126 REMARKS ON THE 



amples ; but the most striking are at the Louran in Galloway, 

 and at St Michael's Mount in Cornwall. ' 



It is many years since Sir James Hall laid before this So- 

 ciety an account of his observations on the granite district of 

 Galloway, of which the Louran forms a part; and to the perse- 

 vering activity of that gentleman, we are indebted for the dis- 

 play of one of the most interesting exhibitions of granite veins 

 that exists. The peculiarities observable in Galloway, were first 

 pointed out to me by him ; and as he has so lately favoured 

 the Society with a particular account of them, it leaves me no- 

 thing to say regarding that quarter. 



At St Michael's Mount, the shooting of the veins from the 

 great mass of granite, is also most strikingly exemplified. 

 They were here first noticed by Professor Playfair, who com- 

 pares them, most aptly, to the ramifications of the vegetable 

 root * ; for, indeed, nothing can be more illustrative of the phe- 

 nomenon as it is here exhibited. 



It is to be observed that granite veins, particularly when ex- 

 tremely minute, usually differ in texture from the mass to 

 which they belong. While the little peak of St Michael's Mount 

 maintains a similarity of character with all the rest of the 

 Cornish granite, not only in point of internal structure, but 

 with respect to the tin and copper veins which traverse it, as 

 well as by the massive blocks, hewn by the corroding hand of 

 time, which ornament its summit; the veins that set off from 

 it, gradually become finer as they recede, but still preserve the 

 perfect character of the rock. 



The importance deservedly attached by Dr Hutton to the 

 phenomena of granite veins, gave rise to a variety of hypothe- 

 ses among those who were inclined to consider this rock as 

 the original deposite, who have accounted for their formation 

 in different ways. 



It 



* Illustrations of the Huttonian Theory, f. 318. 



