DEPARTMENT OF NATURAL SCIENCES. 



ON SOME POINTS IN THE GEOLOGY OF NORTH- 

 ERN WISCONSIN. 



BY ROLAND IRVING, A. M. E. M., 

 Agsistant State Geologist of Wisconsin. 



When the title of my paper was sent to the secretary, in an- 

 swer to his request, I had intended to give in detail all the 

 facts I could collect bearing on the question of the age of the 

 copper bearing rocks of Lake Superior — the subject propos- 

 ed in the title then sent — including also the observations 

 made by myself and my assistants in northern Wisconsin ; 

 and to elaborate a subject which is briefly stated without theo- 

 retical discussion in my report on the geology of that region, 

 now before the legislature. My double professional duties 

 have however, rendered it impossible for me to do this at all 

 satisfactorily, so that I have been obliged to give up present- 

 ing an exhaustive paper to the Academy. It has seemed to 

 rae, however, that the very interesting discoveries made by my 

 party, bearing on the relations of the copper bearing series of 

 rocks, and the Silurian sandstones of the west end of Lake Su- 

 perior, should be presented to the Academy in some way. I 

 had supposed also that the members of the geological corps 

 would be expected to give some account of the results of their 

 work, — I propose, then, to give briefly an outline of the geol- 

 ogy of the district which has been under my charge, includ- 

 ing a bare statement of the discoveries alluded to. This I am 



