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MOUNTAIN RANGES 



that cross from the mountains to the sea. Over 

 this rocky boundary, the rivers which descend from 

 the mountains over the western tract precipitate 

 themselves, either in falls or long rapids, and emerge 

 into the tide level to assume at once a totally new 

 character. South of North Carolina, this line of 

 primary rocks leaves the tide and retires much near- 

 er to the mountains, though it still preserves its gen- 

 eral features, separating the rolling and picturesque 

 region of the older rocks from the tertiary plains 

 next the ocean ; and, though its base is not any 

 longer laved by the tide, as in Virginia, Maryland, 

 and Pennsylvania, it still produces rapids and cata- 

 racts in the southern rivers which cross it. Ranging 

 for so very great a distance with a remarkable uni- 

 formity of outline and height, on an average be- 

 tween 300 and 400 feet above the tide, it constitutes 

 an admirable geographical as well as commercial 

 limit. Several of the chief cities of the Atlantic 

 States stand upon this boundary, from the obvious 

 motive of seeking the head of navigation. The up- 

 per tract, which has been called the Atlantic Slope, 

 possesses a very variable width, being narrow in 

 the New- England states and in New- York, where 

 the mountains approach the coast, but expanded in 

 Virginia and the Carolinas, where it has a breadth 

 of about 200 miles, ascending from the tide- waters 

 in an undulating, hilly surface, to a mean elevation 

 of about 500 feet near the mountains. As it ap- 

 proaches these, its hills swell into bolder dimen- 

 sions, till we gain the foot of the Blue Ridge, or first 

 chain of mountains. This tract then consists al- 

 most exclusively of the older sedimentary and strat- 

 ified primary rocks, such as gneiss, mica slate, &c. 

 It forms a fine hilly country, exhibiting a marked 

 uniformity in the direction of its ridges and valleys, 

 running very generally northwest and southwest, or 

 parallel with the mountains. The ridges, though 

 not high, are long, and the fertile intervening val 



