IV MOUNT SESALEKA 53 



The Coast between Naivaka and Koro-ni-solo at the 



FOOT OF the north SLOPE OF THE SESALEKA RANGE. — 

 Basaltic andesites, and olivine-basalts of the Naivaka type occur 

 on this coast. A rock of more acid character, light grey and much 

 altered, is exposed at the surface where the track crosses the head- 

 land projecting into Ruku-ruku Bay. It is one of the propylites 

 referred to in my description of the second genus of the augite- 

 andesites (p. 269). The felspars of the groundmass give the small 

 extinctions of oligoclase ; and in this respect it differs from the 

 other augite-andesites. Besides the altered plagioclase phenocrysts 

 there is much microporphyritic augite but slightly changed. 

 Calcitic and other alteration products occur in the interstitial 

 glass. 



Mount Sesaleka. — This is the name of the highest peak, 

 1,370 feet, of a remarkable ridge-shaped range, which is very 

 precipitous on the east and north-east sides, where there is a sheer 

 drop apparently of 500 or 600 feet, whilst on the other sides the 

 slope is more gradual, especially on the north where there is a 

 gentle descent to the sea. The actual summit is bare, rocky, and 

 narrow. There is a curious native legend relating to a pond on 

 the top of this hill. From what Mr. Wittstock tells me, it seems 

 probable that there is a spring near the summit. Close to the top 

 are the remains of an old " koro-ni-valu '' or war-town ; whilst 

 numbers of shells of species of Cardium, Cypr^a, and Strombus, 

 such as would be used for food, lie about. Many years ago there 

 was a prolonged siege of this stronghold, which is referred to here 

 as indicating that the defenders had some independent water- 

 supply. 



In ascending from Koro-vatu on the west side basic agglomer- 

 ates and agglomerate-tuffs were found exposed as far as half-way 

 up. In the upper half occurred at first fine-grained calcareous 

 tuffs, bedded and dipping gently down the slope, composed of 

 palagonite-debris, mineral fragments and calcitic material and 

 displaying a few macroscopic tests of foraminifera. These tuffs 

 became non-calcareous and coarser as one approached the summit. 

 A specimen obtained from the top is coarse-grained, being composed 

 of fragments of basic glass, usually palagonitised, much augite, a 

 little plagioclase and fresh olivine, but no tests of foraminifera, the 

 size of the fragments being usually "S-rS mm. Massive rocks 

 were rarely exposed on this side ; but half-way up in a stream 

 course I came upon an exposure of a porphyritic olivine-basalt 

 containing a fair amount of devitrified interstitial glass. Its 



