10 THE CORAL REEFS OF THE MALDIVES. 



Gardiner has well shown that the topography of the central Maldivian 

 basin almost precludes the idea that it was formed by the subsidence of a 

 large central island. 1 But it seems to me he is hardly correct in stating 

 that the shallower water lies in the centre of the plateau and that the depth 

 gradually increases in the passages. 2 The deepest part of the central basin 

 between South Male and Ari is in the centre ; but as I have stated, there is 

 a more marked dip of the central plateau to the eastward than to the west- 

 ward, the eastern passages being deeper than the western ones. 



That the precipitous slopes of the banks feeing the central basin indicate 

 that they have been built up of corals or other organisms from a deeper 

 plateau from a depth of over one hundred fathoms does not seem to me 

 probable. 3 I should on the contrary consider each of these banks as an inde- 

 pendent one as much as Makunudu, Goifurfehendu, Fadiffolu, Haddummati, 

 and the southern banks. The existence of such banks as North Malos- 

 inadulu and Kolumadulu, — the former rising from a depth of about two 

 hundred fathoms at its southern, of nearly five hundred at its northern 

 extremity, and from over twelve hundred fathoms on the western side ; the 

 latter rising on the northwest from a depth of over two hundred and fifty 

 fathoms, on the northeast from over six hundred, and on the southeast from 

 over eleven hundred fathoms, — can only be explained on the supposition 

 that they are independent banks. The existence of a deeper central valley 

 between North Malosmadulu and Miladummadulu, off Fadiffolu and Koloma- 

 dulu, developed by the soundings of the " Amra," shows a far greater irregu- 

 larity in the depth of the plateau than is assumed by Mr. Gardiner, 4 and 

 naturally modifies to a considerable extent the conclusions he draws from 

 the existence of such a great level central plateau. 5 



According to Darwin 6 there has been a disseverment of large atolls into 

 smaller ones in the Maldives, but that " this process can be observed only in 

 the northern half of the group, where the atolls have imperfect margins con- 

 sisting of detached basin-formed reefs." He imagines the strong currents 



1 Loc. cit., p. 172. 2 Ibid. 



3 Darwin * calls attention to the steepness of the slope off the Maldives in spite of the sandy nature 

 of the bottom of the slopes, slopes which exceed fifty-five degrees. 



4 Loc. cit., p. 174. 6 Loc. cit., p. 175. 6 Coral Reefs, p. 143. 



* Coral Reefs, p. 31. 



