Wave-cut Terraces in Keuka Valley 
45 
since the problem constitutes a unit of investigation. Neverthe- 
less there is nothing incompatible bemeen the altitude of terrace 
No. 3 and a land ice-locked basin for a body of water. 
DEFORMATION OF THESE OLD SHORE LINES. 
From data supplied by Gilbert, it has been estimated that the 
post“Wisconsin deformation of the Iroquois shore line in Cayuga 
valley is 2.7 feet per mile.^^ Fairchild measures the warp of the 
Dana beach in the Seneca valley at 3 feet per mile. In reference 
to the shore phenomena with which we are concerned the latter 
beach is more pertinent in location, and slightly less dissimilar in 
age. The pre-Wisconsin shore lines embody whatever tilting is 
shown by the post-Wisconsin water-levels, plus any earlier deform- 
ation that remained uncorrected by later land movements. 
The shore lines shown in figs, i and 2 have obviously a greater 
tilt than has been reported for the post-Wisconsin beaches. No 
instrumental measurements of the deformation have been made, 
though an attempt was made by a long series of aneroid readings, 
checked with a bench aneroid,^® to approximate a degree of cor- 
rectness; but the line of contact between cliff and terrace is so 
obscured by products of weathering and glacial drift that it is im- 
possible to get any results from this method, although the line is 
distinct enough when viewed from a distance. It is apparent to the 
eye that the highest, and presumably the oldest, terrace is the most 
warped. 
The existence of these wave-cut cliffs, older than the Late Wis- 
consin stage, and their present attitude in reference to the horizon, 
suggest a relation of factors that have a bearing on a phase in the 
drainage history of the St. Lawrence-Susquehanna divide region, 
and on the question of ice-erosion in the Finger Lake valleys. A 
reference to the drainage problem was made under the preceding 
section. The connection with the ice-erosion problem, briefly 
stated, is this: These old cliffs imply an ice-dammed lake that 
R. S. Tarr, Journal Geology^ vol. xii, pp. 79-80, 1904- 
Bulletin Geol. Soc. Am., vol. x, p. 68, 1899. 
In the Journal of Geology, vol. xiv, p. 492, 1907, the writer explains this method 
of working aneroids in pairs. 
