296 POPULAR SCIENCE MONTHLY 



adjust itself in the general averages, as on previous occasions, so that 

 we must consider the effects of power diversion under normal condi- 

 tions. As stated before, when the corrections are made in the discharge 

 calculations prior to 1891, they fall into harmony with those of more 

 recent date. These corrections do not appear in the work of any other 

 writer, but I find them necessary, in order to explain incongruities, and 

 to arrive at a satisfactory understanding of the effects of power diver- 

 sion on Niagara Falls and the Great Lakes. Under these conditions, 

 let us examine the physics of Niagara Eiver. 



10. Basin above the Rapids. — Above Niagara Falls are the Upper 

 Eapids, descending fifty-five feet to the brink of the cataract. These 

 begin as the water passes over a rim of rock (see figures 2, 3, 5) which 

 crosses the river at the head of Goat Island. This is the " critical 

 point," not merely in the distribution of water over the falls, but also 

 in the level of Lake Erie, and indirectly of Lakes Huron and Michigan. 

 Except at one small part near the Canadian side, the rock rim is from 

 two to five feet higher than the rock-floor of the shallowest part of the 

 river, about seventeen miles above the head of the Upper Eapids, and 

 two miles below the outlet of Lake Erie. Throughout this distance 

 the river crosses a depression, refilled with drift, so that here the 

 channel itself was easily excavated to a much greater depth than across 

 the two rock barriers mentioned, thus forming, de facto, a basin begin- 

 ning with the narrows at the Buffalo Water Works, which are only 

 1,850 feet across, soon widening out into the broad stretches of the 

 river on either side of Grand Island, below which they unite into 

 another basin, over a mile wide, above Goat Island and its associated 

 rock rim. This from its greater height than at the Water Works, con- 

 stitutes the true rim of the Erie basin. The slope of the river between 

 these points is due to the narrowness of the outlet of the lake, where 

 the waters are so piled up that they have a velocity reaching to eight 

 miles an hour, while in the basin above Goat Island the current is 

 reduced, and is there from two to four miles an hour. The descent 

 of the river from the lake to the rock rim at the Upper Eapids is about 

 twelve feet. 



11. Depth of Water on the Rim of Upper Rapids. — At mean stages, 

 the average depth of the water in the American channel, as it begins 

 to flow past Goat Island, is less than three feet, with a maximum of 

 4.5 feet. In the Canadian channel, for some 400 or 500 feet from 

 Goat Island, under present ordinary conditions, the water is only from 

 half a foot to one foot in depth, then for another stretch it increases to 

 between two and three feet, bej^ond which the river shoals, so that in 

 ordinary stages the water is seen to descend, not only in almost broken 

 streams, but it is so shallow that the floats which have been sent down 

 the river do not pass over the rock ledges, but are carried by the 



