290 AN ENQUIRY INTO THE NATURE OF [Ch. XIIL 



farther investigations to ascertain, if possible, whether many 

 of the appearances, which are now attributed to forcible 

 elevations by the protrusion of igneous rocks, may not be 

 explained b} the operation of the less energetic, but not 

 inefficient causes which have been indicated. 



If, then, in the examination of the secondary rocks, so many 

 difficulties present themselves, in determining the nature and 

 Origin of their inclined strata, it is not surprising that the 

 more complicated structure of the primary slates renders 

 this enquiry still more perplexing. Some may be of opinion 

 that, in the latter case, the evidence of elevation is much more 

 decisive, since the crystalline stratified rocks almost universally 

 dip at great angles, and abound in curves, contortions, and 

 other supposed marks of violent catastrophes. 



On reference to the former chapter, it will be seen to what 

 extent the primary slates are admitted to be analogous to 

 the secondary rocks, it having been attempted to show 

 that both are traversed by seams or joints, which arise from 

 their concretional structure; and it is now proposed to 

 offer arguments in support of the opinion, that the layers 

 interposed betwen these parallel seams are in their original 

 position. 



It is, however, generally asserted, that the primary strata 

 have been tilted up to their present highly inclined positions. 

 But let us enquire, what are primary strata ? This may be 

 deemed superfluous, since they are such well-known objects, 

 described by most geological writers, who have found no 

 difficulty in recording their directions, dip, and other bear- 

 ings. We must, however, confess that, after much personal 

 examination, and the attentive perusal of the labours of 

 others on this subject, we cannot answer this question. 



Professor Sedgwick and some other geologists have re- 

 garded the primary strata of Cornwall to be parallel with the 

 laminae of these rocks. In conformity with the usual practice 

 of giving the dip of the schistose rocks, we also followed the 



