TYATER AS A GEOLOGICAL AGENT. 189 



cannibals. It speaks well for the security felt in the country, 

 and the rare appearance of beasts of prey, that all these com- 

 pounds scattered in the wood are free from any disturbance, 

 and the isolated huts, which have boards placed against the 

 entrance, thus forming a door, need them chiefly for protec- 

 tion from the cool air of night. 



Every step towards the south and west unfolded new 

 pictures ; splendid woodland scenery, swamps and jungles, 

 where the overpowering beauty of the vegetable world concealed 

 the difficulty of travel, zeribas and villages, clearings for new 

 crops, banana plantations and yam-fields, streams and brooklets 

 on every side. The country rose more and more when we had 

 passed through Negunda, where Mbaga, Gambari's brother, lives. 

 Blocks of granite cropped out on the numerous hills, which must 

 be regarded as the remains of ranges that have been washed 

 away, and the paths down to the brooks gradually became steeper. 

 It is curious to march through a narrow strip of steppe land, 

 and become all of a sudden aware of a dark row of what appear 

 to be dwarf trees lying on the ground, then, coming nearer, to 

 find a descent of from sixty to a hundred feet, and the dwarfs 

 changed into very giants, for they are rooted in the depths below, 

 while only their tops are visible from the level of the plain. 

 The frequent landslips also deserve mention. The farther one 

 pushes in Monbuttu towards the west, that is, in the direction 

 in which the country slopes, the deeper grows the stratum of 

 reddish-brown mould which overlies the clay and the bare rock ; 

 the more luxuriant, too, becomes the vegetation covering the 

 ground, and the more rapidly proceeds the formation of humus 

 produced by its decay. As this loose soil is, moreover, soaked 

 with water throughout the year, small causes, such as the fall 

 of a tree, are capable of producing a gap, and once a point of 

 less resistance has been created, the erosive action of the water 

 flowing towards it from all directions accomplishes the rest. If 

 the water has once succeeded in forcing its way out, the original 

 hole becomes transformed into a ravine, which grows wider and 

 wider as the process of disintegration proceeds, and deeper and 

 deeper, through the excavating action of the water flowing along 

 its bottom. When vegetation has taken possession of the 

 slopes, we have one of those innumerable threads of water with 



