CORAL REEFS AND ISLANDS 211 



Wharton and others have emphasized the importance of 

 the levelling action of the sea on submarine peaks in order 

 to provide flat areas on which coral patches and atoUs 

 might form. 



As an important supplementary theory, Daly has advo- 

 cated " glacial-control," i.e., that the melting of glaciers 

 and snow at the end of the great Ice Age set free so much 

 water as to raise gradually the level of the ocean about 

 30 fathoms, and so submerge the bases of the newly 

 established reefs to that extent, which would have the same 

 effect upon their growth as a sinking of the land to that 

 amount ; but this would be only a temporary and strictly 

 Hmited raising of the sea upon the land, not comparable 

 with the continuous subsidence postulated by Darwin. 



I would remark, finally, that even if his theory has to be 

 rejected, as not applicable to the majority of coral reefs 

 and islands, Darwin did notable service to science in stating 

 the coral-reef problem and attempting its solution. 



