ORIGIN OF THE A TOLL 



229 



while the subsidence was still in progress, if the sinking were 

 not beyond a certain rate. 



A cessation or diminution of subsidence, in the case of the 

 barrier reef about a high island, might result in its becoming 

 covered with verdure like the finished atoll. 



All the features of atolls harmonize completely with this view 

 of their origin. In form they are as various and irregular as 

 the outlines of barrier reefs. Compare Angau of the Feejees, 

 with Tari-tari of the Gilbert Group (p. 133) ; Nairai or Moala 

 with Tarawa ; Nanuku with Maiana or Apam.ama. The resem- 

 blance is close. In the same manner we might find the many 

 forms of lagoon reefs represented among barrier reefs. 



SECTION ILLUSTRATING THE ORIGIN OF ATOLLS. 



AVe observe, also, that the configurations are such as would 

 be derived from land of various shapes of outline, whether a 

 narrow mountain ridge (as in Taputeouea, one of the Gilbert 

 Islands), or wide areas of irregular slopes and mountain ranges. 

 Among the groups of high islands, we observe that abrupt 

 shores may occasion the absence of a reef on one side, as on 

 Moala ; and a like interruption is found among coral islands. 

 Many of the passages through the reefs may be thus accounted 

 for. 



The fact that the submerged reef is often much prolonged 

 from the capes or points of a coral island, accords well with 



