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



oblique push on the ice body (from the northeast)— must have produced 

 stagnation of the ice in the bottoms of the valleys. 



The deficiency of drift filling in the deeper or more open sections of 

 the Finger Lakes basins — in other words, the existence of the basins 

 themselves — suggests comparative stagnation of the bottom ice in those 

 sections. The great burden of subglacial drift was dropped along the 

 drumlin zone (see plate — ) at the north ends of the basins, where the 

 transporting power of the ice lost efficiency. The low-tying but very 

 heavy drift deposit north of the lakes, and which forms their northern 

 barrier, was deposited previous to the retreat of the ice border along that 

 belt, for it is crowned with drumlins which represent the molding by ice 

 of some depth and at some distance from the edge. It should be clearly 

 understood that the drumlin belt filling is not terminal moraine, but 

 subglacial or ground moraine, which the ice sheet rubbed into the valleys 

 and subsequently overrode. If the deeper ice had possessed much move- 

 ment it would have swept the drumlin belt drift filling farther southward 

 into or entirely through the upper parts of the valleys. 



During both the earlier and the later stages, when the ice front was 

 resting at the zone of the recessional moraine which now blocks the 

 valleys and forms the present valley heads and water parting (see plate 

 21), the essential condition of the deeper ice was probably not unlike 

 the former stage. The direction of flow was in line with the valleys, 

 but the depth and pressure were less and the propulsion of the mass 

 from the northward was not so forceful. It does not seem possible that 

 any valley erosion could occur when the ice front was as far south as 

 the valley-heads moraine. Any glacial wear on the bottoms of the 

 Finger Lakes valleys must have been during other stages of the glacier. 



This suggestion of stagnation of the deepest ice applies in less degree 

 to all the smaller Finger Lakes basins. 



Lobations of the ice front in the valle}^s. — The only stage during 

 which it is at all reasonable to suppose that the valleys could have suf- 

 fered ice erosion is that phase of ice advance and retreat when the ice 

 was thinner and the front formed lobations in the valleys. There never 

 were any stream or valley glaciers in the Finger Lakes valleys. This 

 important fact seems to have been overlooked. Valley glaciers are drain- 

 age phenomena and do not flow uphill ; neither do ice fields push 

 glaciers uphill. When the ice front was south of the divide, on south- 

 sloping surface, tongues from the ice front may have pushed forward 

 down the valleys ; but north of the divide the ice front had reentrants 

 on the ridges and merely lobations in the valleys. Consideration of the 

 mechanics of the glacier will show the necessity of this. • The valley 

 lobes represent a small amount of concentration by the flow from the 



