Niagara Falls 



1898 Gilbert, immediately before this communication was read. 1 

 Spencer j_j e j^j usec j j- ne bench-marks at various localities where the 



fluctuations of the lake levels have been registered the last 20-37 

 years. While the recorded measurements vary from about one to 

 two and a half inches during the periods of observation, they have 

 been extended over the lake region, with results closely agreeing 

 with the previous determinations of the writer. This will be 

 better understood using Professor Gilbert's application — 

 namely, — that in 500-600 years, the Erie waters would be on 

 a level with those of lake Huron — in 1 ,000 years they would 

 overflow the natural divide near Chicago — in 2,500 years, the 

 waters would cascade into the Niagara gorge only during high 

 water — and in 3,000 years, the falls would be entirely drained. 

 These changing conditions, based upon the writer's previously 

 discovered rate of terrestrial deformation, would take — 720 

 years for the Erie and Huron waters to be on the same level; 

 1 ,280 years for the overflow into the Mississippi drainage (the 

 artificial canal would reduce this estimate to 720 years) ; and 

 2,600 years for the general drainage of the lakes into the Missis- 

 sippi. In 5,000 years the whole river as far as Buffalo would 

 be drained towards the south. 



In spite of taking the minimum rate of recession and the prob- 

 able errors, the closeness of these results satisfactorily confirms 

 many of the calculations based upon Niagara as a geological 

 chronometer. 



This paper, giving the principal results of investigations into 

 the lake history, thus shows the writer to have been greatly 

 affected by the studies of his co-workers. Indeed, all of the 

 researches by the different observers have been very much dove- 

 tailed, so that our present knowledge of the history of the Great 

 Lakes and Niagara Falls is the result of the labors of many 

 individuals. Besides the names of those already mentioned, we 

 should add those of Shaler, Tarr, Wright, Russell, Upham, 



1 Modification of the Great Lakes by earth movements. Nat. Geog. 

 Mag., vol. VIII, 1897, pp. 233-247. 



624 



