continent, there is no doubt in regard to the fact of the existence
of such an age, and it will be interesting to study some of the physical
changes that have been made by the ice at that period on the surface of
the glaciated area.

CHAPTER XXVII.

GLACIAL AND PREGLACIAL LAKES AND RIVERS.

Since the recession of the ice, preglacial lakes have been filled up and
are now dry land, and river beds have been changed so that new channels
have been cut and new lakes have been formed. Even the imagination, that
wonderful architect, with all its tendencies to exaggeration, palls in
its attempt to give expression in measured quantities to the mighty
power exerted by the great glacier or combination of glaciers that
existed in comparatively recent times. I say recent times, because even
10,000 years is only a mere point of time when compared with the actual
age of our globe.

Some years ago, in company with Dr. Wright, author of the "Ice Age in
North America," I visited Devil's Lake near Baraboo, Wis. At this point
are striking evidences of the work of the ice age. Before the glacial
period the Wisconsin River made a detour some miles west of its present
channel through the high hills in the region of Baraboo. The hills on
each side of Devil's Lake are very precipitous and are formed almost
entirely of rocks. The river at that point passed between two of these
hills. When the ice flowed down it surrounded these hills, yet did not
sweep over their tops, but left great piles of glacial drift, both at
the points where the river channel entered the hills and where it
emerges from them. The channel between the hills was protected and not
filled with the debris. Therefore a deep basin was left, which is kept
filled by the watershed furnished by the surrounding hills. This lake
recedes many feet during the summer, but it is again filled up by the
rains and snows of winter. There is no considerable stream either
flowing into or out from it. It is a lake formed by the glaciers, but in
a different way from those in the gravel deposits at other parts of
southern Wisconsin and northern Illinois.

There are hundreds and perhaps thousands of lakes that have been formed
in one way or another through the power of glacial action. These smaller
inland lakes, so many of which are seen in northern Illinois, southern
Wisconsin, and Minnesota, are due almost entirely to the great deposits
of glacial drift that have been transported with