Page:Popular Science Monthly Volume 73.djvu/299

Rh on previous occasions, although I am aware of a statement by an engineer holding a distinguished position, to the effect that we do not know that the levels are going to recede. This appears to have been said for politic reasons, as the pressure to further divert the water is very strong.

There is much popular curiosity as to the cause of the high water, which is not wholly explained by the rainfall. Mr. E. S. Wheeler, of the U. S. Lake Survey, found in his elaborate study of the physics of the rivers that changes could be produced by ice jams holding back the discharge and raising the lake so high that upon the melting of the snows together with spring rains, the waters could not run out sufficiently fast during the ensuing season, so as to bring the levels of the lakes to their normal condition. These effects could accumulate during succeeding seasons so that the extraordinary stages might last not merely one year, but for several years.

From the foregoing, it must be apparent to any one that no opinions can be formed on power diversion which ignore the fluctuations of lake levels, for as these vary, so do the discharges of the rivers. The mean discharge of the Niagara River for 1901, a year of very low water, was 14,000 cubic feet per second below that of the mean level from 1891 to 1905. This was after the abstraction of a certain quantity of water, the exact amount of which is unknown to me, but probably not reaching 10,000 cubic feet per second. The mean discharge during 1907 reached 15,000 cubic feet per second above the average of the fifteen years mentioned; this being after the artificial abstraction of nearly 18,000 cubic feet per second. Thus the entire diversion of the Niagara waters has been not only concealed by the extraordinary stages of the river, but a further quantity could be withdrawn without any apparent effect upon the falls. The increasing discharge of Lake Erie, during this year, reached the maximum on April 27, when it rose to 60,000 cubic feet per second above the average of the fifteen years mentioned, besides which the diversion was probably nearly 18,000 cubic feet; so that the full use of the franchises of the present power companies would not impair Niagara Falls to-day, but this condition can not last, and it is unfortunate that it should occur at this time, for the sake of those who are interested in the preservation of the falls, as well as in the navigation of the lakes.

In studying the physics of Niagara River, individual months or single years can not be adopted as standards, but I have found that satisfactory results can be obtained by taking groups of five-year periods. Perhaps some other arrangement might prove better. This has resulted in my adopting as standards of lake levels and river discharges, the means of the fifteen years succeeding the lowering of the lake outlets, and the present temporary high water will doubtless