OF THE FALLS OF ST. ANTHONY. 



Discussion. 



901 



The President remarked that the result arrived at by the author 

 gave a period not very dissimilar to that which was determined by 

 Sir Charles Lyell in the case of the Falls of Niagara. 



Prof. W. Boyd Dawkins said that the calculation was based on 

 the assumption that the rainfall had been constant in the district, 

 and that the quantity of water descending over the Falls had been 

 constant. This assumption he regarded as, in all cases, quite un- 

 warranted, considering the changes that we know to have taken 

 place in Europe in consequence of the destruction of forests &c. 

 He noticed the great changes of climate that have taken place in 

 America owing to the same cause. Hence he regarded all attempts 

 to establish a chronology for geological periods by means of such 

 facts as the recession of waterfalls as based on a fallacy. It seemed 

 to him to be the duty of geologists to point out the impossibility of 

 correlating historical and geological time. 



Prof. Hughes thought that there were too many important sources 

 of error in the data to allow us to attach any value to the results : 

 1st, it was doubtful whether the exact amount of former extension 

 of the rock could be estimated from such observations as those re- 

 corded by the earlier travellers ; 2ndly, the period down to which 

 glacial conditions prevailed did not appear, from what he had heard 

 of the paper, to be very clearly made out ; and, 3rdly, if these points 

 could be proved, they would involve such changes, from the climatal 

 conditions that would allow the interception of the streams of neigh- 

 bouring valleys by glacier-ice, to the present state of things, when 

 the existence of saw-mills implied ancient forests being destroyed, 

 that uniformity in the rate of waste certainly could not be assumed. 



