150 A NATURALIST IN THE PACIFIC CHAP. 



concretionary pitchstone, showing little nodular concretions of the 

 size of filberts, and having the microscopical characters of " vario- 

 lite," as described on page 313. This is the only locality of this 

 rock that is known to me. 



My acquaintance with the tract of Nakambuta is, however, 

 very imperfect. But it is apparent that in the pitchstones and in 

 the semi-vitreous basic rocks, sometimes vesicular and amygda- 

 loidal, we get a nearer approach to the products of subaerial 

 eruptions than is to be observed in most other portions of the 

 island. The examination of the Nakambuta peak by some future 

 investigator will bring to light some interesting facts concerning 

 this region. It is not unlikely that during a late stage of the 

 emergence of this region Nakambuta and the other peaks around 

 protruded as active vents above the surface of a shallow sea, at the 

 bottom of which the products of their eruptions accumulated. 



THE VALLEY OF THE NDREKE-NI-WAI AND ITS 

 TRIBUTARIES 



Ndreke-ni-wai, which signifies " the hollow of the water," is the 

 name of a broad tidal estuary, opening into Savu-savu Bay, which 

 is formed by the union, about half a mile above its mouth, of two 

 rivers, the Mbale-mbale River flowing from the north-west past a 

 village of that name, and the Vatu-kawa River, the largest, flowing 

 from the eastward, which I have also named after a village on its 

 banks. The valleys of these two rivers are separated by a moun- 

 tainous dividing-ridge connected by a saddle with the main range. 

 Its highest peaks rise to 2,100 feet above the sea, the elevation of 

 this " divide " rapidly decreasing as it approaches the coast, where, 

 within a mile of the beach, it terminates in some low hills 200 or 

 300 feet in height. 



It may be observed here that a mouth of the river was 

 originally situated 700 or 800 yards to the west of its present 

 site. This old mouth is now represented by a lagoon communi- 

 cating with the Mbale-mbale River above, but closed by the sand- 

 mound of the beach at its lower end, which, however, is occa- 

 sionally broken through when the rivers are in flood. This lagoon 

 is shown in the view facing page 153. 



The valley of the Mbale-mbale River, which is much the 

 smaller of the two rivers, is bounded on the north by the pre- 

 cipitous slopes of the Koro-tini Range, which rise to over 2,000 

 feet, and on the south and west by the lofty Va-lili Range. The 



