NIAGARA FALLS AND VICINITY 23 



Mean annual recession of American falls between 



1842 and 1890 .64 feet 



Mean total recession of Horseshoe falls between 



1842 and 1890 104.51 " 



Mean annual recession of Horseshoe falls between 



1842 and 1890 

 Length of crest line of American falls in 1842 



in 1890 

 Horseshoe falls 



in 1842 

 in 1890 

 Total area of rock surface which has disappeared 



at the American falls between 1842 and 1890 

 or 

 Total area of rock surface which has disappeared 



at Horseshoe falls between 1842 and 1890 

 or 



These changes are graphically shown in the successive crest lines 

 of the Horseshoe falls, given in fig. 19, p. 81. 

 Volume of vvater passing over the falls each 



minute 1 22,440,000 cu. ft 



or 1,402,500,000 pounds 



or more than 7,000,000 tons 



Depth of water in the channel of Niagara river below the falls 2 : 

 (see fig. 18) 



At foot of Horseshoe falls (center) 150 to 200 feet 



Upper Great gorge, from the falls to the beginning 



of the Whirlpool rapids (from soundings) 160 to 190 " 



Whirlpool rapids 35 " 



Whirlpool 150 " 



Outlet of whirlpool 50 " 



Opposite Wintergreen flat 35 " 



Below Foster's flats 70 " 



1 Blackwell, Am. jour. sci. 1844, 46 : 67. 



2 Estimated by Gilbert. Am. geol. 1896, 18 : 232-33 and elsewhere. 



2.18 





1080 



" 



1060 



a 



2260 



a 



3010 



(L 



32,900 



sq. ft 



•755 



acres 



275,400 



sq. ft 



6.32 



acres 



