Page:Popular Science Monthly Volume 66.djvu/502

498 Adding to this total the limits of the American producing companies (16,300), we have for the entire chartered abstraction of the five companies referred to, 48,400 cubic feet per second.

This is of itself a dry and apparently barren fact. Let us look to its bearings upon the structure of the Niagara River and the total flow of waters through its channel.

The Niagara River flows over a rock bottom, on which the strata dip uniformly to the west. The sill or edge of the Falls is ten feet higher on the American than on the Canadian side, the waters at the crest of the American Falls ten feet shallower.

The flow of water through the channel and over the Falls was measured by the United States engineers in 1868, and by Sir Casimir Gzowski in 1870-3, with results varying from 246,000 cubic feet per second (the latter) to a maximum of 280,000 cubic feet per second (the former). The later averages given by the United States engineers, derived from the mean flow of water from Lake Erie at Buffalo during a period of forty years, afford 222,400 cubic feet per second. There are certain constants of abstraction for the Welland and the Erie canals which may be regarded as equalized by the inflow of streams into the river between Buffalo and the Falls, so that the figure which has been generally accepted and has entered into the calculations