xiv 



INTEODUCTOKY LETTER. 



policy forbade to neglect, may be considered, in a measure, a voluntary offering, 

 tendered at little or no additional expense to the Department. 



Of such a character are the researches establishing the palaeozoic base in the 

 Mississippi Valley, and bringing to light fossil remains in rocks that have been 

 hitherto set down in the West as destitute of organic remains.* 



Dr. Norwood's Report exhibits the limit, extent, and range of the trap formations 

 on the south shore of Lake Superior, towards Fond du Lac, and also the various 

 systems of intrusive traps, which can be traced on the north shore, up to the 

 British line ; together with detailed statements touching the mineral veins discovered 

 over that region of country. 



Colonel Whittlesey's Report traces the trap ranges, and defines the boundaries of 

 formations on the south shore, from the Bois Brule as far as the western boundary 

 of Michigan. 



Both exhibit the facts which finally led to the conclusion, that in this part of 

 the Chippewa Land District, there are no copper lands, with sufficient promise of 

 productive veins, to justify the Department in setting them apart as a mineral 

 reservation. 



Throughout this Report, abundant evidence will be found, in proof that both the 

 Upper and Lower Magnesian Limestone formations of Wisconsin and Iowa are 

 lead-bearing, and, to some extent, copper-bearing also. But there will be found, at 

 the same time, the reasons which have governed my recommendation, that here, as 

 on Lake Superior, no mineral reservations should be made. 



To avoid repetition and an unnecessary increase in the bulk of this Report, I 

 have either condensed or wholly omitted many minute details, collected by various 

 members of the corps ; which, though required to establish the bounds of formations, 

 became superfluous after having subserved that special purpose. 



I have also suppressed long lists of barometrical measurements and astronomical 

 observations, necessary in the location and estimation of geological sections ; but, 

 that object served, never likely again to be referred to. 



The local details, found at the conclusion of each chapter, will be chiefly inte- 

 resting to the present settlers, or to those seeking locations in the district of country 

 of which they treat. 



The general reader will find in the Introduction, besides a narrative of events, a 

 brief summary of the leading practical results obtained in the course of the Survey ; 

 while, to the geologist, the sections in each chapter relative to the palaeontological 

 character and mineral contents of each formation ; the lithological and stratigraphical 

 details in Dr. Shumard's Report ; together with the investigations in Chapter V. 

 touching the age of the red sandstones of Lake Superior, and the details connected 



* See, for particulars, § 2, of Chapter I. 



