MUSEUM OF COMPARATIVE ZOOLOGY. 81 



infer from tliis, that he regarded the fissures to be of anterior formation 

 to the traps. He states that " the trap rocks of Lake Superior pass 

 through the red sandstone and conglomerate rocks, and are interfused 

 with them, producing at or near their junction a very porous amygda- 

 loid, which is always found at the lower side of the dyke where it is 

 next to the sandstone." He also remarks that he finds the copper and 

 silver " united together side by side by fusion without any alloying of 

 the silver " ; " the two metals are completely soldered together at their 

 points of contact." This paper was also presented to the Association 

 of American Geologists and Naturalists, at their sixth meeting, April 

 1845, published in their Proceedings (pp. 53- 60), and discussed by 

 Prof. C. U. Shepard (pp. 60, 61). He considered that the copper 

 was derived from the sandstones by the action of the trap dikes upon 

 them. The copper was originally in the primitive rocks, " whose lateral 

 slopes were occupied with cupreous strata derived from the degradation 

 of the surrounding primitive ; and that whenever the trap had slid out 

 beneath these deposits, or in other ways come in contact with them, 

 they would, as elsewhere, bring to the surface rich masses of copper ; 

 but he was inclined to the opinion that they would not give rise to deep 

 and permanent mines." He considered that the sandstones belonged to 

 the New Red. In an earlier portion of the Proceedings (pp. 30, 31), Dr. 

 Jackson remarked that "at the junction of the great dykes with the 

 sandstones of Nova Scotia, Maine, and on Lake Superior, a more violent 

 ebullition took place than that which accompanied the eruption of the 

 trap ranges in Connecticut, for the sandstone and trap are blown into a 

 perfect scoria at the former localities ; amygdaloid resembling the most 

 porous lavas, and immense quantities of trap tuff containing lumps of 

 metallic copper, evince the powerful action of trap on the sandstones 



of Nova Scotia, and on Kewenaw Point, Lake Superior Ou 



Kewenaw Point we have an intimate mixture of copper and trap rock 

 in the amygdaloid, and I at first supposed if the amygdaloid resulted 

 from the interfusion of sandstone and trap, that the copper might have 

 been reduced from copper ores pre-existent in the sandstones ; but the 

 absence of such ores in the sandstone in contact with or near the trap 

 appears to discountenance the idea, and I am more disposed, since I 

 have explored that region, to coincide with the opinion of Dr. Houghton 

 in the belief that the coppei of that region is a part of tlie primary 

 copper of the globe brought up by the viscid trap." At a meeting of 

 the Boston Society of Natural History,* November 6, 1811, he re- 



* Proceedings, I. 203. 

 VOL. VII. — NO. 1. 6 



