TERTIARY AND RECENT DEPOSITS 397 



and from the mountains built of the same rock to the 

 east of the Sand Veld. Where exposed to constant 

 sifting by the wind the sand is white or very light- 

 coloured, but throughout the greater part of the area it 

 is reddish. The red colour is certainly due to oxide of 

 iron, but the source of the iron is not so evident. In 

 sinking wells it is found that the lower layers of sand 

 are paler in colour than those near the surface ; it may 

 be that the rain water, with the aid of organic com- 

 pounds taken up during its passage through the soil, 

 dissolves the iron oxides deep under the surface and 

 brings them in solution to the top where it leaves them 

 as thin films round the sand grains on evaporation. 

 But it is possible that the very fine red dust brought 

 into that part of the country by the strong east winds 

 will account for the red colour of the surface sand. 

 The fertility of the Sand Veld is remarkable, considering 

 the general appearance and nature of the soil, good 

 grain crops being obtained when average winter rains 

 fall ; it is probable that the wind-borne dust adds the 

 necessary constituents to the otherwise extremely poor 

 soil. 



The Sand Veld sand passes somewhat abruptly into 

 the dunes that line the west coast. The proximity of 

 the coast makes itself noticeable by the increase of 

 calcareous matter in the sand ; the carbonate of lime is 

 derived from marine shells which are pounded to dust 

 on the shore and then blown inland. 



Patches of sand dunes of greater size than usual are 

 found south of Saldanha Bay, on the shores of False 

 Bay whence the sand has invaded the Cape Flats, near 



