The Karnes of the Oriskany Valley. — Harris. 385 
valleys have been subjected to considerable modification of 
character. 
The great trunk lines of the drainage of central and west- 
ern New York have in general a direction from west to east. 
They consist, in the main, of lakes P>ie and Ontario and the 
Mohawk river on the north, and the upper branches of the 
Susquehanna on the south. Between these two lines the prin- 
cipal tributaries flow in general north and south. In many 
cases it is a noticeable fact that the sources of north and of south 
flowing streams stand opposite to one another in such a way 
that a traveler may ascend the course of the one and then, ar- 
riving at its source, continue his journey in the same line down 
the course of the other; the two streams in effect occupying 
the two halves of one valley, and draining the same in oppo- 
site directions. The Oriskany and the Chenango constitute a 
case in point. The cause of this phenomenon is probably the 
preglacial invasion of the valley of the stream having the 
more gradual slope and consequently less erosive power, by 
the other, which, on account of greater declivity, has more 
erosive power and being thereby enabled to extend its drain- 
age area more rapidly has succeeded in diverting or reversing 
the course and swallowing up a portion of the valley of the 
weaker stream, the evidence of the robbery being preserved in 
the areal relations of the valley whose drainage has been thus 
transferred. 
The diluvial relations of such streams arc therefore pecul- 
iar. As the ice-sheet melted away, its edge, gradually moving 
back from south to north, would necessarily first expose the 
valleys of the south Mowing streams and then the upper por- 
tions of the valleys of those which now flow toward the north. 
In the former valleys would flow rivers copiously supplied 
from the melting ice and along their courses would he laid 
down deposits of sand, gravel, etc.. in that elongated, forward- 
strewn form of deposit characteristic of the flood-plains of 
streams, in which the detritus is constantly being urged along 
by the impetus of the current. But as the retreating ice va- 
cated the upper portions of the valleys which discharge north- 
ward those valleys would appear as enclosed l>;isins, their 
natural outlets being blocked by the ice-mass which still oc- 
cupied their lower courses. These enclosed spaces would be 
