Ch. XIV.] OF THE STRATIFIED ROCKS. 325 



pass, and with which they are so intimately associated ; that 

 the slates sometimes completely envelope smaller layers or 

 beds of the granitic compounds ; and, vice versa, the latter 

 occasionally contain the former. Granting, however, the in- 

 jection of the granite, it could not be the cause of the eleva- 

 tion of strata, which, as in the Hartz, underlie the granite on 

 one side, and repose upon it on the other ; nor could the 

 granite of Mont Blanc have tilted up the adjacent strata, 

 since it is only a crystalline variety of the talc-schist, similarly 

 circumstanced as to position, being, indeed, analogous to the 

 granite of Sweden and Norway, which is generally considered 

 to be granitic gneiss. It may be argued that these elevations 

 have been effected by concealed masses of granite, from 

 which the injected portions have proceeded, and by which 

 the metamorphosis of the strata has been effected : but 

 this is only conjecture, and by such reasoning all diffi- 

 culties may be as easily overcome ; for it may be imagined that 

 vast mountainous tracts once existed, which, after having 

 supplied the materials for the immense masses of primary 

 strata in the north of Europe, and other regions, were swal- 

 lowed up, or in some wise obliterated by the elevation of the 

 formation to which they had given birth. Ought such specu- 

 lations to be preferred to the simple and self-evident in- 

 duction, that secondary deposits, containing fragments of 

 contiguous primary rocks, are more recent than the form- 

 ations whence the detritus was derived. 



The fel spathic rocks of Cornwall are also adduced by 

 Lyell, as the first example of the alteration of strata, in 

 contact with granite : these various and beautiful rocks are 

 called a coarse argillaceous schist, which is converted into 

 hornblende-schist at its junction with the main mass, or with 

 the veins of granite. If the dark-coloured slate sometimes re- 

 sembles hornblende-schist, it, in numerous other instances, 

 does not assume this appearance : and, even in the former 

 case, we think that this name has only been applied for want 

 of a better. So much, however, has already been said on this 



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