CHAPTER XXIV 



THE DEVELOPMENT OF OTHER CORAL STRUCTURES 



AND THE INDICATIONS OF ALTERATION 



OF LAND-LEVEL 



I HAVE already said that no concrete theory of atoll formation 

 may be considered as at all satisfactory unless the principle 

 that underlies it can also be used to explain the development 

 of other coral formations. It therefore becomes necessary to 

 see what support the ideas connected with the processes of 

 " Sedimentation " will gain from an examination of fringing 

 reefs and barrier reefs. Now I take it as a strong argument 

 for the truth of these views that when I came to apply them 

 to the formation of a barrier reef, I found that I was the third 

 in a succession of investigators who had quite independently 

 conceived that the real factor in the formation of barrier reefs 

 was the process of " sedimentation." 



So long ago as 1856, Professor Le Conte had given it as 

 his opinion that barrier reefs were fringing reefs whose growth 

 was " limited on one side by the muddiness of the water, and 

 on the other by the depth." * 



Dr. Guppy, without knowing of this explanation, had come 

 to the same conclusion, and had published his observations in 

 1884.t When in the Cocos-Keeling atoll — and without a 

 knowledge of either of these papers — I realised that the 

 picture I had drawn of the processes of sedimentation would 

 easily account for all the features of a barrier reef. 



Since the reef-building corals will begin constructing 

 upon any platform that rises to within the area above the 

 Limiting Line of Sedimentation, it follows that a reef will form 



* American Journal of Science, 2nd series, vol. xxiii. p. 46. 

 t Proc. Linn. Soc. N.S.W. vol. ix. Part 4. 



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