NEW PLANETS NEAR THE SUN. 33 



calculate retrogressively the path along which it had been 

 travelling, unseen and unsuspected, during the century pre- 

 ceding its discovery. And now observations which many 

 might have judged to be of little value, came in most use- 

 fully. Astronomers since the discovery of the telescope had 

 formed catalogues of the places of many hundreds of stars 

 invisible to the naked eye. Search among the observations 

 by which such catalogues had been formed, revealed the 

 fact that Uranus had been seen and catalogued as a fixed star 

 twenty-one several times ! Flamsteed had seen it five times, 

 each time recording it as a star of the sixth magnitude, so 

 that five of Flamsteed's stars had to be cancelled from his 

 lists. Lemonnier had actually seen Uranus twelve times, 

 and only escaped the honour of discovering the planet (as 

 such) through the most marvellous carelessness, his astrono~ 

 mical papers being, as Arago said, ' a very picture of chaos/ 

 Bradley saw Uranus three times. 1 Mayer saw the planet 

 once only. 



It was from the study of the movements of Uranus as 

 thus seen, combined with the planet's progress after its dis- 

 covery, that mathematicians first began to suspect the exist- 

 ence of some unknown disturbing body. The observations 

 preceding the discovery of the planet range over an interval 

 of ninety years and a few months, the earliest observation 

 used being one made by Flamsteed on December 23, 1690. 

 There is something very strange in the thought that science 

 was able thus to deal with the motions of a planet for nearly a 

 century before the planet was known. Astronomy calcu- 

 lated in the first place where the planet had been during that 

 time ; and then, from records made by departed observers, 

 who had had no suspicion of the real nature of the body they 

 were observing, Astronomy corrected her calculations, and 

 deduced more rigorously the true nature of the new planet's 

 motions. 



1 Two observations of Uranus, by Bradley, were discovered by the 

 late Mr. Breen, and published in No. 1463 of the Astronomi^fe Natk* 

 richten* 



D 



