260 The Evolution of the Solar System . [May, 
nebulae continue in a diffused state, or become aggregated 
into a sun and attendant planets. 
But as it is by no means probable that the original mass 
approached an equality of diffusion, so it is not probable that 
any such regular arrangement of the minor masses could 
result. As a general rule they must have been smaller near 
the centre of the nebula, and larger in its exterior regions, 
but beyond this general arrangement their sizes must have 
been dependent upon the condition of diffusion in the ori- 
ginal mass. Every condensed portion of this original mass 
would tend to set up a local action of aggregation, and the 
position of the largest secondary aggregate would be 
governed by the possible existence in the original nebula of 
some wide field of denser matter, sufficiently removed from 
the centre to escape the interfering adtion of the vigorous 
central energy. 
Such seems probable to have been the original process of 
mass development in the nebula from which the Solar System 
arose. An allegiance of the mass as a whole to the attractive 
vigour emanating from its centre ; an allegiance of secondary 
condensed portions of the mass to the attraction of their 
centres ; and a gradual formation of minor aggregates as 
constituent portions of the great aggregate ; these secondary 
masses increasing in size, but not regularly outwardly from 
the centre. 
These, however, were not the planetary masses we now 
possess. Nor were they defined rings of condensed matter, 
or of small masses. They were, more likely, a vast number 
of small rotating masses, of every imaginable size, and oc- 
cupying the most irregular positions, circulating around the 
centre in an immense variety of orbits. If, indeed, we con- 
ceive of the original nebula as condensing into a rotating 
disk, we may conceive of this secondary stage of its evolu- 
tion as a gathering of its matter into secondary masses, 
which occupied the whole extent of the original disk. The 
nebular sun in the centre was thus surrounded by an im- 
mense number of planets, of every imaginable size, radius 
of orbit, and speed of revolution, every radius of the circle 
around the centre being occupied, at any one moment, by 
several of these planets. These orbits might be variously 
elliptical, and out of the plane of the Ecliptic. For the 
general motion of the masses would have two components 
of direction, one arising from their allegiance to the central 
energy, and one from their own condensation — this yielding 
motion in a direction opposite to that in which the general 
heat emission took place (as argued at length in the article 
