Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/262

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236
G. Galilæus, his Systeme.

dissenteth from the doctrine of Aristotle and Ptolomy. As again, It is questioned, whether the opponent understood the third motion assigned to the Earth by Copernicus. to this third motion, which the Author assignes to the Terrestrial Globe, as the judgment of Copernicus, I know not which he would mean thereby: it is not that questionlesse, which Copernicus ascribes unto it conjunctly with the other two, annual and diurnal, which hath nothing to do with declining towards the South and North; but onely serveth to keep the axis of the diurnal revolution continually parallel to it self; so that it must be confest, that either the Authour did not understand this, or that else he dissembled it. But although this great mistake sufficeth to free us from any obligation of a farther enquiry into his objections; yet neverthelesse I shall have them in esteem; as indeed they deserve to be valued much before the many others of impertinent Antagonists. Returning therefore to his objection, I say, that the two motions, annual and diurnal, are not in the least contrary, nay are towards the same way, and therefore may depend on one and the same principle. The third is of it self, and voluntarily so consequential to the annual, that we need not trouble our selves (as I shall shew in its place) to study for principles either internal or external, from which, as from its cause, to make it produced.

Sagr.I shall also, as being induced thereto by natural reason, say something to this Antagonist. He will condemn Copernicus,unlesse I be able to answer him to all objections, and to satisfie him in all questions he shall ask; as if my ignorance were a necessary argument of the falshood of his Doctrine. But if this way of condemning Writers be in his judgment legal, he ought not to think it unreasonable, if I should not approve of Aristotle and Ptolomy, when he cannot resolve, better than my self, those doubts which I propound to him, touching their Doctrine. He asketh me, what are the principles by which the Terrestrial Globe is moved The same argument answered by examples of the like motions in other cœlestial bodies.with the Annual motion through the Zodiack, and with the Diurnal through the Equinoctial about its own axis. I answer, that they are like to those by which Saturn is moved about the Zodiack in thirty years, and about its own centre in a much shorter time along the Equinoctial, as the collateral apparition and occultation of its Globes doth evince. They are principles like to those, whereby he scrupleth not to grant, that the Sun runneth thorow the Ecliptick in a year, and revolveth about its own centre parallel to the Equinoctial in lesse than a moneth, as its spots doth sensibly demonstrate. They are things like to those whereby the Medicean Stars run through the Zodiack in twelve years, and all the while revolve in small circles, and short periods of time about Jupiter.

Simp.This Author will deny all these things, as delusions of the fight, caused by the crystals of the Telescope.

Sagr.