Ch. V. 



OF COEAL-EEEFS. 



131 



insensibly, we may infer from what we know of the 

 conditions favourable to the growth of coral, that the 

 living masses bathed by the surf on the margin of the 

 reef, will soon regain the surface. The water, however, 

 will encroach little by little on the shore, the island 

 becoming lower and smaller, and the space between the 

 edge of the reef and the beach proportionally broader. 



No. 5. 



A A — Outer edge of the reef at the level of the sea. 



B B — Shores of the island. 



A' A' — Outer edge of the reef, after its upward growth during a period 



of subsidence. 

 C C — The lagoon-channel between the reef and the shores of the now 



encircled land. 

 B' B' — The shores of the eiicircled island. 



N.B. In this, and the following woodcut, the subsidence of the land 

 could only be represented by an apparent rise in the level of the sea. 



A section of the reef and island in this state, after a 

 subsidence of several hundred feet, is given by the 

 dotted lines : coral-islets are supposed to have been 

 formed on the new reef, and a ship is anchored in 

 the lagoon-channel. This section is in every respect 

 that of an encircling barrier-reef, and is, in fact, 



x 2 



