178 



THE PENOKEE IROX BEARim; SERIES. 



(loiiiinatiug variety some of tlie Ijiotitk' juid cliloritic .slates, novaculite, 

 and a little red clay shale. At the srorge of the Potato river, in tlie NE. ^ of 

 the 8E. \ Sec. 1!), T. 45 N., K. 1 E., Wisconsin, the exposun^s are a<i;-ain large, 

 showing the entire width of the (juartz-.slate. riie })ositions of these ex- 

 posures are shown in Fig. 5. The contact on the south between this .slate 

 and the underlying greenish schist has already l)een de.scribed. The usual 

 vitreous quartzite is found as the uppermost horizon and the l)ody of the 

 formation is made up of thinly laminated feldspathic (piartz-slates. The 

 exposures at the gorge of the West branch of the Montreal (Fig. 9) are 



if^^- 



^^^te*^"«'-'=^^* 



Qiuzrh 



■'ip^ SoiLatem-Comptex.. 



Fni. 0.— il;!]) of I'sposiires at West branch oflloiitro.il river. 



quite similar totlioscon the I'otato, showing tlic lower junction but not the 

 uj)per. From here eastward to the vicinity of Sunday lake the natural 

 ex])osures of the (Quartz-slate incndjcr are much rarer and smaller than 

 tliosc already described. However, in a very large lunnber of places the 

 mining or exploiting operations of the district have unco\ered this forma- 

 tion for small distances. Naturally the most commonly uncovered jiortion 

 of tlu! formation is its uppermost quartzite member, Avhicli is ordinarily 



