384 ON THE GROWTH OF 



began, were inclosed in the rock ; and in some cases were 

 still separable from it without much force. The upper 

 part of the island is a mixture of the same substances in a 

 loose state, with a little vegetable soil ; and is covered 

 with the casuarina and a variety of other trees and 

 shrubs, which give food to parroquets, pigeons, and some 

 other birds ; to whose ancestors, it is probable, the island 

 was originally indebted for this vegetation." 



Mr Chamisso, who accompanied Kotzebue in his voy- 

 age, has published interesting observations on this sub- 

 ject. He informs us that the low islands of the South 

 Sea and Indian Ocean owe their origin principally to the 

 operations of several species of coral. Their situation 

 with respect to each other, as they often form rows, their 

 union in several places in large groups, and .their total 

 absence in other parts of the same seas, induce us to con- 

 clude, that the corals have founded their building on shoals 

 of the sea ; or, to speak more correctly, on the tops of 

 mountains lying under water. On the one side, as they in- 

 crease, they continue to approach the surface of the sea, 

 on the other side they enlarge the extent of their earth. 

 The larger species of corals, which form blocks, measur- 

 ing several fathoms in thickness, seem to prefer the 

 more violent surf on the external edge of the reef ; this, 

 and the obstacles opposed to the continuation of their 

 life, in the middle of a broad reef, by the amassing of 

 the shells abandoned by the animals, and fragments of 

 corals, are probably the reason that the outer edge of the 

 reef first approaches the surface, As soon as it has 

 reached such a height, that it remains almost dry at low 

 water, the corals leave off building higher ; sea-shells, 

 fragments of coral, shells of echini, and their broken off 

 prickles, are united by the burning sun, through the me- 



