84 NEW YORK STATE MUSEUM 
the state passed southwestward to westward into the Mississippi 
valley with very little, if any, drainage into the Atlantic. But by 
the close of the Mesozoic, or the beginning of the Tertianysaacone 
siderable south to southeastward drainage had been established 
along the lines of the Hudson, Susquehanna, and Delaware rivers. 
Have we any explanation for the establishment of these important 
drainages into the Atlantic? One view is that the courses came 
about as a result of the meandering and changing of channels on 
the surface of the low-lying Cretacic peneplain, and that these 
courses were maintained upon the upraised peneplain. Another 
view which the writer would suggest as worthy of consideration 
is that the south and southeasterly drainage lines were established 
as a result of the uplift of the peneplain. Chapter 5 shows 
that the axis of greatest uplift passed through northern New York 
from central Pennsylvania, the region of southeastern New York 
and northern New Jersey not being raised so high. It is very 
reasonable, if not highly probable, that this very warping or slow 
arching up of the peneplain surface inaugurated the present drain- 
age toward the Atlantic because the streams, no matter what their 
previous courses, then naturally must have flowed down that initial 
slope toward the Atlantic. 
After the uplift of the peneplain the larger streams cut down 
their channels most rapidly and would be the first to reach “ grade,” 
that is, a condition in which, because of low velocity, they could no 
longer cut down their channels, though the widening process could 
continue because of side cutting due to meandering of the streams 
back and forth from one side to the other of the channels. Ia 
deep but broad-bottomed, stream-cut valleys so common in New 
York State show that many of the streams had reached a graded 
or nearly graded condition even by the close of the SPertiaiaequin 
southeastern New York, at least, we have evidence to show that 
after the streams had reached grade there was an appreciable 
renewed uplift of the land which again revived the activity of the 
streams. Thus the broad Hudson valley, with minor hills rising 
above its surface, was produced when the Hudson was well along 
_ toward a graded condition and then, as a result of this late Tertiary 
uplift of the land, the present narrow and fairly deep inner channel 
(gorge) of the Hudson was formed. The Hudson cid not reach 
grade in this inner channel, its work having been interrupted by 
the spreading of the great ice sheet over the region. It is not known 
