THE FLORIDA PENINSULA. 
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upon it. Of like origin are the great bank east of the 
Mosquito coast and the reefs on the south coast of Cuba ; 
the Basse-Terre of Guadeloupe is the same, now slightly 
elevated, and the barrier-reefs on the windward side of the 
West India Islands rest on plateaux of similar origin. At 
Barbados the nucleus is a trachytic mass round which 
are terraces formed of mollusca and radiata, still living in 
the sea, which have been successively lifted . 1 The author 
considers that in the West India Islands many volcanic 
masses, which probably have never reached the surface, 
form the foundation of these banks of organisms. 
It would seem probable that reef-building corals had 
little to do with building the peninsula north of Cape 
Florida. The author explains the Alacran reef (atoll- 
shaped) by a growth of corals upwards from a submarine 
bank, and shows that the slope is steep down to a depth of 
thirty fathoms, then more gradual. 
He lays much stress on the importance of currents 
bringing food, and points out that, on the lee side of a 
reef, corals may be killed by the drift of sediment. ‘ When 
Darwin wrote, and when we knew little of the limestone 
deposits formed by the accumulation of the debris of mol- 
luscs, ecliinoderms, polyps, and the like, upon folds of the 
earth’s crust, the basal parts of barrier-reefs were difficult 
of explanation. The evidence gathered by Murray, Semper, 
and myself, partly in districts which Darwin had already 
examined, and partly in regions where his theory of reef- 
formation never seemed to find its proper application, has 
in part removed this difficulty. It tends to show that we 
must look to many other causes than those of elevation 
1 In Three Cruises of the Blake, vol. i. p. 79, Prof. A. Agassiz says : 
1 In some instances coral reefs have unquestionably been uplifted. 
I have seen the elevated reefs of Cuba, of San Domingo, and other 
West Indian Islands, and of Barbados, which are perhaps the most 
striking examples of elevated reefs.’ 
