84 
IOWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
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this new surface the surplus drain- 
age chose consequent courses 
along lines that crossed the old 
divides, and in cutting downward, 
became superimposed upon the 
buried rock divides. 
In the course of the investiga- 
tions it was discovered that every 
one of the major drainage lines 
of eastern Iowa, south of the 
Volga river are superimposed at 
various places along their courses. 
These streams include, besides the 
Maquoketa, the Wapsip inicon and 
the Cedar and their important tri- 
butaries. Former studies by the 
writer have shown that the Iowa 
river' at Iowa City is also a super- 
imposed stream. All are appar- 
ently post-Kansan in age. Where 
they have cut in rock their valleys 
are relatively narrow ; where they 
have cut in drift, they are strik- 
ingly broad. 
In 1895, Gordon, in an article 
in Volume III of the Iowa Geol- 
ogical Survey on the buried river 
channels of southeastern Iowa, 
showed that the Des Moines river 
in Lee county has cut through a 
rock divide, while to the east is a 
burie'd channel deeper by one 
hundred feet than the present Des 
Moines or the Mississippi in that 
latitude. Clearly then the Des 
Moines is a superimposed stream 
and, judging from its features, is 
of the same age as those above 
mentioned. 
It seems to the writer that 
the factor of superimposition of 
