48 ATOLLS. Ch. I. 



abruptly from the unfathomable ocean, with the central 

 expanse studded and the margins symmetrically fringed 

 with oval basins of coral-rock, just lipping the surface 

 of the sea, sometimes clothed with vegetation, and each 

 containing a little lake of clear salt water. 



In the southern Maldiva atolls, of which there are 

 nine large ones, all the small reefs within the lagoons 

 come to the surface, and are dry at low-water spring- 

 tides ; hence in navigating them there is no danger 

 from submarine banks. This circumstance is very 

 remarkable, as within some atolls, for instance those of 

 the neighbouring Chagos group, not a single reef comes 

 to the surface, and in most other cases a few only do, 

 and the rest lie at all intermediate depths from the 

 bottom upwards. When treating of the growth of coral 

 I shall again refer to this subject. 



Although in the neighbourhood of the Maldiva 

 Archipelago the winds, during the monsoons, blow 

 during nearly an equal time from opposite quarters, 

 and although, as I am informed by Captain Moresby, 

 the westerly winds are the strongest, yet the islets are 

 almost all placed on the eastern side of the northern 

 atolls, and on the south-eastern side of the southern 

 atolls. That the formation of the islets is due to 

 detritus thrown up from the outside, as in the ordinary 

 manner, and not from the interior of the lagoons, may, 

 I think, be safely inferred from several considerations 

 which it is hardly worth while to detail. As the easterly 

 winds are not the strongest, their action probably is 

 aided by some prevailing swell or current. 



