350 
Frank Carney 
front, and the drift which accumulates from such an ice-front 1 1 
would take somewhat the outline of an arc whose ultimate radii ;i 
converge towards the dispersion centers of the ice. But it is rare 
that the dispersion centers so completely control the outlines of | c 
the ice in distant parts. With an expanse of intervening lowlands I 
and highlands, the original impulse suffers so many deflections 
that the resultant lines of movement in distal areas betray this 
impulse in only a slight degree; consequently when we are dealing 
with an area quite removed from the ice-dispersion centers, as the j 
St. Lawrence-Susquehanna divide region is, this latter factor may 
be largely neglected. 
Nevertheless the topographic influence exercised by the Ontario 
basin, inducing in the ice, once at least in its progress and once 
again in its retreat, a marked lobation, is a feature so pertinent 
to the whole matter of drift distribution to the south as to warrant 
some consideration. The general features of the Ontario lobe | 
have been understood by glacialists, with a fairly apt apprecia- 
tion, since Chamberlin’s^ work on the moraines of the “Second 
Glacial Epoch.” The contributions to a study of the control 
exercised by this lobe, made by Gilbert, Spencer, Taylor, Tarr, 
Fairchild, and others, constitute an inclusive study that gives 
certainty to a paper which concerns the smaller dependencies 
or valley lobes of this larger body of ice. The Ontario lowland 
formed as it were a great reservoir which insured a degree of con- 
stancy in the position of the ice as it reached southward through 
the Finger lake valleys. 
From a study of existing ice areas, it is probable that cyclic and 
climatic factors manifested themselves in the pulsations of activity 
shown by the continental ice-sheet. The variations of the smaller 
glaciers of Alaska, of the Alps, and of the dependencies to the 
Greenland ice-cap, all point to irregularity in the rate of feeding 
of the ice. When a given region lies leeward of such a basin as 
the Ontario area it is evident that these cyclic or seasonal varia- 
tions will be less manifest, the intervening low section acting as a 
reservoir. In a similar manner rivers are subject to control in 
their flood seasons. Because of this fact there probably were 
fewer important local readvances of the ice in the Finger lake 
region than in such topography as is found in the upper Missis- 
sippi valley. 
^ U. S. Geol. Surv., Third Ann. Rep. (1883), Preliminary Paper on the Terminal 
Moraine of the Second Glacial Epoch. 
