403 
[Davis and Wood. 
Let us consider, therefore, the transverse streams which rose on 
the crystalline lowland peneplain in the latest part of School 
time ; they flowed across the strike of the rocks, that is, in a gen- 
eral way, to the southeast and entered the shallow Cretaceous sea 
somewhere near the line above indicated as marking the limit of its 
northwestward transgression ; but later, as the whole region was 
elevated and the even sea-bottom became a land area of smooth 
surface and gentle southeastward slope, the transverse streams 
from the Highlands must have prolonged their courses in the same 
direction. 
The examination of the present altitude of the remnants of the 
Scliooley peneplain, in paragraphs 15 and 21, gave us reason to 
think that when this plain and its cover were lifted, the slope of the 
cover was not uniformly to the southeast; for the crest of the Pali- 
sades-Rocky Hill trap ridge is not now a level line, as it must very 
nearly have been on the Scliooley peneplain ; it is lowest from 
Amboy to New Brunswick, where the Cretaceous cover still buries 
it; and it rises northward and southwestward from these points. 
The unequal lifting of the Cretaceous sea-bottom, thus indicated, 
gives reason for the convergence of the Passaic and the Raritan from 
the north and west and explains the location of their passage across- 
the Palisades-Rocky Hill sheet where it is still buried. 
We cannot say how much additional length the streams from the 
Highlands gained as they crossed the newly lifted Cretaceous plain,, 
but the process by which it was gained has a modern homologue in 
the growth of the streams that flow southeastward across the low- 
lands of southern New Jersey, where the uplift from the sea is so 
recent and so slight that the streams have not trenched their chan- 
nels through the beds on which they took their birth. But in the 
Triassic portion of the Central plain under consideration, the ele- 
vation by which the rivers grew longer was long ago and the uplift 
was of considerable measure at the margin of the crystalline area, 
whence the surface of the Cretaceous beds sloped with distinct fall 
to the coast of that time, perhaps not far from the present coast 
line. Time, elevation and slope all being allowed, the lengthen- 
ing streams from the Highlands have been able to trench their chan- 
nels deep below the Cretaceous beds on which they took their birth 
and to reveal the unconform able underlying Triassic formation, 
which they traverse in superimposed courses. How far can we find 
evidence in favor of this sketch of their history ? A peculiar por- 
tion of the Central plain may now be examined in this connection. 
