420 
Frank Carney 
making . relatively a slight ascent. And for several miles at a 
stretch no roadway-construction has been attempted. The verti- 
cal measure of the steep part of the side walls is 300-500 feet, 
but we have no proof of the amount of glacial over-deepening in 
this valley; the deepest well, 200 feet, is near the east wall of the 
valley at Moravia and did not reach rock; a conservative estimate 
of the measure of glacial erosion here would be 1000 feet. 
These steep walls are remarkable, but their continuity, giving 
the valley a canal-like effect, an artificial appearance, is more 
remarkable. Rivers widen their valleys by cutting alternately 
against the two walls; thus we generally find a steep slope directly 
across the valley from a gentle slope; a long-range view through 
such a valley is broken by spurs each hiding the end of the next 
one beyond but belonging to the opposite valley-wall. Glacier 
ice is the only agency known to smooth and straighten the sides of 
a valley. 
When glacial erosion thus alters a valley, deepening it and 
cutting back the lower parts of its walls, an abnormal relationship 
is established between the major and tributary streams; the latter, 
instead of flowing into the former at an even grade, drop over 
falls or tumble down cascades in many instances several hundred 
feet. The immediate base-level of a branch stream is the main 
stream, and save in very exceptional cases the branch lowers its 
bed in unison with the major. But after a valley has been glaci- 
ally over-deepened the tributary streams commence to adjust 
themselves to the new base-level, and in consequence have cut 
rapids and gorges; these tributaries then ocupy ‘‘hanging valleys.’ 
Fall Creek valley in the vicinity of Dresserville, and Skaneateles 
Inlet valley also show the result of vigorous glacial erosion. 
Similar evidences of the work of glaciers have been observed 
in many parts of the world. That ice has done work of such 
magnitude, there is almost unanimous agreement among scholars. 
Of necessity, it is impossible to study the actual process of glaciers 
eroding valleys. In some mountainous regions at the present 
time glaciers of the alpine type are at work; the portions of the 
valley from which such ice has recently withdrawn show plainly 
what has been done: a U-profile has been developed, making the 
valley deeper and its bottom broader; the sides and bottom, where 
bare, show scouring, polishing, and scratching, the work of stones 
of all sizes held in the basal and lateral parts of the valley glacier. 
I 
