518 



PROFESSOR J. W. GREGORY. 



G. The Bulu-Vulu to Huambo. 



South of the old mission-house at Saccanjimba is a plateau of about 2 square 

 miles, covered by black soil, but I was unable to find any exposure of the rock which 

 gave rise to it. On the slope southward to the river the first rock observed was a 

 gneiss with a strike of 102°, and up the slope on the southern side the strike is 122°. 

 At the next stream, half an hour to the north of Gordon's Store, the rocks were 

 quartz-schist and saccharoidal quartzite, striking 127° and dipping south-west. 



(l) The Bulu-Vulu. — Gordon's Store is on the track from Katanga to Benguella, 

 and on the north-western edge of a great tract of level, grass-covered plains known 

 as the Bulu-Vulu. They extend eastward beyond Belmont, the chief settlement in 

 Bilie, which was established by the famous Portuguese trader Silva Porto. 



I made an excursion off our main route to examine the nature of this Bulu-Vulu. 

 It consists of black-soil plains. The soil is composed of quartz grains blackened by 

 organic matter. 



Gullies on the side of this plateau show that the sand is about 



sw. 



BtAu Vulu 



C<Lm6enf* J*^ &mp 



HE. 



...•V- uvjri 7 " 



Fig. 7. 



4 feet in thickness, and beneath it is a layer of yellow clay containing loose fragments 

 of a white quartzite. The yellow clay serves as an excellent paint, and is probably 

 due to the leaching of iron from the quartzite. Beneath this clay is often a gravel, 

 which is composed of quartzite and ironstone, and, on the north-western edge of the 

 Bulu-Vulu, rests on gneiss. The Bulu-Vulu may result from the decomposition of a 

 widespread sheet of quartzite ; but it is probably due to a sheet of younger sandstone — 

 the Bihe sandstone, which is the local representative of the Lubilash beds. Coal is 

 said to occur under the Bulu-Vulu ; I could learn, however, of no adequate grounds 

 for this report, which may be based only on the blackness of the soil and on occasional 

 occurrences of a peaty material ; but the existence of coal w T ould strengthen the 

 reference of the Bulu-Vulu sands to the Lubilash beds. 



The relations of the Bulu-Vulu and of the adjacent rocks are shown in the 

 section (fig. 7). 



(2) Cambenge and the Umbal. — Descending from the Bulu-Vulu we passed first 

 a quartzite and ironstone gravel, which probably represents the decomposed outcrop 

 of the Bulu-Vulu sandstones. This layer rests upon gneiss. The quartzites occur 

 beside the stream, which is one of the upper tributaries of the Umbal. On the 

 plateau near Cambenge Station is a handsome pink, granulitic, quartz-felspar gneiss ; 

 it is succeeded to the north of Correo's Stores at Cambenge by a blue diorite-gneiss 



