1872.] THE VICTORIA FALLS. 219 



solution : this lime was deposited in vast lakes, which are 

 now covered with calcareous tufa. One enormous fresh-water 

 lake, in which probably sported the Dyconodon, was let off 

 when the remarkable rent was made in the basalt which now 

 constitutes the Victoria Falls. Another seems to have gone 

 to the sea when a similar fissure was made at the falls of the 

 Orange Eiver. It is in this calcareous tufa alone that fossil 

 animal remains have yet been found. There are no marine 

 limestones except in friths which the elevation of the west 

 .and east coasts have placed far inland in the Coanza and 

 Soniauli country, and these contain the same shells as now 

 live in the adjacent seas. 



Antecedently to the river system, which seems to have 

 been a great southern Nile flowing from the sources of the 

 Zambesi away south to the Orange River, there existed a 

 state of fluvial action of greater activity than any we see 

 now : it produced prodigious beds of well-rounded shingle 

 and gravel. It is impossible to form an idea of their extent. 

 The Loangwa flows through the bed of an ancient lake, 

 whose banks are sixty feet thick, of well-rounded shingle. 

 The Zambesi flows above the Kebrabasa, through great beds 

 of the same formation, and generally they are of hard 

 crystalline rocks ; and it is impossible to conjecture what 

 the condition of the country was when the large pot-holes 

 were formed up the hillsides, and the prodigious attrition 

 that rounded the shingle was going on. The land does not 

 seem to have been submerged, because marine limestones 

 (save in the exceptional cases noted) are wanting ; and 

 torrents cutting across the ancient river beds reveal fresh- 

 water shells identical with those that now inhabit its fresh 

 waters. The calcareous tufa seems to be the most recent 

 rock formed. At the point of junction of the great southern 

 prehistoric Nile with an ancient fresh-water lake near 

 Buchap, and a few miles from Likatlong, a mound was formed 

 in an eddy caused by some conical lias towards the cast bank 

 of this rent within its bed, and the dead animals were floated 



