44 WISCON"SIN" ACADEMY SCIEXCES, ARTS, AND LETTERS. 



they do with a persistent opposite dip and somewhat different strike. 

 Unconformability has been shown to exist between the Laurentian 

 and Huronian in Michigan, but this is the first time that it has 

 been proven in Wisconsin. Northward from the granites the sec- 

 tion has been completed for over sixteen hundred feet. In this 

 space are included two " magnetic oi^e " beds, the southern one 

 hundred and thirty and the northern over five hundred feet thick. 

 Directly above or north from the northern " ore " bed there is a 

 space of fourteen hundred feet upon which exposures have not been 

 found. Above this blank, recent railroad excavations enabled Mr. 

 Wright and myself to subdivide and extend the belt of four hun- 

 dred feet, supposed to be the uppermost member of the Penokie sys- 

 tem, into: a. siliceous schists, one hundred feet; b. blank, (Bad River,) 

 seventy-five feet; c. contorted black slate, two hundred and fifty feet; 

 d. diorites, seventy-five feet; and e. black porphyritic slates, fifty feet. 



Owing to the heavy deposits of drift we were unable to find expos- 

 ures for thirteen hundred feet north from the black porphyritic slates. 



We then found what are probably the latest beds of the Huronian 

 formation, g. black slate, forty feet , h. quartzite, about two hundred 

 and fifty feet, i. slaty am3'gdaloid seventy-five feet. 



The thickness of the formation, I estimate at something over five- 

 thousand feet. The dip is about sixty-six degrees to the north 

 showing entire conform ability throughout. 



It will be observed from this brief outline of the geological sec- 

 tion at Penokie Gap, that there are two important belts left blank. 

 There is no attraction of the needle upon either, which would lead 

 one to susj)ect the presence of magnetic deposits. But the red or 

 hematite ores have no influence on the magnetic needle, they are 

 soft and easily worn away, and never outcrop naturally in the Mar- 

 quette region. Consequently although not exposed on the Penokie 

 range they may yet be found in one of these blank spaces. Represen- 

 tatives of most of the beds of the Marquette sj'stem occur at Penokie 

 gap. This is a strong argument in favor of the existence of the 

 soft or hematite ores in the unexplored belts of the Wisconsin Hu- 

 ronian. 



An accurate geological section ought to be constructed entirely 

 across the Penokie Range at some point from the granites on the 

 south to the undoubted Copper-Bearing Series on the north, even 



