126 GEOLOGY OF THE NEIGHBOURHOOD OF STELLENP.OSCH. 



Star reaches south-east into Jonker's Hoek. Another arm points 

 eastward up Hels Hoogte. A third arm is represented by Ida's 

 Valley, coming down from the west flank of Simonsberg; and a 

 fourth is the Plankenberg^ Valley. The fifth arm of the star- 

 fish is the wide gap by which Eerste River makes its escape to 

 the west. The body of the starfish is formed by the Stellenbosch 

 Flats, and of its arms four are inlets and only one is a water- 

 outlet. Stellenbosch is therefore a hyd'-ographic junction of 

 some little importance. 



The Development of the Eerste River System. 



The course of Eerste River is peculiar : for the first ten 

 miles of its career it runs north-west, then changes its mind at 

 Stellenbosch and turns south-w^est ; south of Faure it again turns 

 abruptly to south-east before it escapes into False Bay. The 

 explanation of this eccentricity demands a mental excursion into 

 remote geological periods, for the birth of the river probably 

 followed close upon the heels of the movements of folding and 

 elevation, which enclosed the Karroo within its girdle of moun- 

 tains ; that is, the initiation of the river may date from late 

 Mesozoic time. 



BCCTMANS KCP 



vIONKEfiS HOCK 



Fig. I. 



Observe that Stellenbosch lies just about the point where 

 the N.-S. folds of the Cedarberg System swing round and be- 

 come the E.-W. folds of the Langberg System ; the strike of the 

 folds is therefore roughly N.W.-S.E. in this part of the country. 

 If Eerste River arose as a consequent stream, its original course 

 must have been roughly S.W.. as its middle course still is. Why 

 has it in its upper course assumed a direction at right angles to 

 this? The answer to this question is supplied by the geological 

 structure of Jonker's Hoek. Stand on the Flats and look to- 

 wards the mouth of the Hoek. On your right hand is Stellen- 

 bosch Mountain, on the left Bootman's Kop ; each of them the 

 end of one of the spurs which enclose the Hoek. The two 

 mountains have a similar architecture, each of them being com- 

 posed of a pyramid of Table Mountain Sandstone resting ujxin 

 a base of granite and old, tilted sediments. The lowest krantz 

 which you can see on the mountain-side marks the base of the 

 Sandstone: follow this horizon from west to east. On the west 

 side of Stellenbosch Mountain it lies some 1,320 feet above sea- 

 level ; on the east side, on account of the gentle north-eastward 

 inclination of the beds, it has declined to about 1,050 feet. Cross- 

 ing the valley to Bootman's Kop, the same horizon is found at 

 an elevation of 2,550 feet (see Fig. i). Go up Jonker's Hoek, 



