g4 THE TENOKEE IRON BEARING SERIES. 



Further, of the xVshlaud mine: 



One iiitfresliiif;- featiuc is tbf- presence of occasional rounded bowlders of 

 quartzite in the ore. Whether these bowlders will disai)i)ear in depth is a problem 

 that may throw some light on the origin of these hematite veins (pp. 141-142). 



Ill his uccount of the Norrie mine he further states: 



As at the Ashland mine, there are large rounded bowlders of (|uartzite in the 

 ore, and the (luartzite next to the (U'e is frequently disintegrated into common sand 



(p. 144). 



The aeeuracv with wliieli the iron-bearinji' Ix'U was located, by means 

 of mag-netie attractions, by the Wisconsin GeoU)gical 8ur\ey between the 

 West Brancli of the Montreal ami the Montreal river, where there are no 

 exposures, has lieen indicated by the (juotations from its re})orts. It 

 appears that Mr. Brotherton, in 1S71», located this belt in the same manner 

 on the Michigan side of the line, althouoli no report of his work lias, so far 

 as I kiK)w, been published. The sugg-estion which Mr. Wright made as to 

 the ore of the Ashland mine being enrich' 1. by percolating waters is inter- 

 estino- as beiii"- in coiiformitv with the conclusions which a, detailed study 

 has developed. The appearance of rounded bowlders of quartzite in the 

 ore at the Ashland and Norrie mines appears to indicate that here, before 

 the beginning of the deposition of the layers of the iron-bearing formation, 

 the underlying <piarlzite was Ijrokeii by erosion. 



Van Hlse (C. li.). Upon the Origin of the Miea-Sehists and Black Mica- 

 Slates of the ronokee-Gogebic Iron Bearing Series. Am. Jour. Sci., 3d series, vol. 

 XXXI, 1S8G, pp. 4u3-45it. 



This i)aper presenfs facts and arguments going to show that certain 

 mica-bearing slates and schists, which in the l?ad river country occur in the 

 upper horizons of the Penokee series, are merely alteration forms of the 

 plainly fragmental rocks which make up the greater part of these -upper 

 horizons. Tlie process by which this alteration has been brought about, 

 and by which in tlie extreme cases the original fragmental textin-e of the 

 rocks has been nearly or (|uite olditerated, has consisted mainly in the 

 development of inuscovite and l)iotite from the feldspar fragments, a sepa- 

 ration of silica taking place at the same time. Besides this main mode of 



