Royal Astronomical Society. 881 



Royal gave orally a continuation of the history of Neptune, embra- 

 cing the ])rincipal points that have been ascertained since his com- 

 munication of Nov. 14, 1846. The planet having been actually dis- 

 covered in the heavens by means of certain predicted elements, the 

 fair presumption was that those elements were very approximately 

 correct. Adopting these elements, therefore, Mr. Hind examined 

 Lalande's and other observations, with the hope of finding some 

 former observation of the planet as a star now missing, but satisfied 

 himself that there was none. In the meantime, the continuation of 

 the observations of the planet in the last months of 1846, and the 

 comparison of them with Professor Challis's early observations of 

 August, led to some unexpected conclusions. It was found that, 

 though one^/«ee of the planet might be very well represented by M. 

 Le Verrier's or Mr. Adams's elements, yet the apparent movement of 

 the planet could not be represented within several minutes. Elements 

 were then investigated from the observations themselves (without 

 any reference to the preceding deductions from the perturbations of 

 Uranus) by Mr. Adams in England (see Monthly Notices for March, 

 p. 244), and by Professor Pierce and Mr. Sears C. Walker in Ame- 

 rica. Attention is particularly due to the former of these investiga- 

 tions, in which are exhibited, not only the results for the different 

 elements, but also for the probable error of each. The most import- 

 ant conclusion was, that the planet certainly moved in a much smaller 

 orbit, and probably in an orbit of much smaller eccentricity, than 

 that indicated by the calculations of perturbation. With elements 

 thus roughly corrected, the orbit was again traced back through the 

 ancient observations ; and it was found by Dr. Petersen of Altona, 

 and Mr. Sears C. Walker, that a star observed by Lalande on May 

 10, 1795, and now missing from the heavens, was very probably the 

 planet. The observation however vi'as marked doubtful in Lalande's 

 printed volume : and to this circumstance is probably due a most 

 remarkable discovery. The manuscripts of Lalande's observations 

 were some years ago transferred by his representatives to the obser- 

 vatory of Paris. To examine into the presumption of doubt in the 

 observation, the astronomers of the Observatory of Paris referred to 

 the originals, and there they found that the observation of May 10, 

 1795, was entered without any expression of doubt at the time; 

 that an observation of May 8, 1795, was omitted in the printed vo- 

 lume ; that it was omitted solely because it could not be reconciled 

 with the observation of May 10 ; and that, upon reducing both pro- 

 perly, they exhibit most distinctly the retrograde motion of a planet 

 nearly parallel to the plane of the ecliptic, the right ascension and 

 the polar distance having both changed in the proper proportion. 

 It seems now inconceivable to us that an astronomer, having his atten- 

 tion strongly called to the difference between the two days' results, 

 should rather assume that there were in the observations two inde- 

 pendent errors (one of right ascension and one of polar distance), 

 than that the body observed was really a planet. With the place of 

 the planet at an epoch so distant, its elements are ascertained with 

 great accuracy. 



