COSMIC PHILOSOPHY 



ing the size of a planet with the size of its orbit, 

 we shall see that, from Neptune to Jupiter, there 

 was a regular increase in the thickness of the 

 rings, such as the theory might lead us to an- 

 ticipate. 



But now after the separation of Jupiter from 

 the parent mass, we encounter a break in this 

 series of phenomena. The thickness of the de- 

 tached rings sinks to a minimum in the case of 

 the asteroids, and then steadily increases again 

 till in Mercury there is once more an approach to 

 the quoit shape. Observe the curious sequence 

 of facts, which hitherto, so far as I know, has 

 never been noticed by any of the writers who 

 have treated of the nebular hypothesis. Since 

 the mass of Mercury is four fifths that of Venus, 

 while the circumference of his orbit is about 

 one half that of the orbit of Venus, it follows 

 that his ancestral ring must have been much 

 thicker than that of Venus. Again, the earth 

 is but little larger than Venus, while the cir- 

 cumference of its orbit exceeds that of the lat- 

 ter nearly in the ratio of five to three, so that 

 it must have originated from a thinner ring. 

 Mars, with an orbit exceeding the earth's in 

 the ratio of eight to five, and containing but 

 one eighth as much planetary matter as the 

 earth, must have been formed from a still thin- 

 ner ring. And since the asteroids, if all piled 

 together, would not make a planet as large as 

 266 



