"Chicago to the Sea." Eastern Excursionist / A complete guide to the principal eastern summer resorts, including: Niagara Falls, the White Mountains, Saint Lawrence and Saguenay Rivers, Montreal and Quebec, the New England sea beaches, etc., and how and when to enjoy them.

by William C. Gage

RETROCESSION OF THE FALLS.

The following extracts from an article written by Prof. Tyndall will be of interest in this connection:—

“The fact that in historic times, even within the memory of man, the Fall has sensibly receded, prompts the question, How far has this recession gone? At what point did the ledge which thus continually creeps backward begin its retrograde course? To minds disciplined in such researches the answer has been and will be, At the precipitous declivity which crosses the Niagara from Lewiston on the American to Queenston on the Canadian side. Over this traverse barrier the affluents of all upper lakes once poured their waters, and here the work of erosion began. The dam, moreover, was demonstrably of sufficient height to cause the river above it to submerge Goat Island, and this would perfectly account for the finding by Mr. Hall, Sir Charles Lyell, and others, in the sand and gravel of the island, the same fluviatile shells as are now found in the Niagara River higher up. It would also account for those deposits along the sides of the river, the discovery of which enabled Lyell, Hall, and Ramsay to reduce to demonstration the popular belief that the Niagara once flowed through a shallow valley.

“The physics of the problem of excavation, which I made clear to my mind before quitting Niagara, are revealed by a close inspection of the present Horseshoe Fall. Here we see evidently that the greatest weight of water bends over the very apex of the Horseshoe. In a passage in his excellent chapter on Niagara Falls, Mr. Hall alludes to this fact. Here we have the most copious and the most violent whirling of the shattered liquid; here the most powerful eddies recoil against the shale. From this portion of the Fall, indeed, the spray sometimes rises without solution of continuity to the region of clouds, becoming gradually more attenuated, and passing finally through the condition of true cloud into invisible vapor, which is sometimes re-precipitated higher up. All the phenomena point distinctly to the center of the river as the place of the greatest mechanical energy, and from the center the vigor of the Fall gradually dies away toward the sides. The horseshoe form, with the concavity facing downward, is an obvious and necessary consequence of this action. Right along the middle of the river the apex of the curve pushes its way backward, cutting along the center a deep and comparatively narrow groove, and draining the sides as it passes them. Hence the remarkable discrepancy between the widths of the Niagara above and below the Horseshoe. All along its course, from Lewiston Heights to the present position, the form of the Fall was probably that of a horseshoe; for this is merely the expression of the greater depth, and consequently greater excavating power, of the center of the river. The gorge, moreover, varies in width as the depth, of the center of the ancient river varied, being narrowest where that depth was greatest.

“The vast comparative erosive energy of the Horseshoe Fall comes strikingly into view when it and the American Fall are compared together. The American branch of the upper river is cut at a right angle by the gorge of the Niagara. Here the Horseshoe Fall was the real excavator. It cut the rock, and formed the precipice over which the American Fall tumbles. But since its formation the erosive action of the American Fall has been almost nil, while the Horseshoe has cut its way for five hundred yards across the end of Goat Island, and is now doubling back to excavate a channel parallel to the length of the island. This point, I have just learned, has not escaped the acute observation of Prof. Ramsay. The river bends; the Horseshoe immediately accommodates itself to the bending, and will follow implicitly the direction of the deepest water in the upper stream. The flexibility of the gorge, if I may use the term, is determined by the flexibility of the river channel above it. Were the Niagara above the Fall sinuous, the gorge would immediately follow its sinuosities. Once suggested, no doubt geographers will be able to point out many examples of this action. The Zambesi is thought to present a great difficulty to the erosion theory, because of the sinuosity of the chasm below the Victoria Falls. But assuming the basalt to be of tolerably uniform texture, had the river been examined before the formation of this sinuous channel, the present zigzag course of the gorge below the Fall could, I am persuaded, have been predicted, while the sounding of the present river would enable us to predict the course to be pursued by the erosion in the future.

“But not only has the Niagara River cut the gorge—it has carried away the chips of its own workshop. The shale being probably crumbled, is easily carried away. But at the base of the Fall we find the huge boulders already described, and by some means or other these are removed down the river. The ice which tills the gorge in winter, and which grapples with the boulders, has been regarded as the transporting agent. Probably it is so to some extent. But erosion acts without ceasing on the abutting points of the boulder, thus withdrawing their support, and urging them down the river. Solution also does its portion of the work. That solid matter is carried down is proved by the difference of depth between the Niagara River and Lake Ontario, where the river enters it. The depth falls from seventy-two feet to twenty feet, in consequence of the deposition of solid matter caused by the diminished motion of the river. Near the mouth of the gorge at Queenston, the depth, according to the Admiralty Chart, is 180 feet; well within the gorge, it is 132 feet.”