244 Prof. Challis's Observations relative to the New Planet. 



In calculating the following second approximations, Mr. 

 Adams used the mean of the two places of Augustas a single 

 place, and of the others he selected nine which seemed to be 

 the best determined, and which were separated by convenient 

 intervals. All the results are calculated for the epoch of 1846, 

 August, 8*0 mean time at Greenwich. ^ ^ ^ 



Heliocentric longitude of the planet referred 

 to the mean equinox of 1847*0 .... 



Heliocentric motion in longitude in 100 days 



Heliocentric latitude south 



Change of heliocentric latitude in 100 days . 



Longitude of the descendinji node . . . . 



Inclination of the orbit 



Distance of the planet from the sun . . . 

 Half the latus rectum of the orbit . . . . 



The first position on which the above results depend, that 

 of August 4, was obtained sixteen days before the planet was 

 in opposition, and the last position, that of January 15, thirty- 

 two days before it was in conjunction. The great variation 

 of the planet's elongation from the sun in this interval, is fa- 

 vourable to the correctness of the above determinations, which, 

 although they cannot pretend to extreme accuracy on account 

 of the short period over which the observations extend, are 

 yet entitled to considerable weight. Mr. Adams has in fact 

 calculated the probable errors of the above results by sup- 

 posing each observation of right ascension or of north polar 

 distance to be liable to an error of 3"; and he finds that there 

 is little probability of their receiving any great amount of cor- 

 rection by taking account of future observations. It may be 

 remarked that the first and second approximations do not 

 differ by any large quantities. Hence it may be inferred that 

 the places of August are deserving of confidence, and that on 

 account of the extension given to the period of observation 

 by including those places, this second approximation to the 

 elements is more accurate than it would have been if it de- 

 pended solely on observations made since the discovery of the 

 planet. 



The calculations give 59' 8" for the planet's heliocentric 

 motion Irom August 4 to January 15. This is so small an 

 arc that it is not possible to deduce with any degree of cer- 

 tainty those elements the determination of which depends on 

 change of tlie heliocentric distance. Mr. Adams has, how- 

 ever, discussed the observations with this object in view, and 

 lias obtained certain limiting results, which, as possessing 

 considerable interest, I here subjoin. 



