Coral Reefs; Volcanic Islands; South American Geology — Complete

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.
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.
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.
The atolls of the larger archipelagoes are not formed on submerged craters, or on banks of sediment.—Immense areas interspersed with atolls.—Recent changes in their state.—The origin of barrier-reefs and of atolls.—Their relative forms.—The step-formed ledges and walls round the shores of some lagoons.—The ring-formed reefs of the Maldiva atolls.—The submerged condition of parts or of the whole of some annular reefs.—The disseverment of large atolls.—The union of atolls by linear reefs.—The Great Chagos Bank.—Objections, from the area and amount of subsidence required by the theory, considered.—The probable composition of the lower parts of atolls.