54 



ME. D. DRAPER OK THE MAEBLE BEDS OE NATAL. [Feb. 1895, 



by granite [boulders ?] except on tbe eastern side, wbere some 

 chloritic schist, apparently also a detached block, occupies a small 

 area. 



An intrusive dyke of flesh-coloured porphyrinic granite (very 

 similar to Shap granite) has disturbed the marble beds at the spot 

 marked f in fig. 1, p. 52. 



The accompanying section (fig. 2) shows the position of the 

 marble-beds with regard to the rocks in their immediate vicinity. 



Fig. 2. — Section across the river-valleys, showing the position 

 of the Marble. 



Fault. 



Umzimkuluana Indwendwa Umzimfrulu N. 



River. Hill. River. Fault. 



AAA = Granite. 



BB = Clay-slate. 



CO = Table-mountain Sandstone. 



DDDD = Marble. 

 E = Debris (ancient course of 

 river). 



The Indwendwa Hill occupies the area between the two rivers, 

 and extends to their junction. It consists mainly of granite, 

 covered with marble, except where the latter has been removed by 

 natural causes, as at tbe top of the hill A in the above section. 



The marble is obscurely stratified, dipping apparently towards the 

 river-valleys on both sides, and having an east-and-west strike. 



The quality of the marble varies from coarsely crystalline lime- 

 stone to the most finely grained statuary marble, and the colour from 

 purest white to deep red. The coarsely crystalline variety contains 

 from 5 to 13 per cent, of carbonate of magnesia. 



A deposit of tufaceous limestone, evidently derived from the 

 weathering of the marble, covers the latter in some places with a 

 layer several feet in thickness. The percentage of magnesia is much 

 smaller in this tufa tban in the solid marble. 



Y. Conclusions. — The marble-beds of the Umzimkulu valley are 

 the only examples of this rock discovered up to the present time in 

 Southern Africa ; and by reason of their mode of occurrence, position, 

 .and general surroundings, they constitute the most interesting feature 

 in the geology of the Natal coast. 



The first question that presents itself is — What is the geological 

 period to which they belong ? 



"Wberever I could discover any rock immediately underlying the 

 marble, it was granite ; and there is no doubt in my mind that the 

 calcareous matter of which the marble was formed was deposited on 

 the granite. At one spot marked * in the section (fig. 1, p. 52) a 



