330 THE CRYSTAL FALLS IROE-BEARING DISTRICT, 



divide between the Michig-amme and the headwaters of the Sturgeon, to the 

 Felch Mountain range, which was then carefully studied for a distance 

 extending 13 miles to the east. 



Until within the last few years the larger part of this area had been 

 very difficult of access, and much of it is difficult still. The rock surface is 

 almost wholly concealed by a cover of glacial deposits of various kinds; 

 dense forest and great swamps also obscure the rocks, and make traveling 

 difficult and slow. It is therefore not a field to invite geological study. 

 While exploration for iron ore has here and there passed the frontiers of the 

 productive ranges on either side, the general ill-success which attended the 

 early enterprises has discouraged the active search that would at least have 

 resulted in important additions to geological knowledge. For these reasons 

 the area as a whole, with the exception of the Felch Mountain range, has 

 remained almost unknown geologically, until our work in 1892. The refer- 

 ences to it in geological literature are consequently but few in number, and 

 are for the most part merely the records of the unrelated observations of 

 casual visitors. 



The district, nevertheless, deserves attention from both the economic 

 and the geological standpoint. The iron-bearing formations of the Mar- 

 quette range extend into it from the north, those of the Menominee range 

 from the south. On the west the ore deposits of the Crystal Falls area are 

 connected geographically at least with the western extension of the Menom- 

 inee range. Between these boundaries the area stands as the largest one 

 remaining in Michigan in which iron-bearing formations are known to occur, 

 but as yet not yielding important bodies of ore. Here, too, if anywhere, 

 the questions of the equivalence or nonequivalence of the individual for- 

 • mations of the Marquette and Menominee iron-bearing series are to be 

 answered. 



It is proper to state that the field study, in consequence of the condi- 

 tions under which this woi'k was done, was almost wholly directed to eco- 

 nomic questions, and that it was not originally anticipated that the results 

 were to be published as a monograph on the district. This will explain the 

 very brief space devoted to the Archean in the following pages. The field 

 work was begun and ended in 1892. Since that time there has been no 

 opportunity to revisit localities, and the conclusions now stand essentially 

 as they were reached in the field. Considering both the obscurity and com- 



