The bed of Niagara is composed of rock which dips gradually and uniformly westward. The ledge is ten feet higher on the American side than on the Canadian. The water of the American fall is therefore ten feet shallower. The amount of water going over the Falls has been variously estimated, engineers differing in their conclusions as much as sixty thousand cubic feet per second. Averages based upon the estimates of United States engineers for forty years, of the amount of mean flow of water passing Buffalo from Lake Erie, shows 222,400 cubic feet per second. This of course does not make allowance for that taken by the Welland and the Erie canals. This is probably about equalised by the amount entering the lake and river between this city and the Falls, so that the figures forming the basis of most computations are 224,000 cubic feet per second. The amount of power capable of development by the Falls is about 3,800,000 horse-power, which would be greatly increased by adding the fall from the beginning of the rapids to the crest of the cataract. Goat Island, situated just off the American shore, divides the waters very unevenly, sending more than three-fourths the volume toward the Canadian shore. Now, as has been seen, less than one-fourth the whole volume pours down the American channel; and as this is much shallower than the main body of water, it is here that any diminished flow will be first felt. At the head of the island the great body of the current turns toward the west, by far the larger amount converging into the funnel of the magnificent Horseshoe Falls. The American channel in contrast contains a very feeble flow, and therefore would be the first to exhibit any dearth of water. Calculations based upon the preceding figures, taking into consideration the length of the Falls, and the difference in elevation of the river's bed at the crest, show that when the flow has been reduced by 184,000 cubic feet per second, or by 40,000 cubic feet, the water in the American channel will be brought down to the rock bottom of the shore's edge. Then, although the Horseshoe Falls will continue to be an object of admiration to the traveller, and although the current will continue to sweep through the American channel and over the American Falls, the beauty and grandeur of the latter will fade away. Let the amount of water abstracted from the river be doubled, and, though the Canadian Falls would still continue an object of admiration, the American channel would be entirely dry.