LETTER OF TRANSMITTAL. 



Department of the Interior, 



United States Geological Survey, 



Washington, D. C, June 30, 1902. 



Sir: I transmit herewith the manuscript, illustrations, and atlas of 

 a monograph on the Vermilion iron-bearing district of Minnesota, by 

 J. Morgan Clements. 



This monograph is the fifth one of a series of six which treat of the 

 iron-bearing districts of the Lake Superior region. The monographs on 

 the Penokee, Marquette, Crystal Falls, and Mesabi disti'icts have already 

 been published. The last of the series is a monograph on the Menominee 

 district, by W. S. Bayley. There has also appeared a monograph on ihe 

 coppei'-bearing rocks, by R. D. Irving. It is planned to close the work of 

 the United States Geological Survey in the Lake Superior country by a 

 final monograph on the Lake Superior region as a whole. 



This report contains the first series of detailed maps of the Vermilion 

 district. This region is one in which the rocks of Archean age contain 

 economic deposits. The geologic mapping of the intricately folded Archean 

 rocks has been a task of very great labor, requiring the full field seasons of 

 several men from 1897 to 1899, inclusive, and a part of that of 1900. The 

 area mapped in detail is about 1,000 square miles. 



The topogi'aphic work for the report was done by Robert Muldrow 

 and E. C. Bebb, with various assistants. The geologic mapping has 

 been done more largely by J. Morgan Clements than anyone else, but 

 W. S. Bayley and C. K. Leith have also done a large amount of areal 

 mapping, and W. N. Merriam has made a number of large-scale, detailed 

 plats of certain areas having exceptional economic importance. My own 

 MON XLV — 03 2 17 



