556 ADDITIONS 



month before the planet was seen. As I have stated in the text, Mr. 

 Adams and M. Le Verrier assigned to the unseen planet nearly the 

 same position ; they also assigned to it nearly the same mass ; namely, 

 2^ times the mass of Uranus. And hence, supposing the density to 

 be not greater than that of Uranus, it followed that the visible diame- 

 ter would be about 3", an apparent magnitude not much smaller than 

 Uranus himself. 



" M. Le Verrier has mentioned for the new planet the name Neptu- 

 nus ; and probably, deference to his authority as its discoverer, will 

 obtain general currency for this name." 



Mr. Airy has given a very complete history of the circumstances 

 attending the discovery of Neptune, in the Memoirs of the Astronom- 

 ical Society (read November 13, 1846). In this he shows that the 

 probability of some disturbing body beyond Uranus had suggested 

 itself to M. A. Bouvard and Mr. Hussey as early as 1834. Mr. Airy 

 himself then thought that the time was not ripe for making out the 

 nature of any external action on the planets. But Mr. Adams soon 

 afterwards proceeded to work at the problem. As early as 1841 (as 

 he himself informs me) he conjectured the existence of a planet exte- 

 rior to Uranus, and recorded in a memorandum his design of examin- 

 ing its effect ; but deferred the calculations till he had completed his 

 preparations for the University examination which he was to undergo 

 in January, 1843, in order to receive the Degree of Bachelor of Arts. 

 He was the Senior "Wrangler of that occasion, and soon afterwards 

 proceeded to carry his design into effect ; applying to the Astronomer 

 Royal for recorded observations which might aid him in his task. On 

 one of the last days of October, 1845, Mr. Adams went to the Obser- 

 vatory at Greenwich ; and finding the Astronomer Royal abroad, he 

 left there a paper containing the elements of the extra-Uranian Plan- 

 et : the longitude was in this paper stated as 323i degrees. It was, as 

 we have seen, in June, 1846, that M. Le Verrier's Memoir appeared, 

 in which he assigned to the disturbing body a longitude of 325 de- 

 grees. The coincidence was striking. " I cannot sufficiently express," 

 says Mr. Airy, " the feeling of delight and satisfaction which I received 

 from the Memoir of M. Le Verrier." This feeling communicated itself 

 to others. Sir John Herschel said in September, 1846, at a meeting 

 of the British Association at Southampton, " "We see it (the probable 

 new planet) as Columbus saw America from the shores of Spain. Its 

 movements have been felt, trembling along the far-reaching line of our 

 analysis,with a certainty hardly inferior to that of ocular demonstration." 



