||And the present,
no less than the past, is a time of change. This is the thought which James
Hutton conceived more than a century ago, but which his contemporaries
and successors were so very slow to appreciate. Now, however, it has become
axiomatic - one can hardly realize that it was ever doubted. Every new
scientific truth, says Agassiz, must pass through three stages - first,
men say it is not true; then they declare it hostile to religion; finally,
they assert that every one has known it always. Hutton's truth that natural
law is changeless and eternal has reached this final stage. Nowhere now
could you find a scientist who would dispute the truth of that text which
Lyell, quoting from Playfair's Illustrations of the Huttonian Theory, printed
on the title-page of his Principles: "Amid all the revolutions of the globe
the economy of Nature has been uniform, and her laws are the only things
that have resisted the general movement. The rivers and the rocks, the
seas and the continents, have been changed in all their parts; but the
laws which direct those changes, and the rules to which they are subject,
have remained invariably the same."
But, on the other hand, Hutton and Playfair,
and in particular Lyell, drew inferences from this principle which the
modern physicist can by no means admit. To them it implied that the changes
on the surface of the earth have always been the same in degree as well
as in kind, and must so continue while present forces hold their sway.
In other words, they thought of the world as a great perpetual-motion machine.
But the modern physicist, given truer mechanical insight by the doctrines
of the conservation and the dissipation of energy, will have none of that.
Lord Kelvin, in particular, has urged that in the periods of our earth's
in fancy and adolescence its developmental changes must have been, like
those of any other infant organism, vastly more rapid and pronounced than
those of a later day; and to every clear thinker this truth also must now
Whoever thinks of the earth as a cooling
globe can hardly doubt that its crust, when thinner, may have heaved under
strain of the moon's tidal pull - whether or not that body was nearer -
into great billows, daily rising and falling, like waves of the present
seas vastly magnified.
Under stress of that same lateral pressure
from contraction which now produces the slow depression of the Jersey coast,
the slow rise of Sweden, the occasional belching of an insignificant volcano,
the jetting of a geyser, or the trembling of an earthquake, once large
areas were rent in twain, and vast floods of lava flowed over thousands
of square miles of the earth's surface, perhaps, at a single jet; and,
for aught we know to the contrary, gigantic mountains may have heaped up
their contorted heads in cataclysms as spasmodic as even the most ardent
catastrophist of the elder day of geology could have imagined.
The atmosphere of that early day, filled
with vast volumes of carbon, oxygen, and other chemicals that have since
been stored in beds of coal, limestone, and granites, may have worn down
the rocks on the one hand and built up organic forms on the other, with
a rapidity that would now seem hardly conceivable.
And yet while all these anomalous things
went on, the same laws held sway that now are operative; and a true doctrine
of uniformitarianism would make no unwonted concession in conceding them
all - though most of the imbittered geological controversies of the middle
of the nineteenth century were due to the failure of both parties to realize
that simple fact.
And as of the past and present, so of the
future. The same forces will continue to operate; and under operation of
these unchanging forces each day will differ from every one that has preceded
it. If it be true, as every physicist believes, that the earth is a cooling
globe, then, whatever its present stage of refrigeration, the time must
come when its surface contour will assume a rigidity of level not yet attained.
Then, just as surely, the slow action of the elements will continue to
wear away the land surfaces, particle by particle, and transport them to
the ocean, as it does to-day, until, compensation no longer being afforded
by the upheaval of the continents, the last foot of dry land will sink
for the last time beneath the water, the last mountain- peak melting away,
and our globe, lapsing like any other organism into its second childhood,
will be on the surface - as presumably it was before the first continent
rose - one vast "waste of waters." As puny man conceives time and things,
an awful cycle will have lapsed; in the sweep of the cosmic life, a pulse-
beat will have throbbed.