| Panr IL. Sacr. iii. §3.] CORAL ISLANDS. 465 
and could not have grown upward therefore from the bottom of a deep 
sea, Darwin inferred that the sites of these coral reefs had undergone a 


































































































































































































































































progressive subsidence, the rate of upward growth of the reefs keeping 
pace, on the whole, with the depression. In this view what is termed a 

SN \ A.DR#6(V 
Fic. 175.—Cuart oF Krezine AToit, InprAn OceAN (AFTER Mr. Darwiy). 
The white portion represents the reef above sea-level, the inner shaded space the 
lagoon, of which the deepest portion is marked by the darker tint. 
Fringing Reef (4 B, Fig. 177) would first be formed fronting the land (1) 
between the limit of the 20 fathom line and the sea-level (ss). 
Growing upward until it reached the surface of the water, it would 
be exposed to the dash of the waves, which would break off pieces 
of the coral and heap them upon the reef. In this way islets 
2H 

