TOPOGRAPHY OF THE INDIAN OCEAN. 9 



the formation of bays by the shutting off of parts of the reef flats either on 

 the windward or on the leeward side of an atoll, for the existence of horses 

 of coral reef rock across certain beaches, and for the formation of coral reef 

 rock patches, pitted and weather-worn, rising above the general level of 

 the surrounding reef flats, for the formation of sinks, for the throwing up of 

 dams, or even for the formation of a gap in the rim of an atoll. To climatic 

 conditions, as affected by the position of islands and groups of islands, we 

 also owe the degree of development of the flora of certain sections, or even 

 its final destruction ; in others these forces begin to act only when the 

 lagoon reefs have risen to sufficient height for tlie outer rim to come under 

 the influence of the action of the sea upon its submerged reef flat rims. 



The soundings taken by the "Amra" do not bear out the statement of 

 Mr. Gardiner that all the various banks of the Maldives (PI. 7) and Lacca- 

 dives (Pis. 7, 8) appear to have been built on the same set of foundations.* 

 Several of the Laccadive banks are separated by depths of more than one 

 thousand fathoms, and the banks from Cora Divh to Cardamum are enclosed 

 by the one-thousand-fathom line. Minikoi is similarly isolated, and the 

 plateau of the fifteon-hundred-fathom line alone can be said to form the 

 foundation of the Laccadives and Maldives (Pis. 7, 8). 



At any rate, the main chain of the Maldives does not lie alone upon a 

 relatively shallow plateau at a depth of about two hundred fathoms.'- Goi- 

 furfehendu is separated from South Malosmadulu by a channel of more than 

 three hundred fathoms, South Malosmadulu from Fadiffolu by over five 

 hundred fathoms. North Malosmadulu from Miladummadulu by about the 

 same depth, Makunudu from Tiladummati by a channel of nearly eight 

 hundred fatlioms, Fadiffolu from Karidu by three hundred and seventy-two 

 fathoms, and from Miladummadulu by seven hundred and sixty-nine fath- 

 oms, — depths greatly in excess of those separating the banks of the central 

 Maldives from North Male to South Nilandu and Mulaku (PI. 1). To the 

 south, Mulaku is separated from the eastern fiice of Kolumadulu by a depth 

 of nearly six hundred and fifty fathoms, and Kolumadulu from Haddum- 

 mati by over eleven hundred fathoms, — depths nearly as great as those 

 separating the banks of the southern Maldives (PL 1). 



1 Loc. ciL, p. 172. - Lnc. cit., pp. 150, 172. 



