Corals and coral islands.

OBJECTIONS TO THE THEORY OF SUBSIDENCE.

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encircled in a single belt; and it would be doing no violence
to principles or probabilities to suppose them once to have
formed a single island, which subsidence has separated by
inundating the low intermediate area. We may thus not
only trace out the general form of the land which once occupied this large area (at least 10,000 square miles), but may
detect some of its prominent capes, as in Wakaia and Direction Island. The present area is not far from 4,500 square
miles. The Feejee Group, exclusive of coral islets, includes
an area of about 5,500 square miles of dry land; while, at
the period when the corals commenced to grow, there were
at least, as the facts show, 15,000 square miles of land, or
nearly three times the present extent of habitable surface.
OBJECTIONS TO THE SUBSIDENCE THEORY.
The objections to the theory of coral reefs which have
been recently urged are mostly independent hypotheses which
are supposed to meet the facts without requiring subsidence,
and not strictly objections to Darwin's theory. Two or three
real objections, however, are among them. The discussion
brings out many points of interest.
An improbability. - So extremely slow a subsidence, keeping pace so well with the upward growth, is improbable.
This objection is put forth by those who are not aware that
so slow subsidences are those with which geology is most
familiar. A movement of the kind has been proved to be
in progress along the coast of New Jersey and some other
parts of the North American Atlantic border, and in western
Greenland; and geology is now inquiring as to whether any
regions are absolutely stable, or wholly free from movement
up or down.