IOWA ACADEMY OF SCIENCES. 
57 
they flow either through the black surface soil or the yellow 
clay below it. Of these streams, North river and Middle river 
enter the Des Moines, while Grand river and the Nodaway 
flow into the Missouri. Although commonly called rivers, 
none of them attain to sufficient size, in Adair county, to 
deserve the name, but all become streams of considerable size 
before losing their identity in the Missouri or the Des Moines. 
The rivers along whose course is found the heaviest timber are 
Middle river and the west branch of the Middle Nodaway, and 
it is on these streams that the greatest variety of species have 
been found and most of the observations have been made The 
prairie in Adair county is practically bare. The only trees or 
bushes ever found upon it in any abundance are the hazel and 
bur oak, and these have been largely grubbed out and 
destroyed. The wild plum, wild cherry and American crab, 
may occasionally be found on th^ high prairie, but they 
very seldom, if ever, occur there unless protected by other low 
timber, and as the bur oak and hazel are destroyed, they van- 
ish also. So it is along the streams that the student of forestry 
must seek his information. 
Even a cursory examination of these streams is sufficient to 
show that, with few exceptions, the southern or western bank 
is steep and rough, while the northern or eastern bank is 
smooth and rises with a gentle slope. Along most of the 
course of Middle river, through the county, the southwestern 
bank consists of steep clay bluffs, densely wooded and rising 
abruptly from the water, while the northeastern bank slopes 
up very gradually from the water — making a wide, level valley 
or bottom, which is usually either destitute of trees, or less 
heavily wooded than are the bluffs of the opposite bank. The 
same condition may be noticed quite generally with regard to 
the smaller streams. In driving along the road it is noticeable 
that the steepest hills face the north or east, and the gentler 
inclines the south or west. The reason for this must be that 
the erosion has been greater on the north than on the south 
bank, owing to the fact that the former receives the full 
rays of the spring sun, while the southern bluff lies in shadow 
most of the day. This, of course, would cause the snow and 
ice upon the northern slope to melt very quickly, making con- 
siderable erosion, while upon the southern bank it would melt 
much more slowly and hence cause much less erosion. Where 
the course of a stream is southward it is the left bank which 
