266 THE NEBULAE HYPOTHESIS. 



But now let us inquire whether, besides these most con 

 spicuous peculiarities of the Solar System, sundry minor onea 

 are not similarly explicable. Take first the relation be- 

 tween the planes of the planetary orbits and the plane of 

 the sun's equator. If, when the nebulous spheroid extend- 

 ed beyond the orbit of Neptune, all parts of it had been 

 revolving exactly in the same plane or rather in parallel 

 planes — if all its parts had had one axis; then the planes 

 of the successive rings would have been coincident with 

 each other and with that of the sun's rotation. But it 

 needs only to go back to the earlier stages of concentration, 

 to see that there could exist no such com])lete uniformity 

 of motion. The flocculi, already described as precipitated 

 from an irregular and widely-diffused nebula, and as start- 

 ing from all points to their common centre of gravity, must 

 move not in one plane but in innumerable planes, cutting 

 each other at all angles. 



The gradual establishment of a vortical motion such as 

 we saw must eventually arise, and such as we at present 

 see indicated in the spiral nebulae, is the gradual approach 

 toward motion in one plane — the plane of greatest momen- 

 tum. But this plane can only slowly become decided. 

 Flocculi not moving in this plane, but entering into the 

 aggregation at various inclinations, will tend to perform 

 their revolutions round its centre in their own planes ; and 

 only in course of time will their motions be partly destroy- 

 ed by conflicting ones, and partly resolved into the general 

 motion. Especially will the outermost portions of the ro- 

 tating mass retain for long time their more or less indepen- 

 dent directions ; seeing that neither by friction nor by the 

 central forces will they be so much restrained. Hence the 

 probabilities are, that the planes of the rings first detached 



have put the question to an astronomer scarcely second in authority to th« 

 one above referred to, and he agrees that this would probably be the pro* 



