22 THE SKY. 



by Sir Wm. Herschell, after whom it was for some time 

 named. 



Another, and the most remote planet in our system, is 

 Neptune, revolving at the immense distance of 2850 millions 

 of miles from the sun, and taking more than 164 years to 

 perform the journey. This planet is only to be seen by the 

 most powerful glasses, and was discovered under very 

 peculiar circumstances, not (like other planets) by chance ; 

 its existence was recognised as necessary to account for 

 certain " perturbations " or deviations in the orbit of 

 Uranus, which was found to take a course differing from 

 what it should, according to computation, and which were 

 only to be accounted for by supposing that another planet 

 existed far out in space, which affected the course of Uranus 

 by its attraction. The idea of finding out where this orb 

 should be, occurred to M. Le Verrier and Mr. Adams, inde- 

 pendent of each other ; they both arrived at nearly similar 

 conclusions, for the positions assigned to the supposed 

 planet so nearly agreed with each other and with its real 

 position, that their calculations have been looked on as the 

 greatest feat of astronomical research. It was discovered 

 by Dr. Galle of Berlin, upon his hearing from Le Terrier 



e position in which at that time it should be sought for. 



by 



tin 



THE PLANETOIDS. 



Upon observing the relative distances of the planets from 

 each other in passing outwards from Mercury, it w r ill be 

 found that each one is placed about double the distance of 

 the one next before it (not exactly, but sufficiently near to 

 form a coincidence almost amounting to a law), they are as 

 follows : 



