50 H. L. FAIRCHILD — ICE EROSION THEORY A FALLACY 



flow, the Hudson and the upper Saint Lawrence valleys, should display 

 maximum effects.* A favorable area for ice erosion is the Ontario basin, 

 and specially the plain and plateau border south of the lake, pa'rtly be- 

 cause of the relation of the ice movement to the land surface and partly 

 because the rocks are unusually soft and non-resistant. The Niagara 

 plain was continuously overridden by the great Ontarian lobe of the 

 Labradorian (Laurentian) ice body, while the Finger Lakes region re- 

 ceived the full force of the southward flow of the spreading Ontarian 

 mass. Western central New York thus offers a most excellent field for 

 the study of glacial erosion, and it is a critical locality, since here more 

 than for any other region in America the claim has been made for deep 

 cutting by the ice. The writer has evidence that such claims are false, 

 and the proofs will be given below in proper sequence. 



Another distinction between the work of continental and alpine gla- 

 ciers must be mentioned here, for it seems to have been assumed that 

 the supposed cutting in the basins of the Finger lakes was done by what 

 were practically stream glaciers. 



To the degree that the margin of the ice body was lobate, or had the 

 flow concentrated along certain lines in the depressions of the land sur- 

 face, the wear would approach that of stream glaciers ; but there is an 

 important theoretical distinction. The alpine glacier is supplied with 

 rock rubbish and cutting tools by the weathering agencies at the valley 

 head and sides. Like a river, the valley glacier is carrying a load of 

 contributed detritus, which renews its cutting power along the margins. 

 The ice mass which occupied the Ontario basin and the Finger Lake 

 valleys had to do their work wholly by the slow abrasion process at the 

 bottom. The short lobes or tongues, which during advance and retreat 

 of the ice sheet occupied the valleys of the Finger lakes, had very little 

 resemblance to alpine glaciers in either origin, form, or effect, for it must 

 be understood that they were pushing uphill. 



EFFECTS IN ADIRONDACK REGION; NORTHERN NEW YORK 



Iii the Adirondacks we have a highland area comparable in some 

 ways with Scotland. It was probably a center of local glaciation and 

 was also overridden by the great ice body from the north. While all 

 students of the area find striking evidence of ice action, no suggestion of 

 deep ice-cut valleys or basins have been made. Personal inquiries of 

 two geologists who are very familiar with the field have elicited neither 



* A recent paper, " Trent River system and the Saint Lawrence outlet," by A. W. G. Wilson, 

 forming pages 211-242 of volume 15 of the Bulletin, furnishes conclusive evidence of slight ero- 

 sive work of the Labradorian ice body north of lake Ontario and in the Saint Lawrence valley. 

 The facts are presented on pages 221-224, with a summary on page 240, and are essentially the 

 same class of evidence as given in the present writing for the south side of the Ontario basin. 



