118 A CENTURY'S PROGRESS IN ASTRONOMY. 



and Dawes' letter was accidentally destroyed by 

 a housemaid. So Adams' theory remained in 

 obscurity. 



The question now came under the notice of 

 Francois Jean Dominique Arago (1786-1853), 

 the director of the Paris Observatory. He 

 recognised in a young friend of his a rising 

 genius, who was competent to solve the problem. 

 Urban Jean Joseph Le Verrier, born at Saint Lo, 

 in Normandy, in 1811, became in 1837 astro- 

 nomical teacher in the Ecole Polytechnique, and 

 in 1853 director of the Paris Observatory. In 

 consequence of differences with his staff he was 

 obliged, in 1870, to resign from this position, but 

 two years later was restored to the post, which 

 he held till his death on September 23, 1877. 



In 1845, ignorant of the fact that Adams had 

 already solved the problem, Le Verrier began 

 his investigations of the irregular motions of 

 Uranus. In a memoir communicated to the 

 Academy of Sciences in November of that year, 

 he demonstrated that no known causes could 

 produce these disturbances. In a second memoir, 

 dated June 1, 1846, he announced that an ex- 

 terior planet alone could produce these effects. 

 But Le Verrier had now before him the difficult 

 task of assigning an approximate position to the 

 unseen body, so that it might be telescopically 



