XI THE KOROTINI RANGE 159 



Descending the northern side of the range I followed the steep 

 slopes down to 1,000 feet above the sea. A rubbly doleritic olivine- 

 basalt, semi-ophitic, and assigned to the same genus (33), prevailed 

 ■on the way ; and it is probable that a waterfall with a drop of 

 50 feet or more that is situated on these slopes indicates a large 

 intrusive mass of this rock. During the rest of the descent to 

 Vandrani, which lies in a valley at the foot of the range, and is 

 elevated about 300 feet above the sea, basic agglomerates and 

 palagonite-tuffs, together with deposits intermediate in character, 

 were exposed at the surface. At times a semi-ophitic doleritic 

 basalt similar to those displayed above, but without olivine, oc- 

 curred in position. The blocks in the agglomerates are formed of 

 a compact semi-vitreous basaltic rock, and are sometimes vesicular. 

 At one place the palagonite-tuffs exhibited signs of alteration, being 

 traversed by small fissures not over a third of an inch broad (5 to 

 8 mm.), and filled with a zeolite behaving like natrolite. 



In some cliffs by the river at Vandrani are displayed fine and 

 coarse non-calcareous palagonite-tuffs, bedded and dipping about 

 15° N. by W. They are penetrated by cracks, 5 mm. in breadth, 

 which are filled with chalcedony. These tuffs are evidently in part 

 derived from acid as well as from basic rocks, though mainly from 

 the latter ; and they show other alteration-characters. At the 

 Tiouth of the Vandrani valley there are exposed in the river-bed 

 :oarse palagonite-tuff sandstones containing a little lime, and 

 probably a few tests of foraminifera. 



Reference may here be made to the mountain of Ravi-koro 

 vhich, when seen from the north-east, rises up as a partially inde- 

 )endent peak, with a broad base and a conical truncated summit, 

 immediately west of the track followed in the descent from the 

 ; ummit of the range to Vandrani. It is probably not much under 

 : !,ooo feet in height, and exhibits bare precipitous cliff-faces on the 

 north side. It would be worthy of the attention of the future 

 i nvestigator. 



Recurring to the principal features of the range between Mbale- 

 j ibale and Vandrani, one may remark the extensive occurrence of 

 basic agglomerates and tuffs on both slopes, the prevalence of 



< livine-basalts, the frequency of the semi-vitreous and vitreous or 

 3 ather pitchstone condition of these rocks, and their semi-ophitic 



< haracter, especially on the summit and north slopes. From the 

 \ esicular structure of the rocks of the Koro-tini Bluff and from the 



< haracter of its tuffs and agglomerates, it is to be inferred that 

 t ley are the direct products of eruptions, probably in shallow seas. 



