590 HERMAN L. FAIRCHILD 
Hammondsport Lake. Probably somewhat later the southern 
end of the Canandaigua Valley was occupied by glacial waters, 
the Naples Lake, which have left a well defined overflow chan- 
nel near Atlanta. “At this level@the Naples Lake floodedwas 
much of the Honeoye Valley upon the west, and the West River 
or Middlesex Valley upon the east, as the recession of the ice- 
sheet had left open. With further removal of the ice-front a 
lower outlet for the Naples Lake was uncovered on the eastern 
border of the Middlesex Valley, about two miles northeast of 
Middlesex village, and a channel was cut by the escaping waters 
leading east toward Potter. . It was the stream which cut this 
channel, and drained the waters of the Canandaigua- Middlesex 
valleys into the Hammondsport Lake, that built the Potter 
Delta. The ravine is about one mile long. Its depth will aver- 
age about 100 feet, mostly in shale, with a width at the bottom 
of about 100 feet, and a uniform gentle grade, with a total fall 
of about so teets At present -iticarries: nomstneam- | The lowes 
end of this channel is not far above the level of the valley plain 
of Flint Creek, which indicates that the channel was effective 
even after the glacial waters in the Flint Creek Valley had found 
an outlet not far higher than the present plain. Indeed, the 
gravel and sand plain of the broad valley bottom is probably 
the filling during the last phase of the glacial waters. The delta 
represents the earlier deposits at the mouth of the down-cutting 
stream in the higher or Hammondsport Lake. There are two 
prominent levels on the delta. Aneroid measurements, using the 
Lehigh Valley Railroad at Middlesex and Rushville as datum, 
make the altitude of the valley plain at Potter about goo feet. 
The lower and broader delta plateau is about 1080 feet, and the 
higher, summit plateau about 1150 feet. This higher level cor- 
responds with the summit levels of the several old deltas in the 
Keuka Valley proper. The lower level represents some stage 
of the Flint Creek Valley waters not positively correlated at the 
time of this writing. As the waters fell in the Flint Creek Val- 
ley, the ancient stream, continually cutting down to the local 
base level, bisected and eroded the earlier delta deposits. 
