122 REMARKS ON THE 



ject in view, during a visit made since I was there, informs me 

 that he could discover no distinction at all. 



It is therefore of importance to ascertain whether the granite 

 of Cornwall be new or old; which will easily be done, by com- 

 paring the appearances it presents, with the descriptions of 

 these rocks as given in the Wernerian school ; it is there 

 taught, that three formations of granite have been ascer- 

 tained. 



The oldest is the basis or nucleus, round which all other 

 rocks have been deposited. The second occurs only in veins, 

 traversing only the granite of the older formation. The third 

 rests on some of the older primitive rocks, in unconformable 

 and overlying position. From this description of its external 

 relations, it is evident that the granite of Cornwall can neither 

 be the second nor third. With respect to its internal structure, 

 we have the following definition : Granite is a granular aggre- 

 gated rock, composed of felspar, quartz, and mica. These al- 

 ternate from large to small, and even to very fine granular. 

 The large and coarse granular usually belong to the oldest ; 

 the small and fine granular to the newest granite formations. 

 Besides felspar, quartz and mica, other fossils sometimes occur 

 in it ; of these, schorl is the most frequent, then garnet and 

 tinstone*. 



At Penzance I observed some buildings constructed of a re- 

 markably fine-grained granite ; but this I nowhere saw in situ: 

 otherwise, from Teign Bridge, where I first set my foot on 

 granite, to the Land's End, it is generally of that character 

 which entitles it to be ranked with the oldest variety, (Nos. 

 8, 21, 27, 34, 35, 54, 55.) In many places it has suffered to a 

 most wonderful extent by decomposition, but where it retains 

 its freshness, no granite can possibly be better characterised. 



The 



* Jameson's Mineralogy, vol. m. p. 102, &c. 



