274 GEOGNOSY OF THE CAPE PENINSULA. 



from which the ground declines gradually to the sea. The 

 amphitheatre formed by these three nwuntains is about five 

 or six miles in diameter, in the centre of which is placed 

 Cape Town. 



The rocks of which this peninsula is composed are few in 

 number, and of simple structure. They are granite, gneiss, 

 clay-slate, greywacke, quartz rock, sandstone, and augite- 

 greenstone, or dolerite. Of these the most abundant are 

 granite and sandstone ; the next in frequency are clay-slate 

 and greywacke ; and the least frequent are gneiss and do- 

 lerite. In some parts, as at the Steinberg, the sandstone is 

 traversed by veins of red iron ore. Abel mentions a vein 

 six feet wide, and extending for upwards of one hundred 

 feet. 



The strata of the Neptunian rocks, or those whose forma- 

 tion is connected with the operation of water, generally 

 range from west to east, — that is, across the peninsula. 

 The southern and middle parts of the peninsula have been 

 but imperfectly examined. Captain Hall remarks, that the 

 same general structure and relations seem to occur all over 

 ihe peninsula as in the mountains around Cape Town. 

 The late Dr. Clarke Abel, in the account of his voyage to 

 China, gives the following description of a fine display of 

 stratification in a mountain that faces the sea, in the neigh- 

 bourhood of Simon's Bay, which was pointed out to him 

 by one of our pupils, an active and intelligent officer, Cap- 

 tain Wauchope, R. N. : — " The sandstone forming the 

 upper part of the mountain is of a reddish colour, very 

 crystalline in its structure, and approaching, in some speci- 

 mens, to quartz rock. Immediately beneath the sandstone 

 is a bed of compact dark-red argillaceous sandstone, passings 

 in many places, into slate of the same colour. This bed 

 rests upon another of very coarse loosely-combined sand- 

 stone, resembling gravel. Under this is another layer of 

 dark-red sandstone, terminating in a conglomerate, consist- 

 ing of decomposed crystals of felspar, and of rounded and 

 angular fragments of quartz, from the size of a millet-seed 

 to that of a plover's egg, imbedded in a red sandstone base. 

 Beneath the conglomerate commences a bed, which I at 

 first took for granite, and which is composed of the consti- 

 tuents of granite in a decomposed state, intermixed with 

 green steatite, and a sufficient quantity of the red sandstone 



