CORAL-REEF HARBORS 203 



interestirif^ only on account of tlicsc qualities. So far as 

 the present writer is aware, no settlement deserving" the 

 name of a port exists on the shores of a crater harbor, though 

 there are sundry of these peculiar havens in the eastern 

 Mediterranean and the East Indies which are occasionally 

 used as shelters by ships. 



The harbors which are produced by the reef-building 

 corals, together with the various marine animals and plants 

 which are associated with them, are among the most inter- 

 esting and important of all classes of havens. They are not 

 only in origin the most peculiar of all inlets of the sea, 

 but the conditions of their development and the circum- 

 stances which lead to their preservation and destruction are 

 also curious and noteworthy. Moreover, in the district of 

 southern Florida organic reefs of this nature are numerous 

 and extensive, and the ports which they form, though as 

 yet relatively little used, are destined in course of time to 

 have great value to this country. 



Coral-reef harbors may be divided into two classes, 

 determined by the physical character of the reefs which 

 lead to their formation. The structures belonging to these 

 distinct groups are barrier reefs, and circular or elliptical 

 formations of the same nature, commonly known as atolls. 

 As the history of these two groups of reefs is essentially 

 that of the harbors which they form, we must briefly trace 

 in outline the methods and conditions of their growth. The 

 growth of all coral reefs depends upon certain polyps which 

 secrete a limestone support for their bodies, having the 

 oro^anic habit of arowinor together in closelv associated com- 

 munities which unite their limestone framework so as to 

 form rock-like masses. These creatures add to the number 



