108 



to sixty fathoms. The sea close outside the reef is profoundly 

 deep, but soundings may sometimes be obtained from some of 

 the breaches. 



III. Fringing Beefs skirt the shores, from which they are not 

 far removed; they have much shallower water on their oceanic 

 side, and a narrower lagoon channel between the reef and 

 mainland, of which they in general form a sloping portion. The 

 reefs fringing the Island of Mauritius afford a good type of 

 this class. Many of these reefs are found in the Eed Sea, on 

 the East Coast of Africa, Madagascar, and the adjacent islands 

 on the North, in the Indian Archipelago, between the Bay of 

 Bengal and New Guinea, and as far as the Salomons Isles; they 

 may be traced at intervals to the south of the Society Isles, in 

 longitude 150°W., and northwards through the Phillipines;^ they 

 also occtu* in the West Indies, and the Peninsula of Florida, 

 forming the keys and reefs that jut out from the mainland 

 into the Gulf of Mexico. As some important observations have 

 of late years been made *on the Fringing reefs of this region, 

 I purpose giving in detail the facts related by Professor 

 Agassiz,* as they throw much additional light on the natural 

 history of Coral formations. The Florida Keys are a line of small 

 islands a few miles from the southern extremity of the main 

 land, at different distances from the shore, stretching gradually 

 seaward, in the form of an open crescent, from Virginia Key, 

 and Key Biscayne, to Key West, at a distance of twelve miles 

 from the coast, which does not, however, terminate the series, 

 for sixty miles farther west stands the group of Tortugas, 

 isolated in the Gulf of Mexico. Although disconnected, these 

 islands are so many parts of a submerged Coral reef, parallel 

 with the shore of the peninsula, and continuous beneath the 

 water, the parts visible above the surface being portions of the 

 reef that have completed their growth, and been elevated above 

 low water-mark: — 



* Proceedings of the American Association for the Advancement of Science, 

 p. 81 : Fifth Meeting, Washington, 1851 ; and in more detail in his Methods of 

 Study in Nativral History. 



