[INTRODUCTORY LETTER. 
TO THE HON. J. BUTTERFIELD, 
COMMISSIONER OF THE GENERAL LAND OFFICE, 
WASHINGTON. 
New Harmony, Inprana, 
October 30, 1851. 
Str :—The Preliminary Reports, forwarded by me from time to time, have fur- 
nished to the Department accounts of the field work ; while the Annual Reports of 
1848 and 1849, heretofore submitted, contain a more full and digested statement of 
the observations and discoveries of each year, made by the Geological Corps, in 
Wisconsin, Iowa, and Minnesota. 
The Final Report, which I now lay before the Department, embraces, in a concise, 
connected, and revised form, the substance of all the previous reports; together 
with a full statement of the results of last season’s operations: thus covering the 
entire ground of the Survey. 
Condensed reports of the Assistant Geologist and of the heads of sub-corps, 
accompany the present Report. These contain detailed descriptions of the districts 
specially assigned to each ; together with generalizations deduced therefrom. 
In the estimation of heights, to be calculated in accordance with my instructions 
above the level of Lake Superior, a long series of barometrical observations became 
necessary. Some of these have been recorded in the form of meteorological tables, 
supplying materials for comparing the climate of Lake Superior with that of the 
Upper Mississippi, and showing the former to be milder and more equable than the 
latter, and, indeed, than that of many portions of the United States, in much more 
southern latitudes. 
I may here remark, however, that it has been my aim, during the entire conduct 
of this exploration, to make the strictly practical and business portion of the Survey 
the chief end and object of our operations. Scientific researches, which to some 
may seem purely speculative and curious, are essential as preliminaries to these 
practical results. Further than such necessity dictates, they have not been pushed, 
except as subordinate and incidental, and chiefly at such periods as, under the 
ordinary requirements of public service, might be regarded as leisure moments; 
so that the contributions to science thus incidentally afforded, and which a liberal 
