millions are ever coming into existence, living out their tiny lives,
dying, and sinking to the bottom.

There upon the ocean-floor gather their remains, a heaped-up multitude
of minute skeletons or shells, layer forming over layer.

It was long suspected that the white chalk cliffs of England were
built up in some such manner as this through past ages. And now at
length proof has been found, in the shape of mud dredged up from the
ocean-bottom--mud entirely composed of countless multitudes of these
little shells, dropping there by myriads, and becoming slowly joined
together in one mass.

Just so, it is believed, were the white chalk cliffs built--gradually
prepared on the ocean-floor, and then slowly or suddenly upheaved, so
as to become a part of the dry land.

Think what the enormous numbers must have been of tiny living
creatures, out of whose shells the wide reaches of white chalk cliffs
have been made. Chalk cliffs and chalk layers extend from Ireland,
through England and France, as far as to the Crimea. In the south of
Russia they are said to be six hundred feet thick. Yet one cubic inch
of chalk is calculated to hold the remains of more than one million
rhizopods. How many countless millions upon millions must have gone to
the whole structure! How long must the work of building up have
lasted!

[Illustration: THREE POLYPS OF CORAL.]

These little shells do not always drop softly and evenly to the