SCIENTIFIC PREDICTION 191 



elements of the orbit which it describes ? ' The con- 

 clusion reached by the calculations recorded in this 

 second paper was that all the so-called anomalies in 

 the observations of Uranus could be explained as the 

 perturbation caused by a planet with a heliocentric 

 longitude of 252 on January 1, 1800. This would 

 correspond to 325 January 1, 1847. 



Airy received Leverrier's second paper on June 

 23, and was struck by the fact that the French mathe- 

 matician assigned the same place to the new planet 

 as had Adams in the preceding October. He wrote 

 to Leverrier in reference to the errors of the radius 

 vector and received a satisfactory and sufficiently 

 compliant reply. At one time the Astronomer Royal 

 had felt very skeptical about the possibility of the 

 discovery which his own labors had contributed to 

 advance. He had always, to quote his own rather 

 nebulous statement, considered the correctness of 

 a distant mathematical result to be the subject of 

 moral rather than of mathematical evidence. Now 

 that corroboration of Adams's results had arrived, 

 he felt it urgent to make a telescopic examination of 

 that part of the heavens indicated by the theoretical 

 findings of Adams and Leverrier. He accordingly 

 wrote to Professor Challis, July 9, requesting him 

 to employ for the purpose the great Northumberland 

 equatorial of the Cambridge Observatory. 



Professor Challis had felt, to use his own language, 

 that it was so novel a thing to undertake observa- 

 tions in reliance upon merely theoretical deductions, 

 that, while much labor was certain, success appeared 

 very doubtful. Nevertheless, having received fresh 

 instructions from Adams relative to the theoretical 



