in. v.] PLANET A RY E VOL UTION. 373 



rings subsequently detached between himself and the present 

 solar surface. The earth, Venus, and Mercury would in such 

 a case have been represented by a triple zone of asteroids, 

 revolving in more or less eccentric orbits, and the portions of 

 planetary matter which constitute the German armies belea- 

 guering Paris might to-day 1 have been peacefully whirling 

 in space, ten million miles removed from the portions which 

 constitute the starving population of that unhappy city. 



Joining together all the foregoing considerations, we have 

 a most interesting array of facts, which I believe have not 

 hitherto been contemplated in connection with one another. 

 Though in the sizes of the planets, superficially regarded, we 

 find no conspicuous symmetry of arrangement, yet in the 

 thickness of the genetic rings, as obtained by a legitimate 

 process of inference, we find a symmetry of disposition that 

 is striking and suggestive. From Neptune to Jupiter we find 

 a progressive increase in thickness that is entirely in con- 

 formity with the nebular hypothesis. From the asteroids to 

 Mercury there is a similar progressive increase which is 

 similarly in entire harmony with the hypothesis. And in 

 the only group of satellites concerning which we have 

 adequate data, there is observed a parallel phenomenon. But 

 in the solar system there is a conspicuous break in the 

 uniformity of succession ; and this break curiously occurs 

 just at the place where, according to the most plausible 

 supposition, there was an arrest or failure in the normal 

 formation of a planet. I have partially succeeded in tracing 

 this arrest or failure to the immediate effects wrought by the 

 mere proximity and gigantic size of the planet just preceding 

 in the order of detachment. Whether it can be shown that 

 this cause, which well-nigh accounts for one of this group of 

 phenomena, will account in some analogous way for the 

 whole group ; whether it can be shown that the detachment 

 Df this gigantic mass may have altered the dynamic relations 



1 That is, in December, 1870. 



