By a simple optical illusion, the tower seems to move with a frightful rapidity, but, happily, in the opposite direction to the fall, for, with the contrary illusion, it would be impossible to look at the gulf from giddiness. Breathless and shivering, we went for a moment inside the top landing of the tower, and it was then that the Doctor took the opportunity of saying to me,— “This Terrapin Tower, my dear sir, will some day fall into the abyss, and perhaps sooner than is expected.” “Ah! indeed!” “There is no doubt about it. The great Canadian Fall recedes insensibly, but still, it recedes. The tower, when it was first built in 1833, was much farther from the cataract. Geologists say that the fall, in the space of thirty-five thousand years, will be found at Queenstown, seven miles up the stream. According to Mr. Bakewell, it recedes a yard in a year; but according to Sir Charles Lyell one foot only. The time will come when the rock which supports the tower, worn away by the water, will glide down the Falls of the cataract. Well, my dear sir, remember this: the day when the Terrapin Tower falls, there will be some eccentrics who will descend the Niagara with it.” I looked at the Doctor, as if to ask him if he would be of that number, but he signed for me to follow him, and we went out again to look at the “Horse-shoe Fall,” and the surrounding country. We could now distinguish the American Fall, slightly curtailed and separated by a projection of the island, where there is another small central cataract one hundred feet wide; the American cascade, equally fine, falls perpendicularly. Its height is one hundred and sixty-four feet. But in order to have a good view of it it is necessary to stand facing it, on the Canadian side. All day we wandered on the banks of the Niagara, irresistibly drawn back to the tower, where the roar of the water, the spray, the sunlight playing on the vapours, the excitement, and the briny odour of the cataract, holds you in a perpetual ecstasy. Then we went back to Goat Island to get the Fall from every point of view, without ever being wearied of looking at it. The Doctor would have taken me to see the “Grotto of Winds,” hollowed out underneath the central Fall, but access to it was not allowed, on account of the frequent falling away of the rocks. At five o’clock we went back to the hotel, and after a hasty dinner, served in the American fashion, we returned to Goat Island. The Doctor wished to go and see the “Three Sisters,” charming little islets scattered at the head of the island; then, with the return of evening, he led me back to the tottering rock of Terrapin Tower.