You may see in museums
specimens of this family, now so rare, all but extinct. And yet
fifty or a hundred different forms of the same type swarmed in the
ancient seas: whole masses of limestone are made up of little else
but the fragments of such animals.
But we have not landed yet on the dry part of the reef. Let us make
for it, taking care meanwhile that we do not get our feet cut by the
coral, or stung as by nettles by the coral insects. We shall see
that the dry land is made up entirely of coral, ground and broken by
the waves, and hurled inland by the storm, sometimes in huge
boulders, mostly as fine mud; and that, under the influence of the
sun and of the rain, which filters through it, charged with lime from
the rotting coral, the whole is setting, as cement sets, into rock.
And what is this? A long bank of stone standing up as a low cliff,
ten or twelve feet above high-water mark. It is full of fragments of
shell, of fragments of coral, of all sorts of animal remains; and the
lower part of it is quite hard rock. Moreover, it is bedded in
regular layers, just such as you see in a quarry. But how did it get
there? It must have been formed at the sea-level, some of it,
indeed, under the sea; for here are great masses of madrepore and
limestone corals imbedded just as they grew.
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