sea, as the rock-layers were being formed, bit by bit, of
earth dropping from the ocean to the ocean's floor, sea-creatures
lived out their lives and died by thousands, to sink to that same
floor. Millions passed away, dissolving and leaving no trace behind;
but thousands were preserved--shells often, animals sometimes.

Nor was this all. For now and again some part of the sea-bottom was
upheaved, slowly or quickly, till it became dry land. On this dry land
animals lived again, and thousands of them, too, died, and their bones
crumbled into dust. But here and there one was caught in bog or frost,
and his remains were preserved till, through lapse of ages, they
turned to stone.

Yet again that land would sink, and over it fresh layers were formed
by the ocean-waters, with fresh remains of sea-animals buried in with
the layers of sand or lime; and once more the sea-bottom would rise,
perhaps then to continue as dry land, until the day when man should
discover and handle these hidden remains.

Now note a remarkable fact as to these fossils, scattered far and wide
through the layers of stratified rock.

In the uppermost and latest built rocks the animals found are the
same, in great measure, as those which now exist upon the earth.

Leaving the uppermost rocks, and examining those which lie a little
way below, we find a difference. Some are still the same, and others,
if not quite the same, are very much like what we have now; but here
and there a creature of a different form appears.

Go deeper still, and the kinds of animals change further. Fewer and
fewer resemble those which now range the earth; more and more belong
to other species.

Descend through layer after layer till we come to rocks built in
earliest ages and not one fossil shall we find precisely the same as
one animal living now.

So not only are the rocks built in successive order, stratum after
stratum belonging to age after age in the past, but fossil-remains
also are found in successive order, kind after kind belonging to past
age after age.

Although in the first instance the succession of fossils was
understood by means of the succession of rock-layers, yet in the
second place the arrangement of rock-layers is made more clear by the
means of these very fossils.

A geologist, looking at the rocks in America, can say which there were
first-formed, which second-formed, which third-formed. Also, looking
at the rocks in England, he can say which