PHYSICAL ASTRONOMY. 55c 



sven than that; inasmuch as the new planet had never been seen at 

 all, and was discovered by mathematicians entirely by their feeling of 

 its influence, which they perceived through the organ of mathematical 

 calculation. 



"There can be no doubt that to M. Le Terrier belongs the glory of 

 having first published a prediction of the place and appearance of the 

 new planet, and of having thus occasioned its discovery by astronom- 

 ical observers. M. Le Terrier's first prediction was published in the 

 Comptes Rendus de VAcad. des Sciences, for June 1, 1846 (not Jan. 1, 

 as erroneously printed in my Note). A subsequent paper on the sub- 

 ject was read Aug. 31. The planet was seen by M. Galle, at the Ob- 

 servatory of Berlin, on September 23, on which day he had received 

 an express application from M. Le Terrier, recommending him to en- 

 deavor to recognize the stranger by its having a visible disk. Pro- 

 fessor Challis, at the Observatory of Cambridge, was looking out for 

 the new planet from July 29, and saw it on August 4, and again on 

 August 12, but without recognizing it, in consequence of his plan of 

 not comparing his observations till lie had accumulated a greater 

 number of them. On Sept. 29, having read for the first time M. Le 

 Terrier's second paper, he altered his plan, and paid attention to the 

 physical appearance rather than the position of the star. On that 

 very evening, not having then heard of M. Galle's discovery, he sin- 

 gled out the star by its seeming to have a disk. 



" M. Le Terrier's mode of discussing the circumstances of Uranus's 

 motion, and inferring the new planet from these circumstances, is in 

 the highest degree sagacious and masterly. Justice to him cannot 

 require that the contemporaneous, though unpublished, labors of Mr. 

 Adams, of St. John's College, Cambridge, should not also be recorded. 

 Mr. Adams made his first calculations to account for the anomalies in 

 the motion of Uranus, on the hypothesis of a more distant planet, in 

 1843. At first he had not taken into account the earlier Greenwich 

 observations; but these were supplied to him by the Astronomer 

 Royal, in 1844. In September, 1845, Mr. Adams communicated to 

 Professor Challis values of the elements of the supposed disturbing 

 body ; namely, its mean distance, mean longitude at a given epoch, 

 longitude of perihelion, eccentricity of orbit, and mass. In the next 

 mouth, he communicated to the Astronomer Royal values of the same 

 elements, somewhat corrected. The note (L.), vol. ii., of the present 

 work (2d Ed.), in which the names of MM. Le Terrier and Adams 

 are mentioned in conjunction, was in the press in August, 1846, a 



