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 

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

 coarse 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 

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

 pendent peak, with a broad base and a conical truncated summit, 

 immediately west of the track followed in the descent from the 

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

 2,000 feet in height, and exhibits bare precipitous cliff-faces on the 

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

 investigator. 



Recurring to the principal features of the range between Mbale- 

 mbale and Vandrani, one may remark the extensive occurrence of 

 basic agglomerates and tuffs on both slopes, the prevalence of 

 olivine-basalts, the frequency of the semi-vitreous and vitreous or 

 rather pitchstone condition of these rocks, and their semi-ophitic 

 character, especially on the summit and north slopes. From the 

 vesicular structure of the rocks of the Koro-tini Bluff and from the 

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

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



