Of Maimanse^ L. Siiperior. 9 



but b^' electro-cbemicai agencies, decomposing some soluble salt, 

 most probably the sulphate, of copper. Such changes may have 

 been aided by the remaining heat of portions of the volcanie 

 masses, by the- presence in them of large quantities of iron in 

 low states of oxidation, and by the further oxidation of that 

 metal evidenced in the red jasper and red laumoniteof the veins^ 

 and the red conglomerate and sandstone associated with the trap. 



One great difEculty in supposing the electro-chemical deposi- 

 tion of copper in these veins, is the want of a conducting surface, 

 and one not likely to be acted on by copper salts, for the com- 

 mencement of the process. Much of the copper, however, even 

 when not exposed to- atmospheric action, is coated with suboxide 

 of the metal ; and I have, in several instances, observed the crys^- 

 tals of calc spar in these veins varnished with a thin coat of perox- 

 ide of iron, or of suboxide of copper, which has been precipitated 

 on their surfaces, and might have formed a better basis for copper 

 deposition than the naked surface of the calc spar. In the deli- 

 cate dendritic forms, the crystallization has evidently commenced 

 from minute points ; and this may have been the case also with 

 some of the larger masses, wdiich often have thin plates or fibres 

 connecting them with the wall of the vein. Such connecting 

 threads, if first deposited, may have served as conductors. 



Such attempts at explanation must, however, in the meantime, 

 be regarded as merely, conjectural ; and it must be confessed, that 

 we can have little accurate conception of the processes that may 

 go on in fissures extending from the bottom of the sea far down- 

 ward into volcanic masses, and in which a great variety of sub- 

 stances are subjected in different degrees to the combined influ- 

 ences of heat, pressure, and aqueous solution. The main fact in 

 relation to the origin of the metallic copper, is that it is a product, 

 not of the fusion of the trap, but of subsequent processes, by 

 which the fissures of that rock were filled by materials regarded 

 as of aqueous origin. 



In some specimens collected by Mr. Pilgrim, of Sault St. Marie 

 for the Montreal Mining Company, in other locations on the north, 

 shore of Lake Superior, and with which I have been favoured by 

 the officers of the Company, I find the following modes of occur- 

 ence, which farther illustrate the above views. 



One of the specimens (17 of the Company's collection) is a 

 portion of a vein of calc spar and agate with dendritic copper, 

 traversing both minerals. The wall of tbe vein appears t© 



