1.]

[Footnote 1140: _Month. Not._, vol. xliv., p. 257.]

[Footnote 1141: _Observatory_, vol. vii., pp. 134, 221, 264.]

[Footnote 1142: _Month. Not._, vol. xlvi., p. 507.]

[Footnote 1143: _Comptes Rendus_, t. cvii., p. 804; _Astr. and
Astroph._, vol. xiii., p. 291; _Astr. Jour._, No. 186.]

[Footnote 1144: _Astr. Jour._, Nos. 342, 436, 508.]

[Footnote 1145: _Astr. Pop._, p. 661; _La Nature_, January 3, 1880.]

[Footnote 1146: _Proc. Roy. Soc. Edinb._, vols. x., p. 429; xi., p. 89.]

[Footnote 1147: _Vierteljahrsschrift. Astr. Ges._, Jahrg. xxi., p. 206.]

[Footnote 1148: _Proc. Roy. Soc. Edinb._, vol. xxiii., p. 370; _Nature_,
vol. lxiv., p. 524.]

[Footnote 1149: _Amer. Jour. of Science_, vol. xx., p. 225.]

CHAPTER IX

_THEORIES OF PLANETARY EVOLUTION_

We cannot doubt that the solar system, as we see it, is the result of
some process of growth--that, during innumerable ages, the forces of
Nature were at work upon its materials, blindly modelling them into the
shape appointed for them from the beginning by Omnipotent Wisdom. To set
ourselves to inquire what that process was may be an audacity, but it is
a legitimate, nay, an inevitable one. For man's implanted instinct to
"look before and after" does not apply to his own little life alone, but
regards the whole history of creation, from the highest to the
lowest--from the microscopic germ of an alga or a fungus to the visible
frame and furniture of the heavens.

Kant considered that the inquiry into the mode of origin of the world
was one of the easiest problems set by Nature; but it cannot be said
that his own solution of it was satisfactory. He, however, struck out in
1755 a track which thought still pursues. In his _Allgemeine
Naturgeschichte_ the growth of sun and planets was traced from the
cradle of a vast and formless mass of evenly diffused particles, and the
uniformity of their movements was sought to be accounted for by the
unvarying action of attractive and repulsive forces, under the dominion
of which their development was carried forward.

In its modern form, the "Nebular Hypothesis" made its appearance in
1796.[1150] It was presented by Laplace with diffidence, as a
speculation unfortified by numerical buttresses of any kind, yet with
visible exultation at having, as he thought, penetrated the birth-secret
of our system. He demanded, indeed, more in the way of postulates than