I will not pretend to say how we ought to
estimate this time, in millions or in billions of years. For my purpose,
the determination of its absolute duration is wholly unessential. But
that the time was enormous there can be no question.
It results from the simplest methods of interpretation, that leaving out
of view certain patches of metamorphosed rocks, and certain volcanic
products, all that is now dry land has once been at the bottom of the
waters. It is perfectly certain that, at a comparatively recent period
of the world's history--the Cretaceous epoch--none of the great physical
features which at present mark the surface of the globe existed. It is
certain that the Rocky Mountains were not. It is certain that the
Himalaya Mountains were not. It is certain that the Alps and the
Pyrenees had no existence. The evidence is of the plainest possible
character, and is simply this:--We find raised up on the flanks of these
mountains, elevated by the forces of upheaval which have given rise to
them, masses of Cretaceous rock which formed the bottom of the sea
before those mountains existed. It is therefore clear that the elevatory
forces which gave rise to the mountains operated subsequently to the
Cretaceous epoch; and that the mountains themselves are largely made up
of the materials deposited in the sea which once occupied their place.
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