MULTIPLE GLACIATION 135 



unlike the upper till that it strongly suggests a separate origin. Some 

 singular topographic features are not satisfactorily explained without 

 appeal to the earlier ice-invasions. The Rutland Hollow, east of Water- 

 town, is an example. Many erosion features, specially in the St. Law- 

 rence District, seem inconsonant with the work of the latest ice. 1 How- 

 ever, we have found no example of interglacial or warm-climate deposits 

 interbedded in the till. Such should be expected and sought, but at 

 present we can only say that multiple glaciation in New York, at least 

 north of Long Island, is quite certain in our philosophy, but that it 

 remains unproven in observation. 



Although our glacial phenomena in New York are doubtless not the 

 effects of merely the latest or Laurentian ice-sheet, the latter so strongly 

 dominates that for purpose of this writing it is impracticable to attempt 

 discrimination, and unless specially noted it will be understood that 

 reference is to the latest, or Wisconsin, glaciation. 



Laurentian (Labradorian) Ice-body 



limits in new york 



The reach or extent of the latest ice-sheet has long been known in a 

 general way through the early work of Upham, Lewis, and Wright in 

 tracing the terminal moraine. In later years the stretches of the ter- 

 minal moraine which lie in New York have been reexamined, on Long 

 Island by Woodworth and Fuller and Veatch and in Cattaraugus County 

 by Leverett. There are two small areas in the State which the ice-sheet 

 did not cover, the south side of Long Island and the district partly in- 

 closed by the northward bend of the Allegany River. 



THWKNKSX 



At its maximum the ice-sheet covered the highest points in the State. 

 the Adirondack (5,344 feet) and the Catskill (4,205 feet) mountains. 

 Judging from the Antarctic and Greenland ice-caps, the surface of the 

 Laurentian shield was a low dome of fairly uniform curvature, unin- 

 fluenced by the irregularities of the submerged land surface. Our only 

 means of estimating the thickness of the ice-cap is hy assuming a gra- 

 dient of the surface slope, as suggested by observations on the existing 

 polar ice-fields. Such data, however, can he safely used only in a sug- 

 gestive way when applied to the Laurentian ioe-shield because the differ- 



IFOI? discussion of this subject see New York Slate Museum Bulletins; N». 145, pp. 

 164-172; No. 160, pp. 17-18. 



