290 
GEOLOGY OF THE FIRST DISTRICT. 
level throughout its entire width from Trenton to Durham. Advancing to the Schuylkill be¬ 
tween Norristown and Reading, he will observe its height above the tide to have augmented ; 
and crossing thence in succession the Susquehannah, the Potomac and the James rivers, he 
will perceive the tract still gradually and uniformly to ascend, until it attains a level of seve¬ 
ral hundred feet above the sea, marking an inclination nearly corresponding to that which 
belongs to many of our large rivers now descending from the Appalachian chain into the 
ocean, 
“ The progressive diminution in the breadth of the formation is strictly in accordance with 
these facts. At the Delaware, adjacent to the presumed ancient estuary or mouth of this 
supposed stream, the width of the deposit amounts to thirty miles ; at the Susquehannah, to 
about twelve ; at the Potomac, to between six and eight; and at the James river, to not more 
than/owr miles. 
“ It may be objected to the argument above advanced touching the regular and gentle as¬ 
cent of the formation towards the southwest, that the existing slopes of the whole district 
southeast of the mountains may have been produced during the elevation of the greensand 
and tertiary strata, at periods subsequent to that which witnessed the drainage of the red 
sandstone valley. 
Did the scope of the present treatise authorize the detailed discussion of this curious 
point, we think that a comprehensive investigation of the existing levels of the respective 
tracts, or, in other words, the relief above the ocean of the several parallel belts of country 
conceived to have successively emerged from beneath the sea, would go far to convince us 
that the channel which received the red shale deposits possessed to a considerable degree at 
least its present gentle slope towards the northeast, during the epoch of its formation, which 
was apparently soon after the cessation of those disturbances which finally elevated the coal, 
“ Let it be observed that the Kittatinny valley, formed of rocks uplifted at the close of the 
older secondary or Appalachian epoch, has the same regular and gradual declension in level 
from the interior of Virginia to the Hudson which we find in the red sandstone belt of the 
parallel valley southeast of it. From an elevation in the vicinity of the New river, approach¬ 
ing one thousand feet above the level of the sea, it slowly descends northeastward, until at the 
Hudson its general surface rises not more than one hundred feet above the tide, "While this 
is true of the plains occupied by the older and middle secondary rocks, no such variation in 
the level of the more recently lifted tertiary plain along the sea-board is discernible. From 
the Roanoke to the Delaware, the tide every where penetrates this latter, and its surface in 
that distance does not descend probably more than one hundred feet. It seems, therefore, 
altogether improbable that the whole of the northeastward descent in the first two valleys, 
that northwest and that southeast of the Blue ridge chain, should have been acquired at the 
time of the elevation of the tertiary, or at any period later than that of the final drainage of 
the middle secondary trough. The disturbances of level which took place at the close of the 
newer secondary or greensand period are still further in favor of the same conclusion for, 
while the strata of that date were raised to a moderate height, averaging sixty or eighty feet 
