Frank Carney 
the old drift as distributed under condition (3). These valleys 
accord with the direction of ice-movement; if they open toward the 
approaching ice, greater obstruction is offered to its progress, 
hence greater erosion results; if they lead away from the feeding | 
ice, the disturbance of the adjacent material may not be so marked. 
In the former case — i.e., the northward flaring valleys — the older 
drift, if not eroded, is apt to be deeply buried because of the in- 
Fig. 3. Contact of the two drifts at Crosby. The broken line marks the 
upper surface of the compact blue till. 
tense aggradational work of the valley lobes which characterized the 
margin of the waning ice-sheet. In the latter case the ice-erosion 
is less effective; the augmented ice-front drainage has degraded, i 
shifted, or covered with later outwash the earlier deposits. The | 
application of this principle probably varies inversely with the ( 
size or width of the valleys. 
