome; and your commands shall oblige you to excuse me in so doing.

The favour will challenge thanks, and not an excuse. But now let Simplicius begin to propose those doubts which disswade him from believing that the Earth, in like manner, as the other planets, may move round about a fixed centre.

The first and greatest difficulty is the repugnance and incompatibility that is between being in the centre, and being far from it; for if the Terrestrial Globe were to move in a year by the circumference of a circle, that is, under the Zodiack, it is impossible that it should, at the same time, be in the centre of the Zodiack; but that the Earth is in the said centre Aristotle, Ptolomy, and others have many wayes proved.

You very well argue, and there is no question but that one that would make the Earth to move in the circumference of a circle, must first of necessity prove, that it is not in the centre of that same circle; it now followeth, that we enquire, whether the Earth be, or be not in that centre, about which, I say, that it turneth, and you say that it is fixed; and before we speak of this, it is likewise necessary that we declare our selves, whether you and I have both the same conceit of this centre, or no. Therefore tell me, what and where is this your intended centre?

When I speak of the centre, I mean that of the Universe, that of the World, that of the Starry Sphere.

Although I might very rationally put it in dispute, whether there be any such centre in nature, or no; being that neither you nor any one else hath ever proved, whether the World be finite and figurate, or else infinite and interminate; yet nevertheless granting you, for the present, that it is finite, and of a terminate Spherical Figure, and that thereupon it hath its centre; it will be requisite to see how credible it is that the Earth, and not rather some other body, doth possesse the said centre.

That the world is finite, terminate, and spherical, Ari-