1 88 1.] The Evolution of the Solar System. 263 
and heterogeneous in diffusion of their materials. Conse- 
quently it seems as if a similar process to that above consi- 
dered must have displayed itself in the planets, the outer 
portions of their substance condensing into numerous smaller 
bodies, and these again gathering, under the influence of 
their larger individuals, into moons. And in the moons we 
have an instance significantly like that of the asteroids. 
For the rings of Saturn seem to present an instance of such 
an array of smaller revolving masses, too much under the 
influence of the planetary attraction to be swept away by 
the outer moons, and with no large mass capable of aCting 
as a minor centre of aggregation of the materials of the 
rings. 
In the astral system, of which our Sun possibly forms 
part, a similar process of aggregation may have gone on ; 
in which case our Solar System would be but the outcome 
of one of the secondary aggregations of the general mass, 
while the vast rarefied space between the spheres of this 
astral system would answer to the lesser rarefied spaces 
between our planets. Likewise, as the comets which apper- 
tain to our system may have arisen from some of the 
original small masses, which retained their independence 
through being forced into very elliptical orbits, so the comets 
which come from without our system may have arisen in 
like matter in this intermediate space, and have gained their 
irregular orbits through the overbalancing attractions of 
Solar Systems. 
If such cometary masses took part in any degree in the 
formation of planets, they would be a disturbing agent 
adding to the tendency of irregularity in the planetary mo- 
tions. Such irregularity, whether arising from this cause 
or from lack of central influence, must be most declared 
outwardly, and in our system is most evident in the outer- 
most planets. The moons of these planets are even un- 
conform able in their motions to the direction of the solar 
influence, but not to that of their immediate attracting 
centre, to which they are simply eccentric.* 
Another question of importance in this connection con- 
cerns the evolutionary processes in the planets, subsequent 
to their condensation into solidified masses. It is generally 
taken for granted that suns and planets now contain their 
* It is very probable, also, that in the condensation of a heterogeneous 
nebula the centre of gravity would not be the centre of volume. If so, the 
mass as a whole would describe an elliptical movement, while its minor com- 
ponents might assume variously elliptical orbits, from their special individual 
relations to this centre of attraction. 
