154 CORAL AND ATOLLS 



found. Under the accumulation of coral boulders, sand, and 

 vegetable debris, which forms the island itself, it still continues 

 unbroken ; and on the lagoon side of the island again, in many 

 places, it juts out as extensive slabs of rock, breaking the sand 

 stretches which form the greater part of the lagoon shore. 



This is all barrier, all one continuous layer of rock, all 

 formed in the same fashion ; and the function which the sea- 

 ward edge now serves has in times past been carried on by 

 every portion of the layer. Although the term " Barrier," as 

 generally used, cannot perhaps be properly applied to this 

 entire rock stratum, still it is only by considering it as a whole 

 that a right understanding of its origin can be arrived at. To- 

 day the seaward part alone acts as a functional barrier proper ; 

 in the geological to-morrow it may be buried under the land 

 accumulation which it has helped to form ; and in the geological 

 yesterday that cemented layer of coral fragments which is 

 found everywhere under the islands was the functional agent 

 in resisting the waves, and in forming the dry land. Since 

 the seaward portion alone can be called the " Barrier," and 

 since the whole layer will have to be referred to again, we 

 will call it the Breccia Platfoem, for it is a mosaic inlay of 

 coral fragments, cemented together into a solid platform, 

 stretching from surf-line to lagoon. 



The barrier is the pioneer of the island, it is dry land 

 potentially, and on the varying influences of wind and waves 

 depends the disposition of the land for which the pioneer has 

 laid the foundation. The dry land that the barrier has called 

 into existence is in reality broken pieces of barrier, for the 

 entire atoll is a debris formation, and the debris is recruited 

 from the seaward edge of the barrier for the most part. 



Imagine for a moment all this debris to be removed : no 

 loose fragments of coral, no sand, no vegetation piled up. All 

 that would remain would be a flat and roughly level ring of 

 coral rock, firmly cemented, and making a broad and flat 

 margin to the lagoon ; only the Breccia Platform would be 

 left in fact. This margin would be mostly awash ; the 

 waves would break on its seaward edge and the ocean swell 



