i88i.] The Evolution of the Solar System . 261 
above referred to). But it is probable that these masses 
were not, as a rule, of great dimensions. It seems more 
likely that a comparatively few great masses would alone 
exist, their production hindering a like process in the re- 
maining portions of the nebula, on the same principle as 
that by which the sun hindered them in regions near the 
centre, through the overbalancing influence of its vigorous 
attractions. We may thus imagine a vast array of such 
revolving masses, as a rule of comparatively small dimen- 
sions, while among them moved a few much larger masses, 
irregularly placed as regarded the centre, but with a general 
tendency to increase of size outwardly. Between these 
masses the nebular substance must have become greatly 
rarefied, it being denuded of its material both by the dense 
masses that moved through it and by the solar attraction, 
this material condensing towards that attracting body, 
whether sun or planet, which had the most vigorous influence 
at each locality. 
These secondary masses, however, would not be related to 
each other as they would to the central mass. In their 
relations with this there would be a balanced agreement 
between the speed of revolution and the force of attraction. 
But in masses moving in nearly parallel orbits around a 
common centre there would be no such resistance to the 
effects of their common attractions. Their orbits would 
tend to approach each other. Every large mass might thus 
bring a lateral force to bear upon the small mass to a consi- 
derable distance on each side. And as scarcely any two of 
the small planets would have precisely the same orbital 
speed, they would constantly overtake, or be overtaken by, 
the larger masses in their annual revolutions, and thus be 
drawn more and more towards these larger centres of force, 
through the effect of lateral pull, until eventually aggrega* 
tion would arise between the parallel moving bodies. 
Such huge original aggregates as we may conceive the 
primary core of Jupiter to have been may have thus swept 
a vast extent of space of its smaller bodies, and gradually 
gathered them into its own mass, its attractive energy 
increasing with every such addition to its matter. Thus the 
few larger spheres may have grown at the expense of the 
smaller spheres, swallowing up all these except those moving 
at their own speed and in a distant part of their own 
orbits. But these again would be subject to perturbations 
from the attractions of distant large orbs, and thus brought 
into positions exposing them to overwhelming lateral at- 
tractions. 
