[32] Many years afterward the author’s attention was called to this statement; he replied, as to the expression above, by saying, he meant that the pressure of the stream was so great that a crowbar, not having sufficient specific gravity to sink, would actually be carried down the stream upon its surface. As incredulous as this may appear, we have it substantiated by no less a person than the late eminent engineer, John A. Roebling, who built the suspension-bridge over the river at the Niagara Falls, in the following letter: “SUSPENSION BRIDGE, _April 28, 1855_. “SAMUEL WILKESON, Esq. “DEAR SIR: I received a copy of _The Democrat_, with your account of my attempting to sound the river. After you left, another attempt was made, with a similar iron, of about forty pounds’ weight, attached to a No. 11 wire, all freely suspended, so as not to impede the fall of the weight. I then let the weight fall from the bridge, a height of 225 feet. It struck the surface fairly, with the point down--must have sunk to some depth, but was not longer out of sight than one second, when it made its appearance again upon the surface, about 100 feet down stream, and skipped along like a chip, until it was checked by the wire. We then commenced hauling in slowly, which made the iron bounce like a ball, when a cake of ice struck it, and ended the sport. “I am satisfied that no metal has sufficient gravity to pierce that current, even with the momentum acquired by a fall of 226 feet. The velocity of the iron, when striking, must have been about equal to 124 feet per second, and, consequently, its momentum near 5,000 pounds. Its surface, opposed to the current, was about fifty superficial inches. This will give an idea of the strength of that current, and, at the same time, hint at the Titan forces that have been at work to scoop out the bed of the Niagara River. “I am now satisfied that our friend, the English captain, was sounding in vain. “Yours respectfully and truly, “JOHN A. ROEBLING.” --ED. NOTE.