t)f Devonshire and Cornwall. 



Of the Vel?is or Shoots of Granite^ which traverse the Grauwacke 

 Formation, 



The last place In Cornwall where I met with veins or shoots of 

 granite in the grauwacke, was at Mousehole near Penzance. As, 

 the attention of geologists, particularly the supporters of the Hut- 

 tonlan Theory, has been strongly directed to facts of this sort, I shall 

 briefly state the observations I have made on this subject, confining 

 myself to what I saw in Devonshire and Cornwall ;* not that I am 

 unacquainted with some of those places on the continent where 

 similar facts have been pointed out,f but because I found them ex- 

 hibited In this part of England in a manner much more striking and 

 less difficult of apprehension. 



1 . We never find these veins or shoots of granite but at the point 

 of junction of that rock with the grauwacke, whether that junction 

 be in high situations or on the sea shore. 



2. These veins are not independent or insulated, but by following 

 their course we can always trace them to a main body of granite, 

 without any interruption of continuity intervening between them. 



* There is a remarkable example of this occurrence of granite veins at the junction 

 with the grauwacke, in New Galloway in Dumfries-shire, on one of the estates of Sir 

 James Hall. Vide third vol, of the Transactions of the Royal Society of Edin. Sir James 

 Hall had a very interesting model of the place made on a pretty large scale, which 

 he has deposited in the collection of the Geological Society. 



Mr. Piayfair also mentions some other facts of this sort, which he has observed in the 

 course of his travels in England and Scotland. Illustrations of the Iluttouian Theory, 

 from p. 307 to 320. 



+ Voyages dansles Alpes,§ 598, 599, 601. 



T 



