establishes the fact that the Gorge is growing longer from its northern end through the agency of the waterfall. These facts show us the river working at a monstrous task. Its work is only partly done. Two questions come to us almost immediately: When this work is done what will it do? and, What did it do before its present work begun? The waters of Lake Erie could never have flowed to Lake Ontario without wearing away at the Gorge we now see. The birth of the river and the cutting of the canyon were simultaneous. Of this much we are assured. A superficial study of a map of North America will show at once a great difference in the northern and the southern sections. From the region of the Great Lakes northward the district is one continuation of lakes, ponds, swamps, and rivers with many rapids. South of the Ohio there are few lakes, and the rivers flow on with almost unbroken courses. Here is a region much older than that to the north; and its waters have had ages more in which to mould down elevations and fill up depressions. The cause of this difference in the characteristics of the streams of the North and those of the South is to be explained by the great Ice Age. As far as we now know there may have been little difference in relief forms between the two sections before the encroachment of the ice. During the glacial epoch the whole northern part of the continent was covered with a thick ice sheet, which was continually renewed at the north, and as continually drifted slowly in a general southerly direction. As this heavy ice cap passed over the surface, it acted somewhat like a river in its erosive power, only working much greater changes. It not only picked up loose particles, but also scoured and wore away solid rocks along its bed. Thus the whole configuration of the country was changed. At the southern terminal of the glacier, where it ended in the ocean, the ice broke away in large bergs, as in the northern seas to-day; but where the advancing ice met the warmer climate on land, it was melted and thus deposited at its terminal all the material it carried. The eroding power of this ice sheet, together with the deposit of its materials on melting, brought about a great change in the configuration of the country. Many old valleys were obliterated, while a number of new ones were carved. As the ice retreated northward with the change of climate, new lakes and rivers were formed. Many times the streams escaping from the lower level of lakes were forced to find an entirely new course, and so to carve a new channel of their own. The region of the Great Lakes and the Niagara River is no exception to this rule; and it is with the ending of the Ice Age that the history of the river begins.