Pleistocene Geology of Moravia Quadrangle 
433 
that has swept ofF much of the ground moraine leaving the surface 
of the country rock quite exposed. Reference was likewise made 
1 under the general consideration of drainage (p. 343) to this ice- 
front stream which gave the gorge to the southeast its present 
development. Here, too, the later post-glacial erosion has been 
slight. 
(8) About one and a half miles due northwest of Summer Hill 
a typical ice-front channel now marks the divide area between 
Dry Run and the Summer Hill tributary of Fall Creek. This 
channel is practically of immediate ice-front drainage develop- 
ment. For a time, however, probably rather brief, the channel 
was the overflow of a slight lake held in the upper portion of Dry 
Run valley. 
(9) Hollow Brook, west of Locke, occupies now for a short 
distance, near the boundary of Genoa and Venice townships, the 
course of an ice-front channel, which is crossed by the east-west 
highway at the point where the present stream occupies the 
former waterway. The genesis of this overflow channel is con- 
nected wdth topographic relationships found on the Genoa sheet. 
Torrential Type. As stated above, this type of channel is con- 
fined to areas of thickened drift, that is, areas where the ice-front 
retreated very gradually. While no pretense is made at mapping 
all channels of this type, it has been thought well nevertheless to 
make specific reference to a few of the better developed illustra- 
tions, or to vicinities where the type abounds. 
(1) On the eastern wall of the Freeville-Moravia valley, it has 
already been noted that the drift assumes a very morainic aspect. 
The torrential overflow channel is here common, and is easily 
differentiated from post-glacial erosion lines. The drainage 
established since the complete retreat of the ice has suffered but 
slight changes. Consequently, the deserted channels, since it is 
evident that they bear no relationship to post-glacial waterways, 
are plainly of the ice-front type. 
(2) In the kame moraine areas from Freeville to McLean and 
northward one notes illustrations of the torrential type of ice-front 
channels. This would be expected, for here the massive accumu- 
lations of drift, prevailingly washed in character, bespeak an 
unusual quantity of ice-front drainage. Some of these channels 
indicate a sub-glacial origin, as it is impossible to associate them 
with the normal development of channels cut by water flow along 
