THE TANGANYIKA PROBLEM. 113 



result that I could find no difference whatever, either in 

 its dampness or its consistency, at least, any that it was 

 possible to correlate with the different plants that grew 

 upon it. In the soil under a great clump of acacias 

 there was as little moisture, and it was of the same 

 consistency as that upon which there was nothing but a 

 scanty covering of grass ; neither can difference of climate 

 or rainfall be invoked. Park-lands occur in the Semliki 

 valley where it is very wet, and also on the Albert Edward 

 plains where it is very dry. 



From general observations, however, it soon becomes 

 apparent that park-lands are by no means distributed 

 haphazard over the surface of the country ; they never 

 occur, for example, on hill sides or upon rocky ground. 

 They are invariably found upon alluvial plains like those 

 formed by rivers, or upon old lake deposits ; that is, they 

 only occur on flats made up either of blown sand or 

 of ground of aqueous origin ; but although they are 

 definitely related to flats of the above sorts, this fact at 

 first sight perhaps makes the whole matter more perplexing- 

 still, for such flats are by no means invariably covered 

 with parks. Thus there are wide districts on the Semliki 

 plains which are covered with heavy forest, and there are 

 similar alluvial areas covered with heavy forest only along 

 the Zambesi river, and indeed in many places elsewhere. 

 What can it be, then, which in some places inaugurates 

 and maintains a natural African park ? This question is a 

 great puzzle, and the answer to it is not at all apparent on 

 the surface of things. I obtained, however, what there is 

 every reason to believe is a clue to the whole matter, during 

 my visit to the Albert Nyanza. On that journey I 

 descended from the western slopes of the Mountains of the 

 Moon on to the plains of the great central valley, which I 



