BY W. G. WOOLNOUGH. 451 



Korobalavu Range, is a very interesting district drained chiefly 

 by the Waiqa, a fairly important tributary entering the Waini- 

 mala north of Nacau. Crossing the saddle from Naivucini on 

 the road leading west to Botenaulu and Narokorokoyawa, the 

 track rises over the tuffs, agglomerates, and lavas of Nacau until 

 an elevation of about 675 feet above the Waiuimala is reached, 

 and then drops to the valley of the AVaiqa. At the summit of 

 the pass there occur great angular boulders of a very remarkable 

 diorite porphyry. In section it is found that this rock is some- 

 what quartzose and ver}' rich in hypersthene, so that it shows 

 relationship to the more acid members of the charnockite group. 

 The western slope is over decomposed rocks of a similar character 

 in situ. The remarkable nature of the rock was not recognised 

 in the field, and its relationships to its neighbours are therefore 

 obscure and must be left for a future expedition to determine. 

 The level of the Waiqa River is 575 feet below the crest of the 

 ridge. The stream occupies a fairly broad open valle}', the most 

 open of any stream of its size which I have sesen in the island. 



Granite puts in its appearance at a point between Tavua and 

 Nuku; as above explained, the dividing line between this and 

 the charnockite-like rock is not determinate. Some distance 

 west of Tavua the granite is strongly gneissic in character, and 

 associated with this we have a narrow belt of very schistose I'ock 

 whose relationships are concealed bj'^ lack of outcrops. 



For some distance west of Nuku the track crosses alluvials, 

 but about two miles west of the town decomposed granite in situ 

 is met with. This rises in high hills which form the eastern 

 boundary of the Upper Wainimala Valley. At the crest of the 

 ridge which separates the Waiqa Valley from that of the Waitabu, 

 the road-level is about 1480 feet above the sea; at the highest 

 point of the range it is at least 200 feet higher than this. In 

 the valley of the Waitabu undecoraposed granite is met with in 

 situ, but some distance to the west the rock is apparently slaty; 

 exposures are, however, very poor. 



It will be seen that the main direction of the Waiqa is about 

 W. and E., this course being imposed upon it by ranges of 



