5 66 THE POPULAR SCIENCE MONTHLY. 



plunge over Niagara Falls every minute, all the water of the lakes 

 making the circuit of the Falls, the St. Lawrence, the ocean, vapor, 

 rain, and lakes again, in 152 years. Through the Illinois Canal 

 about 8,000 cubic feet of water are taken every minute from Lake 

 Michigan to the Illinois River; through the Welland Canal 14,000 

 cubic feet flow every minute from Lake Erie into Lake Ontario, 

 and through the Erie Canal 30,000 cubic feet pass every minute 

 from the same lake into the Hudson. Thus, 52,000 cubic feet of water, 

 which Nature would give to Niagara, are diverted every minute by 

 artificial channels, some into the Mexican Gulf and some into the Bay of 

 New York. Add this to 18,000,000, it is as a drop in the bucket, and 

 would make no appreciable difference in the character of the Falls or 

 their rate of recession. Was there ever a time when the Niagara was 

 appreciably a greater river than now ? 



Below the Falls, on the Canada side, is a terrace, extending along 

 the river-bank, and attaining a height of 46 feet. It contains 

 river-shells, and is an old river-bank. A corresponding bank is found 

 on the New York side, although much broken and eroded. If a tour- 

 ist will stand on the New Suspension Bridge and cast his eye along 

 these ancient banks, his first impression will be that the Niagara which 

 flowed against them was vastly greater than the river which flows 

 now nearly 200 feet below him. But, if his eye will follow the Cana- 

 dian terrace above the Horseshoe, he will see it falling lower and lower, 

 till, at the head of the Rapids, it merges into the present bank. From 

 this point upward the river is contained within low banks, and 

 bounded by a plain whose monotony is not broken by a hill or terrace. 

 A glance at the section (Fig. 1) will make this clear to the eye of the 

 reader. The surface of the river from Buffalo to Lake Ontario is 

 represented by the line R, R ; the banks, from Buffalo to the Rapids, by 

 the dotted line t, t and the old banks, from the Rapids to the Whirl- 

 pool, by a continuation of the same line. It will be seen that this line 

 rises as the surface of the river falls. The slope from the head of the 

 Rapids to the Falls is nearly 50 feet, and the terrace opposite the 

 Falls attains a height of 46 feet. 



We turn now to Goat Island. A walk around the island, by the 

 margin of the river, will show us what immense denudation its lime- 

 stones have suffered. The extent of this denudation can be seen in our 

 section of the island (Fig. 2). To wear away such beds of limestone, the 

 river, for many ages, must have flowed over the island. And as the 

 upper beds of fluviatile drift, marked, d in our section, are a little be- 

 low the level of the highest terrace, we must infer that the river, when 

 contained in these ancient banks, covered the island, and was eroding 

 its beds of limestone. 



By all this we see that the Niagara itself has made the Rapids, 

 and that, as it cut its way downward, its forsaken banks have assumed 

 the character of terraces. And we see, by the low banks and absence 



