I 

 376 RECAPITULATION OF THE OBJECTIONS [Ch. XVI. 



may attempt to explain, by attributing it to the metamorphic 

 period, when both rocks were in a state of complete or semi- 

 fusion : but such a solution cannot be extended to granite- 

 veins, which, according to the established theory, were 

 injected into hard rocks, capable of being fractured, and of 

 furnishing small angular fragments. Lastly, in their inter- 

 ference with other veins, they intersect, and are themselves 

 intersected by, quartz- veins, which possess both true and 

 contemporaneous characters : thus indicating, according to 

 the axiom, " that a vein which traverses another is more 

 recent than the one intersected ; " that granite-veins have not 

 only been introduced into the containing rocks, but also ex- 

 isted prior to their formation. 4. Concerning the mineral 

 veins, which occur in primary rocks, we contend that, so far 

 from the present state of our knowledge on this subject being 

 sufficiently advanced to justify any theory, it is so very imper- 

 fect, that we have not even accurate descriptions of the 

 objects themselves, the very elements on which the generalis- 

 ation ought to be founded : and we have adduced numerous, 

 and several of them new, facts, to show that, if any opinion 

 be permitted, that of their contemporaneous origin is the 

 more plausible. That mineral veins cannot be defined to be 

 the contents of fissures, we have attempted to establish by the 

 following objections: 1. No line of distinction can be 

 drawn between veins of segregation and true veins, the former 

 of which are said to be coeval with the consolidation of the 

 traversed rock, and are admitted to characterise some of the 

 metalliferous veins of Cornwall. Nor can we discriminate 

 between large and small veins, or such as are supposed to 

 be indefinite in extent, and those which are entirely comprised 

 within the limits of our observation ; that is, between the 

 commonly called true and contemporaneous veins. 2. As 

 regards the origin of true veins in fissures, we contend that 

 such variously inclined cracks and chasms, extending for 

 considerable lengths and depths, are. incompatible with the 

 laws of gravity ; that the great contortions of veins are not 



