238 Royal Astronomical Society. 



vations of an interior satellite of Uranus, which had been made in 

 the autumn of last year by Mr. Lassell and M. Otto Struve. The 

 results are in several respects interesting and remarkable. The fact 

 that one observer always saw the close satellite on the northern side 

 of the planet only, while the other as uniformly observed it only on 

 the southern side, is sufficiently curious to invite further investigation. 

 It is however obvious, that the observations at Starfield and at 

 Poulkova are utterly incompatible with each other. While the latter 

 point to an approximate period of 3 d 22 h 10 m , the period indicated 

 by the former is only about 2 d 2 h 43 m- 6. The distance also of the 

 satellite carefully estimated by Mr. Lassell on Nov. 6, 1847, under 

 favourable circumstances and with great probability of considerable 

 accuracy, was only 11"; the position-angle being estimated 349°. 

 Now, assuming the direction of the major axis of the projected orbit 

 to be from 10° to 190°, as determined by M. O. Struve for the satel- 

 lite observed by him ; and assuming also that the apparent ellipticity 

 of the orbit does not greatly differ from that of the orbits of the 

 bright satellites I. and II. ; we find that the distance of the satellite, 

 at its greatest elongation, would be 12''-2, on the supposition that 

 the distance was correctly estimated at 11" when the position-angle 

 was 349°. But this is almost precisely the greatest elongation 

 theoretically due to a satellite revolving about Uranus in the period 

 indicated by Mr. Lassell's observations. We are thus led to the 

 conclusion, that there are at least two satellites interior to the nearest 

 bright one : and to avoid the confusion which might arise from ap- 

 plying numbers of any kind to the smaller satellites, I beg permission 

 to denominate them for the present, a, b, c, &c. in the order of di- 

 stance from the primary ; — a being the satellite observed by Mr. Las- 

 sell, and c the satellite observed by M. O. Struve. 



M. O. Struve suggests that the satellite observed by him may lose 

 much of its light when in the northern portion of its orbit ; and this 

 may be the reason why Mr. Lassell did not see it on Nov. 6, 1847, 

 on which favourable night c must have been near its greatest north- 

 ern elongation. On all the other nights when a was observed by 

 Mr. Lassell, c was very close to the planet, with one exception only, 

 on Sept. 14, at which time c was near its greatest elongation south- 

 wards, and might perhaps have been seen if the night had been suf- 

 ficiently good. Neither Mr. Lassell, however, nor myself then ob- 

 serving with him, perceived any such object in that place. 



It should here be stated, that the estimated position for Sept. 14, 

 as given in the printed table, appears to be erroneous. It is incon- 

 sistent with the diagrams independently made at the time by Mr. 

 Lassell and myself, which, taking the measured position of II. as a 

 guide, show that the position of a was about 80° north preceding ; — 

 whereas the angle as printed is 80° north following . It seems clear, 

 therefore, that the angle should be 350° instead of 10°. This being 

 rectified, and the position-angles computed for the times of observa- 

 tion, by reckoning back from the peculiarly valuable observation of 

 Nov. 6 as an epoch, and assuming a period of 2 d 2 h 43 m, 6, the esti- 

 mated angle minus the calculated angle comes out, for Sept. 14 = — 2°; 

 for Sept. 27 =-2°; for Sept. 29 = + 1°; for Oct. 1 = 4-2°. 



