17 
Pre-Wisconsin Drift in Finger Lake Region 
of streams tributary to the Keuka Lake outlet. Along the lateral 
from the south coming in at Milo Mills, the older drift, where not 
very coarse, shows a tendency to lamination, the result apparently 
of excessive pressure. We have noted the same condition in other 
localities of this region. 
The most persistent expression of this bluish drift is found in the 
Keuka outlet valley, which is transverse to the direction of ice- 
movement. The valley is very mature. Naturally the Wisconsin 
ice-sheet did less corrasive work here than in the arms of Keuka 
Lake. 
Erosion and color. Furthermore, the line of contact of the two 
drifts in the exposure about Dunning’s and about North Crosby 
gives a suggestion as to the manner and amount of the erosion. 
The former contact is about 65 feet above lake-level; the latter, 
about 90 feet. In east-west cross-section the contact line is a 
series of sags and swells, or anticlines and synclines, presumably 
parallel to the direction of ice-progress, indicating its tendency to 
groove or plow the subjacent surface. 
The color of this old drift is strikingly blue in contrast with the 
adjacent yellowish Wisconsin deposits, and the color persists even 
in the detached masses that are seen in exposures of the recent drift. 
It apparently is not the result of post-Wisconsin alteration; the 
till has been too much protected for that, and its compactness argues 
against infiltering waters as the agent. The bluishness covers 
the bowlders and is constant in the matrix. Evidently the color 
antedates its erosion and burial by Wisconsin ice. 
AGE OF THIS DRIFT. 
The evidence presented in this paper does not warrant an opin- 
ion as to the particular pre-Wisconsin epoch of glaciation with 
which this drift correlates. Critical study should be given a wider 
area southward to the outermost moraine of the Wisconsin drift; 
the numerous exposures noted in the limited territory already 
examined suggests that other superposed sections nearer the 
margin may show the older drift in a weathered condition. 
The freshness of the subjacent bluish till about Keuka Lake 
does not suggest its correlation with the highly weathered till in 
