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THE POPULAR SCIENCE MONTHLY.
of the glaciers that the river began the task of cutting a new channel for itself the one it now occupies; but when the ice reached and crossed the channel and entered Kentucky, this partly
Map showing the Effect of the Glacial Dam at Cincinnati (Claypole). (From Transactions of Edinurgh Geological Society.)
made new way was likewise obstructed. As a result the water rose higher and higher, backing farther and farther up its valley, until its estimated depth varied from three hundred to six hundred feet.
