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No. 1. — Notes on the Geology of the Iron and Copper Districts of 

 Lake Superior. By M. E. Wadsworth. 



There are probably no regions of like extent in the United States that 

 have attracted greater interest or attention than the Copper and Iron 

 districts of Lake Superior. The most discordant views have been held 

 concerning their geology, and the origin of their ore deposits. There 

 are also probably no districts in this conntry which have been more accu- 

 rately studied, taking all of the conditions into consideration, than these 

 were some thirty years ago. The geolog}-, including the origin of their 

 ore deposits, was then, for the time and methods of study, stated with a 

 remarkable degree of accuracy, so far as it has been our province to 

 observe or judge. It would not, then, be our duty to write concerning 

 these districts, wei'e it not that the almost universal belief of geologists 

 at the present time regarding one, and in some respects the other dis- 

 trict, is so entirely at variance with the facts as we interpret them. 

 Before giving the facts it is necessary to present to the reader some of 

 the various ideas held regarding the geology of both districts. We shall, 

 however, in the main confine ourselves to those parts which we have 

 visited, except so far as observations elsewhere have a bearing upon our 

 work, or upon the questions which we wish to discuss. 



It seems best to take up these views in chronological order, even if it 

 does impart a dictionary flavor to this paper. Fii'st in order, then, we 

 propose to discuss 



The Iron District. 



The earliest writer that it is necessary to quote here is Henry R. 

 Schoolcraft, whose Narrative Journal of Travels, etc. was published at 

 Albany in 1821. He speaks of the granite at Granite Point (p. 158), 

 and of its being traversed by veins of greenstone trap. He gives the 

 composition of the former rock, and advances his reasons for considering 

 that it occupied its present position before the deposition of the over- 

 lying sandstone. He does not attempt to give the age of the sandstone, 

 although he thinks " its position would indicate a near alliance to the 

 * old red sandstone.' " 



VOL. VII. — NO. 1. 1 



