236 HISTORY OF PHYSICAL ASTRONOMY. 



Sect. 4. Application of the Newtonian Theory 

 to the New Planets. 



WE are now so accustomed to consider the New- 

 tonian theory as true, that we can hardly imagine 

 to ourselves the possibility that those planets which 

 were not discovered when the theory was founded, 

 should contradict its doctrines. We can scarcely 

 conceive it possible that Uranus or Ceres should 

 have been found to violate Kepler's laws, or to 

 move without suffering perturbations from Jupiter 

 and Saturn. Yet if we can suppose men to have 

 had any doubt of the exact and universal truth of 

 the doctrine of universal gravitation, at the period 

 of these discoveries, they must have scrutinized the 

 motions of these new bodies with an interest far 

 more lively than that with which we now look for 

 the predicted return of a comet. The solid esta- 

 blishment of the Newtonian theory is thus shown 

 by the manner in which we take it for granted 

 not only in our reasonings, but in our feelings. But 

 though this is so, a short notice of the process by 

 which the new planets were brought within the 

 domain of the theory may properly find a place 

 here. 



William Herschel, a man of great energy and 

 ingenuity, who had made material improvements 

 in reflecting telescopes, observing at Bath on the 

 13th of March, 1781, discovered, in the constella- 

 lation Gemini, a star larger and less luminous than 



