572 FRANK CARNEY 
angle not covered by this drift might include much of New York state; 
but this supposition is hardly in harmony with accepted facts con- 
cerning the centers of ice-dispersion. ‘Theoretical consideration, 
therefore, leads to the conclusion that in the Finger Lake region of 
New York the late Wisconsin drift sheet covers at least the ice- 
erosion remnants of older drift. Students of glacial geology have 
already tentatively presumed earlier glaciation in this region.? 
That there has not already been reported some observed evidence 
of pre-Wisconsin drift in the Finger Lake region is doubtless due to 
one of two causes: workers may have felt that such drift should be 
highly weathered; or that at this distance north of the ice-margin 
erosion was so vigorous as to have removed the earlier drift. In all 
probability ice-erosion has removed most of the weathered horizon of 
the old drift, mingling it so thoroughly with fresh débris that it is not 
easily identified. In walking over the fields of the lake country one 
notes the presence of small bowlders which are very much weathered, 
bowlders that remind him of the general condition of stones in the 
areas of old drift; this is the most pertinent suggestion of the earlier 
glaciation of this region. 
PRE-WISCONSIN DRIFT IN GENERAL 
The older drift sheets have been studied more thoroughly in the 
Mississippi basin than elsewhere; their chronological sequence is 
generally established on the degree of weathering exhibited. In the 
case of the Sub-Aftonian’ and the Iowan,3 the lithological content is 
made a discriminating feature; the absence of water-laid material is 
a feature usually emphasized in describing the Kansan drift, whereas 
the blue or blue-gray color of the unweathered Illinoian is pointed 
out.5 Where the formations of different sheets of drift are super- 
posed, the distinctions may be more accurately recorded; but good 
sections of this imbrication are rare. Some contact sections, all from 
tR. S. Tarr, Journal of Geology, Vol. XIV (1906), pp. 18, 19; Bulletin of the 
Geological Society of America, Vol. XVI (1905), p. 217; H. L. Fairchild, zbid., p. 66. 
2 W. J. McGee, U. S. Geological Survey, Eleventh Annual Report (1891), p. 497- 
3 Chamberlin and Salisbury, Geology, Vol. III (1906), p. 384. 
4Ibid., p. 389. 
5 F. Leverett, Monograph XXXVIII, U.S. poles Survey (1899), p. 28; 
Monograph XLI (1902), p. 272. 
