Niagara

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 ST Lawrence River). 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-theLake, 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 Bird's-eye sketch of Niagara river and gorge, from the north.

L.E., Lake Erie.

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EE,

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Escarpment.  
  
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B,

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Buffalo.

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L,

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Lewiston.  
  
N,

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Niagara Falls, N.Y.

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Q,

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Queenston.  
  
F,

W,

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Niagara Falls, Ont.

Whirlpool.

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D,

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St Davids.  
  
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.

The problem of the river's age is of much interest to geologists, because its solution would aid in establishing a relation between the periods and ages of geologic time and the centuries of human chronology. The great Canadian glacier, which in the Glacial period alternately crowded forward over the Great Lakes region and melted back again, so modified the face of the land by erosion and by the deposit of drift that the waters afterwards had to find new courses. The Niagara river came into existence when the waning of the glacier laid bare the western part of the Ontario basin, and the making of the gorge was then begun. If it were supposable that the lengthening of the gorge proceeded at a uniform rate, the computation of the time would be easy, but there are various modifying conditions. (1) The limestone is not equally thick all along the gorge; in one place it is 90 ft., and in several places as little as 35 ft. (2) The height of the cataract has varied from 155 ft. to more than 300 ft. (3) For a short distance at the whirlpool the limestone and shale were replaced by softer material, sand and clay. The river here touched a more ancient gorge, which had previously been concealed by drift except at the escarpment. The diagram shows the breach in the escarpment at St Davids directed towards the sharp turn of the river gorge at the whirlpool. (4) The size of the river has varied. While the glacier was gradually melting the lakes underwent a complicated series of metamorphoses, and there were two separate epochs when the discharge from all the basins beyond Lake Erie followed other routes, and during these epochs the Niagara drained only one-eighth of its present territory. The variation in the size of the river is the most important of the modifying conditions, and at the same time least amenable to computation.

The parts of the gorge eroded by the full river are now marked by deep pools, the powerful cataract having dug far down into the shale. The parts eroded by the depleted river are comparatively narrow and shallow, the weaker cataract having been unable to clear away the fallen blocks of limestone. The work of the full river is illustrated by the main division of the present cataract, called the Horseshoe Fall, which wore its cliff back 335 ft. in 63 years. The work of the depleted river is less adequately represented by the narrower and shallower American Fall; where the present rate of recession is about one-twenty-fifth as fast. In making two-thirds of the gorge the full river probably consumed between 5000 and 15,000 years. If the depleted river worked one-tenth as fast, the period required for the remaining third was five times as long; but the relative rate is wholly conjectural. A weighing of the evidence now available indicates 25,000 years as a lower limit for plausible estimates of the age of the river, but yields no suggestion of an upper limit.

## Authorities

James Hall, Natural History of New York: Geology, Part IV. (Albany, 1843); Sir Charles Lyell, Travels in North America (London, 1845); John Tyndall, "Some Observations on Niagara," Pop. Sci. Mo. (1873); J. Pohlman, "The Life-History of Niagara," Trans. Amer. Inst. Mining Engineers (1888); G. K. Gilbert, "The History of the Niagara River," Sixth Ann. Rep. Corn. State Reservation at Niagara (Albany, 1890), and Rate of Recession of Niagara Falls (Washington, 1907), being Bulletin 307 of the United States Geological Survey; A. S. Kibbe, "Report of the Survey to determine the Crest Lines of the Falls of Niagara in 1890," Seventh Ann. Rep. Corn. State Reservation at Niagara (Albany, 1891); G. K. Gilbert, "Niagara Falls and their History," National Geographic Monographs (New York, 1895); "Niagara Number," Cassier's Magazine (July, 1895); J. W. Spencer, "Niagara as a Timepiece," Pop. Sci. Mo. (May 1896); F. B. Taylor, "A Short History of the Great Lakes," Studies in Indiana Geography (Terre Haute, 1897); and "Origin of the Gorge of the Whirlpool Rapids at Niagara," Bull. Geol. Soc. Amer. (1898). (G. K. G.)