THE GEOLOGICAL HISTORY OF THE COLONY 435 



feet of tillite at Kimberley, for instance, were probably 

 formed during the deposition of the uppermost part of 

 the southern tillite. 



The tillite in the south of the Colony was probably 

 formed entirely under water; into the sand and mud 

 there being deposited the pebbles and boulders, many 

 of them well scratched, were dropped by the floating ice 

 that drifted southwards from the shore. 



No remains of animals have been found in the tillite, 

 so the question of the nature of the water in which it 

 was deposited is unsettled. The absence of marine 

 shells is certainly presumptive evidence against the 

 water having been a part of the ocean, for it is well 

 known that a cold climate is by no means unfavourable 

 to marine life at the present day. Many genera of 

 molluscs and crustaceans are represented by unusually 

 large species in arctic and antarctic regions. In any 

 case the absence of fossils is difficult to explain, but 

 considering also that only land or fresh-water forms 

 have been found in the beds underlying and overlying 

 the tillite it is more probable that the water in the 

 Dwyka basin was fresh than salt. The absence through- 

 out the Karroo formation of deposits of rock salt, 

 gypsum or other substances that accumulate in inland 

 basins with no outlet is good evidence that the basin in 

 which the rocks were formed was kept fresh by the 

 continual escape of the water. 



We may picture to ourselves a great inland water 

 basin, with one or more outlets to the ocean towards 

 the south, and covering what is now the southern part 



of the Cape Colony, at the commencement of the 



28* 



