on the Geological Phcenomena near Cape Town. 535 



The author also alludes to the vegetable and other debris brought to- 

 gether by the rains, and to the commencement by this means of an 

 embryo lignite formation on one side of the Cape Flats. 



Springs. — The well-water in Cape Town is considered unwhole- 

 some. Under Table Mountain is a spring which rises from the gra- 

 nite, and is computed to throw out daily 150,000 gallons; and at 

 Newlands near Wynberg is a spring of sufficient volume to work two 

 mills, and to discharge daily 850,000 gallons. That these springs 

 are not the result of accumulations from the heights, is proved, Mr. 

 Clarke says, from their not varying with the season, and because the 

 water cannot be made to rise above the level at which it appears. 



Detritus. — The accumulations described under this head are en- 

 tirely local, being derived from the subjacent or neighbouring rocks. 

 The smooth and rounded granite boulders also do not extend beyond 

 the range of the granite, but Mr. Clarke is of opinion that the ancient 

 currents which flowed over the Cape Flats may have assisted in their 

 partial removal, and may have rounded some of them. In the in- 

 terior, masses of granite, similar to the Tors of Dartmoor, are stated 

 to occur. 



Geological changes. — The first points noticed by Mr. Clarke, are 

 the protrusion of the granite through the slates at the Lion's Head, the 

 consequent vertical position of the schistose beds, the occurrence of 

 fragments of granite in blocks of sandstone; and the proofs deducible 

 from the granite veins which penetrate and alter the gneiss, as well as 

 traverse the superincumbent sandstone, of the granite, since its first 

 elevation, having been re-heated. He also alludes to the quartz veins 

 which are crossed by others of the same nature, as evidences of there 

 having been two periods of action during which the rock was fissured 

 and veins formed ; and to the trap dykes, as proofs of igneous acti- 

 vity since the consolidation of the granite. He likewise mentions 

 the softening or the decomposition of the granite where traversed by 

 trap dykes. 



The author next describes the changes in the relative level of land 

 and sea. Everything, he says, tends to confirm the inference, that 

 the whole country was at a comparatively recent period under water. 

 Thus the shingle beds, resting upon granite, at Cobler's Hole, prove 

 an elevation of at least 400 feet since the present species of testacea 

 inhabited the adjacent seas ; and he adds, " The water-worn masses 

 of sandstone and the hollows in the beds of that rock in situ, iden- 

 tical with those now produced by sea-waves beating against a cliff, 

 equally prove the condition of previous elevation ; and the steep sides 

 of the granite, in parallel lines of coast, also lead to the conclusion that 

 they were so modified by currents acting in lines coincident with their 

 direction." The occurrence of marine shells in the sand at the Cape 

 Flats likewise shows that the sea once covered that district ; and the 

 grooves and scratches at the Lion's Rump, Mr. Clarke observes, 

 justly lead to the inference of elevation. Before the commencement 

 of these changes in the relative level of land and sea, False Bay and 

 Table Bay must have been united by; a sheet of water more than 



