in Rocks and Recent Rock Flexures. 413 



gists full of scientific enthusiasm have like the late Mr. Bell 

 explained the Tryfan sands and gravels and in addition our 

 bowlder clays as sea bottom pushed up by land ice ; but twenty 

 years' careful work in the drift leads me to utterly disbelieve in 

 the universality of this agency. Unless we are to throw on 

 one side all the usual -methods of geological investigation it 

 were difficult to believe that current bedded and stratified sand 

 and gravel full of shell fragments to all appearance exactly 

 like a modern beach has been pushed up and landed on the 

 top of a mountain spur — a spur of Snowdon in fact. If the 

 inexorable logic of glacial events in America requires this 

 interpretation I for one prefer to consider that there must be 

 some great flaw in the premises. 



Still whoever is right on this point, evidence has been accu- 

 mulating rapidly on the American side of the Atlantic of 

 glacial and post- glacial elevations and subsidences on a much 

 more prodigious scale. According to Dr. George M. Dawson 

 there have been orogenic disturbances both to the east and 

 west preceding and during the Glacial period amounting to in 

 one case not less than 3000 feet. Laurentian rocks derived 

 from the east are found at elevations on the west amounting to 

 in round figures 4000 feet and several thousand feet above 

 their possible origin. He is of opinion that the subsidence of 

 the Cordillera region of the west was accompanied by an ele- 

 vation of the Laurentian highlands of the east. All these 

 facts are set forth in his highly interesting presidential address 

 to the Royal Society of Canada.* 



The ancient beach lines of the Great Lakes as shown by 

 Gilbert and Spencer evidence considerable differential vertical 

 movements and the latter sees proof from buried river chan- 

 nels and other evidences that the American continent within 

 geologically recent times stood several thousand feet higher 

 than at present and more recently several hundred feet lower. 

 The communication by Prof. J. D. Dana " On the Long Island 

 Sound in the Quaternary Eraf points also to considerable dif- 

 ferential movements. Mr. Warren Upham has also enumerated 

 a great many instances of Quaternary changes of level in a 

 paper in the Geological Magazine 4 



The Pacific coast in California according to Prof. LeConte 

 and Prof. Davidson of the U. S. Coast Survey give additional 

 evidences of former elevation in the existence of subaqueous 

 river channels as well as evidence of another character existing 

 in some of the islands. 



* Trans, of Royal Soc. of Canada, vol. viii, Sec. IV, 1890. 



f This Journal. Dec, 1890, pp. 425-437. 



% Quaternary Changes of Levels, Geol. Mag., Nov., 1890, pp. 492-497. 



