500 



Mr Gardiner, The Coral Reefs of 



[Mar. 7, 



Group. The following list of the coral islands with their heights 

 and depths will make this still clearer : 





The lagoons inside all the barrier reefs in the above list are 

 singularly free from shoals; this, probably, is largely due to the 

 fine mud, caused by the solution of the limestone, killing the 

 corals by which such shoals are mainly formed, and, as it coats the 

 bottom, allowing few firm foundations for the larvae to fix them- 

 selves upon. 



The elevation of Thikombia-i-ra, which was probably the last 

 upheaved of the limestone islands to the east of Fiji, raised with 

 the reef a long bank to the east. On this side there is a fringing 

 reef about 3 miles broad, while round the greater part of the 

 island no reef has as yet been formed. On the bank a number of 

 isolated reefs are now growing up and it appears as if a barrier 

 reef is being formed. A long time, however, would be required 

 for this to reach the surface, and so in the meantime a fringing 

 reef has been formed, and, the depths being favourable, is pushing 

 its growth rapidly over the whole bank, perhaps to form ultimately 

 a barrier reef in quite a different manner. 



According to Dana 1 " an atoll-reef without green islets, or with 



1 Loc. cit., p. 356. 



