s, and many of them are
preserved for all time.

Thus what is sandy beach to-day may, a few million years from now, be
uncovered as a ledge of sandstone with the prints of waves distinctly
shown, and fossil shells of molluscs, skeletons of fishes, and branches
of seaweed--all of them different from those then growing upon the
earth.

In the neighbourhood of Cincinnati there have been uncovered banks of
stone accumulated along the border of an ancient sea. From the sides of
granite highlands streams brought down the sand built into these oldest
sandstone rocks. The fine mud which now appears as beds of slate was the
decay of feldspar and hornblende in the same granite. Limestone beds are
full of the fossil shells of creatures that lived in the shallow seas.
Their skeletons, accumulating on the bottom, formed deep layers of
limestone mud. These rocks preserve, by the fossils they contain, a
great variety of shellfish which had limy skeletons. The sea fairly
swarmed along its shallow margin with these creatures. We might not
recognize many of the shells and other curious fossils we find in the
rock uncovered by the workmen who are cutting a railroad embankment.
They are not exactly like the living forms that grow along our beaches
to-day, but they are enough like them for us to know that they lived
along the seashore, and if we had time to examine all the rocks of this
kind preserved in a museum we should decide that seashore life was quite
as abundant then as it is now. The pressed specimens of plants of those
earliest seashores are mere imprints showing that they were pulpy and
therefore gradually decayed. Only their shape is recorded by dark stains
made by each branching part. The decay of the vegetable tissue painted
the outline on the rock which when split apart shows us what those
ancient seaweeds looked like. They belonged to the group of plants we
call kelp, or tangle, which are still common enough in the sea, though
the forms we now have are not exactly like the old ones. Seaweeds belong
to the very lowest forms of plants.

[Illustration: Crinoid from Indiana]

[Illustration: _By permission of the American Museum of Natural History_

Ammonite from Jurassic of England]

[Illustration: _By permission of the American Museum of Natural History_

Fossil corals Coquina, Hippurite limestone]

The limestones are full of fossils of corals. Indeed, there must have
been reefs like those that skirt Florida to-day bui