J. W. Spencer — Duration of Niagara Falls. 455 



Akt. LXIII. — The Duration of Niagara Falls / by 

 J. W. Spencer. 



[Read before the meeting of the American Association for the Advancement of 

 Science, Aug. 20, 1894.] 



Contents : 



1. Conjectures as to the Age of Niagara Falls. 



2. Modern Topography. 



3. Geology of the District. 



4. Ancient Topography and the Basement of the River. 



5. Discharge of the Niagara River. 



6. Modern Recession of the Falls. 



7. Sketch of the Lake History and the Nativity of Niagara River. 



8. Episodes of the River and the Duration of Each. Age of the Falls. 



9. Confirmation of the Age of the Falls by the Phenomena of Terrestrial 



Movements. 



10. Relationship of the Falls to Geological Time. 



11. End of the Falls. 



12. Conclusions. 



1. Conjectures as to the Age of the Falls. 



About the year 1760, Sir William Johnson acquired pos- 

 session of Niagara Falls, and from that time its recession 

 impressed itself upon the few observers, so that when Andrew 

 Ellicott made the first survey of the chasm, shortly before 

 1790, he was informed that the cataract had receded twenty 

 feet in thirty years ; whereupon he concluded that its age was 

 55,440 years.* Bakewell's estimate, in 1830, reduced its dura- 

 tion to about 12,000 years, f According to Lyell, in 1841,^ 

 the Falls was about 35,000 years old, and this conjecture was 

 generally accepted until a few years ago., The first steps 

 taken towards the determination of the age of the falls were 

 those to ascertain the rate of actual recession. In 1842, Prof. 

 James Hall triangulated the cataracts ;§ in 1875, | the Lake 

 Survey ; in 1886,1 Prof. K. S. Woodward ; and in 1890,** 

 Mr. Aug. S. Kibbe repeated the measurements. In 1819,ff 

 the International Commission surveyed the river, and showed 

 that the apex of the cataract was very acute, yet it does not 

 appear that the measurements could be compared with the 

 later surveys made for the determination of the rate of reces- 



*" Journal of William Maclay," Appletons, 1890. 



f Cited in "Travels in North America in 1841," by Sir Charles Lyell, vol. ix, 

 p. 27. 



% The same. 



§ "Natural History of New York," Part IV, vol. iv, p. 184. 



|| Lake Survey Chart. 



*f[ Report of the meeting of the Am. As. Ad. Sc. in Science, Sept., 1886. 



**7th Rept. Com. State Res. Niag., 1891. 



f f Printed by the U. S. Lighthouse Board. 



