In the third and last section the shale continues its downward dip, and at several places entirely disappears. The rock lying upon it is quite compact, and some of it very hard. The deep water into which the falling water was formerly received partially protected the shale, so that many centuries must have elapsed before the excavation of this section was completed. Its average width is eleven hundred feet.
Sixty rods below the American Fall is the upper Suspension Bridge. From this bridge, looking downward, no one can fail to be impressed with the serene and quiet beauty of the mirror below, reflecting from the surface of its emerald and apparently unfathomable depths life-size and life-like images of surrounding objects. The calm, majestic, unbroken current is in striking contrast with the fall and foam and chopping sea above.
The greatest depth of the water in mid-channel between the two Suspension Bridges, as ascertained by measuring, is two hundred feet. But it must be borne in mind that this is the depth of the water flowing above the immense mass of rock, stones, and gravel which has fallen into the channel. The bottom of the chasm, therefore, must be more than a hundred feet lower, since the fallen rocks, having tumbled down promiscuously, must occupy much more space than they did in their original bed. There are isolated points, as at the Whirlpool and Devil's Hole, where the river is wider than in any part of this section, but the depth is less. Taking into consideration both depth and width, this is the finest part of the chasm. And for this reason chiefly, when the great cataract was at a point about one hundred rods below the upper bridge, it must have presented its sublimest aspect. The secondary bank on each side of the river is here high and firm, whereby the whole mass of water must have been concentrated into a single channel of greater depth at the top of the Fall than it could have had at any other point. And here the mighty column exerted its most terrific force, rolling over the precipice in one broad, vertical curve, water falling into water, and lifting up, perpetually, that snowy veil of mist and spray which constitutes at any point its crowning beauty.