AGASSIZ: FIJI ISLANDS AND COliAL IlEEFS. 



89 



into the fringing reef flats. There are two important passes on the 

 southeastern face,^ the Tongan aud the American Passages. The latter 

 is a narrow tongue of the ocean cutting into the eastern face of the 

 slope of the atoll with over 100 fathoms in depth, and opens into a 

 wide deep submarine valley extending westward into the heart of the 

 eastern lagoon. The Tongan Pass is a similar, but much shallower and 

 shorter, tongue of the ocean. On the western side the Andiwathe Pass 



NORTHEAST POINT OF VANCA MBALAVU. 



leads into a long deep lagoon formed by the outer reef and the west 

 coast of Vanua Mbalavu. This western lagoon is connected on the 

 south with the principal lagoon to the east of the island by a narrow 

 and shallower passage over the fringing reef north of Malatta Island, 

 and on the north by the passages leading round ]S'"gillangillali Island into 

 the passage of that name opening through the northwestern horn of the 



VANCA MBALAVU, LOOKING WEST. 



outer reef, and which extends, gradually widening eastward, along the 

 northern shore of Vanua Mbalavu until it opens beyond Avea Island 

 into the large eastern lagoon. Along the northern face of the lagoon 

 are situated Avea and Sovu Islands. About two miles from the 



1 An exception to the usual rule, that entrances to lagoons are on the lee side. 



