The coral islands, reefs, and beds with which the Pacific Ocean is
studded and garnished, were built up of materials which a certain
kind of insect quarried from the sea-water. The currents of the sea
ministered to this little insect; they were its _hod-carriers_. When
fresh supplies of solid matter were wanted for the coral rock upon
which the foundations of the Polynesian Islands were laid, these
hod-carriers brought them in unfailing streams of sea-water, loaded
with food and building-materials for the coralline: the obedient
currents thread the widest and the deepest sea. Now we know that
its adaptations are suited to all the wants of every one of its
inhabitants,--to the wants of the coral insect as well as those of the
whale. Hence _we know_ that the sea has its system of circulation: for
it transports materials for the coral rock from one part of the world
to another; its currents receive them from rivers, and hand them over
to the little mason for the structure of the most stupendous works of
solid masonry that man has ever seen--the coral islands of the sea.