CORAL REEFS, AND ISLANDS. 251 



canoe." 1 Although reference has been made only to 

 such portions of the reef formations as have been 

 reared to the water's level, it must be remembered 

 that there may also be submerged banks, which are 

 in effect continuous with the elevated portions, and 

 form a part of the reef ground. The extent to which 

 these structures can be developed may be inferred 

 from the dimensions recorded ; as, for instance, to 

 the west of the two large Fiji Islands there is pro- 

 bably three thousand square miles of reef-ground. 

 The Exploring Isles have a barrier eighty miles in 

 circuit ; the western shore of New Caledonia has a 

 reef throughout its extent of two hundred and fifty 

 miles, and for a hundred and fifty miles beyond ; 

 whilst the Australian barrier forms a broken line of 

 some one thousand two hundred and fifty miles in 

 length. 



Not only are we interested in the area which may 

 be covered by a reef-ground, but also of the thick- 

 ness to which some of the reefs may attain, and here 

 again we must fall back on the calculations made by 

 Dr. Darwin and Professor Dana. If it were possible 

 to raise one of these coral-girt islands we should find 

 that the barrier reefs stand like walls upon the 

 deeply-submerged slopes, or, in the case of the 

 fringing reefs, in the shallowest water, approaching 



1 Dana, " Corals and Coral Islands," p. 105. 



