MOST ABUNDANT IN IGNEOUS DISTRICTS. 107 



similar spars and ores can be produced in the laboratory by 

 chemical and electrical means, and all the more certainly 

 that heat is present to facilitate the operation. What can 

 be simulated on the small scale by art we may readily be- 

 lieve to be producible by nature on the large, and thus to 

 chemical and electro - chemical agency are now generally 

 attributed the formation of vein-stuffs and their associated 

 ores. We have spoken of the greater efficiency of heated 

 waters in dissolving and holding in solution mineral and 

 metallic matters, but the effects of water in general (whether 

 hot or cold) must not be overlooked, it being the grand 

 medium through which the contents of veins have been 

 conveyed to their present positions. It is this belief .in 

 chemical solution and re-deposition which distinguishes 

 the modern theories of mineral veins from the older views 

 of sublimation through igneous or plutonic action. 



Whatever may have been the immediate agent of infil- 

 tration and deposition, one thing is certain, that veins, 

 and especially metalliferous ones, are most abundant in 

 areas that have been long subjected to igneous action. 

 There is the closest connection, and necessarily so, between 

 the two phenomena, as it is only in convulsed districts that 

 rents and fissures can occur, and in such districts also that 

 such fissures have the greatest chance of being most rapidly 

 filled with mineral and metallic precipitates. Wherever, 

 therefore, there are old hill-ranges and primary areas that 

 have been repeatedly subjected to subterranean forces, there 

 we may expect veins and cross-veins each set representing 

 a long course of time, and being for the most part filled 

 with its own special ores and vein-stuffs. All portions of 

 a hill-range may not be rich alike, for there are certain 

 centres in which the producing forces seem to have acted 

 with greater intensity, or at all events to have been longest 



