232 THE GEOLOGY OF BRITISH EAST AFRICA part hi 



that rose upon it were cut off from their lower courses, and 

 were reversed in direction. They flowed to the centre of the 

 depressed region, where they collected as a great lake. The 

 second of the series of faults which made the main Rift Valley 

 probably happened at the same time, and increased its size and 

 depth, while others enlarged that of the Albert Nyanza. The 

 climate of Africa must then have been less arid than at present. 

 The snowfields of Kenya were certainly larger, and great 

 glaciers flowed from these for several thousand feet down the 

 flanks of the mountain.^ The heavier rainfall helped the 

 growth of lakes, which extended over places that are now sandy 

 deserts. This period may therefore be called the " Naivashan," 

 from the Masai word for lake. The first of these extinct lakes 

 which we crossed was in the Kedong basin, where we entered 

 the Rift Valley. There on the face of the Kikuyu scarp, 

 which forms the eastern wall of the valley, are the terraces of 

 an ancient lake. This I propose to name Lake Suess, after 

 Prof Edward Suess of Vienna, whose Das Antlitz der Erde 1 

 venture to regard as the most original and suggestive geological 

 work that has appeared since Lyell's Pi'inciples. The terraces 

 of this lake are perfectly visible when seen from a little distance, 

 though often difficult to trace in the jungle that covers the face 

 of the cliff. The terraces were formed by the conservative 

 action of the water, which protected the part of the valley wall 

 below its surface, while that above it was exposed to the wind 

 and rain. The cliff was therefore driven back, while the debris 

 which fell from it accumulated on the floor of the lake. The 

 terraces show that Lake Suess at one time reached the height 

 of 400 feet above the present floor of the valley, along which it 

 extended for a considerable distance. 



It is probable that the outlet of the lake was to the north, 

 whence a river flowed along the Rift Valley, through the basins 

 of Baringo and Basso Narok. There it was joined by a 

 river, the Turquell, which, as we shall see in another chapter, 

 probably received the drainage of the basins of the Victoria 

 and Albert Nyanzas, through the valley occupied by the 

 Salisbury or Musaniya lake-chain." 



1 The evidence for this is stated at length in a paper on ' ' The Glacial Geology of 

 Mount Kenya," Quart. lour. Geol. Soc. vol. 1. (1894), pp. 515-530. 



- For topographical information which supports this idea I am indebted to Major 

 Williams, R.A. 



