482 GEOLOGY OF CAPE COLONY 



has recently been published by Dr. C. F. Juritz. 1 He 

 found amongst other things that the purer waters came 

 from the Table Mountain and Stormberg series and 

 that those from the Uitenhage, Dwyka and Bokkeveld 

 formations were the most saline. 



It is impossible to discuss thoroughly the influence 

 of the different formations in various parts of the Colony 

 upon the water supply, but the following brief notes 

 may be of value. 



In the granite regions of the North-West and Bechu- 

 analand water is generally got in valleys at the base of 

 the rotten granite, a variable thickness of which overlies 

 the solid rock. The wells in granite, gneiss, or mica- 

 schist are usually of considerable depths. In Northern 

 and Western Cape Colony the Dwyka formation covers 

 many thousands of square miles, and in the majority of 

 instances the water in wells is brackish and often un- 

 drinkable. The saline constituents are, however, ir- 

 regularly distributed through the rock, and it is by no 

 means rare to find two wells side by side, one giving salt 

 water and the other fresh. This peculiarity prevents 

 generalisation, but in a large number of cases the salt is 

 found to have gravitated towards pans and vleis, and 

 better water, usually inferior in quantity however, is 

 obtained on the slopes of the depressions. 



Another peculiarity is that where the older formation 

 has been just recently stripped of its covering of Dwyka 

 " tillite " it usually fails to give a strong supply ; further 

 away where the " glaciated surface " has been denuded 

 and weathered the conditions become more favourable. 



1 Agricultural Journal of the Cape of Good Hope, vol. xxxii., 1908. 



