482 VAST AMOUNT OF SUBSIDENCE. (cHar. xx, 
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 in- 
terchanged. 
