395 
[Davis and Wood. 
Consider first the valleys formed on that part of the peneplain 
that was never covered by Cretaceous beds. Even the smoothest 
part of the uncovered crystalline rocks of the Highlands cannot 
have been reduced to absolute flatness at the end of the Schooley 
cycle ; the restoration of their surface that we have attempted has 
shown that a residual relief of some distinctness probably remained 
before the present valleys were begun. The harder rocks resisted 
weathering more stubbornly while the softer ones were worn down 
to the lowest level, and this difference must have been maintained, 
though with decreasing distinctness, to the end. Just before the 
elevation of the Highlands that we are about to consider, the streams 
must have wandered sluggishly with almost imperceptible slope 
along broad lowlands of northeast and southwest trend, between 
faint dividing swells of land of the same direction. Many such 
longitudinal streams would find escape southeastward in a single 
transverse master stream, after the fashion of old mountain drain- 
age in general. When the whole area was lifted and tilted to the 
southeast, the sluggish streams were revived and entered a new cy- 
cle of their long life. The smaller streams followed the lead of 
their masters, but without changing their position, although the 
tilting of the old plain might in some cases reverse their direction 
of flow. All would be in accord with the slope of the country that 
they drained, but as the slope was in most cases the residual of the 
relief of the old plain and not necessarily in accord with any an- 
cient constructional slope, the streams should not be called “conse- 
quent” in the meaning of that word, as it was first employed by 
Powell. Whatever their origin on the ancient plain, they are now 
simply “revived.” 
The case would be different with that part of the old Schooley 
plain that had been submerged under the shallow Cretaceous sea 
and that now rose with the Cretaceous cover on its back. Here the 
land, as it rose from beneath the waters, would appear as a smooth 
surface, with gentle seaward slope ; and the streams that ran out 
across it from the crystalline area, or that headed upon it, would 
follow its slope to the retreating ocean in the southeast. Then after 
a moderate amount of channel cutting, the unconformable underly- 
ing rocks would be discovered, and the streams persisting in the 
courses taken on the smooth Cretaceous surface, would of necessity 
traverse the under rocks with little reference to their structure. 
Valleys cut by such streams have been called “superimposed” by 
