560 THE GEOLOGY OF SOUTH-EASTERN AFRICA. [!N"0V. 1 894, 



shows in a marked manner the characteristics of a volcanic ash (see 

 above, p. 555) ; and when the matrix is reduced to powder, and 

 pressed into clay, it does not show the sticky, plastic nature of a 

 glacial clay, but is sandy and friable. 



Note. — In the section just described, each distinct layer was seeu 

 to be separated from the one next above by a clear line of division. 



EXPLANATION OF PLATES XXII. & XXIII. 

 Plate XXII. 



Fig. 1. Diagrammatic section o e the Drakensberg and the High-veld plateau. 

 (Approximate distance = 390 miles.) This shows the sedimentary 

 deposits lying horizontally in relation to the igneous and Primary 

 rocks. The Dwyka, Ecea, and Beaufort Beds are seen to thin out 

 northward, while the Molteno Beds thicken in the same direction. 

 The Primary and Basement-rocks underlying the Dwyka Conglomerate 

 are in all probability continuous from the coast to the Klip Stapeland 

 beyond, as they appear in all the deeper valleys on the eastern flank 

 of the Drakensberg. At Lang's Neck the coal-seam in the Molteno 

 Beds suddenly drops from 5600 to 4000 feet above sea-level, a drop 

 which no doubt indicates a considerable fault. 



Fig. 2. Diagrammatic section from the Mont-aux- Sources on the Drakensberg to 

 St. Lucia Bay, on the East Coast. (Approximate distance = 220 miles.) 



Plate XXIII. 



Section from Hartebeest-Fontein in the Transvaal to Vrede.fort in the Orange 

 Free State, partly based on Dr. Molengraafs researches. (Approximate 

 distance = 50 miles.) The lower portion of the sandstone (A) includes 

 beds of boulders, consisting principally of masses of gold-bearing con- 

 glomerate. The breccia (B) consists chiefly of irregular fragments 

 of shale, quartzite, and sandstone, similar to Nos. 1, 2, and 3 ; and it 

 denotes the existence of a great fault, and downward displacement 

 and disappearance of the strata between the granite and the dolomite. 

 The Table-mountain Sandstone contains auriferous conglomerates in 

 its middle portion as well as in the upper (' Black Reef) series : and 

 the pebbles are larger in the former than in either the upper or lower 

 beds. The section at De-Wette Drift, Vaal River, about 12 miles 

 south of Potchefstroom, is conclusive as to the position of the dolomite 

 with respect to the overlying and underlying rocks, which are nearly 

 vertical at this point, and clearly exposed in the river-bed. 



[For the Discussion on this paper, see p. 5G4.] 



