X1V INTRODUCTORY 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 palseozoic 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 Brulé 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 ees an 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 paleontological 
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. 
