CORAL ISLANDS. 387 



form the coral islands do not resemble each other ; but 

 this, and the extent of each, probably depends on the 

 size of the submarine mountain tops, on which their basis 

 is founded. Those islands which have more length than 

 breadth, and are opposed in their greatest -extent to the 

 winds and waves, are richer in fruitful islets than those 

 whose situation is not so adapted to a quick formation. 

 In the large island-chains, there are always some single 

 islets which have the appearance of high land ; these lie 

 upon an angle projecting into the sea, are exposed to the 

 surf upon two sides, consist therefore almost entirely of 

 large blocks of coral, and are destitute of smaller frag- 

 ments of shells and coral sand to fill up the intervals. 

 They are, therefore, not adapted to support plants re- 

 quiring a depth of soil, and only afford a basis to high 

 trees, provided with fibrous roots, (as the Pisonia, Cor- 

 dia Sebastiana, L. ; Morinda citrifolia, L. ; and Pan- 

 danus odoratissimus, L.), which, at a distance, give to 

 these, always very small islands, the form of a hill. The 

 inner shores of the island, exposed to the surf, consist of 

 fine sand, which is washed up by the tide. Between the 

 small islands under their protection, and even in the mid- 

 dle of the inner sea, are found smaller pieces of coral, 

 which seek a quiet abode, form in time, though very 

 slowly, banks, till they at last reach the surface of the 

 water ; gradually increase in extent ; unite with the 

 islands that surround them ; and at length fill up the 

 minor seas, so that what was at first a ring of islands, 

 becomes one connected land. The islands which are so 

 far formed, retain in the middle a flat plain, which is al- 

 ways lower than the wall that surrounds them on the 



