Page:Darwin Journal of Researches.djvu/504

This page has been validated.
482
[CHAP. XX.
VAST AMOUNT OF SUBSIDENCE.

oscillations of level; we see in each barrier-reef a proof that the land has there subsided, and in each atoll a monument over an island now lost. We may thus, like unto a geologist who had lived his ten thousand years and kept a record of the passing changes, gain some insight into the great system by which the surface of this globe has been broken up, and land and water interchanged.