Atlantic Ocean 
Davis and Wood.] 
2 
394 [Nov. 20, 
Tertiary time, and the valleys excavated in 
it were well advanced toward their present 
stage by the time of the glacial period. 1 
These changes from the Schooley pene- 
plain may be more clearly conceived by 
comparing fig. 4 with fig. 5. The restored 
Schooley peneplain is FED. The soft 
limestones of the crystalline region FE are 
worn down to valleys YY ; the weak Creta- 
ceous beds EDV are stripped off for many 
miles from their ancient western edge E and 
are worn down low, except where a few 
harder beds hold out a little way against 
the forces of destruction ; and the soft Tri- 
assic shales thus laid bare are opened out 
into lowlands, XX, between the hard trap 
sheets which still hold their crest lines near 
the surface of the Schooley plain. The ma- 
terial eroded below the surface of the 
^ Schooley peneplain, FED , and its partial 
& cover, EDV , has been transferred to the 
ocean floor, FOX, where it probably forms 
those Tertiary beds which are not repre- 
sented within New Jersey. 
24. Somerville cycle of drainage in the 
Highlands and on the Central Plain. A 
deductive consideration of the origin of val- 
leys gives reason for suspecting that the 
valleys by which the drainage of the Som- 
erville cycle was carried on were of two 
kinds : one originating on that part of the 
Schooley peneplain that was never trans- 
gressed by Cretaceous beds ; the other orig- 
inating on the Cretaceous cover that over- 
lapped the southeastern part of the pene- 
plain. 
1 In this connection, the reader should consult McGee’s 
study of the Columbia formation, in which the production 
and the elevation of this and other baselevelled areas are 
correlated with the first glacial epoch, l. c., 376, 465. 
