2(5 -PHILOSOPHICAL TRANSACTIONS. [aNNO 1665'. 



superior excellency of the glass used by them, to his own, except this difference 

 may be imputed to that of the air, or of the eyes. 



Signior Campani's Answer: and M. Auzout' s Animadversions upon it. 



iV" 4, p, 74. 



The other part of this French tract, containing Campani's answer, and M. 

 Auzout's reflections upon it, begins with the pretended shadows of the ring upon 

 Saturn, and of Saturn upon the ring. Concerning which, the said Campani declares 

 that he never believed them to be shadows made by the ring upon the disk of 

 Saturn, or by the body of Saturn upon the ring, but the rims of these bodies, 

 which being unequally luminous, did show these appearances. In which expli- 

 cation, forasmuch as it represents that the said Campani meant to note only the 

 inequality of the light, which, he says, his glasses discovered, M. Auzout 

 does so far acquiesce, that he only wishes that his own glasses would show him 

 those differences. 



Next, to the objection made by M. Auzout against Signior Campani, touch- 

 ing the proportion of the length of the ring to its breadth, Campani replies, that 

 the glasses of M. Auzout show 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 rejoins, that he is displeased at his being 

 destitute of better glasses, but that it will be very hard in future to convince 

 Campani, touching the proportion of the ring, seeing 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. 



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. Upon which M. 

 Auzout wonders, why Campani then has not marked it in his figure ; and would 

 gladly know whether that sally be more easy to discover than the shadows of the 

 satellites, which Campani believes Auzout has not seen ; and whether he be assured, 

 that those obscure parts, which he there distinguishes, do not change : for if 

 they should not change, then Jupiter would not turn about his axis, which yet, 

 he says, it does according to the observation made by Mr. Hook, May 9, 1665, 

 inserted in the first papers of these Transactions. The full discovery of which 

 . particular also he makes to be a part of Cassini's and Campani's work, seeing that 

 they so distinctly see the inequalities in the belts, and also sometimes other spots 

 besides the shadows of the satellites: where he exhorts all the curious, that have an 



