418 G. K. Warren— Valley of the Minnesota and Mississippi. 
about 800 miles. This was the only part specified in the law 
authorizing this investigation, but it was necessary in order to 
present the subject itself properly to include the whole distance 
from the mouth of the Minnesota to the Ohio; this is an extent 
of about 760 miles along the general course of this valley, and 
we have prepared a map of it in twenty-two sheets on a scale 
of two inches to a mile. The mannef in which this is done is 
described in Chapter VI of this report. 
General map and profile prepared for publication.— Although we 
have, in constructing the map, exhausted all means of obtain- 
ing knowledge in regard to this part of the Mississippi Valley, 
there are some parts of it too little determined to make its pub- 
lication as a whole, advisable, and therefore we have only pre- 
pared for publication the index map of those twenty-two sheets, 
on a scale of six miles to an inch. (lf photo-lithographed it 
may vary from this scale.) Here, again, generalizations have 
led us to make this index map include the Minnesota River 
Valley. That valley, under another clause of the law, was also 
made a part of my investigation, and a map in twenty sheets on 
a scale of two inches to the mile was made for it. The map 
rt of Arkansas, and northward to include a part of the basin 
of the Red River of the North. It is designated as Diagram 1, 
in five sheets. 
The two systems of the United States land surveys, one on 
each side of the river, are so checked upon each other in its 
construction and by special surveys by ourselves, that the val- 
ley on this small scale is probably as correct as it can be repre- 
sented. The whole of the flood-plain is shaded with light ruled 
lines, except the principal Jakes and water-courses, which are 
shaded with heavy lines. The alluvial terraces above overflow 
are shaded with dots. The high banks or bluffs are without 
shading. On sheet five there are some overflowed lands that 
are above the Mississippi floods, which have special shading. 
In order to complete a presentation of the Mississippi g 
plain to the Gulf of Mexico, the page Diagram A is added, 
red from Plate II of the report of Humphreys and Abbot 
on the physics and hydraulics of the Mississippi. a ee 
eneral considerations as to the formation of the Missiesthys 
Valley have caused me to present also the page Diagram 5, 
showing the Mississippi basin as it is, and extending northward 
to include the Lake Winnepeg basin with the ancient extension 
of the lake southward and outflow through the valley of the 
Minnesota and Mississippi Rivers. 
