144 THE TENOKEE IKON BEAEING SERIES. 



of this fraginental textvire puts the formation in strong contrast with the 

 chert and hniestone of the limestone member immediately underlying it, 

 and with tlie various ferruginous and cherty rocks of the immediately over- 

 lying Iron-bearing member, all of which rocks are entirely without tlie frag- 

 mental texture, and whatever their mode of deposition, are certainly not in 

 the nature of mechanical sediments. 



Geographkal extent. — From the western end of the Penokee range, on 

 the south line of Sec. 14, T. 44 N., R. 4 W., Wisconsin, to the southeast 

 corner of Sec. 17, T. 47 N., R. 43 W., Michigan, a total distance of 52 miles, 

 the outcropping edge of the Quartz-slate formation forms a continuous belt. 

 West of the western end of the Penokee range, as shown on the maj)s here- 

 with, all of the rocks of the Iron-bearing series disappear from sight, but in 

 T. 44 N., R. 5 W., Wisconsin, they appear again, and here the same quartz- 

 slate may be traced for a distance of something more than 3 miles. Whether 

 the horizon is recognizable farther to the east than the easternmost point m 

 Michigan alxive mentioned is, however, in some doubt. This question is 

 considered separately in a subsequent chapter. 



From the western end of the Penokee range eastward to the vicinity of 

 Simday lake, the width of the outcrop of these slates, which dij) nearly al- 

 ways at a high ang-le to the northward, presents only very slight -vai-iations. 

 To the east t)f Sunday lake, however, there is a somewhat rapid expansion. 

 In the northern part of Sec. 24, T. 44 N., R. 4 W., Wisconsin, the width is 

 600 feet ; at Penokee gap, on Bad river, it is 450 feet ; at mount Whittlesey, 

 near the northwest corner of Sec. 16, T. 44 N., R. 2 W., Wisconsin, it is 450 

 feet; at the gorge of the Potato river. Sec. 19, T. 4,5 N., R. 1 E., Wisconsin, 

 it is 475 feet ; at the passage of the West branch of the Montreal river, Sec. 

 27, T. 46 N., R. 2 E., Wisconsin, it is 450 feet; at the Aurora mine, NE. ^ 

 Sec. 24, T. 47 N., R. 47 W., Michigan, its jjossible maximum is 580 feet; 

 on the west side of Sec. 13, T. 47 N., R. 46 W., Michigan, its possible maxi- 

 mum is 600 feet; and in the southern part of Sec. 10, T. 47 N., R. 45 W., 

 Michigan, the width is 1,000 feet, this great increase in width being due in 

 part to a flattening in the northward dip, and in part to an actual increase 

 in thickness. 



