222 RAPIDS — BIRDS. 



admirably, and are always in good humour ; they 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 compass, which, when spread over the much 

 larger surfaces 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 difference between the 

 rivers in the north and south must be sufficiently 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 peace- 

 fully on their nests above the roaring torrent. An ibis * 

 had perched her home on the end of a stump. Her loud, 

 harsh scream of " Wa-wa-wa," and the piping of the fish- 

 hawk, are sounds which can never be forgotten by any 



* The Hag! dash, Latham ; or Tantaltis capensis of Lich. 



