GALILEO AND HIS JUDGES. 159 



be so called (for it hardly amounted to that), has 

 been solved within living memory. It was noticed 

 that the planet Uranus showed signs of perturbation 

 from some unknown reason ; and even the work I 

 have just quoted, ' ' Whewell's History of the Inductive 

 Sciences," published in 1847, contains the following 

 sentence : " Uranus still deviates from his tabular 

 place, and the cause remains yet to be discovered." 

 Two astronomers, one French and one English, 

 Le Verrier and Adams, found out the cause by 

 discovering the existence, each independently of the 

 other, of an exterior planet revolving in an orbit 

 more distant by far than that of Uranus ; to this 

 planet the name of Neptune has been given, and his 

 existence is one more confirmatory proof of the theory 

 of gravitation. 



The Copernican system had been built up and 

 consolidated by Newton's great discovery ; but 

 another piece of evidence, of a most important 

 character, was added by the investigations of Bradley, 

 Professor of Astronomy at Oxford, and afterwards 

 Astronomer Koyal ; this careful observer, while 

 engaged in endeavouring to detect such an apparent 

 motion of the fixed stars (so called) as would indicate 

 an annual parallax, noticed that another motion 

 existed different from that which the annual parallax 

 would produce, and for which he could not account ; 

 the apparent orbits described by the stars observed 

 depended on the distance of the stars from the pole 

 of the ecliptic ; the phenomenon was different from 



