THE CAPE SYSTEM 129 



fault from a narrow strip of younger rocks (Ecca and 

 Cretaceous) between it and the sea (Fig. 3). The differ- 

 ence in level between the sandstone on the coast and 

 that forming the plateau behind the coast is due to the 

 cutting back of the lower terrace by the sea at no very 

 remote period, and certainly not to folds or faults bring- 

 ing the sandstone down near the coast. 



The Table Mountain series is remarkably constant 

 in lithological characters throughout its extent. The 

 maximum thickness is about 5,000 feet, and of this more 

 than 4,000 feet are sandstones or quartzites, often false- 

 bedded. The difference between a sandstone and a 

 quartzite is that the component grains are more loosely 

 held together in the former than in the latter, in which 

 the cementing material is quartz. When a sandstone 

 is broken, the fresh face is rough and dull, owing to the 

 fracture passing round or between the grains of sand 

 which form the rock ; a quartzite, on the other hand, 

 has a smoother and brighter face because the fracture 

 passes through the component grains, which are closely 

 joined together by the siliceous cement. It is some- 

 times found that a large block of sandstone long exposed 

 to the weather becomes a quartzite near the outer sur- 

 face, owing to the deposition of silica between the 

 grains. On the other hand, some quartzites become 

 loose and crumbly outside on account of the removal of 

 the cement. 



The whitish-grey colour of so much of the sandstone 

 belonging to this series is due to weathering. At a 



distance of one or two feet from the outside the rock is 



9 



