ii8 A NATURALIST IN THE PACIFIC chap. 



Nandronandranu, but on account of the wood no view was ob- 

 tainable. In this locality between 1,300 and 1,400 feet soapy 

 palagonitic clay-rocks and coarser palagonite-tuffs are displayed 

 on the surface. No organic remains are to be noticed in the 

 specimens collected here, but they are much affected by hydration. 

 Judging from the fossiliferous character of similar deposits over a 

 large part of the island, it is highly probable that these tuffs and 

 clays are also submarine. 



Afterwards a descent was made to an undulating region about 

 I J miles across and elevated between 750^ and 850 feet. The 

 blocks there displayed on the surface are composed of a dark 

 rather compact augite-andesite with a specific gravity of 275 (see 

 genus 13) and of an altered greenish aphanitic augite-andesite 

 with a specific gravity of 2-59 in which calcite occurs as an 

 alteration product (genus 16). Aphanitic rocks of this character 

 as shown below, are very prevalent in the north-west and north 

 parts of the Nandronandranu district, but are not usually 

 altered. 



(2) The North-west Part of the Nandronandranu 

 District. — The best route to follow here is to take the track from 

 Nambuna to Ndrawa. After crossing the upper portion of the 

 Wainunu table-land one reaches the headwaters of the Ndavutu 

 River and then ascends the watershed between the Ndreketi and 

 Wainunu river-systems, reaching Savulu, about 1,050 feet above the 

 sea, where a solitary house marks the site of an old mountain town. 

 This region is much cut up in deep valleys usually 200 to 300 feet 

 deep, which are occupied by affluents of the Ndrawa branch of the 

 Ndreketi, flowing north. The valley of the main affluents is from 

 400 to 500 feet in depth ; and this constant ascent and descent of 

 steep and often slippery valley sides makes the journey very 

 tedious. 



At Savulu one stands within the Nandronandranu district. 

 Behind lies the Wainunu table-land with its olivine basalts ; but 

 here aphanitic augite-andesites prevail and extend to Ndrawa and 

 beyond. They are exposed in position in the stream-courses and 

 furnish most of the blocks and pebbles found in the bed of the 

 main Ndrawa River for miles down its course towards the sea. 

 They are dark, compact, and non-porphyritic rocks and are all re- 

 ferred to genus] 16 of the augite-andesites as described on page 279. 

 They vary, however, in certain features, as in the specific gravity, 

 the amount of glass, &c. The residual glass is, however, usually 

 small ; but in a stream-course east of Savulu I found in position at 



