( I 4) 
The nebular theory is, essentially, as follows : in the remote 
past, there existed a vapor-like mass of incandescent gas which 
stretched itself in vast dimensions through a part of infinite space.* 
This nebulous mass had a motion of rapid rotation, with a di¬ 
rection from west to east. Whence the matter came of which 
the mass consisted, we do not know, nor the source of its intense 
heat, nor the cause of its rotation. These facts are inscrutable. 
As the mass revolved, it radiated constantly into space a portion 
of its heat, whereby it grew less hot, and, like all cooling bodies, 
was in a state of continual contraction, which implies an in¬ 
creasing density and an ever increasing velocity of rotation. Re¬ 
volving bodies have a tendency to throw oil from themselves the 
portions about their periphery : this is marked in fluid bodies, 
and much more so in those of a gaseous consistence. In accor¬ 
dance with this well-known mechanical principle, a ring was 
given off from the primitive nebulous mass, and, subsequently, a 
series of rings, all of which continued to revolve about the central 
mass, and in the same direction as before, i. e. from west to east.f 
The matter of which these rings consisted being of different den¬ 
sity in different places, the denser portions acted as centres of 
special attraction, the less dense gravitating toward them, until, 
after a time, the rings were broken into fragments, which latter 
still continued to revolve, from west to east, about the great mass 
at the centre, along a course in space before occupied by the 
parent-rings .\ But these fragments had acquired still another 
motion, and now revolved upon their own axes, also from w’est to 
east. By the principle already enunciated, many of these re¬ 
volving fragments now acted as sub-centres for the evolution of 
rings, and these secondary rings, like the first series, broke into 
rotating fragments, the direction of motion for these masses, 
whether upon their own axes or about a parent-body, being always 
from west to east. This process of ring-making was finally 
brought to an end by the cooling, and consequent solidification, 
of the masses. The central body of the nebula became the sun, 
the fragments of the primary rings, the planets and asteroids, 
while from the secondary rings arose the planetary satellites. 
* Fig. i. fFig. 2. X Fig. 3. 
