CORAL REEFS, AND ISLANDS. 273 



it, is constantly recovering its level, owing to the 

 tendency of the coral animals to regain the surface, 

 by renewed perpendicular structures ; these con- 

 stitute, first a reef encircling the island at a distance, 

 and subsequently, when the inclosed island has 

 wholly subsided, an atoll. According to this view, 

 which regards islands as the most prominent parts, 

 or the culminating points of the submarine land, the 

 relative position of the coral islands would disclose 

 to us, what we could scarcely hope to discover by the 

 sounding line, viz., the former configuration and 

 articulation of the land." l 



Admirable as this short outline of the theory may be 

 it is scarcelysufficient,andneeds to be supplemented by 

 Darwin's own account of his theory, as set forth in his 

 "Journal," and still further expanded in his larger work. 



"We have seen that we are driven to believe in 

 the subsidence of those vast areas, interspersed with 

 low islands, of which not one rises above the height 

 to which the wind and waves can throw up matter, 

 and yet are constructed by animals requiring a 

 foundation, and that foundation to lie at no great 

 depth. Let us then take an island, surrounded by 

 fringing reefs, which offer no difficulty in their struc- 

 ture, and let this island with its reef, represented by 

 the unbroken line in the woodcut (fig. 54), slowly 



1 Humboldt's "Views of Nature/' Illustrations, p. 262. 

 London, 1850. 



T 



