Ch. XV.] OF THE PRIMARY ROCKS. 363 



section of lodes, a class of phenomena which has been more 

 studied than any other on the subject of veins, and which is 

 still considered to establish the axiom laid down at a very 

 early period, that a vein which traverses another is more recent 

 than the one intersected. Mr. Carne, in the paper already 

 alluded to, has attempted, on this principle, to ascertain the 

 relative ages of the Cornish veins, or rather we should say 

 of the true veins ; for his other two orders, the contem- 

 poraneous and doubtful, have not been included in this con- 

 sideration. But we do not propose to walk in the same 

 track, preferring our free and heterodox mode of enquiry, by 

 bringing all kinds of veins, without any exception, to the test 

 of this rule. 



In the first place, contemporaneous veins, or veins of 

 segregation, very frequently intersect each other, giving rise 

 to the usual appearances of dislocations and displacements. 

 This fact could not escape notice, and Mr. Carne attempts to 

 explain it away, by asserting that " these phenomena are only 

 apparent ; as it is, in general, easy to perceive that what seem 

 to be separate parts of the same vein, are different veins, 

 which terminate at or near the cross vein." We would ask, 

 do not the intersected portions of true veins often possess the 

 same character ? We are aware that the point in question 

 has not been very extensively investigated, for the obvious 

 reason, that the miner is not much interested in it ; and such 

 an examination, indeed, would be generally rendered very 

 difficult, as the points of intersection are commonly obscured 

 by a blending together of the matrices, and more especially by 

 decomposition. The determination of this question is not at 

 present very material, since it is admitted that this mark of dis- 

 tinction cannot always be detected in contemporaneous veins. 



But how do these veins comport themselves, when they 

 interfere with doubtful veins ? When contemporaneous quartz- 

 veins (that is, such as are short, crooked, and of irregular 

 size) meet granite-veins, whether in granite or in slate, they 

 are sometimes intersected thereby, at other times they are 



