VOL. XXXII.] PHILOSOPHICAL TRANSACTIONS. 665 



quite 5^ feet, with the Hugenian telescope, the focal length of whose object- 

 glass is 123 feet: and we find, that the former will bear such a charge, as to 

 make it magnify the object as many times as the latter with its due charge ; and 

 that it represents objects as distinct, though not altogether so clear and bright; 

 which may be occasioned partly by the difference of their apertures, that 

 of the Hugenian being somewhat the larger, and partly by several little spots 

 in the concave surface of the object metal, which did not admit of a good 

 polish. 



Notwithstanding this difference in the brightness of the objects, we were 

 able, with this reflecting telescope, to see whatever we have hitherto discovered 

 by the Hugenian ; particularly the transits of Jupiter's satellites, and their 

 shadows over his disk; the black list in Saturn's ring; and the edge of his 

 shadow cast on his ring, as represented by fig. 14, pi. 15. 



We have also seen with it several times the 5 satellites of Saturn; in vievi^ing 

 of which, this telescope had the advantage of the Hugenian, at the time when 

 we compared them; for being in summer, and the Hugenian telescope being 

 managed without a tube, the twilight prevented us from seeing in this, some of 

 those small objects, which at the same time we could discern with the reflecting 

 telescope. 



Observations on the Satellites of Jupiter and Saturn, made with the same Tele- 

 scope. ByJohnHadley^Esq.F.R.S. N° 378, p. 385. 



Mr. Hadley gave the Society an account of some of the most remarkable ob- 

 servations he had made with his reflecting telescope, before he presented it to 

 the Society. 



In observing Jupiter's satellites, he has seen distinctly the shadows of the 

 first and third satellites cast on the body of the planet ; Mr. Folkes and Dr. 

 Jurin, being present, affirmed, that Mr. Hadley had likewise shown them the 

 shadow of the third satellite through the same telescope. 



In observing Saturn, when that planet was about fifteen days past the opposi- 

 tion, he saw the shadow of the planet cast on the ring, and plainly discerned 

 the ring to be distinguished into two parts, by a dark line, concentric to the 

 circumference of the ring. The outer or upper part of the ring seemed to be 

 narrower than the lower or inner part, next the body, and the dark line, which 

 separated then), was stronger next the body, and fainter on the outer part 

 towards the upper edge of the ring. Within the ring he discerned two belts, 

 one of which crossed Saturn close to its inner edge, and seemed like the shadow 



VOL. VI. 4 Q 



