Pre-Wisconsin Drift in Finger Lake Region 
7 
south valleys, the troughs of the present lakes, their tributaries; 
primary, secondary, and lesser, had developed a variety of trans- 
verse valleys. So in whatever direction the ice-mass moved there 
must have been localities, of rather limited extent, where ice- 
erosion was less active; also localities where the deposition of ice- 
debris was more pronounced. The combined effects of glacial 
erosion by the different invasions has not removed all the residual 
soil, the regolith of preglacial weathering.^® Nor would a suc- 
ceeding ice-sheet carry oflF all the drift deposited by a preceding 
invasion. Therefore it remains to inquire into the conditions 
most favorable to the deposition, and least favorable to the ice- 
erosion of former drift-sheets. 
Deposition of drift. Aside from the ground moraine, the thick- 
ness and irregularity of which attest the heterogeneously dis- 
tributed load which is being carried by the retreating ice, the local- 
ized deposits of debris represent in the first place a reaction of 
climatic factors that cannot be specifically determined; and, in 
the second place, the influence of topography upon the detailed 
outline of the ice-front. Climatic control evidently occasioned 
the pulsations of halt and retreat marked by the irregularly spaced 
belts of thickened drift; while the distribution of drift within the 
belts themselves is due both to local topography and to the topog- 
raphy of the areas passed over, in so far as these areas have con- 
tributed to the load of the ice. Furthermore, the broader out- 
lines of these irregularly spaced belts reflect the reaction of the 
larger topographic features and the general direction of ice-move- 
ment from the dispersion centers; in consequence of this we have 
the moraines of ice-lobes. It follows, then, that no satisfactory 
control can at present be announced for the spacing of these belts. 
Nevertheless, the influence of topography upon the detailed 
expression of the drift within the belt admits of closer definition. 
We would refer particularly to the following three conditions: 
(i) In a uniformly level area the ice-front would be without pro- 
H. L. Fairchild, Bulletin of the Geological Society of America^ vol. xvi (1905), 
pp. 53-55; R. S. Tarr, American Geologist, yo\. xxxiii (1904), p, 287, andF. Carney. 
The writer’s unpublished notes on the Moravia (N. Y.) quadrangle afford further 
proof of the presence of preglacial weathered products in place. 
