PRE-WISCONSIN DRIFT IN FINGER LAKE REGION 585 
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 opinion 
as to the particular pre-Wisconsin epoch of glaciation with which this 
drift correlates. Critical study should be given a wider area south- 
ward 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 New 
Jersey described by Salisbury. Nevertheless, this feature does not 
preclude identity of epochs, since the latter drift, which was never 
covered by a later till-sheet, has been subject to agents of disinte- 
gration during a period that has sufficed for the development of a 
well-advanced drainage system, the major streams having attained 
“levels more than 100 feet below the levels of the lowest summits on 
which the drift occurs.”’* 
SUMMARY 
This old drift, where now exposed, with one doubtful exception, is 
fresh in appearance; is very compact in structure, sometimes foliated ; 
its bowlders preserve striae; its upper surface shows erosion, pre- 
sumably somewhat beyond the removal of the weathered horizon 
which may be the source of some of the rather rotten crystallines now 
mingled with the recent drift.? 
tR. D. Salisbury, loc cit, p. 759. 
2 The writer has just noted Gilbert’s paper, “‘ Bowlder-Pavement at Wilson, N. Y.”’ 
(this Journal, Vol. VI [1898], pp. 771-75). The pertinent feature of this paper is the 
recognition of the possibility of two till-sheets, and of the certainty of ‘“‘an epoch of 
local till-erosion by a glacier. The epoch may be a mere episode interrupting a period 
of till deposition by the same glacier, or it may be a part of a stage of readvance follow- 
ing a long interglacial period” (p. 774). 
