108 Transactions of the South African Philosophical Society. 



and a comparatively new one. The old one was started before the 

 eruption of the Drakensberg volcanoes, and was developed on a 

 comparatively featureless plain. It consisted of a number of rivers 

 having their sources along a straight line which ran through the 

 country in a direction roughly 60° E. of N. From this watershed, 

 w^hich can still be clearly traced from the Cape Peninsula to Delagoa 

 Bay, a distance of about 1,000 miles, the waters flowed on one side 

 in a south-easterly direction and on the other in a north-westerly 

 one. The watershed now is only once cut through by the Orange 

 Eiver. After this principal river system was developed stresses in 

 the earth's crust forced the strata round the coast into folds whereby 

 the main mountain ranges of South Africa were formed, but all this 

 went on so slowly that the old rivers were able to cut their way 

 through the folds as quickly as the ground rose across their courses, 



OELACOA an 



EAST LONDON 

 ORT ELIZASETM 



lUiLimUlUJJ PEf^M.AM SHQSE ..»E 

 ■■"»""■ WATER-SHeO 

 •••••• LINE OF rfOuC'^NOtS 



Fi(i. 2. 



Mcap of South Africa showing the rehition of the rivers to the water-shed and 

 the hne of volcanoes. It also shows the parallelism between the probable course 

 of the Permian shore-line, the water-shed, the line of volcanoes, and the present 

 shore-line on the south-east of the continent. 



and for this reason we get the extraordinary gorges that traverse 

 all the mountain ranges in the south-west of the Colony. When 

 the mountains were formed the old simple drainage system was 

 naturally disturbed, and a new one was instituted to accom- 

 modate the new order of things, and in this way we get the two 

 systems, a new one superimposed on an old one. Looking now at 

 the area in wliich the volcanoes occur (Fig. 2) one notices that the 

 rivers on the north-west side of the watershed arise in exactly tlie 

 same manner as those on other parts of the same watershed. On 



