TRANSITION ROCKS. 129 



below, could have created the disturbance among the stratified 

 rocks, so conspicuous when in contact with granite. As it is a 

 self-evident position, that a rock which is cut by a true vein, 

 must have existed in a solid state previous to the formation of 

 that vein ; so is it equally obvious, that if the vein can be tra- 

 ced into an adjoining mass, of which it is found to be a part, 

 that mass must stand in the same relation, in point of period, 

 to the rock which contains the vein, as the vein itself does : 

 as also, that if pieces of one rock be found imbedded in 

 another, the including rock must have been of subsequent 

 formation to the included. No theory, however, but that 

 of Dr Hutton can account for these appearances : to no- 

 thing but force can the position be attributed, which the 

 stratified rocks have assumed in the vicinity of the unstratified; 

 and nothing but matter injected in a liquid state, could possi- 

 bly have formed the shoots which traverse from the great mass 

 of granite perforating the stratified rock, and at the same time 

 envelope detached fragments of that rock. As the idea of vio- 

 lence in these operations has been so frequently combated, I 

 cannot refrain from noticing here, a very striking mark of it I 

 met with at Coul in Ross-shire, when visiting Sir George 

 Mackenzie. There the strata of gneiss are much disturbed 

 by the invasion of granite veins : near which, on the outside 

 curvatures of some of them I perceived rents similar to what we 

 might expect on bending a flattened mass of clay, nearly de- 

 prived of moisture. I am fortunately enabled to present to 

 the Society specimens illustrative of this interesting fact (Nos. 

 68, 69.) 



In the theory of Dr Hutton, we find also some grounds to 

 account for the diminution of grain in the substance of the 

 veins. The same cause to which, in a former paper, I at- 

 tributed the gradation in the texture of greenstone, may 

 be supposed to have acted here. It does not, however, ob- 



Vol. VII. R serve 



