304 NINETEENTH CENTURY. PT. III. 



pulling he had to calculate where another body must be to 

 draw it away from them. This he accomplished, and it is 

 very remarkable that the great French astronomer Leverrier 

 also worked out the same problem, without having heard 

 that Adams had done it. 



In the year 1838 Leverrier had begun a long series of 

 calculations, which were only completed in 1874 (see p. 461), 

 to find out the varying attractions, and by that means the 

 size and weight, of the different planets, and while he was 

 at work at this he became convinced that there must be some 

 unseen body pulling at Uranus. Now it so happened that 

 just at the time when Adams and Leverrier began to feel 

 after this supposed planet, Uranus had lately been very 

 much disturbed, and so they knew that he must have 

 approached near to the disturbing cause, and this showed 

 them in which part of the heavens the attracting planet 

 ought to be. 



Leverrier published his calculations in the Journal of 

 the Academic des Sciences at Paris in November 1845 and 

 June 184*6, and when the Astronomer-Royal read the papers 

 he was astonished to find that the French astronomer had 

 fixed the place of the unknown planet within one degree of 

 the spot which Adams had named. This led him to suggest 

 that a search should be made for it, and Professor Challis 

 of Cambridge actually observed and recorded its place on 

 August 4 and 12, 1846, but having no chart of that part 

 of the heavens, was not able to identify it. Meanwhile 

 Leverrier published another paper on August 31,1 846, stating 

 still more accurately where the planet ought to be found. 

 This paper he sent to his friend M. Galle, of the Berlin 

 Observatory, on September 23, 1846, asking him to look in 

 that part of the sky which he pointed out. M. Galle did so, 

 and on that same night^ by Jollowing out the instructions. Jound 



