262 Transactions of the South African Philosophical Society. 



extremities and furnished with conical brass penetrating points. 

 They are driven down through the sand until the saturated soil is 

 penetrated. Over most of this area, however, the depth of soil is 

 probably not sufficient to warrant their adoption. 



In some of the valleys sub-surface dams might be built, and by 

 that means the water, which under ordinary conditions makes its 

 way slowly down below the river-bed, brought up to the surface. 

 Such a dam is constructed by excavating a trench across the (dry) 

 river-channel, extending it down to the bed-rock, and then filling it 

 with masonry. 



This system has been extremely successful in California, and there 

 are numerous places here where similar dams could be built, e.g., 

 down the Molopo and Setlagoli Eivers. 



With regard to boring for water I do not think that it is advisable 

 to go beyond a depth of 400 feet ; such few borings as have exceeded 

 this do not yield any great supply. 



The question of size of borehole is of no great importance ; the 

 advantage of a 6-inch hole over a 4-inch one is to a great degree 

 imaginary, as their actual relative capacities have the ratio 100 to 95." 



In conclusion, I think that for many years to come the under- 

 ground supplies will prove sufficient for average needs, although it 

 is improbable that anything great will be done in the way of 

 irrigation. 



As a cattle-raising country this part of the Cape Colony is un- 

 equalled, and when the great tracts of ground, thickly covered with 

 grass and bush and as yet unoccupied and unsurveyed, are con- 

 sidered, it is to be hoped that greater facilities and inducements may 

 be given by the Government to persons desirous of settling here, 

 so that the potentiality of this vast area may in the future become 

 a reality. 



* C. Slichter, loc. cit., p. 85. 



