CONTRIBUTIONS TO THE GEOLOGY OF BENGUELLA. 513 



North of the Queve River, between it and the track, are hills of schistose 

 quartzite, which is intruded by a boss of diorite-porphyry in which the base has been 

 altered to a granular, hornfelsed mosaic. The edge of this rock is a blue hornfelsed 

 quartz-porphyry. From this point the route continues over a quartzite gravel. On 

 the northern bank of the Lumbanda or Lumbwambwa River are the Ambussa Hills, 

 which trend to a little south of east ; they consist of schistose quartzite with a well- 

 developed flaser structure and numerous quartz veins. Some bands are schistose- 

 conglomerates and perhaps crush-conglomerates. The rock strikes to 87°. Near 

 the western end of this ridge are the ruins of a prehistoric stone fort, whence the 

 view southward across the plain includes the hill of Bavi or Kubave, the northern 

 face of which has a fine cirque-like hollow. 



Just north of the western end of the Ambussa Hills is an exposure of granite, 

 unusually rich in biotite. This rock disappears beneath the schistose quartzites, 

 which extend thence to Bailundo ; they are well exposed about the Culele River, 

 where the rock is coarse and saccharoidal (No. 151 ) ; and as similar rocks are exposed 

 where we crossed the line of the Lumbanganda Mountains, they are probably also 

 composed of the schistose and saccharoidal quartzites. 



The hill beside the fort at Bailundo consists of coarse pink gneiss (No. 152) of 

 which the strike is to a little north of east. The rock, no doubt, belongs to* the 

 same series of gneisses as those of the Lengwe Gorge ; but it represents the pinkish 

 granitoid gneisses of the Laxford type of the Lewisian Series, and not the common 

 biotite-gneiss. 



From Bailundo we turned north-eastward towards Ochilesa and soon left the 

 Bailundo gneiss. It is succeeded by a granulitic quartzite that weathers into sand- 

 stone, and is often covered by a litter of ironstone conglomerate. The route passed 

 to the west of the Ueia Mountains, some spurs of which have the rough craggy 

 weathering of the schistose quartzites. About 3 miles from Bailundo is a lateritic 

 ironstone conglomerate, including blocks of granulitic quartzite. The quartzite 

 beneath this conglomerate contains angular fragments of felspar, and resembles some 

 of the non-schistose Dalradian Quartzites of the Scottish Highlands. 



From 4 to 5 miles north-east of Bailundo the track passes over an area of a 

 rich, red chocolate soil, which continues in patches for about 3 miles. They are 

 succeeded by the ordinary yellow loamy soil. Where the rock that gives rise to 

 this chocolate soil could be found it always proved to be igneous, and generally an 

 olivine-dolerite. Coarse biotite-gneiss reappears about 10 miles north-east of 

 Bailundo, near one of the last streams which pass through the Culele to the Cuivo. 

 This gneiss is of the Lewisian type ; it contains bands 1 inch thick, which are pink 

 owing to the abundant felspar, and 4-inch veins of pegmatite. 



Fourteen miles from Bailundo the higher ground is covered by a gray, light, 

 loamy soil due to the decomposition of the schistose quartzites ; but on the floor of 

 the gullies and on the lower land to the south and east of our camp were bosses of 



