PREFATORY NOTE. 



In the following pages, first published in 1842, as a companion 

 volume to his Journal of Researches^ Charles Darwin divided 

 coral-reefs into three great classes, each of which is, however, 

 formed upon the same type, and each succeeds the other in 

 general plan of formation 'in much the same way, as childhood 

 passes into youth, and youth into manhood.' The first class, or 

 'fringing-reef (Fig. 1), generally surrounds islands, or skirts 



Fig. 1.— Fringing-Reef. 



great masses of continent, and has a channel of shallow water 

 between it and the shore and a gently sloping sea-bed on its 

 ocean side. Examples are numerous : — The Sandwich Islands, 

 the Seychelle Islands, the Solomon Isles, the Friendly Isles, 

 the Navigator Isles, the New Hebrides, and Mauritius, are 

 margined with this kind of reef; they are also common in the 

 Red Sea, on both its African and Arabian shores, and they 

 form a prolongation from the southern extremity of the promon- 

 tory of Florida. They surround the Nicobar Islands, and skirt 

 nearly the whole of the islands of the West Indies. The reefs 

 on the Florida coast are extending inland, and from the rate of 

 their encroachment upon the shore Louis Agassiz 1 has tried 



1 Natural History Studies, 



