1889 .] 
391 
[Davis and Wood. 
THE CENTRAL PLAIN AND THE HIGHLAND VALLEYS. 
21. Elevation of the Schooley peneplain and its consequences. 
We now enter a later cycle in the development of the state. The 
lowlands, which were so broadly worn in Jurassic and Cretaceous 
time on the Schooley baselevel and partly sealed over along their 
coastward margin with Cretaceous sediments, are now no longer low- 
lands, but have at sometime in the past been elevated ; and wide 
valleys and lowlands of a second order have been opened in their 
formerly uniform surface. The geographic cycle in which these 
newer valleys and lowlands have been produced is now to be inves- 
tigated. Certain general considerations may precede the special 
study of the case. We know that while the old Schooley baselevel 
peneplain has been elevated, it was not necessarily raised at once 
from its original to its present position ; it may have, for a time, 
resided at some other altitude, perhaps at an intermediate height 
between its former and its present stand ; and the present position 
of the land may have been assumed only after a second or third 
change of elevation. Again, if the land has stood at any altitude 
intermediate between the Schooley baselevel and the present for 
a considerable time, there should be topographic indication of it in 
the occurrence of topographic forms developed with respect to the 
position referred to. Finally, forms of this kind will be mo fc st ap- 
parent in the region of the softest rocks, for there the rate of de- 
velopment is most rapid. 
We therefore now take the area of the weak Triassic and Cre- 
taceous formations as the region for first examination. It is as 
proper to select this district in the present case while we are look- 
ing for the signs of relatively recent geographic development, as it 
was to take the area of the hard crystalline rocks of the Highlands 
in searching for records of a long past time. 
22. The Central Triassic and Cretaceous plain on the Somerville 
baselevel. The interstream surface of the Triassic lowlands where 
traversed by the railroads west and southwest of Bound Brook are, 
clearly enough, dissected portions of a once continuous plain of 
moderate elevation, but high enough for the streams to sink dis- 
tinct channels below it. The same process of reasoning as that em- 
ployed in studying the old Highland peneplain leads to the conclu 
sion that this Triassic plain marks an old baselevel ; it is not a 
constructional surface, in sympathy with the rocks below, for the red 
