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 débris. 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 the ice. Wherever these "kettle holes" are found large bodies of ice have become anchored, while the ice behind it has carried the drift until it is covered over and piled up at the sides. When these ice mountains melted away depressions were left which in some cases have resulted in lakes, and in others simply dry kettle holes. This process has been hinted at in a former chapter, but we give it here as one of the kinds of lakes formed during the glacial period. They are found everywhere that glacial action has prevailed. They are found in great abundance in some parts of New England on the margin of the terminal moraine. These lakes, however, are comparatively insignificant as compared with the great inland seas like Lake Superior and Lake Michigan, that undoubtedly owe their origin largely to the ice age. There are other factors, however, that enter into the formation of the great chain of lakes on the northern boundary of the United States besides those mentioned, that have brought into existence the smaller inland lakes.