nel for the old
river. The same process filled up the Valley of the Mohawk to more than
100 feet in depth and also raised the Valley of the Hudson. This caused
the new channel to be made through the Niagara River and a new route to
the ocean for the drainage of all the chain of lakes through the St.
Lawrence. It will be seen that the bottoms of all of these great lakes
to a certain extent were worn out by the action of running water, except
Erie. The great glaciers widened them out, and in the case of Lake Erie
scooped it out. At the same time it built great dams across the outlets
which raised the surface of the water to a much higher level and caused
them to form new outlets, thus changing the whole face of the country
over which the ice drifted.

The glaciated region of North America is among the most productive in
the world, and in many respects presents a most pleasing landscape.

Other lakes besides these mentioned have been formed during the ice
period through blocking the course of a river by the ice itself. Dr.
Wright, during the time he traced out the line of the terminal moraine,
discovered that the ice sheet crossed the Ohio River at a point near
Cincinnati, where there is a great bend to the northward in the river.
With the exception of this point and perhaps another point below, the
edge of the great ice sheet kept a little north of the Ohio River. At
this point, however, the ice seems to have filled the valley from hill
to hill, which very naturally would form a great dam or lake in the Ohio
Valley. Of course such a lake could not be permanent, because, when the
ice melted away, it again opened the channel and allowed the water to
flow off.

Some years before this discovery was made there were terraces found
along the banks of the Ohio River and its tributaries that had been the
subject of much speculation. It is well known that by the action of
water from rainfall, earth, gravel, and other debris will wash down the
side of a hill or mountain until it strikes a water level, and there it
will build out a terrace near the level of the water surface. The width
of these terraces will be determined by the time the water has stood at
that level and the extent and nature of the soil from which the debris
comes. The evidences that are cited, pro and con, would fill a small
volume, but it is sufficient to say here that the sum of the evidence
goes to show that there was an ice dam formed at a point near Cincinna