GEOLOGICAL EXPLORATIONS AND LITERATURE. 101 



their equivaleiicp with tin' Pciiokcc strata, wliich stroiifily impress me as holding 

 charaeters strikiiifily similiar to those of the Huroiiiaii shites of hike Huron and the 

 Aniuiike slates of Guntiiut lake and Tliunder hay. This resemhlanee impressed me 

 from the beginninff; hnt I feel reluctant to controvert the jiidsinent of the Wisconsin 

 geologists. 



But while I hold the decision in abeyance, I take the liberty to ofl'er a few points 

 for consideration : 



(1) We discover the strong lithological resemblance referred to. 



(2) The lithological characters are unlike those of the ore-bearing strata of the 

 Gogebic, Marrjuette, and Vermilioii regions. 



(3) The ore also is magnetic instead of hematitic. 



(4) It is diffused through the laminated sheets of the formation, as at Gunfliut 

 lake, and not segregated in lodes, as in the other regions mentioned. 



(5) A higher system of black slates, apparently unconformable on the hematitic 

 schists, appears to exist in the Gogebic and Marquette regions, as it certainly does in 

 the eastward jirolongation of the Vermilion schists. 



(G) At the distance of 15 to IS miles in a direct line SSE. of the Gogebic range, 

 is a well known line ol' magnetic attractions, sitch as are exerted by the magnetitic 

 schists of Penokee gap. 



(7) These lines of attraction, though as far as I know they lie too far south, may 

 nevertheless, when more accurately located, be found in the strike of the Penokee 

 schists, especially if the great exposure a mile north of Penokee station affords a 

 reliable indication of the strike; for that is S. 67° E. But this is ])robably distiu'bed 

 somewhat by the great fault. 



Should the Penokee slates l)e identified with the Animike (true Huronian) then 

 the Marquette or Kewatin system will be found underlying, aiul the Juxtaposition of 

 the Penokee slates with the (supjiosed) Laurentian schists on the south, may be due 

 to an overslide accompanying the formation of the gieat fault. If the dislocation 

 resulted from a horizontal movement, instead of an upthrow, then the strata on the 

 east side nuist have sli|)i)ed southward over 900 feet; and, if the movement was con- 

 fined to the Penokee slates, they may tlius have concealed a thin representation of 

 the Kewatin which, on the identiflcation assumed, is at present, wanting at this 

 point (pp. 194-1!).")). 



Our own observations as to the occurrences of the rocks south of the 

 Aurora mine differ radically from those of the Professors Winchell. 

 The granite south of the Aurora, described hx N. H. Winchell as consist- 

 ing of three parallel knol)s iiiterstratiHed with quartzite, was found to he 

 granite cut by fine grained dike-rocks. Wiuchell's quartzite-slate is then 

 a dike which cuts the gninitc These dikes are separated from the gran- 



