210 
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 w^hich 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 Slopes 
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- 
