Relations of Trap-Bocks with Ores of Copper. 25 



influences on numerous cupriferous veins, whose development 

 is also subordinate to them ; 2d, Containing accidentally oli- 

 gistic iron enclosed in globular shapes in their masses, and 

 sulphuret of nickel disseminated in contemporaneous crys- 

 tals ; 3(/, Presenting relations of contact with the multi- 

 plied repositories of oligistic iron. 



The schalstein of Dillenburg, the blatterstein of the Harz, 

 and the gabbro of Italy, rocks which we have assimilated, as 

 resulting, the whole three, from metamorphic influences de- 

 veloped at the point of contact with the masses of trap, have 

 a common character of the most striking kind, which is the 

 strong red colour they impart to a great portion of the rocks 

 they contain. In their normal state, these rocks are green, and 

 exhibit, in a more or less distinct form, the characters of the 

 trap masses to which they happen to be subordinate, establish- 

 ing the passage between the eruptive rock and the upraised 

 stratified rocks. The proportion of protoxide of iron which 

 they contain in this normal state, prevents us supposing the 

 reddening here to be the result of a simple superoxidation of 

 pre-existing iron; the iron is superadded, and in such quantity 

 that the rocks are connected by transitions and relations of 

 contact to concentrations of pui'e ores. 



In order to account for the reddening of these metamorphic 

 rocks, we have, therefore, strong reasons to admit the same 

 theoretic explanation as for the generation of the subordinate 

 ores ; and this explanation necessarily extends to the simple 

 reddened clay-slate of Dillenburg, the red flinty slate of 

 the Harz, the galestri of Tuscany, and those red jaspers 

 which the Italian peasants so expressively name mnftoni 

 (bricks). Now, in the present state of our geological know- 

 ledge, we can only ascribe this generation of oligistic iron 

 to subterranean emanations ; these emanations have followed 

 the outbursting of the trap-rocks, since we find the products 

 of them in certain veins which intersect the traps ; they are, 

 therefore, to the trap rocks, what the products of Solfataras 

 now are to the volcanoes of the present period. 



Concentrations of oligistic iron in highly ci"ystalline re- 

 positories such as that of Rio in the island of Elba, leave no 

 doubt upon the mind. We can conceive the posterior arrival 



