VOL. VIII.] PHILOSOPHICAL TRANSACTIONS. 51 



motion, showed itself to be a true planet : which we found by comparing it, 

 not only with Saturn and his ordinary satellite, discovered in l655 by Mr. 

 Huygens, but also with other fixed stars. 



These observations show a motion of this new planet that is very manifest in 

 respect of the fixed stars, but less sensible in respect of Satum. Yet it appears, 

 that from Oct. 25, to Nov. 1, its distance from Saturn increased westward, and 

 from that time to Nov. 6, it diminished; so that its greatest digression from 

 Saturn happened in the beginning of Nov., and was found to be of 8 minutes, 

 or of lOJ diameters of Saturn's ring. Whence it followed, that if this planet 

 were a satellite of Saturn, it must be about the end of Sept. in the inferior part of 

 its circle, and at the beginning of Nov. in the superior part ; and that its revo- 

 lution about Saturn was of a long duration, since for 1 2 days together it not 

 only remained on the same western side of Saturn, but there was also little 

 change of apparent distance between them. The greatest digression of this 

 planet was treble to that of the ordinary satellite, and this enabled us to judge 

 the time of its revolution to be quintuple, applying to the satellites that propor- 

 tion which Kepler noted in the principal planets, between the periodical times 

 and their distances. * 



We again got sight of Saturn, Nov. 12, l6, 17, ig, 23 ; but we could find no 

 appearance of the new planet. Dec. 1 6, we found that Saturn had resumed 

 his round figure, and that on the east of him there was a small star, far distant, 

 in a straight line with Saturn, and with his ordinary satellite, which was also 

 eastward, and but little distant from Saturn. And Dec. 24, we saw this satel- 

 lite in the west, and a star on the east, less distant from Saturn than that we 

 had seen the l6th. But the weather did not permit us to ascertain whether it 

 was the same. At length, Jan. 18, 23, 25, of the year 1672, we saw on the 

 west of Saturn, sometimes one star, sometimes many, far distant, almost in a 

 direct line with his ordinary satellite; which made us hope to see again the new 

 planet towards its greatest western digression. But these observations were the 

 last which the weather suffered us to make, before Saturn became lost in the 

 beams of the sun. 



After my return from a journey to Provence, having brought with me from 

 Marseilles, in the beginning of Nov. 1672, an excellent telescope of 35 feet, 

 which Campani had made by order of his Majesty ; we set it up in the Royal 

 Observatory, directing it to Saturn, as soon as the weather would permit, to 

 look for the new planet. In the first observations, made Dec. 13 and 17, we 

 perceived a star to the west, remote from Saturn, which in both these obser- 



* Namely, the squares of the periodical times, proportional to the cubes of tlie distances. 



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