234 THE GEOLOGY OF BRITISH EAST AFRICA part hi 



information, from which their existence is inferred, is unsatis- 

 factory. But of the existence of such a series there is now no 

 doubt. 



We have thus rapidly summarised the main outlines of the 

 geology of British East Africa. The first striking fact is that, 

 with the exception of a narrow strip upon its margin, the 

 country has never been below the sea. The second point of 

 interest is that the history of the region may be divided into 

 three stages : — 



1. The Archean, represented by igneous and schistose 

 rocks. 



2. The long uneventful interval between the Archean and 

 the Cretaceous. 



3. The subsequent complex series of volcanic eruptions 

 and earth-movements. 



This threefold division reminds us at once of the geology 

 of Brazil and of the southern or peninsular half of India, the 

 histories of which agree very closely with that of East Africa. 

 Thus Southern India consists in the main of gneiss and schists ; 

 upon these occur slates and quartzites (the Cuddapah series) 

 much like those of Karagwe. Then comes a long recordless 

 interval, until, in the Cretaceous, plateau eruptions poured out 

 the 200,000 square miles of Deccan Traps, which correspond 

 with the Kaptian series of Africa. After this the scarp of the 

 Western Ghats was probably formed in the same manner as 

 the scarp of the East African plateau. 



The main interest in the geology of British East Africa 

 is in the last of the three periods. This is complex, for it 

 has three parallel histories — those of the volcanoes, of the 

 lakes, and of the earth -movements. In the previous sketch 

 the effort has been made to combine the three narratives into 

 a continuous story ; but the following table shows them 

 independently : — 



[Table 



