CORAL REEFS. 359 



9.— REMARKS ON THE THEORY OF CORAL 

 REEFS. 



Bij W. J. CLUNIE8 ROSS, B.Sc. Loud., F.G.S. 



\_Abstract.'] 



Among the results of Mr. Charles Darwin's observations 

 made during the voyage of the Beagle in 1835 and 1836, 

 was his well-known theory of coral reefs, by which he sought 

 to account for the origin of the three classes of fringing 

 reefs, barrier reefs, and atolls. This theory was very gene- 

 rally accepted for a long time, but during recent years has 

 been questioned by several writers. Shortly after the 

 account of the Beagle s voyage was published, however, the 

 theory was disputed by a man who had had exceptional 

 opjiortunities of studying the phenomena of coral reefs ; and 

 as his " remarks " have never been published, and have as 

 much force now as they had 50 years ago, an abstract of 

 them is given, together with some other suggestions. 



The man to whom allusion has been made was Captain 

 J. C. Ross, who colonised the Keeling or Cocos Islands, in 

 the Indian Ocean, in 1826. The Cocos were visited by 

 Uarwin in 1836, and while there he thought he obtained 

 proofs in support of his theory that atolls always indicate an 

 area where the sea bottom has been sinking. One of these 

 was the finding of posts standing in the water. These, he 

 states, had formerly been the posts of a house which had 

 been abandoned owing to the sinking of the land. The posts 

 had really never been part of a house, but had been placed 

 in the water between tide-marks for a particular purpose. 

 The structure of the islands also shows that there had been 

 elevation rather than subsidence, since masses of coral, 

 evidently in the places where they had grown, are found at a 

 height of 20 feet above high water-mark, and, since the 

 Cocos form a true atoll, this is distinctly opposed to the Dar- 

 winian theory. It is further pointed out that the growth of 

 coral, which goes on below low water-mark, would not pre- 

 serve the islands with their covering of cocoanut trees from 

 submergence, since that w^ould require additions to the top of 

 the islands and not to their sides. 



A consideration of the supposed areas of elevation and 

 subsidence which Darwin thought he could recognise in the 

 Pacific and Indian oceans shows that they by no means 

 support his theory. In the areas of subsidence, which he 

 says are characterised by atolls and barrier reefs only, there 



