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so far acquiesce, that he only wishes, that his own Glasses would shew him those differences. Next to the Objection, made by Monsieur Auzout, against Signor Campani, touching the Proportion of the Length of the Ring to its breadth, Campani replyeth, that the Glasses of Monsieur Auzout, shew not all the particulars, that his do, and therefore are unfit for determining the true Figure and breadth of the apparent Ellipsis of the Ring. To which M. Auzout rejoyns, that he is displeased at his being destitute of better Glasses, but that it will be very hard for the future to convince Campani touching the Proportion of the Ring, seing that the breadth of the Ellipsis is always diminishing, although, if the declination of the Ring remains always the same, one can at all times know, which may have been its greatest breadth. But he assures, that the breadth of the Ring is not the half of its length, and that it doth not spread out so much beyond Saturn’s Body, as he hath alleged. And withal desirs to know, what can be answered by Sig. Campani to M. Hugens who being persuaded, that the Declination of the Ring is not above 23 deg. 30′ having seen the Ring to spread out above the Body of Saturn, concludes, in a Letter to M. Auzout, that the length of the Ring is more than treble the Diameter of Saturn’s body, which, according to Campani, is only as about 67 to 31. Which difference yet dos not appear to M. Auzout to be so great; but that M. Hugens perhaps will impure it to the Optical reason, which he (Auzout) hath alleged of the Advance of the light upon the obscure space; although he is of Opinion, he should not have concluded so great a Length, if he had not seen the Breadth spread out more, than he hath done: for (saith he) if the Length of the Ring be to the body of Saturn, as 212 to 1. and the Inclination be 23 deg. 30′ the Ring will be just as large, as the body, without spreading out; but if the Ring be bigger, it will a little spread out; and if it were treble, it must needs spread out the half of its breadth, which hath not so appeared to him.
Further, to M. Auzout's change of Opinion, and believing that the Advance or Sally, seen by him in Jupiter, was the shadow of one of his Moons, Campani declares, that he would not have him guilty of that change: Whereupon M. Auzout wonders, why Campani then hath not marked it in his Figure; and would glad-
