

106 



BULLETIN OF TIIK 



two metals form an alloy when melted together. It is probable that 

 the separation in the rooks is due to the cooling from fusion being so 

 extremely gradual as to allow the two metals to solidify se2)arately, at 

 their respective temperatures of solidification — the trap being an igne- 

 ous rock, and ages often elapsing, as is well known, during the cooling of 

 a bed of lava, covered from the air." We may remark here that Hunt's 



r 



edition of Ure*s Dictionary, 1878, states that the West Canada copper 



mines are the most important iu America. Such carelessness of state- 

 ment should hardly be allowed in a work of its purported character- 

 Mr. A. R. C. Selwyn, in the Canadian Naturalist,* opposes the use of 

 the numerous names based upon purely theoretical hthology ; i. e. No- 

 rian, Montalban, Taconian, Kewccnian, etc., in the crystalline rocks. 

 He includes the Copper-bearing rocks in the Huronian. His views, how- 

 ever, were objected to by Mr. Thomas Macfarlane.f Mr. Sclwyn's paper 

 "was again published in the Report of Progress of the Canada Geological 

 Survey for 1877 - 78 (A, 15 pp.). 



In the third edition of Prof J. D. Dana's Manual of Geology (p. 778) 

 we are given his views concerning the deposition of the copper at Lake 

 Superior as follows : " When eruptions of melted rock have taken place, 

 fliey have often brought not merely the heat of great depths to tho 

 surface, but also, various mineral materials encountered on the way up, 

 and especially some of the metals or their ores. 



*' The fissures were in general deeper than those that gave origin to 

 veins of segregation, for the latter did not reach to where melted rock 

 could fill them, and hence had to be filled by Avliat they could 

 get through the slower process. They consequently nmst have de- 

 scended to regions of very high temperatin^e. As in a volcanic conduit, 

 ■whatever at these depths, in the heated subterranean region adjoining 

 the opened passage-way, was ready to pass into a state either of vapor 

 or liquidity, would have been forced, by the pressure to which it was 

 subjected at those depths, to escape, if possible, by the way made for 

 the liquid rock, and would have ascended either along side of the latter, 

 or within its mass; and -at the same time, a portion would have been 

 liable to be forced into the wall rock of the fissure wherever it was not 

 of too close a texture to receive it. The mineral material that could take 

 advantage of such an opportunity, or be aided in it by the heat of tho 

 ascending melted rock, would be that, as just implied, which was most 

 easily fused or vaporized ; and this includes certain metals and their 



* 1879, {2,) IX. 17-32. 



1 Remarks on Canadian Stratigraphy, Can. Nat. and Geo!., (2,) IX. 91 -102. 



.■i 



4 





