Correspondence. 59 
for January, IS??, and from itProf. Tarr has drawn certain conclusions. 
What he has quoted and his comments, under the caption. "Reviews of 
Opinions of previous Writers." are as follows: 
"Simonds shows that there are in this region two classes of valleys — 
gorges, 'true valleys of erosion.' and rounded, smoothed valleys. Of the 
latter he says: 
•"'Noting in addition [to their even slope] the depth at which the 
water flows and the small number of cascades and waterfalls, the con- 
clusion is at once reached that these valleys have been acted upon by 
some agency not now in operation.' 
"He can easily understand the gorges, but cannot explain the broad 
valleys by erosion, and therefore concludes thai 'these deep, well-worn 
valleys are undoubtedly the work of glacial action.' According to this 
author the glacier divided near the present site of Ithaca, one lobe mov- 
ing southward, the other carving out Six Mile creek. 
•' This, which seems to be the first statement of the glacial origin of 
Cayuga valley, is based upon the inability of the author to conceive of 
the formation of a broad, deep valley by river erosion and transporta- 
tion. It seems strange that he should not have noticed that this valley 
was but one of a type which exists in that region with directions vary- 
ing through all degrees of the compass, and hence, that all are not 
capable of explanation by glacial erosion."* 
Again, under the caption, "Observations and Interpretations," he 
says: 
" Evidence of Six Mile creek. — At the head of the lake, in the city of 
Ithaca, the valley divides — one part, known as the Inlet valley, contin- 
ues south westwardly and then southerly; the other, called Six Mile creek 
valley, extending in a southeastern direction. The latter is evidently a 
tributary to the former, which was the preglacial main valley. Tin ;se 
two valleys are the ones which Simonds and Poote believe to be due to 
ice action. They are both distinctly preglacial in form and are joined 
by mature tributaries. "f 
What I did say upon the subject of valleys was as follows: 
"At Ithaca there' are two distinct types of river or creek valleys — the 
one with rounded and well-worn sides, the other bordered by precipi- 
tous walls of rock. To the latter class belong Cascad ilia and Fall creeks, 
which How into the Ithaca plain from the east. Their valleys are true 
valleys of erosion, having been formed since the withdrawal of the vast 
ice-sheet which swept over this port ion of North America in Quaternary 
time. With the exception of Six Mill' creek valley and thai of Cayuga 
Inlet, which open into the lake basin from the southeast and south 
respectively, all the streams of this immediate vicinity How through 
deep cuts or canons, in which they descend by numerous cascades and 
water-falls to t he lake. As their valleys are mere chasms, they make 
no appreciable change in the general contour of the land. Willi val- 
leys of the first type, however, the effeel is of an entirely differenl char- 
♦Bnlletin, G. S. A., vol. v, p. 344. 
fBulletin, G. 8. A., vol. v,p. :*50. 
