IOWA ACADEMY OP SCIENCES. 
209 
except possibly that part of the great river which lies between 
Montrose and Keokuk, where, for ten or twelve miles, it flows 
over a rock bed, making rapids so shallow as to necessitate a 
canal for the accommodation of river traffic during low water 
stage. 
A detailed explanation was given regarding the principal 
streams of the southeastern part of the state, and the conclusion 
reached that all except the Mississippi above Keokuk are run- 
ning in old channels. 
EXTENSION OF THE ILLINOIS LOBE OP THE GREAT 
ICE SHEET INTO IOWA. 
BY FRANCIS M. FULTZ. 
In the great southern flow of ice, two streams, one coming 
through Iowa and the other through Illinois, apparently merged 
their forces in the valley of the Mississippi. This union 
extended from somewhere near where Clinton now stands to 
about the present site of St. Louis. It is not at all likely that 
the ice streams first met at the northern point indicated; for the 
center of the movement on the Illinois side was well over 
towards the eastern part of the state, and likewise the center 
of the Iowa lobe was a goodly distance away from the Missis- 
sippi. From these centers the advancing frdnts deployed to 
the right and left, thus producing movements diverging from 
the central axis. It was these spreading fan-like margins 
which first met somewhere near the present line of the Missis- 
sippi — just where it would be difficult to say — not unlikely as 
far south as the mouth of the Des Moines river. Prom this 
meeting point the ice would rapidly fill up the valley in both 
directions. To the southward the two streams would imme- 
diately merge and flow as one current. To the northward the 
ice would pile up until the general level of the two ice fields 
was attained, when the motion would practically stop, until, 
through the increasing volume of ice, the width of the direct 
forward motion in each stream had increased to such a degree 
