172 A NATURALIST IN MID-AFRICA. 



Another curious feature of Ruwenzori which 

 seems to be much doubted by geologists is 

 whether there is any evidence of glaciation. 

 Personally I am inclined to think that three of 

 the valleys have once been occupied by glaciers 

 to a level of about 5,200 feet — that is to say, 7 

 or 8 miles in one case. 



Two of these valleys, the Mubuku and Nyam- 

 wamba, have a broad open U -shape in transverse 

 section ; another, the Butagu, has the following 

 appearance (Fig. 28). 



Now all the other valleys on Ruwenzori which 

 I saw have the typical V-shape of erosion valleys 

 in a tropical rainy climate. 



The shape of these three valleys is, it seems 

 to me, very much what one would expect in them 

 if they had once been filled by a glacier. 



In the Nyamwamba there is a very curious 

 ridge, apparently consisting of small boulders 

 and stones, which runs obliquely across the 

 valley ; the section and plan in Fig. 28 will make 

 its arrangement clearer. I thought this might 

 be of the nature of a moraine, although the Hat 

 bed of the valley continues some distance below 

 this point. 



Another point which may be taken as in favour 

 of glaciation is the occurrence of numerous large 

 rounded boulders having all the appearance of 

 roches moutonndes; some of these are 10 feet 

 high. 



