434 ^EW YORK STATE MUSEUM 



the small, linear forms on the attenuated drumlin border in the 

 Waterloo-Seneca Falls district, but the work was on a much larger 

 scale. The direction of the drift molding in the western district, it 

 should be noted, is that of the prevailing direction of the continental 

 glacier over the region. 



Depth of the drumlin-making ice. We have no conclusive 

 facts on this topic but some suggestive data. The relationship of 

 the Waterloo-Seneca Falls moraine, and of the ice-border drainage 

 channels on the west, to the south edge of the main drumlin series 

 seems to locate definitely the edge of the ice sheet during that 

 episode. North of the Finger lakes region the receding ice front 

 was continuously bathed by glacial lake waters, and the moraines 

 were laid down under water. The moraine above named seems to 

 correlate with certain deltas and outlet channels to the east. If the 

 correlation is correct the water in which the moraine was deposited 

 had a surface altitude, present elevation, of about 900 feet. The 

 depth of water at the ice front was therefore about 400 feet, since 

 the moraine tract lies at about 500 feet. 



As the moraine is weak, largely because the drift load had been 

 incorporated into the drumlins in the rear, we may assume that the 

 ice was not heavily anchored in the lake water by its load of rock 

 rubbish. In order to retain its place under the buoyancy of the 

 waters it must have been at least 450 feet thick, or 50 feet above 

 the water. Taking this as the minimum depth of ice at the glacier 

 margin and assuming a surface slope of 30 feet to the mile, the eleva- 

 tion of the surface of the glacier over Clyde, 12 miles north of the 

 moraine, would be (9504-30x12) about 1310 feet. Since the general 

 base of the Clyde drumlins is about 400 feet elevation the depth of 

 ice in the center of the drumlin belt was about 900 feet. The drum- 

 lins are less than 200 feet high, which gives a depth over their tops 

 of more than 700 feet of ice. This is merely suggestive. 



Complex history. It is very likely that there are undiscovered 

 and unsuspected elements in the Pleistocene history of central- 

 western New York, and that it is much more complicated than it 

 now appears. Probably there has been more than one epoch of ice 

 invasion and retreat along with heavy erosion by glacial and non- 

 glacial waters. As we see the drumlins today they represent in their 

 forms, in each series, the latest ice work; but it is quite possible that 

 some of them were related to an earlier ice sheet. 



