remarkable degree; and that certain laws may he inferred
from the examination, of far more importance than the
mere explanation of the origin of the circular or other kinds
of reef.
If there had been space, I should have made a few general
remarks, before entering into any detail. I may, however,
just notice the remarkable absence of the reef-building
polypi over certain wide areas within the tropical sea:
for instance, on the whole west coast of America, and, as I
believe, of Africa (?), and round the eastern islands in the
Atlantic ocean. Although certain species of lamelliform
zoophytes are found on the shores of the latter islands, and
though calcareous matter is abundant to excess, yet reefs
are never formed. It would appear that the effective species
do not occur there; of which circumstance I apprehend no
explanation can he given, any more than why it has
been ordained that certain plants, as heaths, should be
absent from the New World, although so common in the
Old.W
ithout entering into any minute geographical details,
I must observe, that the usual direction of the island groups
in the central parts of the Pacific, is N.W. aud S.E. This
must be noticed, because subterranean disturbances are
known to follow the coast lines of the land. Commencing
on the shores of America, there are abundant proofs that the
greater part has been elevated within the recent period,
but as coral reefs do not occur there, it is not immediately
connected with our present subject. Immediately adjoining
the continent there is an extent of ocean remarkably
free from islands, and where of course there exists no possible
indication of any change of level. We then come to a N.W .
by W. line dividing the open sea from one strewed with
lagoon islands, and including the two beautiful groups of
encircled islands the Society and Georgian Archipelagoes.
This great band having a length of more than four thousand
miles by six hundred broad must, according to our view, be an
area of subsidence. We will at present for convenience sake
pass over the space of ocean immediately adjoining it, and
proceed to the chain of islands including the New Hebrides,
Solomon, and New Ireland. Any one who examines the
charts of the separate islands in the Pacific, engraved on a
large scale, will be struck with the absence of all distant or
encircling reefs round these groups : yet it is known that
coral occurs abundantly close in shore. Here, then, according
to the theory, there are no proofs of subsidence; and in
conformity to this we find in the works of Forster, Lesson,
Labillardiere, Quoy, and Bennett, constant allusion to the
masses of elevated coral. These islands form, therefore, a
well-determined band of elevation: between it and the great
area of subsidence first mentioned there is a broad space of
sea irregularly scattered with islets of all classes; some with
proofs of recent elevation and merely fringed by reefs ; others
encircled; and some lagoon islands. One of the latter is
described by Captain Cook as a grand circle of breakers
without a single spot of land; in this case we may believe
that an ordinary lagoon island has been recently submerged.
On the other hand, there are proofs of other lagoon islands
having been lifted up several yards above the level of the sea,
but which still retain a pool of salt water in their centres.
These facts show an irregular action in the subterranean
forces; and when we remember that the space lies directly
between the well-marked area of elevation and the enormous
one of subsidence, an alternate and irregular movement seems
almost probable.
To the westward of the New Hebrides line of elevation
we have New Caledonia, aud the space included between it
and the Australian barrier, which Flinders, on account of tlie
number of reefs, proposed to call the Corallian Sea. It is
bounded on two sides by the grandest and most extraordinary
reefs in the world, and is likewise terminated to the
northward by the coast of Louisiade,—most dangerous on
account of its distant reefs. 'S’his, then, according to our
theory, is an area of subsidence. I may liere remark, that
as the Barrier is sujiposed to be produced by tlie subsidence