VOL. XIII.J PHILOSOPHICAL TRANSACTIONS. 580 



waited till I had gotten a competent number of observations, the most con- 

 siderable whereof are these. 



An. l682, November 13d. 13h. 00m. P.M. the satellite appeared on the 

 north-side of Saturn, and a perpendicular let fall from it on the transverse dia- 

 meter of the ring, fell upon the middle of the dark space of the following ansa; 

 and the same night, igh. 00m., it had passed the conjunction, and the per- 

 pendicular fell exactly on the western edge of the globe of Saturn, as in fig. 1 , 

 pi. 18. The northern latitude, and retrograde motion, made it evident that the 

 satellite was then in perigaeo. 



Again, November 21 d. l6h. 15m. this satellite of Saturn was on his south- 

 side, the perpendicular on the line of the ansae fell on the middle of the dark, 

 space of the western ansa, and the same night, igh. 00m., the perpendicular 

 fell precisely on the centre of Saturn, and the distance therefrom was somewhat 

 less than one diameter of the ring, as in fig. 2, by this it was evident that the 

 satellite was in apogaeo. 



I observed it in apogaeo again on the 24th of January l683, at 8h. 00m. 

 P.M. the perpendicular on the line of the ansae fell exactly on the western limb 

 of the globe of Saturn, and at Qh. 30m. P.M. the said perpendicular fell within 

 the globe more than half way to the centre, and the distance from the line of 

 the ansae towards the south seemed much about one diameter of the ring. 

 Fig. 3. 



Lastly, February gd. l683, 8h. 10m. P.M. it was again in apogaeo, and I 

 could by no means discern towards which side it inclined most, nor whether the 

 transverse diameter of the ring, or the distance of the satellite therefrom were 

 the greater ; so that at that time it was precisely in apogaeon. Fig. 4. 



To compare with these, I chose two out of those of M. Huygens, which 

 seemed the most to be confided in; the first made 1659, March 14d. st. n. 

 12h. 00m. at the Hague; when the satellite appeared about one diameter of the 

 ring under Saturn, but it was gone so far to the westward, that he concluded, 

 that about 4 hours before, or 7h. 40m. at London, it had been in perigaeo. 

 Fig. 5. 



Again, March 22d. 1659, lOh. 45 m. the satellite was a whole diameter 

 above the line of the ansae, and the perpendicular thereon fell nearly on the 

 extremity of the eastern ansa. See fig. 6. 



By the first of my observations it appears that the satellite was in perigaeo 

 1682, November 13d. I7h. 00m. nearly, at which time Saturn was 3* 21** 

 39' from the first star of Aries, in the ecliptic, but the earth reduced to Saturn's 

 equinoctial, and the satellite was 9^ 23° 46' from the same first star of Aries. 

 And March 4d. 1659, 7h. 40m. Saturn's place in- the ecliptic was 6» 0° 41', 



VOL. II. 4 F 



