8o Report S.A.A. Advancement of Science. 



and the edge is continually crumbling away as the slopes composed of 

 soft clay disintegrate, thus giving rise at first to blocks of ferruginous 

 surface quartzite, which subsequently break down into smaller frag- 

 ments. The fragments work down into the subsoil, and rest as a 

 layer of gravel upon the sloping surface of the clay. 



During periods of drought, the whole surface becomes dried, 

 and, when the October rains set in, a large amount of moisture is 

 absorbed, which renders the clay greasy. Every year, then, the 

 covering of gravel sub-soil slides a little down hill, and the effect 

 is that of a glacier-borne ground moraine ; in road cuttings along 

 the hill sides, this sheet of gravel can be seen riding over obstacles, 

 covering up earlier river-channels, and thinning out in the elevations 

 of the contours of the ground. There is evidence in this, that when 

 the valley in which Grahamstown stands was first cut in the 

 peneplain, there was a greater rainfall, and the river channels were 

 kept open ; now the surface of the hill-sides, on the north of the 

 town, at any rate, have been covered up by this sheet of slowly mov- 

 ing gravel, and the surface of the ground does not show the presence- 

 of the earlier river-courses. 



In England, the same solifluction occurs in the chalk districts. 

 At Lingheath and Brandon, in Suffolk, the sand and gravel lying on 

 the chalk, occurs as a very wide-spread deposit, containing palaeo- 

 lithic implements ; it covers almost the whole face of the country 

 reaching the highest ground, and plunging into the valleys quite 

 irrespective of the present drainage system. (*) 



(5) S. B. J. Skertchly, Mem. Sect. Survey, England & Wales, Manufacture 

 of Sun-prints, London, 1879, p. 6. 



