Science, Geology and Physics 



the Ontario basin was raised, causing the backing of the waters 1898 

 so as to reduce the descent of Niagara river to its present amount. 

 In 1886, after the third survey of Niagara Falls (by Prof. 

 Woodward) , the rate of recession was found to be much greater 

 than had formerly been supposed. Prof. Gilbert then made a 

 short study of the falls, the conclusions concerning which are 

 summed up as follows by that author: 1 " The problem admits 

 of expression in an equation: 

 Age of gorge equals Length of gorge. 



Rate of recession of falls. 



— Effect of antecedent drainage. 



— Effect of thinner limestone. 



— Effect of thicker shales. 



— Effect of higher fall. 



— Effect of more floating ice. 



± Effect of variation of detrital load. 



± Effect of chemical changes. 



± Effect of changes of river volume. 

 ' The catchment basin was formerly extended by including 

 part of the area of the ice sheet; it may have been abridged by 

 the partial diversion of Laurentian drainage to other courses." 

 He had divided the length of the gorge by the maximum rate 

 of recession, finding the product to be 7,000 years. If the 

 equation be carefully examined, together with the cited quota- 

 tion, all the important changing effects in the physics of the river 

 would lessen the estimated age of the cataract below 7,000 

 years, except the effect " by partial diversion of the Laurentian 

 drainage to other courses," of which no evidence was suggested; 

 nor was any lengthening of time shown as necessary, by the 

 long interior height of the falls. Henceforth, Prof. Gilbert was 

 naturally quoted as an authority that the age of the falls was 

 only 7,000 years. This conclusion did not satisfy the writer, 



1 The place of Niagara Falls in geological history. Gilbert. Proc. 

 A. A. A So yol. XXXV, 1 886, pp. 222-223. 



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