XVI LETTER OF TRANSMITTAL. 



Ill the vicinity of the mines and the iron-bearing' formations the exami- 

 nation of the district has been of the most detailed character, practically all 

 of the ledges having been visited and advantag-e having been taken of 

 vindergTOund workings and borings. Moreover, in order to determine the 

 succession, for large areas, it was necessary to make a close magnetic 

 survey with the dial compass and dip needle. In the areas more remote 

 from the mines the work was of a less detailed character. 



The western half of the district is treated by J. Morgan Clements in 

 Part I of this monograpli. The eastern half of the district, with the excep- 

 tion of the Sturgeon River tongue, is treated l)y H. L. Smyth in Part II. 

 The chapter upon the Sturgeon River tongue was prepared by W. S. Bayley. 

 My own part of the work has been a general supervision of the entire survey, 

 with frequent trips into the region to assist in solving the general structural 

 problems. 



To the gentlemen who furnished the complete results of their surveys 

 for the first two seasons, we are deeply indebted. The drawing for the 

 maps was done by E. C. Bebb. The colored plates were prepared by 

 J. L. Ridgway. 



Very respectfully, your obedient servant, 



C. R. Van Hise, 



Geologist in Charge. 



Hon. Charles D. Walcott, 



Director United States Geological Survey. 



