358 ON THE APPARENT DISLOCATIONS [Ch. XV. 



the latter. Since, therefore, the systematic characters of 

 these orders are so indefinite, and since Nature does not 

 appear to have made any discrimination between them, we 

 think that we are justified in concluding that the veins which 

 traverse the primary rocks are all of the same nature ; and if 

 so, it follows, that all are contemporaneous, since some are 

 indisputably of this character. Thus furnishing another 

 argument in addition to those already advanced, that the 

 granite and the slate are likewise contemporaneous, being 

 modifications of the same mass, only differing from each other 

 in structure, the result of the same constituent particles 

 variously aggregated. 



In confirmation of this view, we will proceed to enquire 

 whether the appearances of veins which are supposed to indi- 

 cate a mechanical origin, furnish satisfactory evidence in 

 support of this opinion. 



True veins, or veins of fissure, as they are sometimes 

 termed, are defined to be "the mineral contents of vertical 

 or inclined fissures, nearly straight, and of indefinite length 

 and depth/' * This is Mr. Game's definition ; and, as far as 

 we are aware, it has not been objected to by geologists : 

 indeed, it accords with the idea long entertained, that veins 

 were originally open fissures. In the first place, we object to 

 this statement because the Cornish veins are never straight 

 throughout their course, and their sides are never parallel for 

 any considerable distance, since the veins are constantly 

 varying in their width : for, as stated in the ninth chapter, 

 veins undulate both in the direction of their course and 

 descent, forming curves, which in general appear to be very 

 irregular. That veins are very complicated in their course 

 is proved by the fact that no inconsiderable skill is requisite 

 in dialling ; whereas, if they were nearly straight, this oper- 

 ation might be easily performed, if not dispensed with altoge- 

 ther. As regards the indefinite length and depth of veins, 



* Geol. Trans, of Cornwall, vol. ii. p. 51. 



