Ch. IV.] SCHISTOSE GROUP OF CORNWALL. 49 



courses. These rocks might have been treated of in a distinct 

 chapter, or in connection with granite, but the plan here 

 adopted is preferred, in order to present a faithful descrip- 

 tion, as free as possible from theoretical opinions concerning 

 their nature. 



By the term granitic rocks is understood such compounds 

 as have already been described as forming portions of the 

 central masses of granite. They seldom resemble true 

 granite, but exhibit most of the species of shorl-rock, proto- 

 gine, eurite, and felsparite, more particularly of those kinds 

 which are porphyritic. These granitic rocks are most abun- 

 dant in the vicinity of the granite ; and very commonly, though 

 not invariably, are found to underlie towards the main mass 

 of granite at very considerable angles, averaging about 70 or 

 75 : that is, their dip generally differs from the inclination 

 of the laminae of the schistose rocks, which usually slope from 

 the granite. The direction of these granitic rocks is, in 

 general, from N.E. to S.W. ; corresponding, in this respect, 

 -with the greater portion of the slates, and with the principal 

 metalliferous veins : and like these, also, their course is not 

 in an undeviating straight line, but is variously curved ; and 

 this character is also detected in their underlie. The great 

 elvans of Polgooth mine may be referred to, as affording 

 illustrations of this circumstance. 



Concerning the kinds of slate, with which these granitic 

 courses are connected, and the relations which they respect- 

 ively bear to each other, it will be necessary to adduce some 

 examples in detail; for this important subject will furnish 

 some leading arguments in the subsequent examination of the 

 prevailing theory. 



The varieties of felsparite, described as one of the Cornish 

 granitic rocks, are more frequently met with amongst those 

 slates which have a similar hard compact felspar basis, as 

 cOrnubianite, actynolite rock, and some of the species of 

 greenstone. Examples of this association may be seen in 

 Dolcoath, and other mines situated near the junction of the 



