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Book I.
$\scriptstyle {\underbrace {\quad \quad \quad } }$aſſur’d in but one Comet, what it was that is the Cauſe of that ſtrange Appearance, ſhould we not make that a Standard to judge of all others by? ’Tis therefore an Argument of noArguments from their Similitude, of no ſmall weight. small Weight that is fetch’d from on their Relation and Likeneſs; and to reaſon from what we ſee and are ſure of, to what we cannot, is no falſe Logick. This muſt be our Method in this Treatiſe, wherein from the Nature and Circumſtances of that Planet which we ſee before our Eyes, we may gueſs at thoſe that are farther diſtant from us.

The Planets are ſolid, and not without Gravity.And, Firſt, ’tis more than probable that the Bodies of the Planets are ſolid like that of our Earth, and that they don’t want what we call Gravity, that Virtue, which like a Loadſtone attracts whatſoever is near the Body to its Center. And that they have ſuch a Quality, their very Figure is a Proof; for their Roundneſs proceeds only from an equal preſſure of all their Parts tending to the ſame Center. Nay more, we are ſo skilful now-a-days, as to be able to tell how

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