CHAPTER III 



GEOLOGY 



INTRODUCTION 



'tn every country in which a geological survey has been started 

 A the economic development of the mineral resources has been 

 its real object and justification; scientific results are either acces- 

 sory or contributory to this object, or they are by-products. But 

 if the development of the mineral resources is the main object, the 

 preparation of a geological map of the country is the chief method 

 employed by a survey to reach this end.' This quotation from 

 Sir Thomas Holland (1934) gives in a nutshell the application of 

 geology to economic progress. The importance of the geological 

 map cannot be over-emphasized, but geological surveys and maps 

 are dependent in their turn on good topographical maps. A sig- 

 nificant illustration of this fact is the development of the U.S. 

 Geological Survey which eventually had to become responsible 

 for all topographical, though not geodetic, surveying. 



Although the revealing of mineral resources has been the main 

 object of geology in Africa up to now, much of the work done by 

 geological surveys is of more immediate interest to other depart- 

 ments as Sir Albert Kitson (1929) has shown. The characters of 

 many soils, especially the sedentary types, depend in large degree 

 on the nature of the underlying rocks. 



In locating underground water-supplies geologists have been 

 able to indicate large artesian basins, local basins, and waterlogged 

 superficial deposits. Some geological departments actually under- 

 take boring and well-sinking operations, and during the recent 

 depression, the work of several of them was reduced almost 

 entirely to problems of water-supply. In connection with the 

 planning of public works, geological surveys are of value in dis- 



