184 DIRECTION OF GLACIATION 



proportion of sandy calcareous material and is intensely 

 hard. The inclusions are seldom glaciated. 



Where the Dwyka first appears on the coast of Pondo- 

 land, near St. John's, it is faulted down against the 

 Table Mountain beds that form the mountain through 

 which the St. John's River flows just before reaching 

 the sea. To the north-east of St. John's, along the 

 western flank of the high plateau of Table Mountain 

 sandstone that borders the coast, the tillite rests directly 

 upon the sandstone ; no part of the Bokkeveld or Witte- 

 berg series has been left between the two formations, 

 which stand in the same relation to one another as in 

 Calvinia, north of the Oorlog's Kloof River. In Natal 

 the tillite rests upon an uneven surface of the Table 

 Mountain sandstone and Pre-Cape rocks. The rock in 

 Pondoland has precisely the same general appearance 

 as in Calvinia and the Western Karroo, but there is not 

 quite the same assemblage of rocks among the boulders. 



A considerable amount of information regarding the 

 source and movements of the glaciers or ice-sheet which 

 produced the glacial deposits can be gathered from the 

 direction of the striae on the roches moutonnees and from 

 the characters of the various boulders found in the 

 tillite. 



From Vryburg to beyond Prieska the general direc- 

 tion of movement appears to have been towards the 

 south-west, but there was a marked deviation to the 

 south and even a little east of south in the neighbourhood 

 of Beer Vlei as well as many minor local deflections. The 

 inferred course of the ice-sheet is indicated in Fig. 12. 



