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 NIAGARA, a river of North America, running northward from Lake Erie to Lake Ontario, and carrying the discharge of all the Laurentian or Great Lakes, except Lake Ontario (see ). It constitutes part of the boundary between the United States and Canada, separating the state of New York from the province of Ontario. It is navigable from its head to Chippawa, 16 m., and from Queenston to its mouth, 6 m. The intervening 9 m. include a series of rapids and the Falls of Niagara. On the right bank are Buffalo, Tonawanda, Niagara Falls, Lewiston and Youngstown, of New York; on the left bank, Chippawa, Niagara Falls, Queenston and Niagara-on-the-Lake, of Ontario.

The Falls of Niagara are justly celebrated for their grandeur and beauty, and are viewed every year by from 800,000 to 1,200,000 visitors. They are in two principal parts, separated by an island. The greater division, adjoining the left bank, is called the Horseshoe Fall; its height is 155 ft., and the length of its curving crest line is about 2600 ft. The American Fall, adjoining the right bank, is 162 ft. high and about 1400 ft. broad. The water, being supplied by a lake, is free from sediment, and its clearness contributes to the beauty of the cataract. In recognition of the importance of the waterfall as a great natural spectacle, the province of Ontario and the state of New York have retained or acquired title to the adjacent lands and converted them into parks, which are maintained at public expense for the convenience and pleasure of visitors. The cataract is thus a great aesthetic asset of the people of the world; but its perpetuity has been threatened because it is also a great economic asset of the bordering nations. The flow of water in the river at mean stage is 222,000 cub. ft. per second, at low stage 176,000 cub. ft. The descent of this stream at the Falls, and in the rapids just above them, affords a theoretic water power equal to nearly four million horse power, and it is estimated that three-fourths of this is practically available. The annual value of the power must be reckoned in millions of pounds sterling, at least, and possibly in tens of millions. In the utilization of this natural power a beginning has been made; about 15,000 cub. ft. of water per second are now used for the development of electric power, and much larger appropriations have been authorized. As the full development of the economic value involves the diversion of the river from its channel and the destruction of the cataract as a scenic feature, the economic and aesthetic interests are antagonistic. An agitation started by the champions of scenic beauty led to negotiations looking to the regulation of economic exploitation by international agreement.

The river has no valley. The belt of land it crosses consists of two plains separated by a high cliff or escarpment facing towards Lake Ontario. The stream runs half its length on the upper plain, drops at the falls into a narrow gorge through which it courses 7 m. to the escarpment, and then traverses the lower plain in a deep channel. Under the lower plain are soft shales. The crest of the escarpment is a bed of limestone, nearly level, and this bed is visible in both walls of the gorge to the falls, where it is 60 ft. thick. From this firm brink the cataract plunges down into a deep pool or basin hollowed from the soft shale, and the resulting agitation causes further wear of the shale and the continual undermining of the limestone, which breaks away in blocks. Thus the site of the cataract retreats up stream and the gorge is lengthened; the average rate, measured from 1842 to 1905 being about 5 ft. a year. It is evident that the whole gorge has been dug out by the river, and many attempts have been made to determine the time consumed in the work.

NIAGARA, FORT, an American fortification, on the E. side and at the mouth of Niagara river, opposite the Canadian village