CONTENTS 
Introduction ......... page 1 
CHAPTER I. 
ATOLLS OR LAGOON ISLANDS. 
SECTION I. — DESCRIPTION OF KEELING ATOLL. 
Corals on the outer margin— Zone of Nullipora — Exterior reef— Islets 
—Coral-conglomerate— Lagoon — Calcareous sediment— Scari and 
Holuthurise subsisting on corals — Changes in the condition of the 
reefs and islets — Probable subsidence of the atoll— Future state 
of the lagoons 7 to 27 
SECTION II. — GENERAL DESCRIPTION OF ATOLLS. 
General form and size of atolls, their reefs and islets — External slope 
— Zone of Nulliporfe — Conglomerate— Depth of lagoons — Sedi- 
ment — Reefs submerged wholly or in part — Breaches in the reef 
— Ledge -formed shores round certain lagoons — Conversion of 
lagoons into land . . . . . . . . 27 to 43 
SECTION III. ATOLLS OF THE MALDIVA ARCHIPELAGO- 
GREAT CHAGOS BANK. 
Maldiva Archipelago — Ring-formed reefs, marginal and central— 
Great depth 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 dissever- 
ment of large atolls — The Great Cliagos Bank — Its submerged 
condition and extraordinary structure . . . . 43 to 5o 
