i68 CORALS AND CORAL ISLANDS. 



or false stratification is everywhere seen in the rock, the 

 inclination of the planes differing very little from the slope of 

 the shore up which the waves push dead shells, pieces of 

 coral, (S:c. After a breeze, coarse materials are found strewing 

 the beach, a light wind leaves a finer deposit, and in the 

 succeeding calm the sea appears milky from fine calcareous 

 matter suspended in the water ; this is deposited in the form 

 of free, impalpable mud, which invests marine plants and 

 other objects, to which it adheres with great tenacity, and be- 

 comes a source of annoyance to the collectors of Algae. All 

 these alternations of fine and coarse materials may be observed in 

 the limestone. [The rock corresponds to the beach sand-rock.] 



".Along the south beach, the sand is thrown up by the 

 waves to an elevation nearly equal to that of the highest point 

 of the island, and during the gale of Oct. 1841 the greater 

 part of it was submerged, so that, at first sight, it might ap- 

 pear that the whole island was the result of sand thrown up 

 at such times. But although I observed no beds in the lime- 

 stone that prove, like those of our Tertiary, that the animals, 

 whose remains they contain, lived and died on the spot, yet 

 in its structure it shows the result of long-continued, steady 

 wave-work that cannot be referred to any other cause. 



"On Key West I found in the rocks no beds of coral re- 

 taining their original position, although large fragments are 

 scattered through the mass. 



" Some of the small Keys, such as the Mangrove Keys, 

 are the result of gradual deposition of sedimentary matter, 

 and many of those interspersed among the larger islands have 

 not yet reached the level of high water, but are nevertheless 

 covered by a dense growth of this curious tree. It would be 

 difficult to imagine a plant better adapted to island-making 

 than the mangrove. Its long pendulous seeds fall into the 

 shallow water, stick in the soft mud, and take root ; the bud 

 proceeding from the opposite extremity, soon shoots up above 

 water and sends down branches almost perpendicularly into 

 the mud; these take root and produce other trees, and so on. 

 Besides these, lateral shoots are given off", and, at a distance of 



