168 ME. G. W. LAMPLTTGH ON THE [May I907, 



Another result of the slow recession of the gorge is evident in the 

 relation of the tributaries to the main river. On the north, these 

 feeders radiate from the Batoka Upland, while on the south they 

 mostly hold a north-easterly course at a low angle to that of the 

 Zambezi. Above the Palls, the tributaries flow to the Zambezi in 

 channels sunk very slightly below the general level of the plateau 

 and make their confluence in open estuary-like inlets ; but below 

 the Palls they are precipitated, before reaching the main river, into 

 gloomy chasms that lead into the Batoka Gorge ; and these become 

 longer in proportion to their increasing distance from the Palls. 

 Thus the country bordering the main gorge is slashed by pre- 

 cipitous ravines that stretch back farther and farther into the 

 plateau as we go eastward, so that a great wedge of exceedingly 

 broken country, very difficult to traverse, has been produced, 

 expanding eastward on both sides of the river from its apex at the 

 Palls. Where the influence of the rejuvenated drainage has been 

 longest established, certain of the larger tributary rivers, as for 

 example the Matetsi and the Deka, have likewise had time to 

 widen out the lower reaches of their valleys, but all sooner or later 

 entrench themselves within precipitous canons when traced back 

 towards the plateau. The same rule appears to apply also far to the 

 eastward of the country examined. Thus the Kafue Biver, a great 

 tributary which joins the Zambezi from the north some 220 miles 

 below the mouth of the Deka, is described as having a comparatively 

 sluggish and navigable course for 20 miles back from its confluence ; 

 but at the head of this low- level stretch the river tumbles in a 

 succession of foaming cataracts for 2 miles through a rugged 

 gorge which leads up to the high plateau ; and before reaching this 

 sharp descent, in which it loses over 1000 feet of altitude, 1 the 

 stream has flowed placidly in a broad shallow channel over the 

 undulating plateau for several hundred miles. 



This tearing-down of the high plains at their edges and the 

 gradual lengthening of the low-level channels is the ruling factor 

 in the physiographical development of the Zambezi basin everywhere 

 below the Victoria Palls. Therefore this region may be separated 

 naturally into two sharply-marked divisions: — (1) The unbroken 

 plateau with mature drainage-features ; and (2) the region of 

 rejuvenated drainage. In ground-plan the boundary between these 

 divisions forms a succession of gradually deepening loops around 

 the tributary streams, and, as already mentioned, steadily recedes 

 from the main river on both sides as it goes eastward. 



Between the network of gorges that characterizes the second 

 division there are irregular patches of flat ground, representing 

 fragments of the old plateau ; but this country is almost everywhere 

 rugged and stony from the ready transport of the surface-products 

 of weathering into tbe gulches by the torrential rains. Where 



1 A. St. H. Gibbons, ' Africa from South to North through Marotseland ' 

 (London, 1904) vol. i. pp. 65-66 ; andC. Hardiog, ' In Remotest Barotseland' 

 (London, 1905) pp. 319-20. 



