SOME PROBLEMS OF RESEARCH ^ 



more sudden change in the African's activity than any other factor, 

 may fit in with the scheme, and in Uganda, times of food shortage, 

 due to failure of the short rains in the preceding years, appear to be 

 similarly periodic. 



Perhaps more important than the periodicity of general climate 

 are the less obvious changes in the minute climate surrounding a 

 single animal or plant. Little enough is known about this subject 

 yet, but it is certain that the temperature and humidity surround- 

 ing a human being, for example, alter to an astonishing degree in 

 the course of a day, and this must have great effect on his physical 

 and mental vigour. Similarly in vegetation; work at Amani has 

 shown how the air in a few cubic feet around a coffee bush or over 

 a patch of earth changes to a degree which would never be 

 imagined from the study of meteorological instruments in screened 

 cases. 



Passing to the changes in water-supply due to man's interven- 

 tion, the environment in many arid parts is being altered to an 

 extent which must influence human customs and social behaviour; 

 for example, in the northern Emirates of Nigeria the discovery of 

 a water table at one hundred to one hundred and fifty feet below 

 the surface has led to the boring of numerous wells, so that areas 

 of pasturage which were formerly available only during wet 

 seasons can now be centres of human activity throughout the 

 year. In Tanganyika, similar activity will soon lead to the settle- 

 ment of peoples in areas of pasturage, which formerly were given 

 over to tsetse fly. Such changes influence also the original habi- 

 tations of the people involved, because the old pastures, which 

 are to-day being impoverished by overstocking, can be allowed to 

 rest during the all-important dry season, and may therefore return 

 to their original value. The general result of such activity is to 

 cause the settlement of wandering peoples on definite areas of 

 land, a change which is a principal object of most of those respon- 

 sible for agriculture in Africa. 



The soils are determined by the structure of the land and under- 

 lying rocks, the water-supply, especially rainfall, and also by vege- 

 tation. The soil-vegetation unit as a controlling factor in environ- 

 ment is only now being recognized by scientists, but it is significant 

 that the Africans themselves still know more about it than we, for 



