peculiarities in their structure. The distribution, also, of the different
kinds of coral-reefs, and their position with relation to the areas of
recent elevation, and to the points subject to volcanic eruptions, fully
accord with this theory of their origin. (A brief account of my views on
coral formations, now published in my Journal of Researches, was read May
31st, 1837, before the Geological Society, and an abstract has appeared in
the Proceedings.)


(DESCRIPTION OF THE PLATES.

PLATE I.--MAP SHOWING THE RESEMBLANCE IN FORM BETWEEN BARRIER CORAL-REEFS
SURROUNDING MOUNTAINOUS ISLANDS, AND ATOLLS OR LAGOON ISLANDS.)

In the several original surveys, from which the small plans on this plate
have been reduced, the coral-reefs are engraved in very different styles.
For the sake of uniformity, I have adopted the style used in the charts of
the Chagos Archipelago, published by the East Indian Company, from the
survey by Captain Moresby and Lieutenant Powell. The surface of the reef,
which dries at low water, is represented by a surface with small crosses:
the coral-islets on the reef are marked by small linear spaces, on which a
few cocoa-nut trees, out of all proportion too large, have been introduced
for the sake of clearness. The entire ANNULAR REEF, which when surrounding
an open expanse of water, forms an "atoll," and when surrounding one or
more high islands, forms an encircling "barrier-reef," has a nearly uniform
structure. The reefs in some of the original surveys are represented
merely by a single line with crosses, so that their breadth is not given; I
have had such reefs engraved of the width usually attained by coral-reefs.
I have not thought it worth while to introduce all those small and very
numerous reefs, which occur within the lagoons of most atolls and within