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, Cyprasa, 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 '5-1*5 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 



