iM 
‘ 
AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 111 
The formation of the great barrier reef of the southern shores of Viti 
Levu is due to causes very similar to those which have given its present 
physiognomy to the northern coast of Cuba between Nuevitas and 
Matanzas. Along those parts of the island where denudation and 
erosion proceed rapidly owing to the soft character of the shore rocks, 
very extensive flats have been formed like those south of Ovalau. When 
the reef barrier flats have been eroded from a harder base, like volcanic 
rocks, the flats are less prominent; they are somewhat more extensive 
where the old elevated coralliferous limestone formed the shore hills; or 
the reef flats may disappear altogether when the harder volcanic rocks 
have been only little affected by erosion or denudation. From the na- 
ture of the negro-heads scattered upon the reef flats it is generally a 
simple matter to ascertain the character of the base of the reef flats of 
an atoll or of a barrier reef. 
: 
| 
4 
MOTURIKI CHANNEL. 
The islands of Ovalau and of Moturiki (Plate 7), which are enclosed 
by the northeastern extremity of the Viti Levu barrier reef, are both of 
ENTRANCE TO LEVUKA. 
volcanic formation, a kind of conglomerate or breccia similar to that 
found at Mbengha, Tavuki in Kandavu, and in many other places in 
Fiji. The highest peak of Ovalau rises to a height of nearly 2,100 feet, 
