A glance at a map shows a low range of hills or rather a gentle swell in the land surface forming the watershed between the lakes and the streams flowing to the south. At the time of the farthest southerly extension of the glacier it reached beyond this elevation; and its waters were discharged into the rivers flowing to the south. When the southern terminal had retreated to the north of this divide, but still blocked all outlet to the north or east, there was doubtless a number of lakes here discharging their waters across the present low watershed to the south. Some of these ancient valleys can still be traced for long distances of their course. These lakes passed through their varying history as those of to-day, their surface troubled by wind and storm and their waves leaving indelible carvings upon their shores. One of these lakes occupied what is now the western end of Lake Erie, shortly after the ice front had passed to the north of the watershed mentioned. There are still very definite markings which show that its waters were discharged across the divide by a channel into the present Wabash River and thence into the Ohio. This channel can be traced throughout most of its course very easily. There are at least four distinct shore lines preserved to us, which show four successive levels of the lake as it reached lower outlets before the Niagara River was born. All of these old shore lines can be traced throughout most of their courses. As the ice continued to retreat, next we notice the greatest change in elevation of the surface of the water. The ice front finally passed to the north of the present Mohawk River, thus allowing the waters to escape by that outlet, and, as a consequence, lowering the surface of the lakes by over five hundred feet. This drained a great extent of land and dropped the surface of Ontario far below the present level of the Niagara escarpment. Then for the first time the Niagara began to flow, and its Falls began their work. Immediately upon the formation of this new, lower lake it began the work of leaving its history carved upon the rocks, sands, and gravels which formed its shores. Its first ancient beach is more easily traced for almost its entire course than any of the other old levels. It does not even take the trained eye of the scientist to see its unmistakable history written in the sands. The earliest western travellers describe the Ridge Road running along this old, deserted beach as showing unmistakable signs of having been an ancient shore line of the lake. [Illustration: The Horseshoe Fall, July, 1765. From an unsigned original drawing in the British Museum.]