ORGANIC AGENCIES, 111 



fresh water, overgrown with vegetation, and overdotted 

 with higher spots, called hummocks. Going south from 

 the coast, the next thing that attracts attention is a line 

 or string of limestone islands (keys) a' a , stretching in a 

 curve from Cape Florida to the Tortugas, a distance of 

 one hundred and fifty miles. Between these and the 

 southern coast is an extensive shoal, almost a mud-flat, 

 navigable only to small fishing-craft. The width of this 

 shoal is thirty to forty miles. It is overdotted with small, 

 low, mud islands, overgrown with mangrove-trees, and 

 entirely different from the true keys. Outside of the line 

 of keys, and separated from it by a ship-channel, five to 

 six miles wide and three to four fathoms deep, is a con- 

 tinuous line of living reef, a" a". On this, by the action 

 of the waves, a few small islands have commenced to 

 form. Outside of all sweep the deep waters of the Gulf 

 Stream, G S. 



Formed by Coral Agency. Now, the whole area 

 thus described is a recent coral formation, and has been 

 added to Florida in recent geological times. The proof 

 of this is complete. 



First : On the living reef, islands have just commenced 

 to form. Some are yet only a collection of large coral 

 fragments, the nucleus of an island. Some are more 

 compacted by smaller fragments thrown in among the 

 larger. Some are small but perfect islands i. e., coral/ 

 sand, and mud have been thrown upon and completely 

 buried the large masses. But none of these are yet 

 clothed with vegetation, much less inhabited by animals 

 and man. Next come the larger inhabited islands of the 

 line of keys. On cutting into these, the same structure 

 as described above is revealed. Undoubtedly these are 

 a string of wave-formed coral islands, and here was once a 

 line of living reef ; but the corals have long ago died, be- 

 cause cut off from the open sea by the formation of another 

 reef farther out. Next comes the southern coast. Ex- 



