168 



adjacent to the presumed ancient estuary or mouth of this sup- 

 posed stream, the width of the deposit amounts to thirty miles ; 

 at the Susquehanna to about twelve; at the Potomac to be- 

 tween six and eight, and at the James river to not more than 

 four miles. 



It may be objected to the argument above advanced touching 

 the regular and gentle ascent of the formation towards the south- 

 west, 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, approaching 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 



