the animals and plants living upon it at the time, and were
then succeeded by long intervals of repose, when all things returned
to their accustomed order, ocean and river deposited fresh beds in
uninterrupted succession, the accumulation of materials went on as
before, a new set of animals and plants were introduced, and a time of
building up and renewing followed the time of destruction. These periods
of revolution are naturally more difficult to decipher than the periods
of rest; for they have so torn and shattered the beds they uplifted,
disturbing them from their natural relations to each other, that it
is not easy to reconstruct the parts and give them coherence and
completeness again. But within the last half-century this work has
been accomplished in many parts of the world with an amazing degree of
accuracy, considering the disconnected character of the phenomena to be
studied; and I think I shall be able to convince my readers that the
modern results of geological investigation are perfectly sound logical
inferences from well-established facts. In this, as in so many other
things, we are but "children of a larger growth." The world is the
geologist's great puzzle-box; he stands before it like the child to whom
the separate pieces of his puzzle remain a mystery till he detects their
relation and sees where they fit, and then his fragments grow at once
into a connected picture beneath his hand.

It is a curious fact in the history of progress, that, by a kind of
intuitive insight, the earlier observers seem to have had a wider, more
comprehensive recognition of natural phenomena as a whole than their
successors, who far excel them in their knowledge of special points,
but often lose their grasp of broader relations in the more minute
investigation of details. When geologists first turned their attention
to the physical history of the earth, they saw at once certain great
features which they took to be the skeleton and basis of the whole
structure. They saw the great masses of granite forming the mountains
and mountain-chains, with the stratified rocks resting against their
slopes; and they assumed that granite was the first primary agent, and
that all stratified rocks must be of a later formation. Although this
involved a partial error, as we shall see hereafter, when we trace the
upheavals of granite even into comparatively modern periods, yet it held
a great geological truth also; for, though granite formations