By RICHARD PROCTOR.

The material life of a planet is beginning to be recognized as being no less real than the life of a plant or of an animal. It is a different kind of life; there is neither consciousness such as we see in one of those forms of life, nor such systematic progress as we recognize in plant-life. But it is life, all the same. It has had a beginning, like all things which exist; and like them all, it must have an end.

The lifetime of a world like our earth may be truly said to be a lifetime of cooling. Beginning in the glowing vaporous condition which we see in the sun and stars, an orb in space passes gradually to the condition of a cool, non-luminous mass, and thence, with progress depending chiefly on its size (slower for the large masses and quicker for the small ones), it passes steadily onward toward inertness and death. Regarding the state in which we find the earth to be as the stage of a planet’s mid-life—viz., that in which the conditions are such that multitudinous forms of life can exist upon its surface, we may call that stage death in which these conditions have entirely disappeared.

Now, among the conditions necessary for the support of life in general are some which are unfavorable to individual life. Among these may be specially noted the action of those subterranean forces by which the earth’s surface is continually modeled and remodeled. It has been remarked with great justice, by Sir John Herschel, that since the continents of the earth were formed, forces have been at work which would long since have sufficed to have destroyed every trace of land, and to have left the surface of our globe one vast limitless ocean. But against these forces counteracting forces have been at work, constantly disturbing the earth’s crust, and, by keeping it irregular, leaving room for ocean in the depressions, and leaving the higher parts as continents and islands above the ocean’s surface. If these disturbing forces ceased to work, the work of disintegrating, wearing away, and washing off the land would go on unresisted. In periods of time such as to us seem long, no very great effect would be produced; but such periods as belong to the past of our earth, even to that comparatively short part of the past during which she has been the abode of life, would suffice to produce effects utterly inconsistent with the existence of life on land. Only by the action of her vulcanian energies can the earth maintain her position as an abode of life. She is, then, manifesting her fitness to support life in those very throes by which, too often, many lives are lost. The upheavals and downsinkings, the rushing of ocean in great waves over islands and seaports, by which tens of thousands of human beings, and still greater numbers of animals, lose their lives, are part of the evidence which the earth gives that within her frame there still remains enough of vitality for the support of life during hundreds of thousands of years to come.

This vitality is not due, as seems commonly imagined, to the earth’s internal heat. Rather the earth’s internal heat is due to the vitality with which her frame is instinct. The earth’s vitality is in reality due to the power of attraction which resides in every particle of her mass—that wonderful force of gravitation, omnipresent, infinite in extent, the property whose range throughout all space should have taught long since what science is teaching now (and has been foolishly blamed for teaching), the equally infinite range of God’s laws in time also. By virtue of the force of gravity pervading her whole frame, the crust of the earth is continually undergoing changes, as the loss of heat and consequent contraction, or chemical changes beneath the surface, leave room for the movement inward of the rock-substances of the crust, with crushing, grinding action, and the generation of intense heat. If the earth’s energy of gravity were lost, the internal fires would die out—not, indeed, quickly, but in a period of time very short compared with that during which, maintained as they constantly are by the effects of internal movements, they will doubtless continue. They are, in a sense, the cause of earthquakes, volcanoes, and so forth, because they prepare the earth’s interior for the action of her energies of attraction. But it is to these energies and the material which as yet they have on which to work, that the earth’s vitality is due. She will not, indeed, retain her vitality as long as she retains her gravitating power. That power must have something to work on. When the whole frame of the earth has been compressed to a condition of the greatest density which her attractive energies can produce, then terrestrial gravity will have nothing left to work on within the earth, and the earth’s globe will be to all intents and purposes dead. She will continue to exercise her attractive force on bodies outside of her. She will rotate on her axis, revolve around the sun, and reflect his rays of light and heat. But she will have no more life of her own than has the moon, which still discharges all those planetary functions.

But such disturbances as the recent earthquakes, while disastrous in their effects to those living near the shaken regions, assure us that as yet the earth is not near death. She is still full of vitality. Thousands—nay, tens, hundreds of thousands of years will still pass before even the beginning of the end is seen, in the steady disintegration and removal of the land without renovation or renewal by the action of subterranean forces.—The Contemporary Review.