Yol. 6^ 



GEOLOGY OF THE ZAMBEZI BASIN. 



189 



overhung by picturesque buttresses and isolated pinnacles, carved 

 by the Zambezi in its search for the easiest passage when entrapped 

 among the transverse trenches. Generally, where the river breaks 

 away from these trenches, they are continued as deep rain-gullies 

 into both walls of the canon ; or they form the subsidiary canons of 

 tributary streams, into the waters of which the Zambezi itself may 

 penetrate for some distance at times of high flood. 1 These features 

 are admirably illustrated in the broad floor of the gorge at the 

 Tshimamba Cataracts, shown in the sketch-plan below (fig. 5) and 



Pig. 5. — Sketch-plan of the Batolca Gorge at the Tshimamba 

 Cataracts, showing ivater-jUled inlets and steep gullies prolonging 

 the east-and-ivest reaches of the Zambezi beyond its angular 

 bends. (Approximate scale : 2 inches — 1 mile.) 



The water-area at the dry season is shown in black, and the dotted line marks 

 the space covered at floods. 



in PI. XIII, where the river, at low water, twice forms a X in 

 breaking away from its east-to-west trenches. At this place I 

 found it not easy to determine whether the placid water of the 

 straight reach on the south came into it from the east or from the 

 west, even when I had traversed the flood-flat and stood at its 

 rectangular termination. 



As a typical example of the effect of these structures on the 



1 From Chapman's description it would appear that the gorge of the Gwai 

 inust also be of this character at its mouth. 



