NEBULAR HYPOTHESIS. 19 



much weight. It is represented, for instance, 

 that the matter of the solar system could not, in 

 any conceivable gaseous form, fill the space com- 

 prehended by the orbit of Uranus. If this be the 

 case, let it be allowed as a difficulty. It is pointed 

 out that the planets do not increase regularly in 

 density from the outermost to the innermost. 

 Their sizes are also not in a regular progression, 

 though the largest, generally speaking, are towards 

 the exterior of the system. It was not, perhaps, 

 to be expected, that such gradations should be 

 observed; but, grant there was some reason to 

 look for them, their absence constitutes only an- 

 other and a slight difficulty. Then we know no 

 law to determine the particular " stages at which 

 rings are formed and detached." Be it so — 

 although something of the kind there doubtless 

 is, as the distances of the planets, according to 

 Bode's law, observe a geometrical series of which 

 the ratio of increase is 2. From these objections, 

 which cannot now be answered, let us pass to 

 some which can. 



It has been said that a confluence of atoms to- 

 wards a central point, as presumed by the nebular 



