The tunnel which receives these waters after leaving the turbines is no less than six thousand seven hundred feet long, and discharges below the Falls just past the suspension bridge. Its cross-section somewhat resembles a horseshoe in shape, and this sectional area is three hundred and eighty-six square feet throughout, the average height and width being twenty-one and sixteen feet respectively. The company owning the mills connected with this tunnel, together with the Niagara Falls Hydraulic Power and Manufacturing Company, of which mention has been made, are the only ones using water to any great extent on the American side. On the Canadian side, three great canals are drawing water from the river. It is the construction of these mammoth Canadian power plants, and the devising of means for leading water to the turbines together with the development of a plan for the disposal of the waste water by means of some form of tail race, which must necessarily consist of a monster tunnel broken through the solid rock, which has developed some of the greatest and most unique engineering problems ever before dreamed of, and which has presented a work hazardous and spectacular in the extreme. To meet the engineering problems concerned in locating the three Canadian plants along the shore of the river, involving the taking of water by some form of canal, and the disposal of waste water through tunnel or by other means to the lower river, each without interfering with any of the other plants, taxed even Yankee engineering ingenuity. One company had to unwater a considerable area of Niagara River at Tempest Point where the waters have a great depth and the current is of high velocity. From here then a tunnel, the largest in the world, must be broken through solid rock, under the bed of the river, to a point directly behind the great sheet of water plunging over the apex of the V formed by Horseshoe Falls. A second company takes its water through a short canal to its wheel-pits, which are sunk about half a mile above Horseshoe Falls in Queen Victoria Park, discharging it through a tunnel two thousand feet long into the lower river. To find room for the third of these companies was a puzzling problem for some time. Finally the difficulty was solved by a departure from the plan of the other companies, both in the manner of taking water from the river and in the location of the power-house. Instead of locating the wheel-pits above the Falls as in the case of the others, this company has it power-house located in the Gorge below the Falls along the lower level. It takes its water from farther up the river than any of the companies, thus being further removed from any difficulties arising from recession of the Falls besides obtaining the additional power to be given by the descent of the rapids to the crest of the cliff, which amounts to about fifty feet. The water is taken from near the Dufferin Islands through the