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This etext was prepared by Sue Asscher
CORAL REEFS
by CHARLES DARWIN
EDITORIAL NOTE.
Although in some respects more technical in their subjects and style
than Darwin's "Journal," the books here reprinted will never lose their
value and interest for the originality of the observations they contain.
Many parts of them are admirably adapted for giving an insight into
problems regarding the structure and changes of the earth's surface, and
in fact they form a charming introduction to physical geology and
physiography in their application to special domains. The books
themselves cannot be obtained for many times the price of the present
volume, and both the general reader, who desires to know more of
Darwin's work, and the student of geology, who naturally wishes to
know how a master mind reasoned on most important geological
subjects, will be glad of the opportunity of possessing them in a
convenient and cheap form.
The three introductions, which my friend Professor Judd has kindly
furnished, give critical and historical information which makes this
edition of special value.
G.T.B.
CORAL REEFS.
TABLE OF CONTENTS.
CRITICAL INTRODUCTION.
INTRODUCTION.
CHAPTER I.
--ATOLLS OR LAGOON-ISLANDS.
SECTION 1.I.--DESCRIPTION OF KEELING ATOLL. Corals on the
outer margin.--Zone of Nulliporae.--Exterior reef.--Islets.--
Coral-conglomerate.--Lagoon.--Calcareous sediment.--Scari and
Holuthuriae subsisting on corals.--Changes in the condition of the reefs
and islets.-- Probable subsidence of the atoll.--Future state of the
lagoon.
SECTION 1.II.--GENERAL DESCRIPTION OF ATOLLS. General
form and size of atolls, their reefs and islets.--External slope.-- Zone of
Nulliporae.--Conglomerate.--Depth of lagoons.--Sediment.--Reefs
submerged wholly or in part.--Breaches in the reef.--Ledge-formed
shores round certain lagoons.--Conversion of lagoons into land.
SECTION 1.III.--ATOLLS OF THE MALDIVA
ARCHIPELAGO--GREAT CHAGOS BANK. Maldiva
Archipelago.--Ring-formed reefs, marginal and central.--Great depths
in the lagoons of the southern atolls.--Reefs in the lagoons all rising to
the surface.--Position of islets and breaches in the reefs, with respect to
the prevalent winds and action of the waves.--Destruction of
islets.--Connection in the position and submarine foundation of distinct
atolls.--The apparent disseverment of large atolls.--The Great Chagos
Bank.--Its submerged condition and extraordinary structure.
CHAPTER II.
--BARRIER REEFS. Closely resemble in general form and structure
atoll-reefs.--Width and depth of the lagoon-channels.--Breaches
through the reef in front of valleys, and generally on the leeward
side.--Checks to the filling up of the lagoon-channels.--Size and
constitution of the encircled islands.-- Number of islands within the
same reef.--Barrier-reefs of New Caledonia and Australia.--Position of
the reef relative to the slope of the adjoining land.--Probable great
thickness of barrier-reefs.
CHAPTER III.
--FRINGING OR SHORE-REEFS. Reefs of Mauritius.--Shallow
channel within the reef.--Its slow filling up.--Currents of water formed
within it.--Upraised reefs.--Narrow fringing-reefs in deep seas.--Reefs
on the coast of E. Africa and of Brazil.--Fringing-reefs in very shallow
seas, round banks of sediment and on worn-down
islands.--Fringing-reefs affected by currents of the sea. --Coral coating
the bottom of the sea, but not forming reefs.
CHAPTER IV.
--ON THE DISTRIBUTION AND GROWTH OF CORAL-REEFS.
SECTION 4.I.--ON THE DISTRIBUTION OF CORAL-REEFS, AND
ON THE CONDITIONS FAVOURABLE TO THEIR INCREASE.
SECTION 4.II.--ON THE RATE OF GROWTH OF CORAL-REEFS.
SECTION 4.III.--ON THE DEPTHS AT WHICH REEF-BUILDING
POLYPIFERS CAN LIVE.
CHAPTER V.
--THEORY OF THE FORMATION OF THE DIFFERENT CLASSES
OF
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