STRUCTURE OF CORAL REEFS. 103 



While some islands have only narrow fringing reefs, others 

 are almost or quite surrounded by the distant barrier, which 

 stands off like an artificial mole to protect the land from an 

 encroaching ocean. The barrier is occasionally ten or fifteen 

 miles from the land, and incloses not only one, but at times 

 several, high islands. From reefs of this large size, there are 

 all possible variations down to the simple fringing platform. 



The inner channel is sometimes barely deep enough at low 

 tide for canoes, or for long distances may be wanting entirely. 



HIGH ISLAND WITH BAKRIER AND FRINGING REEFS. 



Then, again, it is a narrow intricate passage, obstructed by 

 knolls or patches of coral, rendering the navigation dangerous. 

 Again, it is for miles in length an open sea, in which ships 

 find room to beat against a head wind with a depth of ten, 

 twenty, or even thirty fathoms. Yet hidden reefs make cauiion 

 necessary. Patches of growing corals, from a few square feet 

 to many square miles in extent, are met with over the broad 

 area inclosed by these distant barriers. 



These varieties of form and position are well exemplified 

 in a single group of islands — the Feejees ; and the reader is 

 referred to the chart of this x^rchipelago at the close of this 

 volume. 



Near the middle of the chart is the island Goro ; its shores, 

 excepting the western, are bordered by a fringing reef 1 he 

 island Angatc^ south of Goro, is incircled by a coral break- 

 water, which on the southern and western sides runs far from 

 the shores, and is a proper barrier reef, while on the eastern 



