258 RAPIDS.— BIRDS. 



leap into the water without the least hesitation, to save the 

 canoe from being caught by eddies or dashed against the rocks. 

 Many parts were now quite shallow, and it required great address 

 and power in balancing themselves to keep the vessel free from 

 rocks, which lay just beneath the surface. We might have got 

 deeper water in the middle, but the boatmen always keep near 

 the banks, on account of danger from the hippopotami. But, 

 though we might have had deeper water farther out, I believe 

 that no part of the rapids is very deep. The river is spread 

 out more than a mile, and the water flows rapidly over the rocky 

 bottom. The portions only three hundred yards wide are very 

 deep, and contain large volumes of flowing water in narrow com- 

 pass, which, when spread over the much larger surface at the 

 rapids, must be shallow. Still, remembering that this was the 

 end of the dry season, when such rivers as the Orange do not 

 even contain a fifth part of the water of the Chobe, the differ- 

 ence between the rivers of the north and south must be suffi- 

 ciently obvious. 



The rapids are caused by rocks of dark brown trap, or of 

 hardened sandstone, stretching across the stream. In some 

 places they form miles of flat rocky bottom, with islets covered 

 with trees. At the cataracts noted in the map, the fall is from 

 four to six feet, and, in guiding up the canoe, the stem goes 

 under the water, and takes in a quantity before it can attain 

 the higher level. We lost many of our biscuits in the ascent 

 through this. 



These rocks are covered with a small, hard aquatic plant, 

 which, when the surface is exposed, becomes dry and crisp, 

 crackling under the foot as if it contained much stony matter in 

 its tissue. It probably assists in disintegrating the rocks ; for, in 

 parts so high as not to be much exposed to the action of the 

 water or the influence of the plant, the rocks are covered with a 

 thin black glaze. 



In passing along under the overhanging trees of the banks, 

 we often saw the pretty turtle-doves sitting peacefully on their 

 nests above the roaring torrent. An ibis* had perched her 

 home on the end of a stump. Her loud, harsh scream of 



* The Hagidash, Latham ; or Tantalus capcnsis of Lich. 



