34 THE PENOKEE IRON BEARING SERIES. 



netic oxides of iron in proportions varying from 1 or 13 i)cr cfut up to 60 and 80 per 

 cent of the whole. The entire series has a nearly uniform dip west of north, generally 

 at a very high angle. Tlie thickness never varies far fi-om 4,000 feet, a figure obtained 

 by actual measurement. (P. 48.) 



The estimate thus given for the tliickiiess of tlie iron series falls far 

 sliort of the truth, as the writer himself was able to show after further 

 work. The mistake arose from a misconception during- the first field 

 season's work, of the nature <jf the up}>er inica-schist or micaceous quartz- 

 ite member of the iron series. This member was not at the time examined 

 closely" and was supposed to belong with a higher series. 



Irving (R. D.). On Some Points in the Geology of Northern Wisconsin. 

 Trans. Wis. Acad. Sci., Arts and Letters, vol. ii, 1S7.V74, pp. 107-119, with map and 

 section. (Published 1874.) 



This is essentially the same paper as the last referred to. 



Whittlesey (Charles). Physical Geology of Lake Superior. Proc. Am. 

 Assoc. Adv. Sci., 1875, l.'4th Meeting, part 2, pp. 60-72. (Published Salem, Massachu- 

 setts, 1876.) 



This paper is published only in abstract. It gives in outline some of 

 the author's views as to lake Superior geology. It contains only a few 

 very general and incidental references to the Penokee-Gogebic district. 



Brooks (T. B.). On the Youngest Hurouiau Rocks South of Lake Superior, 

 and the Age of the Copper-Bearing Series. Am. Jour. Sci., 3d series, vol. xi, 1876, 

 pp. 206-211. 



This paper maintains that the large development of granite south of 

 the Menominee river in Wisconsin is the youngest member of the Huronian 

 or Iron-bearing series of that region, and then proceeds to draw a parallel 

 between this Menominee granite area and certain granites that lie north of 

 the Penokee range ui the vicinity of Bad river, Wisconsin, which he main- 

 tains are in the right position to be again the uppermost member of the 

 Iron-bearing series of this region. We quote from his argument: 



A careful consideration of all the facts to be observed in the Menominee region 

 confirms me in this hypothesis, which is further supjiorted, as it seems to me, by 

 observations in the Penokie Iron region (Bad river), Wisconsin. 



