eneous into
the heterogeneous. Let us trace this truth in detail.

Without committing ourselves to it as more than a speculation, though a
highly probable one, let us again commence with the evolution of the
Solar System out of a nebulous medium. The hypothesis is that from the
mutual attraction of the molecules of a diffused mass whose form is
unsymmetrical, there results not only condensation but rotation. While
the condensation and the rate of rotation go on increasing, the
approach of the molecules is necessarily accompanied by an increasing
temperature. As the temperature rises, light begins to be evolved; and
ultimately there results a revolving sphere of fluid matter radiating
intense heat and light--a sun. There are reasons for believing that, in
consequence of the higher tangential velocity originally possessed by
the outer parts of the condensing nebulous mass, there will be
occasional detachments of rotating rings; and that, from the breaking up
of these nebulous rings, there will arise masses which in the course of
their condensation repeat the actions of the parent mass, and so produce
planets and their satellites--an inference strongly supported by the
still extant rings of Saturn. Should it hereafter be satisfactorily
shown that planets and satellites were thus generated, a striking
illustration will be afforded of the highly heterogeneous effects
produced by the primary homogeneous cause; but it will serve our present
purpose to point to the fact that from the mutual attraction of the
particles of an irregular nebulous mass there result condensation,
rotation, heat, and light.

It follows as a corollary from the Nebular Hypothesis, that the Earth
must once have been incandescent; and whether the Nebular Hypothesis be
true or not, this original incandescence of the Earth is now inductively
established--or, if not established, at least rendered so highly
probable that it is an accepted geological doctrine. Let us look first
at the astronomical attributes of this once molten globe. From its
rotation there result the oblateness of its form, the alternations of
day and night, and (under the influence of the moon and in a smaller
degree the sun) the tides, aqueous and atmospheric. From the inclination
of its axis, there result the many differences of the seasons, both
simultaneous and successive, that pervade its surface, and from the same
cause joined with the action of the moon on the equatorial protuberanc