LETTER OF TRANSMITTAL. 



Department of the Intekior, 

 U. S. Geological Survey, Lake Shperiok Division, 



Madison, Wis., Ma// I, IS.90. 



Sir: I tniusiuit lierewitli the iiiiiuust'ript of a lueiiioir ujxtn the Peuo- 

 kee iron-beariiig series of Miclii*»'aii and Wisconsin, by the late Prof. 

 Roland D. Irviny and myself. 



Prof. Irving's death occurred so early in life tlint, while his c(nitri1)u- 

 tions to geology are large, his later works show that he li;id hut fairlv 

 entered the period which would have been the most fruitful in scientific 

 results. The report submitted was designed by Prof. Irving to be the first 

 of a series which should treat each of the iuiportant inju-^jroducing districts 

 adjacent to Lake Superior. To him who built up the division and who 

 planned this investigation is very largely due whatever excellence tliis 

 volume may have. I must necessarily assume, for the most part, the 

 responsibility for the present form of the memoir. 



The field survey for the present report began five years ago. The 

 sea.sons of 1884, 1885, and the larger part of that of the following year I 

 srave to this work. For a time in 1885 and in 188fi Prof. Irviuo- accom- 

 panied the })artA' in person. WIk'U the work began the district was one 

 which explorers had Ijut fairh' entered and no rnilroad reached any part of 

 the range except the Wisconsin ("entral, which crosses it at Penokee g-ap. 

 The district has since developed into one of the most imjxtrtant iron-pro- 

 ducing areas of the country, its product in the lake Superior region beuig 

 exceeded by that of the Marcpiette district only. 



Before the beariunincr <>f this investigation Prof Irviuo- hitd done a 

 large amount of field work uj)ou a portion of tlm range for the Wisconsin 



