Reports and Proceedings—Geological Society of London. 139° 
Gorge, which was investigated by the author in 1905, under the 
auspices of the British Association. 
The physical features of the country fall into two well-marked 
divisions :—(1) The unbroken plateau, a portion of the great central 
basin-plain of South Africa. (2) The area of rejuvenated drainage, 
a wedge-shaped tract having its apex at the Victoria Falls, due to the: 
lowering of the trunk-drainage by the erosion of the deeply cut gorge.. 
The following rock-systems are described :— 
. Kalahari Sands, Chalcedonic Quartzite, and other surface-deposits. 
. Flagey Sandstone of Boomka. 
. Batoka Basalts. 
. Wankie Sandstones and Coal-measures (= Matobola Beds and ? Escarpment. 
Grits of Molyneux). 
1. Fundamental Complex of Metamorphic and Igneous Rocks. 
bo oo He Or 
(1) The Fundamental Complex was studied im sti only at one 
point, near the Wankie Coal-mine. The position of its outcrop north 
of the Zambezi is inferred from the character of the river-borne 
detritus in some of the stream-beds. 
(2) The Wankie Series consists of massive sandstones and pebbly 
erits, containing boulders near the base, with intermediate flaggy 
sandstones and shales with coal-seams. ‘This series is abruptly 
truncated on the south-east side, along the Deka River, bya great 
fault which brings in the Batoka Basalts; but reasons are given for 
supposing that beds of similar character reappear at the northern 
margin of the Basalts, north of the Zambezi, beyond the district 
examined, 
The Deka Fault is described in some detail, and its important 
influence upon the structure of the country is discussed. It is 
suggested that the ‘ Sijarira Quartzites’ of Molyneux, of the country 
farther to the north-east, may be only the indurated and contorted 
sandstones that accompany this great fault. 
(3) The Batoka Basalts were found to extend unbrokenly from the 
Victoria Falls eastward to the mouth of the Deka, and southward to: 
the edge of the Kalahari Desert; and it is shown that they also cover 
a very wide area to the southward and westward of the region 
traversed. They consist of a succession of massive laya-flows and 
flow-breccias ; no intercalated sediments were found in the districts 
examined, nor was any eruptive centre discovered. Some curious 
structures observed in basalts are described ; and it is remarked that 
the zigzagging character of the stream-gorges below the Victoria Falls. 
is due to the differential erosion along the strong joints and fault- 
planes in these rocks, under the alternating conditions of wet and dry 
seasons. 
The age of the Basalts is discussed, and it is considered that they 
are probably Mesozoic, and may date back to the later stages of the 
period of volcanic activity represented by the Stormberg Beds of the 
more southerly part of the continent. 
(4) Some limited patches of Flaggy Sandstone, etc., seen near the 
head of the Deka Basin, appear to represent sediments newer than 
the Basalts, and may be equivalent to part of the Forest Sandstone of 
Mr. A. J. C. Molyneux and Mr. F, P. Mennell. 
