214 THE GEOLOGY OF BRITISH EAST AFRICA part hi 



" geologically unique in the long conservation of ancient terres- 

 trial conditions. This inference is further supported by the 

 concomitant absence throughout the larger portion of all this 

 vast area, i.e. south of the Equator, of any of those volcanic 

 rocks which are so often associated with oscillations of the 

 terra firina." 



For a while every addition to our knowledge of the geology 

 of the equatorial region seemed to confirm the truth of this 

 hypothesis by showing that it consisted of one solid block of 

 gneiss and schist. These rocks were proved by Speke to 

 form the basis of the central basin ; they were found to the 

 east of this by Thornton (1862), Gustav Rose (1863), and 

 Roth (1864) ; to the north and north-west by Baker, Schwein- 

 furth, Emin, and Junker ; to the south by Livingstone, Burton, 

 and Speke ; and to the west, in later times, by Wolf and 

 Wissmann.-^ 



That part of Murchison's theory, which affirms that Central 

 Africa has never been below the level of the sea, is still in 

 harmony with the known facts, for no deposits of marine 

 origin have as yet been found in the interior. The sedimentary 

 beds, found by Speke and Stanley to the west of the Victoria 

 Nyanza, and recently described by Cornet in the Upper Congo, 

 have yielded no fossils to indicate the conditions under which 

 they were formed. It was hoped, however, that the deposits of 

 the long series of lakes would contain the bones of the land 

 animals, that lived on the plains around them ; just as the South 

 American -pampas have supplied those of giant sloths, the 

 United States prairies those of horned reptiles, the Karroo of 



^ The five chief contributions to our knowledge of the geology of British East Africa 

 are those of Thornton (1862), Beyrich (1878), and Sadebeck (1879) for the stratigraphy 

 of the coast region ; of Miigge (1886) and the joint memoirs of von Hohnel, Rosiwal, 

 Toula, and Suess (1892) for the petrography and physical geography of the interior. 

 Much incidental light is thrown on the country by the works of Blanford (1870) and 

 Baldacci (1891), and of Ebert (1887) and Cornet (1894), of whom the two first describe 

 Abyssinia, and the two last German East Africa and the Upper Congo. The petro- 

 graphical studies on rocks from Kilima Njaro by Rose (1863), Roth (1864), Bonney 

 (1886), Hyland (1889), and Tenne (1890) must also be noticed. Information as to the 

 range of the various rocks, used in the construction of the map, occurs in the records of 

 most travellers who have written on the country, especially in those of Speke, Baker, 

 Stanley, Stuhlmann, Baumann, and Scott Elliot for the Nyanza region ; of Hildebrandt, 

 Thomson, Piggott, Lugard, and Hobley for the eastern half of the country. Gibson's 

 short account {Proc. Brit. Assoc. 1893, PP- 75^1 759) of his traverse from Mombasa 

 to Uganda, so far as it goes, is admirable. It did not, however, seem advisable to 

 burden the present chapter with references to this literature, for it is only in the case of 

 the Archean rocks and the coast deposits that previous results have been incorporated. 

 Reference to Suess's important memoir is given in the Introduction. 



