XV COAST RANGES 217 



of the Wainikoro River and the Mount Thurston Range.— 

 Of this region I know very little. The highest peak according 

 to the chart has an elevation of about 1,600 feet. Some 

 indication of the character of the inland rocks may be obtained 

 from that of those exposed on the coast between Nakarambo 

 and Waimotu where, as observed on page 208, grey pyroxene- 

 andesites, coarse in texture and almost holo-crystalline in structure, 

 protrude through agglomerates of the same materials. When on 

 the way from Ngelemumu to Wainikoro I crossed the extreme 

 northern prolongation of this range where the elevation above the 

 sea is only 700 feet. Non-calcareous basic tuff-clays occur on the 

 slopes ; but the deeper-seated rocks, judging from an exposure on 

 the east side, are dark grey altered pyroxene-andesites penetrated 

 by fine cracks filled with a mosaic of quartz and having a specific 

 gravity of 27. On the summit I found a gritty sandstone-like rock, 

 of which my specimen has been lost. In a stream at the foot of 

 the east slope occur small blocks of b^lsaltic andesite probably 

 derived from a dyke. The region of acid rocks, such as quartz- 

 porphyries, oligoclase-trachytes, &c., is not entered until about two 

 miles south-west of Wainikoro. 



The Coast Ranges and Sea-border, between Mbuthai- 



SAU AND THAWARO OR MBEKANA BAY 



We have in this region the mountains and hills at the coast and 

 the low-lying plains inland. This feature of the north side of 

 Vanua Levu is very remarkable. For some sixty miles, that is to 

 say, for more than half the length of the island, between the 

 mouth of the river Ndreketi and Thawaro or Mbekana Bay, Vanua 

 Levu possesses this character. The coast ranges west of Lam- 

 basa, where basic rocks evidently prevail, have been referred to on 

 pages 13s, 136. Those east of the Lambasa mountains as far as 

 Thawaro Bay will be dealt with here; and instead of basic we 

 find acid rocks, such as quartz-porphyries akin to the rhyolites, 

 oligoclase-trachytes, pumice-tuffs, &c. 



The sea-border is here characterised not by a continuous range 

 running parallel to the coast, as in the case of the district between 

 Nanduri and the Ndreketi River, but by a number of separate 

 groups of hills and lesser mountains, separated by deep gaps or 

 valleys which are occupied by tidal rivers and extensive mangrove 

 swamps. The tide ascends these rivers into the plains behind the 

 coast ranges, so that a depression of only 30 feet would convert 



