290 



THE OCEAN. 



BoLABOLA. 



island of Bolabola, however, is surrounded by a ring 

 of land almost unbroken, on which are growing 

 groves of cocoa-nuts ; the reef being wholly elevated 

 above the sea. 



The openings in the reefs in the larger islands 

 are almost invariably placed opposite the mouth 

 of a river. One can readily understand, that a 

 current of fresh water would be detrimental to the 

 health of a polype formed for living in the sea, 

 and therefore the openings here might have been 

 expected. But this effect is increased by the sedi- 



