THE FLORIDA REEFS. 79 



still in an active state of formation. Even the elevated reefs of 

 Cuba and of the other West India Islands, though older, prob- 

 ably belong, nevertheless, to the most recent deposits of the 

 kind we know. The difficulty of explaining the constant re- 

 newal of the coral faces of the atolls of the Pacific, and their 

 present condition, on the supposition of their having existed 

 from the time of the early tertiaries, was one of the main 

 causes which led Darwin to seek for some other agency, like 

 subsidence, to explain the renovating process of the original 

 structure. In some instances coral reefs have unquestionably 

 been uplifted. I have seen the elevated reefs of Cuba, of San 

 Domingo, and other West India Islands, and of Barbados^ 

 (Figs. 39, 46), which are perhaps the most striking examples of 



Fig. 46. — Terraces near Fort Charles Light House, Barbados. 



elevated reefs. They are too well known to need more than a 

 passing notice here. The terraces they form show plainly the 

 successive stages of arrest in the agency of elevation, and there 

 is no difficulty in accounting for their existence especially in a 

 volcanic region hke the West Indies ; but that there should 

 have been an extensive area of subsidence, in which the rate of 

 subsidence was so evenly balanced with the rate of coral growth 

 as to create and maintain the necessary conditions for reef for- 

 mation, is less easy of explanation. 



The cap of rhizopod earth for' which Barbados is noted dates 

 back to a time when the volcanic centre round which the coral 

 reefs have grown in more recent times was still at a considerable 

 depth below the level of the sea. This large accumulation of 

 rhizopodial earth is an excellent example in favor of the theory 



^ The trachytic cone forming the base crop out on the surface in the northeast- 

 upon which the successive terraces of em part of the island. 

 Barbados have been elevated is seen to 



