300 GORALS 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, the Chagos Group; and, north and east of 
northern Madagascar, Saya de Malha, Amirante, Cosmoledo ; 
and also, nearer northern Madagascar, a series of raised atolls 
from Farquhar Island to Aldabra Island. 
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. 
