CORAL ISLANDS. I97 



of delicately-branclied corals. At the head of the lagoon we crossed a 

 narrow islet, and found a great surf breaking on the windward coast, 

 I can hardly explain the reason, but there is, to my mind, much 

 grandeur in the view of the outer shores of these lagoon islands. 

 There is a simplicity in the barrier-like beach, the margin of green 

 bushes and tall cocoa-nuts, the solid fiat of dead coral-rock, strewed 

 here and there with great loose fragments, and the line of furious 

 breakers, all rounding away towards either hand. The ocean, throw- 

 ing its waters over the broad reef, appears an invincible, all-powerful 

 enemy ; yet we see it resisted and even conquered by means which at 

 first seem most weak and insufficient. It is not that the ocean spares 

 the rock of coral ; the great fragments scattered over the reef, and 

 heaped on the beach whence the tall cocoa-nut trees spring, plainly 

 bespeak the unrelenting power of the waves. Nor are any periods of 

 repose granted ; the long swell caused by the gentle but steady action 

 of the trade-winds, always blowing in one direction over a wide area, 

 causes breakers almost equalling in force those during a gale of wind 

 in the temperate regions, and which never cease to rage. It is im- 

 possible to behold these waves without feeling a conviction that an 

 island, though built of the hardest rocks — let it be porphyry, granite, 

 or quartz — would ultimately yield and be demolished by such an 

 irresistible power. Yet these low, insignificant coral islets stand, and 

 are victorious ; for here another power, as an antagonist, takes part 

 in the contest. The organic forces separate the atoms of carbonate 

 of lime, one by one, from the foaming breakers, and unite them into 

 a symmetrical structure.. Let the hurricane tear up its thousand huge 

 fragments, yet what will that tell against the accumulated labour of 

 myriads of architects at work night and day, month after month ? 

 Thus do we see the soft and gelatinous body of a polyp, through the 

 agency of the vital laws, conquering the great mechanical power of 

 the waves of an ocean which neither the art of man nor the inanimate 

 works of Nature could successfully resist." 



We have said that these coral formations are of three forms, to 

 which the names of atolls, barrier reefs, and fringing reefs, have been 

 applied. We have spoken of atolls ; we shall now say a few words 

 on barrier and fringing reefs. 



The barrier reefs are formations which surround the ordinary 

 islands, or stretch along their banks. They have the form and 

 general structure of atolls. Like atolls, the barrier reefs appear 

 placed on the edge of a marine precipice. They rise on the edge of 

 a plateau which looks down on a bottomless sea. On the coast of 



