Finger Lake Region of Central N. Y. — I'arr. 283 
(Figs. 2-4). Locall}- these broadened portions of the valleys 
have liecn called amphitheatres. In those cases where the 
post-Glacial streams have followed older gorges for a con- 
siderable distance, as in the case of Six Mile creek, the gorge 
valley is decidedly broader than in the distinctly post-Glacial 
sections. 
The influence of the older gorges, the effect of alternating- 
layers of shale and sandstone of varying hardness, and the 
influence of joint planes, account for the wonderful variety 
of form in the gorges of this vicinity and the varied beauty 
of the numerous waterfalls. A more detailed consideration of 
this phase of the drainage problem of central New York will 
be undertaken in another paper. 
The Theory of Glacial Erosion: Since the publication of 
Lincoln's paper,* and of my own on lake Cayuga, t the theory 
of glacial erosion has been held as the most rational ex- 
planation of the phenomena in the Finger Lake region. The 
upper mature hanging valle}-s were not then fully recognized ; 
but the glacial erosion theory was nevertheless based upon the 
fact that distinctly mature valleys, descending toward the two 
Finger lakes, were rock-enclosed at their bottoms at an eleva- 
tion above present lake level. Though the existence of older 
gorges had been determined in one or two cases, their abun- 
dance and their relation to the mature hanging valleys were 
not understood. 
If the hanging valleys of the Finger lake region may be 
taken as evidence of glacial erosion, the amount of this erosion 
is prodigious. From the evidence of a number of valleys, as 
well as from that of the steepened lower slopes of the main 
valleys, the edge of the hanging valleys nearest the axis of 
the main valle}-s may be placed at not less than the 800 foot 
contour. This edge is, in a number of instances, less than one 
mile from the axis of the main valley. The hanging vallevs 
have such maturity of form that a moderate grade mav con- 
fidently he assumed for their bottom slope, eliminating, of 
course, the gorges later cut in their bottoms. Continuing this 
grade onward beyond the present edge of the hanging vallevs 
would not carry their bottoms greatly below the level of the 800 
* Amer.Jour. Sci., vol. xliv, 1892, pp. 290-.301. 
t Bull. Geol. Soc. Anier., toI. v, 1894., pp. :^39-356. 
