2*78 ACCOUNT OF THE STRUCTURE, &C. 



tains the place which granite really occupies, in respect of the 

 other parts of the mineral kingdom ; it is one that from ana- 

 logy might be expected to take place, and it is highly favour- 

 able to the opinion, that granite does not derive its origin from 

 aqueous deposition. It seems, indeed, to be an instantia cru- 

 ris, with respect to the two theories concerning the formation 

 of rocks. 



The sandstone, which covers the granite at the Cape, has the 

 appearance of being a very extensive formation ; and is pro- 

 bably a part of the same which Barrow, Lichtenstein, and 

 other travellers, have mentioned as composing many of the 

 principal mountains over a great tract of Southern Africa. The 

 tenuity of the parts holding together large masses of that rock, 

 and indicating a singular approach to equilibrium between the 

 causes that produce, and those that resist decay, was observed 

 on the summit of the Table Mountain, as already mentioned j 

 and similar appearances excited the surprise of the two tra- 

 vellers just named, in some of the most inland tracts which 

 they visited. 



Plates XIV. and XV. are representations of veins of granite 

 connected with the main body of that rock, and penetrating 

 into beds of killas or grauwaky, which are nearly vertical. 



ix. 



