82 NEW YORK STATE MUSEUM 



will have reached the upper end of the island and will draw off all 

 the waters from the American falls, which by that time will have 

 receded only about half way to the Goat island bridge. All the 

 islands will then be joined by a dry channel to the mainland, an 

 event which was anticipated in the year 1848, when, owing to an ice 

 blockade in the Niagara river near Buffalo, the American fall was 

 deprived of all its waters for a day. As already indicated by Gil- 

 bert's forecast, in from two to three thousand years from now, or 

 long before the falls have even reached the head of Grand island, 

 the drainage of the great lakes will be reversed, provided the land 

 continues to rise northward as it has in the past, and Niagara will 

 carry only the drainage of the immediate neighborhood. From a 

 majestic cataract it will dwindle to a few threads of water falling over 

 the great precipice, such as may be seen during the summer season 

 in the upper falls of the Genesee at Rochester. 



Age of Niagara 



Speculations as to the age of Niagara have been indulged in ever 

 since men began to recognize that the river had carved its own 

 channel. The length of time required for the excavation of Niagara 

 gorge is not merely of local interest but serves as a basis for esti- 

 mating the length of time since the disappearance of the Laurentian 

 glaciers from this region, and incidentally it has served as a chro- 

 nometer for approximately measuring the age of the human race 

 on this continent. From insufficient data Sir Charles Lyell esti- 

 mated the age of Niagara at 36,000 years, while others have assumed 

 an age as high as 100,000 years or more. 



No reliable basis for estimating the age of the gorge was known 

 till a series of surveys were made to determine the actual recession 

 of the cataracts. From these the following variable rates of reces- 

 sion of the two falls have been obtained. 1 



1 Report N. Y. state engineer. 1890. 



