﻿648 ME. G. E. J. PRETJMOMT ON THE GEOLOGY OE THE [Aug. I905, 



direction, by half a mile in width. Its elevation above the neigh- 

 bouring plain is nearly 600 feet. The plains surrounding these 

 hills are thickly clothed in underwoods of brush and scrub, but the 

 greater part of the mountains is bare of all vegetation, as generally 

 are most granitic peaks. 



The formation is a strongly-foliated gneiss, the laminae of 

 which show much contortion and crumpling. Bands of quartz, of 

 black mica, and others of more felspathic nature, alternate suc- 

 cessively one with the other in many places. The strike of this 

 formation varies between 30° and 50° W. of N., but may be said 

 to average a north-westerly and south-easterly direction. At the 

 top of Mount Bundukwa the dip is 80° to 85° south-westward, but 

 at the foot of a cliff on the north side, and nearer the level of 

 the plain, we found the beds less steeply inclined, dipping there 

 only 55° to 60° south-westward. 



The rocks found at Mount Bundukwa offer an element of interest, 

 in having enclosed within them large crystals of kyanite. Occa- 

 sionally, garnets and tourmaline were also noted in the rocks. 



Mount Yambili, situated next to Mount Nangango, and 

 about 2| miles east of Mount Bundukwa, is identically of the same 

 nature as the preceding, but on its western side we found at the 

 foot of the hill blocks of granite formed of large elements, 

 and from those blocks specimens of mica in slabs 4 to 5 inches 

 square were obtained. 



The plains surrounding the hills are mostly made up of alluvium, 

 with here and there small rocky outcrops of a character analogous 

 to those observed on the bigger hills. 



Bomokandi River— Mount Tena. 



Going up the Bomokandi River from Poko to Rungu, granitic 

 rocks are seen at two rapids situated between these two localities, 

 but no strike can be noted. 



East of Rungu the road follows a swampy tract of land on the 

 northern bank of the river. About 20 miles west of Mount Tena, 

 granite appears before one reaches the mountainous group. Here, 

 Mount Tena forms a prominent feature of the landscape, rising to 

 a height of 4900 feet above sea-level. The mass of the mountain 

 is about 3 miles in length from north-west to south-east, and a 

 mile in width. Its northern extremity is prolonged north-west- 

 ward by a series of hills, of lesser elevation, towards and up to 

 Mount Negbada. Mount Tena at its crest forms a succession of 

 three rocky summits trending in the axial north-westerly and south- 

 easterly direction, the central summit being slightly the highest. 

 At the foot of Mount Tena iron-bearing rocks only are in evidence, 

 and the whole mountain is a mass of iron-ore. Near 

 the top appears an enormous outcrop of massive haematite, with 

 magnetite disposed in beds striking north and south, and dip- 

 ping westward about '80°. On the east side the slope is precipitous, 

 and presents the aspect of a cliff formed by the outcrops of iron-ore. 



