CHAPTER XX

Keeling Island — Singular appearance — Scanty Flora — Transport of seeds — Birds and insects — Ebbing and flowing springs — Fields of dead coral — Stones transported in the roots of trees — Great crab — Stinging corals — Coral-eating fish — Coral formations — Lagoon islands or atolls — Depth at which reef-building corals can live — Vast areas interspersed with low coral islands — Subsidence of their foundations — Barrier-reefs — Fringing-reefs — Conversion of fringing-reefs into barrier-reefs, and into atolls — Evidence of changes in level — Breaches in barrier-reefs — Maldiva atolls, their peculiar structure — Dead and submerged reefs — Areas of subsidence and elevation — Distribution of volcanoes — Subsidence slow and vast in amount.