a single vast ocean of matter of immense tenuity, spread all alike over
all space as far as nowhere, and comparatively little different within
itself when looked at side by side with its own final historical
outcome. In Mr. Spencer's perspicuous phrase, evolution in this aspect
is a change from the homogeneous to the heterogeneous, from the
incoherent to the coherent, and from the indefinite to the definite
condition. Difficult words at first to apprehend, no doubt, and
therefore to many people, as to Mr. Matthew Arnold, very repellent, but
full of meaning, lucidity, and suggestiveness, if only we once take the
trouble fairly and squarely to understand them.

Every sun and every star thus formed is for ever gathering in the hem of
its outer robe upon itself, for ever radiating off its light and heat
into surrounding space, and for ever growing denser and colder as it
sets slowly towards its centre of gravity. Our own sun and solar system
may be taken as good typical working examples of how the stars thus
constantly shrink into smaller and ever smaller dimensions around their
own fixed centre. Naturally, we know more about our own solar system
than about any other in our own universe, and it also possesses for us a
greater practical and personal interest than any outside portion of the
galaxy. Nobody can pretend to be profoundly immersed in the internal
affairs of Sirius or of Alpha Centauri. A fiery revolution in the belt
of Orion would affect us less than a passing finger-ache in a certain
single terrestrial baby of our own household. Therefore I shall not
apologise in any way for leaving the remainder of the sidereal universe
to its unknown fate, and concentrating my attention mainly on the
affairs of that solitary little, out-of-the-way, second-rate system,
whereof we form an inappreciable portion. The matter which now composes
the sun and its attendant bodies (the satellites included) was once
spread out, according to Laplace, to at least the furthest orbit of the