THE TANGANYIKA PROBLEM. 



characters of primary fresh-water stocks — Palreontological record of the appear- 

 ance of the primary fresh-water stocks — This, synchronous with other geological 

 phenomena — The universal distribution of the primary fresh-water stock inex- 

 plicable on the assumption of migration — Want of evidence of any capacity for 

 migration — The zoological facts seem to suggest a former difference in the sea 

 itself — Increase of salt in fresh-water shown to be prejudical to certain 

 animals — Effects of this as exhibited in Lake Shirwa — Artificial production of 

 similar results — Experiments of Loeb, Herbst, and others, show that a change 

 in the character of sea-water may produce variation — General evidence for a 

 continually increasing salinity in the sea — The action of this in the production 

 of modern fresh-water faunas — Present view of the nature of fresh-water 

 faunas .............. 



CHAPTER III. 



THE PHYSIOGRAPHICAL FEATURES OF THE AFRICAN INTERIOR. 

 THE GREAT CENTRAL RANGE. 



Necessity of a knowledge of the topography of the Great Lake Region — Our views 

 are changing with respect to the interior — Recent observations lend no support 

 to the older conceptions which sprang from Murchison's erroneous hypothesis 

 respecting African stability — Demonstration of the existence of a Great 

 Central Range a chief result of the Tanganyika expeditions — Characters of 

 this range — Scott Elliot's early appreciation of its existence — The east and west 

 drainage slopes — The existence of deep valleys (Eurycolpic folds) parallel with 

 the range — These, rock valleys, not formed by ice — Disturbance of old aqueous 

 deposits, caused by the formation of the Great Central Range — Character of 

 the Great Central Range in the region of Nyassa — Absence of true volcanoes 

 along the ridges of the range — Wide effects of the formation of the Great Cen- 

 tral Range — The "griiben" of Suess ; Eurycolpic folds — Characters of these 

 folds in the region of Nyassa — Characters of the folds in the region of Tan- 

 ganyika — Disturbance of the valleys and ridges in relation to the Great 

 Central Range ............ 31 



CHAPTER IV. 



SUPERFICIAL GEOLOGY OF THE REGION OF THE GREAT 

 AFRICAN LAKES. 



Evidence respecting the nature of the central African region before the formation 

 of the Great Central Range — Continuation of the movements which have pro- 

 duced the Great Central Range — Recent discovery of vast aqueous deposits in 

 the interior — Value of these in ascertaining the past history of the continent — 

 Method of treating the subject in relation to the observations made during the 

 Tanganyika expeditions — Vastness of the regions to be considered — Character 

 of the southern section of the region of the Great African Lakes — Nature of 



