534 



SCIENTIFIC RECREATION S. 



concerning its physical constitution, which is assumed to be similar to that 

 of Jupiter, while the changes of temperature and seasons must vary im- 

 mensely. The names of the moons are Ariel, Umbriel, Titania, and Oberon. 

 The outer pair can be seen without much difficulty. 



NEPTUNE. 



The existence of this planet was determined by calculation before it had 

 been seen at all. Uranus was observed to be disturbed in his orbit, moving 



sometimes faster than at others; and even be- 

 fore Uranus had been discovered Saturn and 

 Jupiter had been seen to be affected by some 

 body in the system. M. Leverrier determined 

 to ascertain the cause of this, and came to 

 the conclusion that some other planet was in- 

 fluencing Uranus. The Newtonian theory here 

 received a most convincing proof. While 

 Leverrier was calculating, Mr Adams of Cam- 

 bridge leaped to the same conclusion, and wrote 

 the result of his calculations to Professor Airy, 

 and the planet was seen, but not reported upon. 

 Meantime Leverrier published his calculations, 

 and the observers at Berlin detected the new planet in September 1846. 



Very little can be said concerning Neptune, as its distance is .too great 

 for observation. It is at 2,746,000,000 of miles from the sun, and takes 

 164 years to go round it (60,126 days). It is about the same size as 

 Uranus. It has one moon, which moves round the planet in 5 d 2i h , and is 

 of great size. 



Fig- 595. Neptune in field of view with 

 stars of 6th, jth, 8th, and gth magnitudes. 



