Corals and coral islands.

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CORALS AND CORAL ISLANDS.

we observe the same peculiarities illustrated on a much grander scale. Along the southern shores of Viti Levu, the coral
reef lies close against the coast; and the same is seen on the
east side and north extremity of Vanua Levu. But on the
west side of these islands, this reef stretches far off from the
land, and in some parts is even twenty-five miles distant, with
abroad sea within. This sea, however, is obstructed by reefs,
and along the shores there are proper fringing reefs.
The forms of encircling reefs depend evidently to a great
extent on that of the land they enclose. That this is the case
even in the Argo reef, and such other examples as offer now
but a single rock above the surface of the enclosed lagoon, we
shall endeavor to make apparent, if not already so, when the
cause of the forms of coral islands is under discussion. Yet it
is also evident that this correspondence is not exact, for many
parts of the shores, and sometimes more than half the coasts,
may be exposed to the sea, while other portions are protected
by a wide barrier.
In recapitulation, we remark, that reefs around islands mnay
be (1) entirely encircling; or they may be (2) confined to a larger or a smaller portion of the coast, either continuous or interrupted; they may (3) constitute throughout a distant barrier;
or (4) the reef may be fringing in one part and a barrier in
another; or (5) it may be fringing alone: the barrier may be
(6) at a great distance from the shores, with a wide sea within,
or (7) it may so unite to the fringing reef that the channel between will hardly float a canoe. These points are sustained
by all reef regions.
It is to be noted that the fringing and barrier reefs here
pointed out are not the whole of the coral reef; they are only
the portions that have been built up to the water's level. Between them, and also outside of all, there are the submerged