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. Ihave 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 like 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 
1 The traehytie cone forming the base crop out on the surface in the northeast- 
upon which the successive terraces of ern part of the island. 
Barbados have been elevated is seen to 
