33D 
Tuk Precuacial, VALLEYS OF THE Uprrr MISSISSIPPI AND ITS 
FIASTERN TRIBUTARIES. 
Harry M. CLeM. 
So far as the writer is aware, there has been no attempt to compile 
a map showing the results of researches upon the preglacial drainage of 
the region indicated in the title. The following paper addresses itself to 
that task, together with a brief discussion of the reason for believing that 
certain streams shown on the map were preglacial. Only the briefest out- 
line can be given in this short discussion, which merely undertakes to 
pioneer the large field lying before it. 
The attempt has been made to map accurately the preglacial channels 
of the area in question, but this may not always have been attained, for 
several reasons. The literature is not adequate in all the fields of the area, 
and often the statements made are not so clear as might be desired. The 
word “probable” is very frequently used and renders mapping difficult, 
if not impossible. Occasionally, authors differ, and in such cases the one 
which seemed to be the better authority is followed, and the dissenting 
theory mentioned in the text. No attempt has been made to give a critical 
discussion of the different theories. Any reader who may desire more 
detailed information than this paper furnishes can find all that is of im- 
portance in the accompanying biblicgraphy, or he may look there for cor- 
rection or verification of any points in the discussion with which he may 
disagree. 
The greater portion of the region covered in this paper is so deeply 
buried in drift that only the major details of the ancient preglacial topog- 
raphy are apparent. The multiplicity of minor topographie details that 
give final expression to the landscape are so completely buried from sight 
that it may never be known how the ancient surface appeared before the 
advent of the glacier. Only by a multiplicity of borings could a general 
idea of the details of that buried topography be obtained, and that is im- 
possible except where some deep-seated natural resource induces men to 
sink deep wells. Thus innumerable small valleys have been obliterated and 
1Not published here. 
