CORAL REEFS, AND ISLAiVDS. 283 



to account for their origin or for their growth. They 

 would present the same appearance in a slowly- 

 rising, a stationary, or a slowly-sinking area. Their 

 outside boundary was ever marching further outward, 

 on submarine shoals and banks, and ever, as it 

 advanced in that direction, its rear ranks were melted 

 and dissolved away. Their inner boundary the 

 shores of some island, or of some continent might 

 be steady and unmoved, or it might be even rather 

 rising instead of sinking. Still, unless this rising 

 were such as to overtake the advancing reef, the 

 lagoon would grow, and if the shores were steady, it 

 would widen as fast as the face of the coral barrier 

 could advance. Perhaps, even if such a wonderful 

 process had ever occurred to Darwin, even if he 

 had grasped this extraordinary example of the ' give 

 and take' of nature, of the balance of opposing 

 forces, and agencies, which is of the very essence of 

 its system, he would have been startled by the vast 

 magnitude of the operations which such an explana- 

 tion demanded. In its incipient stages this process 

 is not only easily conceivable, but it may be seen in 

 a thousand places, and in a thousand stages of 

 advancement There are islands, without number, in 

 which the fringing reef is still attached to the shore, 

 but in which it is being 'pitted,' holed, and worn 

 into numberless pools on the inner surfaces, where 

 the coral is in large patches dead or dying, and where 



