III.—Recession of the Niagara Falls

Extract

For many years Niagara Falls and the Great Lakes of America have been special subjects of my researches. These at last have been completed under the Commission from Dr. Robert Bell, acting Director of the Geological Survey of Canada, and later of Mr. A. P. Low, Director, with results beyond anticipation. These were obtained through precise instrumental measurements, borings, and soundings, not hitherto undertaken.

My recent survey of the crest-line (1904–5), compared with that of Professor James Hall, 1842, shows the mean rate of recession to have been 4·2 feet a year, with the average breadth of the gorge produced by the falls being 1200 feet. But a longer record (agreeing with the more recent) has been found by Mr. James Wilson and myself in discovering the position of the Falls in 1678, from the crude description and picture made by Father Hennepin at that time. Between 1890 and 1905 the rate of greater recession diminished.

I succeeded in making soundings under the Falls and throughout the Gorge by the use of Tanner-Blish self-registering tubes, depending upon the hydrostatic pressure, as the current was too strong for the use of an ordinary line. At the Whirlpool, and at some other places, it was necessary to work from a cable swung across the Gorge. Under the Falls themselves, the sounding tubes were inserted in a specially designed buoy which the force of the Fall drove down to the rocks, that had collapsed beneath the Falls themselves. These were reached at 72 feet, while the floor of the river beyond varied from 84 to 100 feet below the surface of the river.