SECOND EDITION. xi 



POSTSCRIPT TO THE SECOND EDITION. 



(1). The planet exterior to Uranus, of which 

 the existence was interred by M. Le Verrier and Mr. 

 Adams from the motions of Uranus (vol. n. Note 

 (L) ), has since been discovered. This confirmation of 

 calculations founded upon the doctrine of universal 

 gravitation, may be looked upon as the most re- 

 markable event of the kind since the return of 

 Halley's comet in 1757 ; and in some respects, as a 

 more striking event even 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 Verrier 

 belongs the glory of having first published a pre- 

 diction of the place and appearance of the new 

 planet, and of having thus occasioned its discovery 

 by astronomical observers. M. Le Verrier's first 

 prediction was published in the Comptes Rendus de 

 I'Acad. des Sciences, for June 1, 1846, (not Jan. 1, 

 as erroneously printed in my Note.) A subsequent 

 paper on the subject was read Aug. 31. The planet 

 was seen by M. Le Galle, at the Observatory of Berlin, 

 on September 23, on which day he had received an 



