Prof. Challis's Observations relative to the Neiso Planet. 243 



By a measurement taken with the position circle on Jan. 1 5, 

 under very unfavourable circumstances, this angle was found 

 to be 65°. I am unable to account entirely for my not having 

 noticed the ring at an earlier period of the observations. It 

 may, however, be said that an appearance like this, which it 

 is difficult to recognise except in a good state of the atmosphere, 

 might for a long time escape detection, if not expressly and 

 I'epeatedly looked for. To force itself on the attention, it 

 would require to be seen under extremely favourable circum- 

 stances. Previous to the observations in January, the planet 

 had been hid for more than three weeks by clouds. The 

 evenings of January 12 and 14 were particularly good, and 

 the planet was at first looked at in strong twilight. Under 

 very similar circumstances I have twice seen with the North- 

 umberland telescope the second division of Saturn's ring, 



I communicated to Mr. Lassell of Liverpool, who was the 

 first to suspect the existence of a ring, my observations upon 

 it, accompanied with a drawing; and I have received from him 

 in return a drawing of the appearance presented in his twenty- 

 feet reflector, closely resembling mine both as to the form and 

 the position of the ring. Mr. Lassell writes, " I cannot refuse 

 to consider that your observation puts beyond reasonable doubt 

 the reality of mine." Li this conclusion I concur, and ac- 

 cordingly in communications to the Royal Astronomical 

 Society and to Schumacher's Astronomisclie Nachrichten, con- 

 taining my reduced observations, I have ventured to express 

 my conviction of the existence of a ring. 



By micrometer measures taken with the Northumberland 

 telescope, I find the apparent diameter of the body of the 

 planet to be very nearly 3". 



The above account includes all the observations on the 

 planet I could obtain before its disappearance in the solar rays. 

 By the kindness of Mr. Adams I am able to add some par- 

 ticulars respecting its orbit, which he has derived by calcula- 

 tion from the reduced places with which I furnished him. As 

 was stated in the former I'eport, Mr. Adams calculated first 

 approximations to the elements, by employing the ptaces I 

 obtained on August 4 and 12 in the course of searching for 

 the planet, wilii observations since the discovery extending to 

 October 13. For the sake of comparison with the second ap- 

 proximations, I now give the first results. 



Heliocentric longitude . . . . 32°6 39 Aug. 4, 1846. 

 Longitude of the descending node. 309 43 

 Inclination of the orbit .... 145 



Distance of the planet from the sun 30*05 

 S2 



