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 ca'led 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 the 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 



