of Devonshire atid Cornwall. 147 



6. The width of these veins does not always diminish as they 

 recede from the main body of granite. Sometimes after a very 

 slender beginning, they swell out, or divide into ramifications. 



7. I did not find the veins extend very far, nor rise perpen- 

 dicularly, on the contrary, I always observed those at the surface 

 to be conformable with the planes of inclination of the ground. 



8. At the point of contact of these two rocks I never found the 

 one disseminated in small quantities through the other, the granite 

 never mixes with the grauwacke, but both retain their distinct 

 characters.* 



9. In breaking a part of these veins with the hammer it gene- 

 rally happens that the grauwacke separates from the granite, which 

 proves that there was no penetration, but only juxta-position, as if 

 the one had been moulded in the crevices of the other. 



Several of these facts appear to me not very easily reconcilable 

 with the following assertion in the work of Mr. Playfair : I quote 

 it in his own words, " It remains certain therefore, that the whole 

 " mass of granite and the veins proceeding from it are coeval, and 

 " both of later formation than the strata.'" \ 



To the latter part of the above quotation, I cannot assent ; I con- 

 ceive, that at the time the grauwacke was deposited upon the granite, 

 the water in which its particles were suspended, meeting with por- 

 tions of the granite, a little more elevated than the general plane of 

 the surface, left them exposed, and filled up the spaces between 



* At least, if any thing of the kind has been observed, it has never been at such a 

 distance as we might expect it to be, if produced by so considerable a force as that which 

 the Huttonians suppose, but only at the edges; and in this case, it may have happened 

 that the granite was softened by the grauwacke acting upon it as a solvent, so far as to 

 permit pieces of that rock to amalgamate with it. 



t Illustrations of the Huttouian Theory, § 82. 



t2 



