The Niagara River

by Archer Butler Hulbert

Cave of the Winds in Winter.

The many variable factors entering into the calculations so far discussed, have led to an earnest search for some means of determining the age of the river, which does not involve so many indeterminate and unknown quantities. This means of calculation, and one which seems to be much more free from unknown factors, seems to have been hit upon by Professor George Frederick Wright, whose calculations are based upon the rate of enlargement of the mouth of the river at the Niagara escarpment, where the Falls first began their existence. The cliffs at the mouth of the Gorge, as is the case with the newer portions of the river and indeed is characteristic of all canyons when first formed, were undoubtedly almost perpendicular when they were first cut by the rushing waters of the Niagara River. The mouth of the Gorge at Lewiston is of course the oldest part of the river; and if it were possible to measure the age of this part, this would surely give the date of the birth of Niagara. Immediately upon the formation of the Falls at Lewiston, the waters began the cutting of the Gorge; and immediately upon the formation of a gorge there was set to work upon its walls the disintegrating agencies of the atmosphere, free from indeterminate variables, tending to pull down the cliffs upon each side of the stream which jealously walled it in.

This work has gone on year after year and century after century, without being affected by either the volume of the river's waters or the shifting in the elevation of the land. The work of the atmospheric agencies in enlarging the mouth of the Gorge has had the effect of changing its shape from that of a rectangle, whose perpendicular sides were 340 feet, to a figure with a level base formed by the river, whose sides slope off at the same angle on each side. Now if it were possible to measure the rate at which this enlargement is taking place, the problem of determining the age of the river would be a more simple one.

The relative thickness of the different layers of material forming the walls of the Gorge is not the same throughout; at the escarpment at Lewiston, the summit is found to consist of a stratum of Niagara limestone, about twenty-five feet thick. Beneath this layer of lime is to be found about seventy feet of Niagara shale. The Niagara shale rests upon a twenty foot layer of hard Clinton limestone, which in turn is supported by a shale seventy feet thick. Forming the base is twenty feet of hard Medina sandstone, beneath which is another sandstone which is much softer and much more susceptible to erosion and the disintegrating forces of the atmosphere. These thick layers of shale form the part upon which the atmospheric powers exert their energies, undermining the strata composed of material which with much more effect resists the attempt of any agency to break it down. As the shale is removed from beneath the harder layers immense masses of the latter fall and form a talus along the lower part of the cliff. This in brief is the manner in which the mouth of the Gorge is growing wider.

The present width of the mouth of the Gorge at the water's level is 770 feet. It is not likely that the river was ever any wider than now at this point, since its narrowest portion is over 600 feet, and this where the hard layer of Niagara limestone is much thicker than at the mouth. The current here is comparatively weak, so that there has been little erosion due to it. On the contrary the falling masses of sandstone and limestone have probably encroached somewhat upon the ancient margin of the stream, its weak current being unable to sweep out these obstructions which have formed an effectual protection to the bank.

The observations necessary to Dr. Wright's calculations were taken along the line of a railroad, which, very opportunely, had been constructed along the eastern cliff. Here for a distance of about two miles the course of the road runs diagonally down the face of the cliff, descending in that distance about two hundred feet, and in its descent laying bare the layers of shale upon which the observations must be made. Along the course of the road at this point, watchmen are continually employed to remove obstructions falling down or to give warning of danger when any large masses fall. The disintegration goes on much more rapidly in wet thawing weather than at other times of the year. Often in the spring the whole force of section hands is required for several days to dispose of the material of one single fall. At the rate of one-fourth of an inch a year of waste along this cliff there ought to fall slightly over six hundred cubic yards annually for each mile where the wall is 150 feet high. At this rate the enlargement at the terminal of the Gorge would take place, Dr. Wright estimates, in somewhat less than ten thousand years. No accounts have been kept by the railroad of the amount of fallen material, but some estimate can be made from the cost of removal of the falling stone, together with the observations of the watchmen, one of whom has been in the employ of the railroad in this capacity for twelve years, and also by noticing the distance to which the cliff has receded since the construction of the road.

Only a superficial observer can see at once that the amount of removal has been greatly in excess of the rate mentioned above. The watchman, of whom mention has been made, was in the employ of the company which constructed the road in 1854, and therefore knows where the original face of the cliff was located. At one point, where the road descends to the Clinton limestone, the whole face of the Niagara shale is laid bare. Here the shale has been removed to a distance of twenty feet from its original position, and the rocks forming the roof overhang to about that distance. Now this mass of shale must have been removed since 1854. This would require a rate of disintegration much in excess of the one assumed. Necessarily some allowance must be made for the fact that the atmospheric agencies have here had a fresh section of the shale upon which to work. Yet making all due allowance for the above condition, the rate at the mouth of the Gorge could not have been much less than that assumed above. The actual process of the enlargement has been periodic. As the falling shale undermines more and more the capping hard layers, from time to time these latter fall in immense masses. Any calculation of age based upon a few years of disintegration would be worthless; but one based upon centuries would come very near a true average. The walls of the Gorge were at first perpendicular, but as the undermining, process goes on they become sloped more and more, the falling masses forming a protection to the lower parts of the softer strata. One fact, however, to be noticed is that this protecting talus has never as yet reached so high as to stop the work of the disintegrating agencies. The horizontal distance from the water's edge back to the face of the Niagara limestone, which forms the top of the cliff, is 380 feet. On the above assumption of the rate of recession as one-fourth of an inch annually, the rate at the top of the cliff must have been about one-half inch for each year. From the observations made, it is difficult to believe that the retreat of this upper portion has been at a lower rate than a half-inch yearly; if this be true, this new line of evidence places the birth of the Niagara and the beginning of the cutting of the Gorge at Lewiston at about ten thousand years ago.