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IOWA ACADEMY OP SCIENCE 
thickness had been deposited. Then, when the Missouri swung 
back to the west side of its flood-plain again, trace of which is seen 
in the fresh cliffs and steep bluffs facing the bottoms so close by, 
the little stream cut down to its present level. It is known to be 
only a few years since the river has again returned to the east of 
its valley, and the little stream has already begun to build a new 
alluvial fan or delta on the adjacent plain, though it has not yet be- 
gun to deposit between the hills. 
The basin of the nameless water-course has only about a ninth 
or tenth of that of the Wabonsie, and consequently it would take 
much longer time to erode and deposit as much material, but on 
the other hand the water not being so abundant and constant might 
not distribute the material so widely. How far this might com- 
pensate cannot be estimated closely. A few centuries would seem 
to be ample estimate for the time since the burial of the “Lansing 
man.” 
