2. 



AN EXPLANATION OF THE OBSERVED IRREGULARITIES IN THE MOTION 

 OF URANUS, ON THE HYPOTHESIS OF DISTURBANCES CAUSED BY 

 A MORE DISTANT PLANET; WITH A DETERMINATION OF THE MASS, 

 ORBIT, AND POSITION OF THE DISTURBING BODY. 



[From the Memoirs of the Royal Astronomical Society, Vol. xvi. (1847). Appendix to 

 Nautical Almanack (18ol). Read November 13, 1840.] 



1. THE irregularities in the motions of Uranus have for a long time 

 engaged the attention of Astronomers. When the path of the planet became 

 approximately known, it was found that, previously to its discovery by 

 Sir W. Herschel in 1781, it had several times been observed as a fixed 

 star by Flamsteed, Bradley, Mayer, and Lemonnier. Although these obser- 

 vations are doubtless very far inferior in accuracy to the modern ones, they 

 must be considered valuable, in consequence of the great extension which 

 they give to the observed arc of the planet's orbit. Bouvard, however, to 

 whom we owe the tables of Uranus at present in use, found that it was 

 impossible to satisfy these observations without attributing much larger 

 errors to the modern observations than they admit of, and consequently 

 founded his Tables exclusively on the latter. But, in a very few years, 

 sensible errors began again to shew themselves, and, though the tables 

 were formed so recently as 1821, their error at the present time exceeds 

 two minutes of space, and is still rapidly increasing. There appeared, 

 therefore, no longer any sufficient reason for rejecting the ancient obser- 



