Vol. 70.] MIOCENE OF THE VICTORIA STANZA, ETC. 139 



schist at its base. It is noteworthy that the amphibolite of Nira 

 occurs exactly on the prolonged line of strike of the schist. This 

 chloritic schist perhaps represents the strongly-sheared selvage of a 

 zone of amphibolites lying north of the broad zone of gneiss that 

 occurs on the south of the Kuja Plain (see p. 140). 



At Kikongo, the junction of the Miocene beds with its basement- 

 floor is greatly obscured by down wash and murrain ; but, on the 

 eastern side (in the Kitama Valley), a boss about 100 yards in 

 -diameter of the underlying igneous basement crops up. The rock 

 is a highly-altered and decomposed horn bleu de-porphyrite 

 with massive jointing, and probably represents an ancient intrusive 

 mass ; the microscope reveals no evidence of any pressure-meta- 

 morphism. In this case, and in several others, it was impossible 

 to obtain fresh and unaltered rock-specimens, owing to the great 

 depth to which alteration has taken place. 



South of Kikongo the lower slopes immediately below the deposits 

 consist only of quartz-ironstone breccia, and the underlying rock was 

 not revealed until I reached a point 2 miles away to the south, where 

 a very much weathered and chloritized amphibolite rises out of its 

 thick mantle of ironstone-breccia. It is not unlike a much-altered 

 and coarser variety of the amphibolite of Nira. The rock is but 

 slightly schistose (dipping 67° south-westwards), and shows the 

 north-westerly and south-easterly strike which is characteristic of 

 the metamorphic area east of the Victoria Nyanza. It has weathered 

 deeply to a rich orange-brown soil with some quartz, exactly in the 

 manner of the other amphibolites. 



The next hill on the east, separated b} r a broad shallow valley, 

 only shows the usual quartz-ironstone breccia, but it is traversed 

 by a reef (striking north-east and south-west) of brownish quartz, 

 10 feet thick, veined with white quartz. The neighbouring hills on 

 the east and south-east are similar in appearance and composition. 



South of Nira and Kachuku the wide alluvial plain of the 

 Kuja Valley extends for 5 miles, unbroken in relief excepting 

 for nests of termites, 10 to 15 feet high. Towards the lake-shore 

 the brown sandy soil occurs in gentle ridges, probably marking old 

 storm-ridges. Very often the soil is black between the ridges, 

 Avith occasional angular pieces of basalt derived from the regur 

 which occurs near the shore between Nira and Karungu. The 

 Miocene deposits probably extended originally for a considerable 

 distance southwards over the site of this alluvial plain. The 

 Kuja flows now along the southern border of the plain ; in the 

 dry season its banks rise about 20 feet above the river-level, and 

 consist of homogeneous brown alluvium without any shells. In 

 one place (below the last ford), a layer of black alluvium (derived 

 from regur from the north) is intercalated midway in the brown 

 river-mud ; but there is no sign of shaly lamination. 



Almost immediately south of the river is a wide zone of grey 

 gneiss of granitic appearance. The outlying hills, such as Naka- 

 nero (altitude, 4040 feet) and Angaohi (4006 feet), rise out of river- 

 alluvium to a height of about 300 feet above it, and were obviously 



