CHAPTER X. 



GEOLOGY. 



rpHE difficulty of African geology can only be 

 understood by those who have unsuccessfully 

 attempted to understand it, amongst whom I 

 include myself. There is not a single clue to the 

 structure of the continent as a whole so far as my 

 experience has gone ; and I am afraid that the 

 whole of my work has been more in the nature of 

 contradicting other people's theories and adding 

 to the number of inconvenient and irreconcilable 

 facts, than of constructing any plausible sugges- 

 tions. 



Thus in Egypt one finds in a section from 

 Alexandria to the Second Cataract, first lime- 

 stone hillocks, then nummulitic limestones, and 

 then the Nubian sandstones. In West Africa I 

 found an Archaean series near the coast, and 

 subsequently a rock at about 3,000 to 4,000 feet, 

 which somewhat reminded me of the Nubian 

 sandstones. 



In South Africa, after passing the complicated 



12 163 



