LE VERRIER AND ADAMS PLANET. 



Fit? 1. 



the spirit of the reasoning by which the 

 solution of the problem has been accom- 

 plished. 



For this purpose, it will be necessary, 

 first, to explain the nature and character 

 of those disturbances which were observed 

 and which could not be ascribed to the 

 attraction of any of the known planets ; 

 and, secondly, to show in what manner an 

 undiscovered planet, revolving outside the 

 known limits of the solar system, could 

 produce such effects. 



5. At the epoch of this celebrated dis- 

 covery, the solar system was supposed to 

 consist of the principal planets, Mercury, 

 Venus, the Earth, Mars, Jupiter, Saturn, and 

 Uranus, revolving round the sun, in the order 

 in which we have given their names, and at 

 distances bearing to each other the propor- 

 tion which is represented with tolerable 

 exactness in fig. 1. Between Mars and 

 Jupiter a group of very minute bodies, 

 called planetoids or asteroids, had been 

 discovered, occupying the place of a planet, 

 which had been supposed to be wanting in 

 the system. Since the discovery which now 

 engages us, the number of these planetoids 

 discovered has been greatly increased, its 

 amount being at the time we write (1st 

 February, 1855,) not less than 33. 



If the reader will cany in his eye the 

 plan of the solar system thus exhibited, he 

 will find the following observations and 

 reasoning not difficult to comprehend. 



6. The planet Uranus, revolving at the 

 extreme limits of the solar system, was the 

 object in which were observed those dis- 

 turbances which, not being the effects of 

 the action of any of the known planets, 

 raised the question of the possible ex- 

 istence of another planet exterior to it, 

 which might produce them. 



After the discovery of that planet by Sir 

 W. Herschel, in 1781, its motions, being 

 regularly observed, supplied the data by , 



174 



