188 Dr. Mac Culloch on Mineral Veins. 



in different countries, often forms a tolerable, though not an 

 infallible, guide for these ; as must be very evident from con- 

 sidering the irregular displacements of strata : but such rules 

 are still less capable of being extended to other countries, or to 

 remote places. To determine whether the motion of one part 

 of an inclined vein is to be termed an elevation or a depression, 

 it is necessary to take the point of departure from the surface, 

 as in the case of dislocated strata. When a vertical vein is 

 shifted, it is evident that the adjacent rocks must all have been 

 moved by the same quantity in a horizontal direction; an event, 

 as formerly remarked, not favourable to the theory which sup- 

 poses the fractures of strata to be the effect of subsidence. 



The last circumstance which relates to the forms of veins, 

 is their ramification. They are occasionally separated, and 

 again reunited ; certain technical terms being, in mining coun- 

 tries, applied to the intermediate mass. In other cases, they 

 send out slender ramifications ; and sometimes they are found 

 to ramify, at once, into many small branches. 



I have thought fit to separate from that which is matter of 

 justifiable inference respecting the ages of veins, what can only 

 be considered as an hypothesis, and which is, further, neither 

 an intelligible nor an useful one. It has been said, that there 

 are epochas to be traced in metallic veins, or that the metals 

 are of different ages. Thus, for example, it is said that tin is 

 among the oldest metals, because it is found in granite, and 

 that lead is among the newest, because it occurs in the se- 

 condary limestone. I need not enumerate all the particulars 

 contained in assertions so unfounded ; while a fev? simple facts 

 are sufficient to annihilate the whole system. 



Cobalt occurs in granite, in many of the primary schists, and 

 in the secondary sandstones. Copper has been found through- 

 out the whole system, from granite up to trap inclusive. Lead 

 is found alike in the primary aud secondary strata, and iron is 

 universal. I need not extend a Lst of exceptions that over.^ 

 ■whelm the rule. If, again, the nature, or imagined age, of the 

 rock which is traversed by a vein, is to hi made the criterion of 

 th^ age of the Igitter, or ol" the iiickd;d minerftie, it must be 



