GEOLOGY 87 



Africa presents a boundless field of research. Already it has sup- 

 plied important evidence on the history of evolution; in particular, 

 mention may be made of the Transvaal Museum and the researches 

 of its Director, Dr. R. Broom, during the past thirty-five years, on 

 the fossil reptiles of the Karroo. In his book (1932) Dr. Broom 

 remarks (p. 309): 'If any intensive collecting is done in the next 

 twenty or fifty years we shall know not three hundred and fifty 

 species of South African fossil reptiles, but 20,000 to 50,000 species, 

 and we may then not only be able to trace the lines of evolution, 

 but perhaps be able to see what has been the guiding or compel- 

 ling force behind it all.' Farther north, the rich beds of fossil 

 reptiles in Nyasaland and southern Tanganyika have attracted 

 several collecting expeditions from the British Museum, Cambridge 

 University, and elsewhere. The results have contributed greatly 

 to knowledge of the diversity of reptilian life in the mesozoic era, 

 and to that important link in the chain of vertebrate ancestry 

 when reptiles were changing into mammals. 



The study of fossils leads up to the origin of man and the geo- 

 logical contribution which Africa has already made to knowledge, 

 and the important discoveries made by Professor R. Dart, Dr. R. 

 Broom, Dr. L. S. B. Leakey, and others are outlined in Chapter 

 XVIII. The study of ancient man has involved that of stone tools, 

 which are widely used in working out the stratigraphy of recent 

 geological deposits. This in itself may have practical bearings: for 

 instance, Wayland's work on stone tools in Uganda demonstrated 

 the reversal of some of the principal rivers, a result which has been 

 of great importance to those prospecting for alluvial tin. 



Man's history, stone tools, changes in hydrology, tectonics of 

 rift valleys, aquatic fauna and numerous other subjects apparently 

 of academic interest, all contribute to the understanding of the 

 late geological history of Africa, of pluvial periods and arid periods. 

 Understanding of these is of importance in appreciating conditions 

 of aridity in the future, when climatic change may yet take place. 

 Many such problems are concentrated in the region of the great 

 lakes, and the geological survey of Uganda has paid special atten- 

 tion to them (Wayland 1933-4, 19342-5 i934t> and 1935, Groves 

 1932). The subject is considered further in Chapter IV. 



