MARGINAL GLACIAL DRAINAGE FEATURES 537 



rejuvenation that it was tributary to the neighboring Stream A 

 rather than to Cayuta Gorge. This behef is based on the fact that 

 the drift-filled gorge at the mouth of B appears to be hanging well 

 above the present stream in Cayuta Gorge, and that in A, about one- 

 third of a mile above its mouth, there is a break in the continuity of the 

 rock wall on the west side, above which the gorge is decidedly nar- 

 rower; a condition which suggests strongly the entrance of a large 

 tributary gorge from the west. 



For these reasons, though one gorge may be due to rejuvenation, 

 it is believed that the others represent at least three ice invasions with 

 corresponding intervals of deglaciation. 



Evidence as to the interglacial nature of these gorges is of con- 

 siderable importance, owing to the fact that while the multiplicity 

 of glacial epochs has been proven in many parts of the United States, 

 it has not been fully recognized for this region. As late as 1905 we 

 have the following statement from Fairchild' : "It is safe to discuss 

 the history of the region as involving only the Wisconsin glacial epoch, 

 for no evidences of any earlier and more forceful and extended ice 

 sheet have been found." Previous to 1906, Tarr^ held that there was 

 no direct evidence of more than the Wisconsin ice invasion. In that 

 year, however, he published evidence based on the buried gorges 

 which led him to the conclusion that there have been at least two 

 epochs of glaciation.^ Maston^ in 1904 described a series of buried 

 gorges in Buttermilk valley near Ithaca which led him to the belief 

 that at least two and perhaps four ice-sheets had invaded this region. 



TYPE III. LATERAL 



Spencer Summit channel. — A typical lateral channel is found one 

 and one-half miles east of the Lehigh Valley railway station at 

 Spencer Summit, a short distance south of the Thompkins County 

 line and one-fourth mile east of Michigan Creek (Dryden sheet, 

 U.S.G.S., Fig. 6). Beginning just beyond the divide in the deep 

 notch through which the road passes, it follows a southeasterly 

 course along the preglacial valley heading near the notch. For the 



1 Bui. Geol. Soc. Amer., Vol. XVI, p. 67. 



2 Ibid., pp. 217, 237-42. 



3 Jour. Geol., Vol. XIV, 1906, pp. 18-21. 



4 Ihid., pp. 133-51 



