PRE-WISCONSIN DRIFT IN FINGER LAKE REGION 577 
During the interval of deglaciation, stream-channeling, in the 
featureless topography of condition (1), proceeded slowly, since, to 
some extent at least, the streams were consequent. But with a larger 
lapse of time between the periods of glaciation this surface may have 
attained the relief of mature dissection, when it would present to the 
ice of the next invasion an opportunity for more effective corrasive work. 
Each succeeding invasion would remove less of the previously 
Fic. 3.—Contact of the two drifts at Crosby. The broken line marks the upper 
surface of the compact blue till. 
deposited drift; it seems very probable that the resultant of several 
glacial invasions of such featureless topography is somewhat aggrada- 
tional. And the final form given this drift depends upon the width 
and spacing of the moraine belts, if the ice were subject to varying 
relations of feeding and melting; or upon the thickness of drift depos- 
ited in an extensive sheet in case the feeding and melting factors were 
about balanced, the melting being slightly the stronger of the two. 
