XI THE KOROTINI RANGE 163 



opal. The basic glass, of which they are formed, shows incipient 

 crystals, and begins to fuse in an ordinary flame. One specimen 

 obtained here is a doleritic basaltic andesite, slightly ophitic and 

 containing a fair amount of residual glass.^ However, the vitreous 

 and scoriaceous character of most of the rocks on the summit is 

 very remarkable. (Similar rocks occur on the top of Mount 

 Thambeyu where the slopes of the mountain are covered with 

 submarine tuffs and agglomerates.) There is a precipitous descent 

 on the north side of the range to Sueni at its foot, massive basaltic 

 andesites being exposed at first, whilst basic tuffs and agglomerates 

 are displayed lower down. 



The special features of this traverse of the range are the 

 alteration of the tuffs and massive rocks between Nukumbolo 

 and the lower southern slopes, the variation in character of the 

 basic rocks in the upper southern slopes, the occurrence of vitreous 

 vesicular and scoriaceous rocks on the summit, and the restriction 

 of the ordinary basic agglomerates and tuffs to the northern 

 slopes. Any attempt on my part to explain the structure of this 

 part of the range from the data here given would be futile without 

 comparing them with those obtained from other parts of the range. 

 It will be subsequently pointed out that the difficulties will be in 

 part removed if it is assumed that the submarine palagonite-tuffs 

 and agglomerates, that so often cover the flanks of the mountains 

 to their summits, have been in this case largely stripped off by 

 the denuding agencies. 



(S) The Sueni Valley. — My acquaintance with the extreme 

 eastern part of the Koro-tini Range is restricted to the descent of 

 the picturesque valley from Sueni to Koro-utari. It is occupied 

 by a tributary of the Lambasa River, and is bounded on the east 

 side by the lofty slopes of the main range, and to the westward by 

 a mountainous spur that projects far into the Lambasa plains. 

 Sueni lies by the river-side in the midst of mountains which rise 

 steeply on most sides to heights of 2,000 feet and over, and often 

 display precipitous bare faces apparently of volcanic agglomerates. 

 Numerous waterfalls may be observed on their flanks, which, as in 

 other localities, doubtless indicate the occurrence of large intrusive 

 dykes. Sueni is situated about 300 feet above the sea, the descent 

 to Koro-utari at the mouth of the valley, a distance of 3 to 4 miles 

 in a direct line, being about 1 50 feet. 



The river as it flows down the valley from Sueni to Koro-utari 

 traverses a region of basic agglomerates and agglomerate-tuffs. 



1 Referred to genus 9, sub-genus B, of the augite-andesites. 



M 2 



