236 CORAL AND ATOLLS 



of definite subsidence. It does not necessarily follow that the 

 features of this coast-line are brought about by the growth 

 of coral reefs on a sinking basis, for, as Hedley says (" Coral 

 Reefs of the Great Barrier," p. 10): " It may be allowed — 

 though Darwin deprecated the idea — that the continental shelf 

 was ready prepared with numerous banks representing eroded 

 islands, just reaching to within the required distance of the 

 surface, when the first coral builders came." The coral reefs 

 are definitely established upon a sunken basis, but that is not 

 the same thing as saying that the sinking caused their present 

 disposition. 



In this same paper, Mr. Hedley carried on the work of 

 Guppy and of Kramer in the appreciation of the force of the 

 winds and waves in the formation of crescent and horse-shoe 

 islands and reefs, and, on the whole, this wind formation is one 

 of the most distinct advances made in the study of coral 

 structures. 



I think it may therefore be said that there is no one 

 generally accepted method by which it is agreed that all coral 

 formations are brought about. Some reef spots show signs of 

 elevation, and some of depression, and some fail to give any 

 indication of change, so that land movements may not properly 

 be claimed to be the cause of any features that are constant. 

 Upon a stationary basis again, there is no generally accepted 

 method for building the characteristic features of the fully 

 devoloped atoll or barrier reef. 



