FLORIDA REEFS AND KEYS. 207 



and present not the slightest evidence of disturbance, beyond 

 the upward movement which raised them to their present 

 position. The rocky mass of coral along the margin of the 

 Key is undermined by the waves, and otherwise worn into 

 singularly rugged shapes, with sharp projecting points. Even 

 at some distance from the water, bunches of coral project 

 above the surface wherever the overlying sand is washed 

 away. 



" On Bahia-honda similar appearances are presented, where 

 the coral rocks extend seaward ; on the lee of the island a 

 long sand-bank is thrown up, and a lagoon of considerable 

 extent is formed, in which the mangrove tree is seen striding 

 about in the soft mud. This island was washed in two by 

 the last hurricane, and the channel formed has three feet of 

 water at low tide. In the shallow water off many of the 

 Keys, very beautiful patches of Algae, interspersed with living 

 corals, are seen within six or eight inches of the surface. Off 

 Indian and Plantation Keys, dark knobs of coral are visible 

 upon the white mud of the bottom, which render the nav- 

 igation amongst these Keys dangerous. On lower Matacum- 

 ba I traced the rugged coral rocks for a mile in extent ; I 

 also found them on Conch Key, as I did indeed on nearly 

 every island that I examined, where a section could be found 

 on the shore, from which the overlying sands were washed." 



Professor Agassiz gives the following general account of 

 the Keys and Peefs (see also map) : 



" The Keys consist of an extensive range of low islands, 

 rising but a few feet, perhaps from six to eight or ten, or at 

 the utmost to twelve or thirteen feet, above the level of the 

 sea. They begin to the north of Cape Florida, when they 

 converge toward the main land, extending in the form of a 

 flat crescent in a southwesterly direction, gradually receding 



