﻿Vol. 6 I.] GEOLOGY OF PART OF THE CONGO FREE STATE. 653 



The Nile Territory (Lado Enclave). 



The basin of the Uelle rises gradually up to the watershed 

 dividing- it from the Kile Basin. At its highest point, which is 

 situated a little farther east than Aba, I came across granitoid 

 gneiss. 



Travelling eastward, up to Loka, patches of gneiss are the 

 only rocks in evidence. At Loka, Mount Gumbali, the highest 

 summit of that neighbourhood, reaches an altitude of 5730 feet 

 above sea-level, being 2450 feet above the surrounding country, and 

 the mountain appears to be wholly built up of granite. It is a 

 mountain with a double summit, of which the lower dome, under 

 the influence of weathering, has peeled off near the top in such a 

 way that, seen from Loka, the shape bears some resemblance to 

 a Roman helmet. 



Going in a southerly direction from Loka, the ground is found to 

 become considerably lower, and, at the crossing of the valleys of the 



Fig. 3. — Section parallel to that slioivn in fig. 2 (p. 652), but 

 w farther north, at Mudi. Eb 



[For explanation, see fig. 2, p. 652.] 



Kidju and the Kaia whole series of gneisses and metamorphic 

 rocks are met with, striking nearly due north and south, and 

 undulating with the country. 



Towards Kodjokadji the country is again higher and more 

 granitic in character, and forms a small plateau bordering on the 

 Nile. This plateau breaks into the Nile Yalley by two succes- 

 sive ridges, ranging north-west and south-east, built of highly- 

 crystalline rocks. The Nile Valley all along these ridges 

 narrows down extremely, and the river is interrupted by innumerable 

 rapids. 



In the valley itself, and near the Nile, the predominant rock is 

 gneiss, exposed in nearly-vertical beds. These, as we proceed 

 from east to west, are seen to alter their dip gradually into a more 

 horizontal position, until, approaching the summit of the ridges, 

 we find some quartzites and mica-schists dipping south- 

 westward at an angle of only 25° to 30°. This formation strikes 

 40° W. of N., averaging nearly north-west and south-east, and is 

 both regular and persistent. 



The valley of the Nile along this mountainous ridge has an 

 altitude of between 1800 and 2000 feet (above sea-level). 



Lower down the Nile, towards Eedjaf, several dykes of a species 



