Wadsworth.] 208 May 7, 



The origin of these boulders, or rather of similar ores, was found 

 to be as follows : near the Peters River, diabase dikes had cut 

 through the red argillite (see above, under manganese) indurating 

 it and filling it more or less with iron ore. This argillite when 

 broken away and water- worn gave rise to the deceptive boulders 

 mentioned above, which had thus an origin entirely different from 

 the Lake Superior ore. 



ON A SUPPOSED FOSSIL FROM THE COPPER-BEARING 

 ROCKS OF LAKE SUPERIOR. 



BY M. E. WADSWORTH. 



My attention was called by my friend, Professor Hyatt, to this 

 specimen, which he had seen in the collection of Professor James 

 Hall, of Albany. On my application Professor Hall very kindly 

 sent it to me, and permitted all necessary work to be done on the 

 specimen that could be accomplished without injuring its value. 



The great interest attaching to this form is owing to the dis- 

 puted age of the copper-bearing rocks and to its resemblance to a 

 fossil, a resemblance which is so great, that so far as I am aware, 

 every palaeontologist, who has seen the specimen, has taken it for 

 an organic body. That this resemblance is close, is shown by the 

 fact that even the eminent palaeontologists just mentioned have 

 regarded it as a fossil. 



Instead, however, of being of organic origin, it appears to 

 have been formed by the flowing of a pasty lava in such a man- 

 ner as to raise a series of ridges, giving the surface an appearance 

 closely like that of some cephalopods. This lava flow, which 

 evidently was once a basaltic lava, like that of Mt. Etna, or of the 

 Sandwich Islands, has since undergone certain changes which 

 have altered its interior structure and composition. As is the case 

 with all lavas, the structure is more crystalline in the interior, 

 and more compact on the surface. At the present time the dark 

 reddish brown rock is one that would be denominated, by most 

 lithologists, a melaphyr. Much crystallized calcite occurs in the 

 specimen, having the same characters as have nearly all of the sec- 



