472 Mr Gardiner, The Coral Reefs of [Mar. 7, 



are all under 350 feet, but those seen on Tuvutha and Vatu 

 Vara are over 800, and those of Naiau, Mango, Vanua Vatu 

 and Vanua Mbalavu are about 600. The absence of terraces is 

 remarkable, as it is extremely characteristic of Tonga, the Solomon 

 Islands, and Cuba. One is driven from this to the conclusion that 

 elevation must have taken place for each island in one act to its 

 present level, or the undermining and wearing away must have 

 been still greater than I am prepared to admit: Thikombia-i-ra 

 is, I believe, an exception, as its terraces looked very distinct, 

 and it is in no way atoll-shaped ; it stands also quite apart from 

 all the other islands. 



Necessarily each island need not have been elevated to the 

 same height, but two areas of elevation are clearly defined to the 

 north and south of Lakemba, the elevation of which may have 

 been a separate act, as its limestone is nowhere thicker than 

 100 feet, and represents a barrier reef. Northwards the elevation 

 was about 700 feet, but southwards from Vanua Vatu to Ongea 

 about 400. The latter is very regular in neighbouring islands, 

 but yet great variety at the present day exists in the nature of 

 their living reefs. By Kambara and Wangava they are narrow 

 and fringing, while off Fulanga the reef is broader with a boat 

 channel. Namuka and Vanua Vatu have reefs both barrier and 

 fringing, while round the two Ongea the reef is typically barrier, but 

 slightly fringes the southern island. Round the Yangasa Group the 

 reef is a widely separated barrier with a lagoon 20 fathoms deep. 



None of the pure limestone islands show their foundations, but 

 at Kambara the volcanic rock has welled out over the coral. This 

 island is otherwise typical of what a raised atoll might be supposed 

 to be, and here the nature of its foundation is exposed ; it is also 

 shown in the same way in three places on Vanua Mbalavu. The 

 volcanic nature of the rock on Ono, Vatoa, Mothe, Lakemba, 

 Thithia, Kanathea, and Yathata proves that there must have 

 existed here a broad range of volcanic hills. The whole group of 

 Fiji stands on a plateau of 1500 fathoms, so that their general 

 height to bring them within the limits of coral growth, assuming 

 it at 50 fathoms, must have been over 8700 feet! Between the 

 islands and reefs of this range the depths are not usually marked 

 on the charts : in the Nanuka passage, and between Vatoa and 

 Ono there are a few soundings of considerably less than 1000 

 fathoms. There thus seems to be here a special ridge at 1000 

 fathoms, which possibly may be continuous southward with that 

 on which the Minerva reefs are situated. If so, it joins the line 

 of volcanic activity from New Zealand to the Kermadec Islands, 

 which then branches at the Minerva reefs through Tonga to 

 Samoa, and through the Lau Group of Fiji 1 . 

 1 Vide Lister, loc. tit. p. 595. 



