124 REMARKS ON THE 



when viewed from the west, presents the appearance of a 

 square castellated building, which is rendered more conspicu- 

 ous, by being nearly of the same height as the tower of an ad- 

 joining church. There can be no doubt that this singular 

 rock, owes its present appearance to the operations of time on 

 the surrounding materials, which its peculiar composition has 

 enabled it to withstand. 



The killas likewise presents marks of degradation, where the 

 country is composed of that rock. I noticed in some districts 

 the roads mended entirely with quartz, (No. 24.) ; the brilliant 

 white appearance of which, after a shower, had a very curious 

 effect. I could not comprehend by what industry the accu- 

 mulated heaps of this substance were obtained : at last I per- 

 ceived that they were gathered from the adjoining fields, and in 

 some places picked from the surface of a common, by means of 

 a hoe or mattock. That fragments of quartz should occur so 

 unmixed with any others, is only to be accounted for, by sup- 

 posing that they formed the quartz veins in the killas, which, 

 from superior tenacity, resisted decomposition, while the softer 

 parts of the rock, yielding to the action of the weather, were 

 reduced and carried away. 



We thus find, that the granite of Cornwall possesses the 

 characters ascribed by Werner to that of the highest antiquity. 

 Some inferences may likewise be drawn, in corroboration of its 

 title to be classed with rocks of this description, from the na- 

 ture of the metallic veins by which it is traversed. 



In the German account of the relative ages of metals, 

 tin is the third, and wolfram the fourth in order of antiquity *. 

 If veins containing these metals, be considered in other coun- 

 tries as indicative of rocks of the oldest primitive formation, 

 the same application must be made to those of Britain. 



I may now ask, if this be not the Oldest Granite, where are 

 we to find it? as it appears to me impossible that any sub- 

 stance 

 * Jameson's Mineralogy, vol. in. p. 275. 



