18 AFRICAN GAME ANIMALS 



"falling of the keystone" of the great lava arch. Pre- 

 vious to this other masses of lava poured from the volcanic 

 centres of Kenia, Elgon, and Kilimanjaro, and these were 

 later augmented greatly by the Rift Valley flow. Elgon 

 and Kilimanjaro, both of which are crowned by well-pre- 

 served craters, are the most recent volcanic sources of this 

 lava flow, while Kenia, being much older, has been denuded 

 of its crater by weathering and is now capped by a pre- 

 cipitous peak representing the old volcanic neck. The 

 Rift Valley exhibits a score of smaller and still more recent 

 volcanoes; indeed, it is of such recent formation that its 

 many independent drainage systems have not been estab- 

 lished long enough to allow erosion to unite them into a 

 common system. The "falling of the keystone" which 

 established the Rift Valley has been of quite recent date. 

 The Ruwenzori Range, although in close proximity to dis- 

 tricts covered by recent lava flows, is a series of gneissic 

 or crystalline peaks formed by faulting and is without any 

 evidence of volcanic structure. 



The only rocks not of eruptive or igneous origin are a 

 narrow belt of corals and sandstones bordering the coast 

 and extending inland from the seashore to a distance of 

 approximately fifty miles. The newest or most recent of 

 such formations is the coral limestone forming the coast 

 plain, which is of Pleistocene age. Dipping under the coral 

 formation we find a series of shales of Jurassic age, which is 

 exposed for several miles in width near the station of Chan- 

 gamwe. Beyond Changamwe successive exposures of yel- 

 lowish sandstone are encountered between Mazeras, Mari- 

 akani, and Maji ya Chumvi stations, and beyond these a 

 series of grits as far inland as the Taru Hills. The sand- 



