18 THIRD REPORT — 1833. 



itself; ami how tliese facts illustrate relative ages of forma- 

 tion. 



This tendency to an east and west direction of the metallife- 

 rous veins may be observed not only in Cornwall but in the 

 stratified parts of England, in the mining districts of Europe, 

 and in the range of the great veins of Mexico. 



Mr. Robert Fox, having discovered galvanic action to ensue 

 by the connexion of an apparatus, constructed to detect it, with 

 portions of metalHferous veins, suggests whether some analogies 

 may not be traced between electro-magnetic ciu'rents and the 

 directions of veins : nothing upon which any hypothesis can be 

 built seems, however, as yet to have been proposed ; and it may 

 be doubted whether, when this test is apphed to masses of ore, 

 the experiment is not liable to many objections. A principal 

 one seems to be, that by the very act by which we gain access 

 to the vein, we lay it open to atmospheric action, and conse- 

 quently to decomposition. Chemical agency commences, and 

 with it, very naturally, galvanic influences are excited. 



Veins containing ores little subject to decomposition have, I 

 apprehend, been found to give httle or no indications of this 

 nature. 



It may, however, be that this general direction of metallife- 

 rous veins may not obtain as to veins of injection ; and in that 

 case we shall have additional reason to admit more causes than 

 one to have been in operation. This is a matter deserving ex- 

 tensive observation. 



Other veins have been stated to cross the metalliferous veins : 

 they are generally filled in a different manner. If they contain 

 any ores, they are frequently of difterent metals from those in 

 the former. They pass through or traverse the other veins, 

 cutting them through, and sviffering a disturbance to take place 

 in their linear direction, or what the miners significantly term 

 a heave. 



This fact is relied upon as proving that veins are of different 

 ages, as first asserted by Pryce, much insisted upon by Werner, 

 and allowed by Hutton and Playfjiir. 



Those who dispute this inference, therefore, are the advo- 

 cates for the sole operation of contemporaneous causes : they 

 object that rules which have been proposed for ascertaining 

 the exact tendency of such disturbances having been found to 

 be subject to exceptions, tlie proof of dislocation is wanting, or 

 that dislocation has taken place without motion. The latter 

 proposition, at any rate, appears to me to be very difficult to 

 understand ; and I think if any part of this intricate subject is 

 clear and intelligible, it is that the relative age of veins is made 



