Ch. V. 



OF COEAL-KEEFS. 



133 



borne down from the land were consequently lessened, 

 the greater number of the channels with which the reef 

 in its fringing state must have been breached, especially 

 those which fronted the smaller streams, will have 

 become choked up by the growth of coral : on the wind- 

 ward side of the reef where the coral grows most 

 vigorously, the breaches will probably have first been 

 closed. In barrier-reefs, therefore, the breaches kept 

 open by draining the tidal waters of the lagoon-channel, 

 will generally be placed on the leeward side, and they 

 will still face the mouths of the larger streams, although 

 removed beyond the influence of their sediment and 

 fresh-water ; — and this, it has been shown, is commonly 

 the case. 



Eeferring to the following diagram, in which the 



No. 6. 

 A". <a. C' A". 



A' A' — Outer edges of the "barrier-reef at the level of the sea. The 

 cocoa-nut trees represent coral islets formed on the reef. 



C C — The lagoon channel. 



B'B' — The shores of the island, generally formed of low alluvial land 

 and of coral detritus from the lagoon-channel. 



A" A" — The outer edges of the reef now forming an atoll. 



C — The lagoon of the newly-formed atoll. According to the scale, the 

 depth of the lagoon and of the lagoon channel is exaggerated. 



