﻿150 cheosology of the glacial [mav i908, 



Discussion. 



The Pkesident remarked that to many geologists the chief 

 interest of the Author's paper would lie in the evidence brought 

 forward with regard to the value of geological time. As was well- 

 known, the Xiagara Gorge had often been used as a chronological 

 measure, but with wide differences of opinion as to its significance. 

 Modern investigation of the dynamics of denudation had tended to 

 diminish the amount of time once demanded for various kinds and 

 examples of erosion. There would, therefore, probably be a good 

 deal of sympathy with the Author in his endeavour to minimize 

 the length of the period required for the excavation of the Niagara 

 Gorge. But the evidence adduced by him would require to be 

 carefully weighed, together with that which had been brought 

 forward by previous observers. 



Mr. G. W. Lamplugh remarked that the Author's paper afforded 

 one more illustration of the difficulties which were encountered, 

 owing to the complexity and uncertainty of all the factors, when 

 an attempt was made to find a measure in years for even this most 

 recent period of geological time. Only a few months ago, Prof. 

 J. W. W. Spencer had contributed a paper to the Society in which 

 he deduced an age of 39,000 years for the Niagara Falls, from the 

 same data which the Author interpreted as representing a period of 

 less than 10,000 years. Evidently, geologists were still very far 

 from attaining an estimate on which they could rest any con- 

 fidence. Yet the problem held hope of solution, and every sincere 

 effort to solve it deserved a hearing. 



Dr. H. S. Poole remarked that, being acquainted somewhat with 

 glacial conditions on both coasts of Canada, he was impressed by the 

 seeming freshness of the data. Two exposures especially suggested 

 but a short intervening period. In the one case there was a perched 

 granite-erratic, some 5 feet long, resting upon a shaft of Lower Creta- 

 ceous blue shale in the cove next to Nanoose on the eastern shore of 

 Yancouver Island. The height of this shale-column (2 feet 4 inches) 

 gave a measure of the erosion by the tides on soft argillaceous shale. 

 The other case was in the river flowing out of Comox Lake higher 

 up the same shore. The lake was at the foot of a glacier in a deep 

 gorge of the mountain-range bounding the coal-field ; and the accu- 

 mulated morainic matter had choked the outlet and deflected the 

 river to flow over a volcanic barrier along the foot of the range, and 

 over a deposit of Till which the swirling waters of the river had so 

 far but partly removed. 



Prof. P. F. Kexdall joined the previous speakers in thanking the 

 Author for his valuable communication. Opinion in this country 

 was steadily trending in favour of a shorter post-Glacial chronology 

 than that formerly admitted when British geologists were generally 

 under the domination of Croll's astronomical explanation of the 

 cause of the Ice- Age. It was satisfactory to find fresh confirmation 

 of the newer views coming from America. There were two factors 



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