radiating bodies. All this motion is projected into space, and the history of its future work is wholly beyond our comprehension. It may continue to affect the ethereal atoms pervading space for all eternity, without exerting an appreciable influence upon concentrated matter. Even our right to project the law of conservation into the realms of space, where we daily see motion dissipated but never recomposed, has been called in question. Have we the right to assert that this motion, lost to our system, is not lost to the universe? True Science well knows how here to suspend its judgment, but it also knows how to restrain the hopeless cry of ignorabimus.
Mr. Herbert Spencer is therefore right in making evolution the fundamental principle of philosophy, and regarding dissolution, which is its exact opposite and correlate, as practically of very inferior importance. For, so far as the earth itself and the heavenly bodies are concerned, the very existence of such a process is in doubt. So far as our knowledge of the universe, as such, extends, but one law is anywhere observable, and that is the law of evolution. Indeed, evolution is but the process of which the principle is gravitation. Evolution is the concentration and integration of matter; its tendency is toward the condition of stable equilibrium. The contraction of a body is due to the attraction of its molecules. Gravitation alone can explain this tendency, and gravitation necessarily requires it. Evolution is therefore coextensive with gravitation. Whenever gravitation prevails, evolution must prevail. On the contrary, a condition of dissolution would require the prevalence of a force the reverse of gravitation—a repulsive and expansive force. Our acquaintance with the visible universe reveals no region of space where we can assume the prevalence of such a force. On the contrary, many fixed stars, and even nebulae, afford the strongest evidence of being under the dominion of an attractive force. Not, however, but that there exists in the universe abundant evidence of the possibility and reality of a repulsive or dissolving force. This is found, and with the greatest certainty, within the scope of our daily observation of the facts about us. And in at least one instance it is assumed, with a high degree of proof, to manifest itself in regions beyond the limits of terrestrial influence. I refer to the behavior of the tails of comets at perihelion. But wherever we see this force of repulsion, which alone could effect the dissolution of the aggregates already formed, it is wholly subordinate to the force of attraction which has formed them. Phenomena of this nature are but episodes in the history of a system or of a world. Everywhere the opposite phenomena predominate. Everywhere the force of gravity is evolving new aggregates, and bearing old ones on to their final state of complete equilibration.
Let us now turn to the second branch of our subject, and glance for a moment at the phenomena and laws of organic evolution. The first fact that presents itself is, that its primary condition is the influ-
