Prof. Shimek's Criticism — Wright 237 
It should be observed that the principal loess accumula- 
tions are clearly connected with the closing stages of the 
lowan glacial epoch. The loess-covered area of southern 
Iowa begins very abruptly south of the terminal moraine of 
the lowan epoch. AA'hile that area is completely enveloped 
in loess, it is almost entirely absent over the area of the 
northern part of the State which was covered with lowan 
ice. This points with unerring accuracy to the floods of 
the closing stages of this period as the principal source of 
the material thus deposited. A little study of the map will 
show that during those floods a large number of tributaries 
coming into the Missouri river upon its eastern side would 
contribute an abnormal amount of material to that side of 
the river. There are half a dozen such streams coming into 
this area above Council Bluffs, while, below, the Nishna- 
botany, the Tarkio, the Xodaway drain a large basin in 
southern Iowa, coming into the Missouri a short way above 
St. Joseph, where the loess accumulations are more pro- 
nounced than anywhere else, while the Platte river, drain- 
ing a still larger area in southern Iowa though reaching the 
Missouri in the vicinit}' of Kansas City, passes within 
five miles of St. Joseph, and is there connected with the 
Missouri by a low pass, which would be submerged in the 
more moderate of the glacial floods. The influence of these 
contributors of sediment of the lowan glacier will fully 
account for the excess of loess upon the east side of the 
river and for its special occurrence along the valleys of 
these streams themselves. Many other streams similarly 
related to the lowan field cross the loess-covered area 
farther eastward towards the Mississippi river. 
2. Prof. Shimek represents my description of. exten- 
sive level-topped terraces in the loess-covered area as con- 
veying "an exaggerated idea of the extent and frequency 
of such terraces." In reply it is only necessary to say that 
the argument is not dependent altogether upon the extent 
and frequency of such terraces. More special attention to 
one instance adduced will be sufficient here. 
The fort at Leavenworth is situated upon a partialh- 
dissected terrace on the west side of the Missouri river, 
whose general level is about 150 feet above the river. This 
