One more important reflection: There are two, and only two, fundamental conditions of material existence--_space_ and _time_. There are, therefore, two, and only two, cosmoses--space-cosmos and time-cosmos. These have been redeemed from confusion and reduced to law and order and beauty--changed from chaos to cosmos--by science. For this result we are chiefly indebted, in the one case, to Kepler and Newton; in the other, to Agassiz and Darwin. The universal law, in the one cosmos, is the _law of gravitation_; in the other, the _law of evolution_. Traced by analysis to its deepest roots of philosophic truth, the one law may be called the divine mode of sustentation; the other, the divine process of creation. Or again: we have all heard of the “music of the spheres”--a beautiful and significant name used by the old thinkers for the divine order of the universe--a music heard not by human ear, but only by the attentive human spirit. Harmonic relation apprehended by _reason_ we call _Law_, and its embodiment Science; the same apprehended by the imagination and æsthetic sense, we call _Beauty_, and its embodiment _Art_, _music_. Now, in music there are two kinds of harmony, simultaneous and consecutive--chordal harmony and melody. These must be combined to produce the grandest effect. So in cosmic order, too, there are two kinds of harmonic relation--the _co-existent in space_ and the _consecutive in time_. The law of gravitation expresses the universal harmonic inter-relation of _objects_ co-existent in space, the law of evolution, the universal harmonic relation of _forms_ successive in time. Of the divine spheral music, the one is the chordal harmony, the other the consecutive harmony or melody. Combined they form the divine chorus which “the morning stars sang together.” PART II. _EVIDENCES OF THE TRUTH OF EVOLUTION._ CHAPTER I. GENERAL EVIDENCES OF EVOLUTION AS A UNIVERSAL LAW. Let us again remind the reader that evolution means, first of all, _continuity_. The law of evolution, although it doubtless means much more, means, first of all, a law of continuity, or _causal relation throughout Nature_. It means that, alike in every department of Nature, each state or condition grew _naturally_ out of the immediately preceding. In a word, it means that, in the course of Nature, nothing appears suddenly and without natural cause, but, on the contrary, everything is the natural and usually the gradual outcome of a previous condition. This is _now_ admitted by every one in regard to _nearly_ everything: evolutionists apply it to the whole course of Nature. I said this is _now_ admitted by every one in regard to _nearly_ everything; but this has not always been so. The world has come to its present position on this subject only by a very gradual process. Let us then trace rapidly the history of the gradual change, for it will prepare us for much that follows.