376 THE CRYSTAL FALLS IRON-BEARING DISTRICT. 



18 miles in length and 10 in breadth extends easterly into T. 42 and 43, 

 R 28" (p. 14). This east-and-west trending area corresponds in part with 

 the Felch Mountain range, but also includes two adjacent troughs, one to 

 the north of it, and the other to the south. 



Subsequent to the above reports, nothing is known to have been pub- 

 lished containing any matter concerning this iron-bearing area until 1869. 



1869. 



CiiEDNER, Hermann. Die vorsilurischen Gebilde der "oberen Halbinsel vou 

 Michigan" in Nord-Amerika. Zeits. der deutschen geol. Gesell., Vol. XXI, 1869, pp. 

 516-568. With map and three plates of sections. 



In Credner's article we find a considerable advance in knowledge 

 concerning the relations of the rocks of the Felch ]\Iountain area. This 

 advance is indicated by his general map (PI. IX) and by his two profiles 

 (fig. 3, PL IX, and fig. 1, PL X). 



In profile No. 3, going from south to north, the granite is represented 

 as overlain by quartzite, separated by a narrow interval from the marble, 

 which in its turn is overlain by a great thickness of the ore formation. The 

 dip is steep to the north. Unconformably upon the last two formations — the 

 marble and the iron formation — there are caps of Potsdam sandstone, with 

 the beds dipping flat to the north. 



In fig. 1, PL X, the gneiss overlain by the quartzite, dipping steep to 

 the north, are the only pre-Paleozoic rocks shown. The same profile shows 

 the unconformable Potsdam, with Silurian dolomite resting conformably 

 upon it. 



In the text there is mention, with an illustration (fig. 5, PL IX), of the 

 granite dike cutting across the iron formation in the upper course of the 

 Sturgeon River. Beyond this no reference to the area under discussion 

 occurs in the text. 



1873. 

 Brooks, T. B. Iron-bearing rocks (economic). Geol. Surv. of Michigan, Yol. 

 1, 1869-1873, New York, 1873, Part I. 319 pages. With maps. 



In the year 1873 Maj. T. B. Brooks's very important study of the 



Michigan iron ranges appeared, and in it the Felch Mountain area for the 



first time is distinctly separated as "the North Iron Range" from the "South 



Iron Range" of the Menominee River iron region, both together, however, 



constituting the Menominee. 



The north iron range, about 12 miles from the other in the south part of T. 42, • 

 Rs. 28, 29, and 30, is in places a prominent topographical feature. The capping of 



