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._