106 HalVs Remarks on Niagara Falls. 



Art. X.— NIAGARA FALLS — THEIR PHYSICAL CHANGES, 

 AND THE GEOLOGY AND TOPOGRAPHY OF THE SUR- 

 ROUNDING COUNTRY. By James Hall, State Geologist of New 

 York ; Corresponding Member Bost« Soc. Nat Hist, &c. 



The cataract of Niagara and the geology of the surround- 

 ing country, have been often described ; but believing that 

 there are many facts unnoticed, and others which have not 

 had due weight in these considerations, I shall venture a fur- 

 ther attempt at illustrating some important points regarding 

 this great finger post in the path of time. I am far from 

 asserting that the problem regarding the recession or the for- 

 mer condition of this great cascade is settled. So many dis- 

 turbing causes are constantly presenting themselves, that al- 

 though the great principles may be deemed established, yet it 

 is impossible to calculate accurately the effect of these minor 

 influences. Every fact recorded of the past, the present, or 

 the future condition of this cataract will aid in the calculation 

 of the final result, which, some thousands of years hence, 

 may be made with tolerable accuracy. In the mean time we 

 must content ourselves with observing these facts and laying 

 down land-marks for the guidance of those who may follow 

 us in the attempt to decide the effect of time upon these an- 

 cient rocks. 



A striking feature in the Topography of western New York, 

 is the great difference of elevation between the Lakes Erie 

 and Ontario, when taken in connexion with the generally 

 level or but slightly uneven surface of the country, and where 

 there are no disturbances among the strata. The difference 

 of elevation between the other great lakes is comparatively 

 small, although Superior is situated in a disturbed geological 

 region. The elevation of Lake Erie is three hundred and 

 thirtyfour feet above Lake Ontario, and the greater part of the 

 difference is overcome by Niagara river in the space of one 

 mile at the rapids and falls. 



The barrier at the outlet of Lake Erie is formed by a ter- 

 race of limestone which extends from the Hudson river, west- 



