1888.] 519 [Fewkes. 



Bermudas to subsidence of the foundations upon which they rest, 

 showing in the Atlantic one of the few verifications in that ocean 

 of Darwin's beautiful theory of the formation of ring-shaped atolls 

 by submergence of the sea-floor. 



It is believed, however, that the present general contour of the 

 Bermudas, the crescentic islands and the partially or wholly en- 

 closed sounds, 1 are due to erosion of the rock by the sea rather 

 than by subsidence of their foundation. It is also held that the 

 present Bermudas are but small parts, veritable fragments of a 

 much larger island, which once covered a greater area of the oval 

 foundation. The present islands lie on the southern rim of this 

 platform. It is not necessary to suppose that the present Bermuda 

 is a compound atoll due to subsidence of the sea-floor, but the well- 

 marked sounds and lagoons can best be explained as inroads made 

 by the erosion of the sea on the soft rock of which the islands are 

 composed. Analogous forces are now at work on the islands, com- 

 pleting the work which was begun long ago. These forces show 

 here and there over the islands on a smaller scale the same results 

 and the same circular lagoons which on the map give to the islands 

 such a close resemblance to the Pacific ocean atolls. 



Coral islands are divided into two great groups : 1. Those in the 

 process of formation. 2. Those in the process of decay. 



The best illustration of the former group in the Atlantic is the 

 well-known Florida Reefs. Here we have a series of low islands 

 in places much eroded, but nowhere rising very high above the 

 level of the sea. The forces of formation are active. The islands 

 lie in the zone of a profuse coral life and in the neighborhood of 

 an oceanic current well stocked with smaller marine life, which 

 serves for the food of the corals. 



The Bermudas are good illustrations of the second kind of coral 

 islands, or those in process of erosion. They lie distant from the 

 equator where coral life has been evidently more luxuriant for- 

 merly than at present. They are riddled with caves, grottoes and 

 submarine chambers due to erosion. Their surface is covered with 

 a red soil of characteristic composition. Here the forces of decay, 

 or of destruction of the land by erosion, are active. The building 

 of the coral island is here finished, and the sea and air now con- 

 spire to level it below the surface of the ocean. 



1 Castle Harbor, Great Sound and Harrington Sound. 



