42 



THE COKAL REEFS OF THE MALDIVES. 



Bastion at Male. 



either as breakwaters or bastions, which conceal the structure of the island, 

 but it is identical with that of many similar islands throughout the group. 

 Advantage has been taken of a narrow reef flat on the northwest face 

 of the island to build a breakwater enclosing a small harbor with suffi- 

 cient depth to shelter native boats of 

 considerable size. Tbe southern face 

 of Male Island is also flanked on the 

 outer edge of the somewhat dished 

 reef flat by a belt of angular coral 

 blocks more or less eroded and weath- 

 ered, forming a low wall. 



From our anchorage off Male we 

 could see to the northwest two of the 

 remarkable light green rings which 

 are so characteristic a feature of the 

 coral physiognomy of the Maldives (PI. 4). These rings and their endless 

 modifications, due to their age, their size, their position on the primary or 

 secondary plateaus of the group, their exposure to the prevailing winds, their 

 depth from the surface, give us the key to the structure of the coral reefs of 

 the Maldives. 1 



The only structures to which they can at all be compared are the small 

 atolls known as " boilers " in the Bermudas, and which flank the south shore 

 near Sinkey Bay. 2 But the diminutive atolls of the Bermudas owe their 

 origin to other causes than those which have built the rings of the Maldives. 

 The latter are atolls, and no matter what their size may be, they are built 

 up by corals, while in the Bermudas these small atolls are really only large 

 pot-holes, the outer rim of which is protected by the incessant growth of 

 Serpulaa and Alga3 on the edge. All the faros of which the nucleus con- 

 sists of elevated reef rock planed down to the level of the sea have 



1 Darwin * considers the ringlike structure to be contingent on breaches into the lagoon being wide 

 and numerous, thus placing the inner side of the rings in the same condition with the outside of an 

 ordinary atoll exposed to the sea. Hence the margins have grown vigorously outwards, while they 

 have grown upwards during the subsidence to which, according to Darwin, the whole archipelago has 

 been subjected, subsidence and upward growth converting the central space of each little reef into 

 a small lagoon. 



2 A. Agassiz, Bull. M. C. Z., Vol. XXVI., No. 2, Pis. 2-2-26. 



* Loc. cit., p. 141. 



