ary accumulations of which we are
now talking about.

The living corals one sees in the shallow water of the Florida coast
to-day are building land by building up their limy skeletons. The reefs
are the dead skeletons of past generations of these tiny living things.
They take in lime from the water, and use it as we use lime in building
our bones. In each case it is an unconscious process of animal
growth--not a "building process" like a mason's building of a wall. Many
people think that the coral polyp builds in this way. They give it
credit for patience in a great undertaking. All the polyp does is to
feed on whatever the water supplies that its digestive organs can use.
It is like a sea anemone in appearance and in habits of life. It is not
at all like an insect. Yet it is common to hear people speak of the
"coral insect"! Do not let any one ever hear you repeat such a mistake.

Southern Florida is made out of coral rock, but thinly covered with
soil. It was made by the growth of reef after reef, and it is still
growing.

The Cretaceous Period of the earth's eventful history is named for the
lime rock which we know as chalk. Beds of this recent kind of limestone
are found in England and in France, pure white, made of the skeletons of
the smallest of lime-consuming creatures, Foraminifera. They swarmed in
deep water, and so did minute sponge animalcules and plant forms called
Diatoms that took silica from the water, and formed their hard parts of
this glassy substance. The result is seen in the nodules of flint found
in the soft, snow-white chalk. Did you ever use a piece of chalk that
scratched the black-board? The flint did it. Have you ever seen the
chalk cliffs of Dover? When you do see them, notice how they gleam white
in the sun. See how the rains have sculptured those cliffs. The
prominences left standing out are strengthened by the flint they
contain. Chalk beds occur in Texas and under our great plains; but the
principal rocks of the age in America were sandstones and clays.

THE AGE OF FISHES

The first animal with a backbone recorded its existence among the
fossils found in rocks of the upper Silurian strata. It is a fish; but
the earliest fossils are very incomplete specimens. We know that these
old-fashioned fishes were somewhat like the sturgeons of our rivers.
Their bodies were encased in bony armour of hard scales, coated with
enamel. The bones of the spine were connected by ball and socke