THE GREAT OCEAN. SoJ 



(the islands,) which the sea throws up, especially 

 on the windward side, and at tlie projecting angles 

 of the circumference. The reefs and islands, 

 therefore, inclose an internal basin, or lagoon. 

 It is only when the extent of tlie j^lateau is very 

 small, that the lagoon is filled, in which case a 

 single island is formed instead of a group of islands. 

 As far as the dam can be examined, it consists of 

 horizontal layers of a limestone (congeries) formed 

 of coral sand, or fragments of madrepores. Masses 

 of rock, often measuring a fathom, thrown upon 

 the dam, are of the same stone, which often con- 

 tains only larger fragments of madrepores, than 

 the layers exposed to view above ; and we are of 

 opinion, that the whole construction, the table or 

 pkiteau which forms the basis of the group of 

 islands, consists of this same kind of stone. It is 

 a species of rock of new formation, and which 

 still continue to be produced. This same kind 

 of stone, or rock, lies under the same climate, 

 at the foot of all high islands, at least in places, 

 and forms the coral reefs, by which many of them 

 are entirely surrounded. 



The plains at the foot of such mountains, which 

 form the edge or border of the islands, appear to 

 be similar reefs, which the sea, that has formed 

 them, formerly covered when it was higher than 

 it now is. These coral reefs, lying close to high 

 land, sink sloping into the sea, so that the waves, 

 rolling over an inclined plane, loam in surf, and 



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