THE RINGED PLANET. 47 



formed is measurable by the actual difference in dimensions between 

 the globe and its parent cloud-mass, and of course the larger the 

 cloud-mass the greater this difference would necessarily be. It is 

 equally certain that the heat generated by the gathering-in of me- 

 teoric matter would be so much the greater according as the quantity 

 of matter gathered and gathering was greater ; for the heat is pro- 

 duced by the downfall of such matter on the globe it helps to form, 

 and the greater the mass of that globe the greater is its attracting 

 might, the greater the velocity it generates in the falling meteors, 

 and therefore the greater the heat produced when they are brought 

 to rest. 



Saturn, then, would originally be much hotter than our earth, on 

 any theory of the evolution of our solar system — and there are few as- 

 tronomers who doubt that the solar system was wrought by processes 

 of evolution to its present condition. But not only would Saturn be 

 much hotter than the earth, but, owing to his enormous size, he would 

 part with his heat at a much slower rate. On both accounts we should 

 infer that at this present time Saturn is much hotter than the earth — 

 in other words, since our earth still retains no inconsiderable propor- 

 tion of its original heat, Saturn may be assumed to be in a state of 

 intense heat. What his actual heat may be is not so easily deter- 

 mined. We shall presently show reasons for believing that an inferior 

 limit, below which his heat does not lie, is indicated by the fact that 

 he still possesses inherent luminosity. On the other hand, a superior 

 limit is indicated by the fact that his inherent luminosity is not great, 

 and that, in all probability, the thicker cloud-zones of Saturn prevent 

 the passage of the greater part of his light. 1 



We should infer, then, that Saturn in some respects resembles the 

 sun, though of course the very same reasoning which teaches us to 

 believe that Saturn is very much hotter than the earth, leads us also 

 to the conclusion that it is not nearly so hot as the sun. Now, thus 

 viewing Saturn, we should be led to expect, apart from all telescopic 

 evidence to that effect, that he would resemble the sun in certain gen- 

 eral features. For instance, we might expect that he would have spot- 

 zones, while his equatorial zone would be free from spots ; or, if it 

 were thought that so close a resemblance was not to be looked for, 

 then we might still expect that his equatorial zone, like the sun's, 

 would be distinguished from the rest of his surface by some well- 

 marked peculiarity. This is the case. The equatorial zone of Saturn 

 is distinguished by a peculiar brightness from the rest of his surface, 

 insomuch that the late Prof. Nichol was led to regard this zone as the 



1 To prevent misapprehension, it may be as well to remind the reader that the ap- 

 parent continuity of Saturn's cloud-belts by no means implies that they are really con- 

 tinuous, and it is on a priori grounds highly improbable that they are so ; openings in 

 his cloud-zones two or three hundred miles in length and breadth would be quite undis- 

 cernible at Saturn's enormous distance. 



