14 HISTORY OF ASTRONOMY. 



daring mathematician from attacking the problem. 

 Again, in 1837, Mr. Airy repeats the same idea: "If 

 these errors are the effect of any unseen body, it will 

 be nearly impossible ever to find out its place. 11 



In the year 1842, the Eoyal Society of Sciences of 

 Gottingen, proposed, as a prize question, the full discus- 

 sion of the theory of the motions of Uranus, with 

 special reference to the cause of the large and increas- 

 ing error of Bouvard's tables. During the same year, 

 1842, Bessel was engaged in researches relative to this 

 problem ; but his labors were soon interrupted by sick- 

 ness and subsequent death ; and from this time we find 

 but two mathematicians, Mr. Adams, of Cambridge 

 University, in England, and M. Le Yerrier, of Paris, who 

 .busied themselves with the problem. 



It should be remembered, that in accordance with the 

 Newtonian law of gravitation, every body in the solar 

 system attracts every other ; that the attraction of each 

 body is proportioned to its quantity of matter ; and that 

 in the same body the power of attraction varies in- 

 versely as the square of the distance. In order, there- 

 fore, to compute the exact place of a planet in its orbit 

 about the sun, it is necessary not merely to regard the 

 attraction of the central body, but also to allow for the 

 influence of all the other bodies of the 

 solar system. For instance, if the sun 

 alone had acted, Jupiter would revolve 

 around the central luminary in a perfect 

 ellipse, which we may represent by the 

 annexed black curve; but the real orbit 



