i6 
Frank Carney 
4I feet where it forms the bed of the cut, but it is not constant, the 
Wisconsin sometimes forming the entire cross-section of the cut. 
The hardness of the blue till here is evident from the overhanging 
of the bowlders (fig. 3), which may be two-thirds disclosed before 
dropping from the face of the cut. We have not seen in this mate- 
rial bowlders more than a foot in diameter. The sharp angle of ! 
slope which this till maintains in comparison with that of the Wis- 
consin above is evidence also of the compressive force to which 
it has been subject. 
Mixed exposures. About a mile southeast of Branchport, near i 
the point where the old valley joins the Branchport arm of the < 
lake, a creek trenches the recent drift, which here contains scat- ! 
tered masses of blue till. We noted one area at the foot of the 1 
channel wall which may be in place. The Wisconsin drift here 1 
alluded to appears to be from a lateral tongue of ice which fed 
into the valley, thus disturbing the older deposits. I 
Another area where old drift is incorporated with the new is at 
the end of Bluff Point (fig. i). Here is a quantity of debris, largely 
local, dragged around the slope of the bluff. 
Keuka Lake Outlet exposure. The most pronounced section 
of the bluish till may be seen along the outlet of the lake. A 
typical exposure is skirted by the highway and is in sight of the 
New York Central Railroad at Keuka Mills. Here the super- 
jacent Wisconsin is the thinner, measuring a little less than 18 feet, 
while the bluish till measures nearly 30 feet. The ease with which 
the former weathers is demonstrated by the low angle of slope, and 
by the covering of vegetation; the older drift has a steep slope and 
no vegetation (fig. 4), and shows very slight evidence of structure. 
The outlet of Keuka Lake drops 265 feet in its course of scarcely 
7 miles to Seneca Lake; it consists of a rock-bound gorge alternat- 
ing with amphitheater expansions, in which one or both of the 
rock walls are absent where the present course crosses or enters a 
former more mature valley. The older drift is noted particularly 
in these amphitheaters of the present channel. It is probable, 
therefore, that the Keuka basin was tributary to the Seneca basin 
long before the period of bluish-till glaciation. 
This same relationship of drifts is noted in the erosion channels 
