226 



GROWTH OF CORAL. 







BRAIN-STONE CORAL. 



they were found to have risen nearly to the surface, 

 and to have attached themselves to the solid rock. 



There is also a case mentioned of a ship in the 

 Persian Gulf which, in the course of twenty months, 

 had her copper encased with living coral to the 

 thickness of two feet. 



On the other hand, it is asserted, and we doubt 

 not with equal truth, that many reefs do not seem 

 to increase in size in the course of many years. 



When a coral reef has reached the surface, the 

 formation of an island instantly begins ; but it 

 necessarily takes a long time ere this island be- 

 comes habitable by man. Among the first plants 

 that raise their heads to the sea-breeze is the grace- 



