314 CORALS AND CORAL ISLANDS. 



distribute along the shores. It will be observed that this 

 agent, so ineffectual on small islands, is one of vast influence 

 upon larger lands. Mr. Darwin alludes to small patches of 

 coral in the Persian Gulf. Ceylon has some fringing reefs. 



The islands of the Indian Ocean are, to a great extent, 

 purely of coral. Of this character are the Laccadives, Mal- 

 dives, Keeling's, Saya-de-Malha, Almirante, and Cosmoledo. 

 The Chagos Group is of the same character, and the shoal Car- 

 gados is probably similar. The Seychelles are small islands 

 with extensive reefs. 



Madagascar has a fringing reef upon its southwestern 

 point, according to Mr. Darwin, and on some parts of the 

 coast above : also on the north and eastern shores far down as 

 latitude 18° S. The Comoro Islands, between Madagascar and 

 the continent, have large barrier reefs. 



The eastern coast of Africa has narrow reefs extending 

 north with some interruptions from Mozambique, in latitude 

 16° S., to a short distance from the equator. Corals also 

 abound in the Red Sea, occurring in some parts on both shores, 

 though most frequent on the eastern, from Tor, in the Gulf of 

 Suez, to Konfodah. This long continental reef may at first be 

 deemed a little remarkable, after what has been stated about 

 such reefs elsewhere. Yet the surprise is at once set aside by the 

 striking fact that this whole coast, from the isthmus of Suez 

 south, has no rivers, excepting some inconsiderable streams. It 

 affords, therefore, an interesting elucidation of the subject un- 

 der consideration, and confirms the view taken to account for 

 the absence of reefs from many continental coasts. It is a fact 

 almost universal, that where there are large fresh-water 

 streams, there are earthy, or sandy shores ; and where there 

 are no such streams, rocky shores, though not uniformly occur- 

 ring, are common. 



