3G2 COSMIC PHILOSOPHY. [pt. ii. 



hundreds of fragments, of which some few would be rela- 

 tively large, while the numerous small ones would vary end- 

 lessly in their sizes. At this stage, then, instead of a con- 

 tinuous ring, we have a host of satellites, surrounding the solar 

 equator, revolving in the direction of the solar rotation, and 

 following each other in the same orbit. If undisturbed by 

 any powerful attraction from without, these fragments would 

 continue in the same orbit, and would gradually differ more 

 and more in their velocities. Each large fragment would, by 

 its gravitative force, retard the smaller fragment in front of 

 it, and accelerate the smaller fragment behind it, until at last 

 two or three fragments would catch up with each other and 

 coalesce. Thus, in the earliest case known to us, — that of 

 the planet Neptune, 1 — this process went on until all the 

 fragments were finally agglomerated into a spheroidal body, 

 having a velocity compounded of the several velocities of 

 the fragments, and a rotation made up of their several 

 rotations. 



Meanwhile the central mass of the vaporous sun continued 

 to radiate heat and to contract, until, when its periphery 

 came to coincide with what is now called the orbit of Uranus, 

 its centrifugal force at the equator again showed an excess 

 over gravity, and a second equatorial belt was left behind ; 

 and this belt, breaking up and consolidating, after the manner 

 above described, became the planet Uranus. In like manner 

 were formed all the planets, one after another ; and from the 

 detached equatorial belts of the cooling and contracting 

 planets, w T ere similarly formed the satellites. 



A very curious physical experiment, devised by M. Plateau, 

 strikingly illustrates the growth of our planetary system from 



1 It is not strictly impossible that there may be one or two planets exterior 

 to Neptune, and therefore earlier in formation. Supposing the distances of 

 such planets to conform, even as imperfectly as in Neptuue's case, to the law 

 f Titius, these distances must be so enormous as to prevent our readily dis» 

 eovering the plauets, either directly by observation, or indirectly, by infer' 

 Mice from possible perturbations of Neptune's movements. 



