while there will be
increasing angular velocities of parts increasingly remote from the
centre. And while the density of the spheroid continues small, fluid
friction will scarcely at all change these differences.

A like criticism may, I think, be passed on an opinion expressed by
Prof. Newcomb. He says:--"When the contraction [of the nebulous
spheroid] had gone so far that the centrifugal and attracting forces
nearly balanced each other at the outer equatorial limit of the mass,
the result would have been that contraction in the direction of the
equator would cease entirely, and be confined to the polar regions, each
particle dropping, not towards the sun, but towards the plane of the
solar equator. Thus, we should have a constant flattening of the
spheroidal atmosphere until it was reduced to a thin flat disk. This
disk might then separate itself into rings, which would form planets in
much the same way that Laplace supposed. But there would probably be no
marked difference in the age of the planets." (_Popular Astronomy_,
p. 512.) Now this conclusion assumes, like that of M. Babinet, that all
parts of the nebulous spheroid had equal angular velocities. If, as
above contended, it is inferable from the process by which a nebulous
spheroid was formed, that its outer portions revolved with greater
angular velocities than its inner; then the inference which Prof.
Newcomb draws is not necessitated.]

[Footnote 15: It is true that since this essay was written reasons have
been given for concluding that comets consist of swarms of meteors
enveloped in aeriform matter. Very possibly this is the constitution of
the periodic comets which, approximating their orbits to the plane of
the Solar System, form established parts of the System, and which, as
will be hereafter indicated, have probably a quite different origin.]

[Footnote 16: Though this rule fails at the periphery of the Solar
System, yet it fails only where the axis of rotation, instead of being
almost perpendicular to the orbit-plane, is very little inclined to it;
and where, therefore, the forces tending to produce the congruity of
motions were but little operative.]

[Footnote 17: It is true that, as expressed by him, these propositions
of Laplace are not all beyond dispute. An astronomer of the highest
authority, who has favoured me with some criticisms on this essay,
alleges that instead of a nebulous ring rupturing at one point, and
collapsing into a single m