i 4 THE CORAL LANDS OF THE PACIFIC. 



immediately agitated. One of the most beautiful sights in the 

 Pacific is to watch the big white-crested breakers dash them- 

 selves against these reefs. 



Sometimes a reef in Polynesia is thirty feet wide, and the 

 rolling billows of the Pacific extending occasionally in an un- 

 broken line for a mile along the reef are arrested by it, and, 

 curving towards the shore, form a graceful liquid arch, which 

 glitters in the sunlight. The beautiful water-structure then 

 disappears with a loud and hollow roar into the reef, only to 

 be succeeded by another and another. 



In every reef there is a provision for the ingress and egress 

 of craft by openings in the lines of coral, and the traveller will 

 hardly fail to notice that these openings are almost invariably 

 opposite some valley where streams of fresh water flow from 

 the mountain. 



The tallest cocoa-nut trees grow on small islands. In some 

 of the breaches in the reef they serve as lighthouses or beacons, 

 and show the native fisherman where he can get shelter and 

 replenish his stock of fresh water. These islands have a coral 

 formation, and their origin is doubtlessly due to the decaying 

 vegetation or wood dashed in by the sea, and seeds washed to 

 the reef from the beach. 



Dr. Darwin divides coral-reefs into three classes : an atoll 

 (or a sort of ring of coral surrounding a lagoon), which only 

 differs from a barrier- reef in encircling no land ; while a barrier- 

 reef differs from a fringing-reef in being placed at a much 

 greater distance from the land, in consequence of the probable 

 inclination of its submarine foundation, and in the presence of 

 a deep-water lagoon-like space within the reef. I have before 

 remarked that the polyparia cannot exist at much more than a 

 hundred feet below the surface. There can be no difficulty 

 respecting the foundations on which fringing-reefs are based ; 



