NEWS FROM HERSCHEL'S PLANET. 143 



noticed that in this respect the outer planets resemble 

 the sun, whose density is but about one-fourth that of 

 the earth. It seems impossible that the apparent size 

 of any one of the outer planets can truly indicate the 

 dimensions of its real globe. An atmosphere of 

 enormous extent must needs surround, it would seem, 

 the liquid or solid nucleus which probably exists within 

 the orb we see. 



In the case of Jupiter or Saturn, the telescope has 

 told us much which bears on this point ; and as I have 

 indicated in my ' Other Worlds,' and elsewhere, there is 

 an overwhelming mass of evidence in favour of the theory 

 that those orbs are still instinct with their primeval 

 fires. But in the case of Uranus, it might well be 

 deemed hopeless to pursue such inquiries, otherwise 

 than by considering the analogy of the two larger 

 planets. Direct evidence tending to show that the 

 atmosphere of Uranus is in a condition wholly differing 

 from that of our own atmosphere, cannot possibly be 

 obtained by means of any telescopes yet constructed by 

 men. Some astronomers assert that they have seen 

 faint traces of belts across the disc of Uranus ; but the 

 traces must be very faint indeed, since the best tele- 

 scopes of our day fail to show any marks whatever 

 upon the planet's face. Even if such belts can be 

 seen, their changes of appearance cannot be studied 

 systematically. 



It is, however, on this very subject the condition 

 of the planet's atmosphere that the discovery I have 

 now to describe throws light. 



